JP7549835B2 - Radio transmission device and radio transmission method - Google Patents

Description

The present invention relates to a wireless transmission device and a wireless transmission method.

As the demand for high-speed transmission increases, it is necessary to make effective use of frequency bands by efficiently allocating a large amount of spectrum within the allocated frequency band. Examples of cases where effective use of frequency bands is required include satellite communications and cellular systems.

For example, Figs. 14 and 15 are diagrams showing an outline of a wireless communication system in which wireless communication is performed between base stations 100, 100a and terminal stations 102-1, 102-2 via a relay station 101 such as a satellite communication station. Note that in Figs. 14 and 15, the solid arrows indicate communication lines, and the dashed arrows indicate control lines.

In FIG. 14, the line control device 110 installed in the base station 100 is aware of the usage status of frequency bands on the frequency axis, and allocates and releases frequency bands to each of the terminal stations 102-1 and 102-2 through a control line. Note that the line control device 110 may be installed in a line control station 103 that is separate and independent from the base station 100a, as shown in FIG. 15.

Figure 16 shows a schematic diagram of a wireless communication system 120 in a cellular system such as a mobile phone, and an enlarged diagram of one cell 120-1 in the wireless communication system 120. The terminal stations 132-1 and 132-2 are assigned a frequency band by a line control device 131 installed in a base station (also called a node station) 130 in the cell 120-1. Note that when the wireless communication system 120 is a wireless communication system in which cells overlap, such as a macrocell and a microcell, the line control devices 131 installed in each of the overlapping cells may operate in cooperation with each other.

A known wireless communication system that efficiently allocates a large number of spectrum signals within an assigned frequency band is one that includes a wireless transmission device 140 shown in FIG. 17 and a wireless reception device 160 shown in FIG. 18 (see, for example, Non-Patent Document 1).

In the wireless transmission device 140 shown in FIG. 17, the four division filter units 153-1 to 153-4 are equipped with bandpass filters having the same bandwidth shape shown by the dashed lines in FIG. 19(a) and different center frequencies f4-1, f4-2, f4-3, and f4-4. Each of the division filter units 153-1 to 153-4 applies its respective bandpass filter to the spectrum signal generated by the frequency conversion unit 152 shown by the solid lines in FIG. 19(a) to generate the four subspectrum signals shown in FIG. 19(b). Hereinafter, the division into subspectrum signals is also referred to as spectrum division.

The frequency shift units 154-1 to 154-4 shift and distribute the subspectrum signals so that the bands of the four subspectrum signals do not overlap on the frequency axis, as shown in FIG. 19(c). The adder unit 155 adds, i.e., combines, the distributed subspectrum signals to generate a spectrum division synthesis signal. The inverse frequency converter unit 156 converts the spectrum division synthesis signal into the time domain to generate a spectrum division synthesis modulated signal. The spectrum division synthesis modulated signal is amplified by the transmission amplifier unit 143 and then radiated into the air as a radio signal by the antenna 144.

In the wireless receiving device 160 shown in FIG. 18, the four extraction filter units 173-1 to 173-4 are provided with bandpass filters having the same bandwidth shape shown by the dashed lines in FIG. 20(a) and different center frequencies fs4-1, fs4-2, fs4-3, and fs4-4. Here, the center frequencies fs4-1, fs4-2, fs4-3, and fs4-4 are the center frequencies of the subspectrum signals after being shifted by the frequency shift units 154-1 to 154-4 of the wireless transmitting device 140. The bandwidths of the bandpass filters of the extraction filter units 173-1 to 173-4 need only be wide enough to extract each of the four components of the spectrum division synthesis signal generated by the frequency conversion unit 172 shown by the solid lines in FIG. 20(a), and are determined in advance so that the bandwidths do not overlap with each other.

Extraction filter units 173-1 to 173-4 apply their respective bandpass filters to the spectrum division synthesis signal shown by the solid line in FIG. 20(a) to extract four subspectrum signals. Frequency shift units 174-1 to 174-4 apply the shift amounts applied by frequency shift units 154-1 to 154-4 of wireless transmission device 140 to each of the extracted subspectrum signals in the opposite direction. As a result, the center frequencies of the subspectrum signals become f4-1, f4-2, f4-3, and f4-4, which fall within the bandwidth of the spectrum signal.

The subspectrum signals shifted by the frequency shifters 174-1 to 174-4 are combined by the adder 175 to generate the spectrum signal shown in FIG. 20(c). The spectrum signal is converted to the time domain by the inverse frequency converter 176, and then demodulated by the demodulator 164 to obtain the received data. This makes it possible to transmit data by effectively utilizing discontinuous free frequency bands.

Junichi Abe, Katsuya Nakahira, Takatoshi Sugiyama, "Experimental Verification of Blind Phase Compensation Method in Bandwidth Dispersion Transmission", IEICE Technical Report, Institute of Electronics, Information and Communication Engineers, December 2011, vol. 111, no. 336, SAT2011-46, pp. 41-46

By the way, an index value called PAPR (Peak to Average Power Ratio) is known as an index value of signal power. For example, FIG. 21 is a graph showing the change over time in power of the spectrum division synthesis modulated signal, which is the input signal to the transmission amplifier unit 143. The power value at the position indicated by reference numeral 200 on the graph is the peak power value, and the power value at the position indicated by reference numeral 201 is the average power value.

Figure 22 is a graph showing the PAPR value of the spectrum division synthesis modulated signal for each division number when QPSK (Quadrature Phase Shift Keying) is applied as the modulation method performed by the modulation unit 141 of the wireless transmission device 140, and "0.2" is applied as the roll-off rate of the time window function applied by the time window processing unit 151. A spectrum division synthesis modulated signal with a division number of "0" is a modulated signal output by the modulation unit 141. As shown in the graph, compared to the PAPR when the division number is "0", it can be seen that the PAPR increases with each increase in the division number.

23 and 24 are graphs showing the amplification characteristics, which are the relationship between the input power value of the transmission amplifier unit 143 provided in the wireless transmission device 140 and the output power value after amplification. In a typical transmission amplifier unit 143, the peak power operating point is set at the position indicated by reference numeral 300 in FIG. 23, for example, so that the transmission amplifier unit 143 operates in a linear region when the input power value peaks without division. As the number of divisions increases, the PAPR increases, so the input power value increases as indicated by the arrow indicated by reference numeral 401, and the peak power operating point moves to the position indicated by reference numeral 301. At the operating point indicated by reference numeral 301, amplification cannot be performed in the linear region, nonlinear distortion occurs in the signal output by the transmission amplifier unit 143, and communication quality deteriorates. This causes a problem in that a larger amplifier must be applied to the transmission amplifier unit 143.

On the other hand, if the operating point at peak power is set at the position indicated by reference numeral 302 in FIG. 24 so that the input power value peaks when the number of divisions is large and the operation is performed in a linear region, the operating point at average power is set at the position indicated by reference numeral 304. Here, if the peak operating point is set at the position indicated by reference numeral 302 so that the input power value peaks when the number of divisions is small and the operation is performed in a linear region, the back-off value is smaller when the number of divisions is small, so the operating point at average power is set at the position indicated by reference numeral 303. However, if the operating point at peak power is set at the position indicated by reference numeral 302 so that the input power value peaks when the number of divisions is large and the operation is performed in a linear region, the PAPR decreases as the number of divisions decreases, so the operating point at average power moves to the position indicated by reference numeral 304 even when the number of divisions is small. In this case, amplification can be performed in a linear region, but there is a problem that the power of the transmission radio signal obtained by amplifying the spectrum division synthesis modulated signal decreases as indicated by the arrow of reference numeral 500.

When operating with a fixed division number, the above problem does not occur if the operating point is fixed to an appropriate value for that division number. However, depending on the operating situation, it may be desirable to change the division number at any time, or to vary the division number over time. In such cases, conventional wireless communication devices have the problem of being unable to track the operating point to be appropriate according to the division number.

In view of the above circumstances, the present invention aims to provide a technology for a wireless transmission device that divides a spectrum signal, distributes it on the frequency axis, and transmits a wireless signal, which can transmit a wireless signal without degrading communication quality even if the number of divisions changes.

One aspect of the present invention is a wireless transmission device that includes a transmission filter bank section that generates a spectrum signal by converting a modulated signal obtained by modulating transmission data into a frequency domain, and filters the spectrum signal with a number of bandpass filters that corresponds to a predetermined division number, the bandpass filters having some overlapping bands, to generate a plurality of subspectrum signals, distributes each subspectrum signal on the frequency axis so that the bands of the subspectrum signals do not overlap, and generates a spectrum division synthesis modulated signal by synthesizing each of the distributed subspectrum signals and converting them into a time domain; a transmission amplifier section that amplifies the spectrum division synthesis modulated signal; an antenna that transmits the spectrum division synthesis modulated signal amplified by the transmission amplifier section as a wireless signal; and an optimal operating point detection section that operates the transmission amplifier section at an effective operating point of the transmission amplifier section obtained based on the peak-to-average power ratio of the spectrum division synthesis modulated signal for each of the predetermined division numbers and the amplification characteristics of the transmission amplifier section.

One aspect of the present invention is a wireless transmission method that generates a spectrum signal by converting a modulated signal modulated with transmission data into a frequency domain, and filters the spectrum signal with a number of bandpass filters that matches a predetermined division number, the bandpass filters having some overlapping bands, to generate a plurality of subspectrum signals, distributes each subspectrum signal on the frequency axis so that the bands of the subspectrum signals do not overlap, synthesizes each of the distributed subspectrum signals, and converts them into the time domain to generate a spectrum division synthesis modulated signal, operates the transmission amplifier unit at an effective operating point of the transmission amplifier unit obtained based on the peak-to-average power ratio of the spectrum division synthesis modulated signal for each predetermined division number and the amplification characteristics of the transmission amplifier unit, amplifies the spectrum division synthesis modulated signal, and transmits the spectrum division synthesis modulated signal amplified by the transmission amplifier unit as a wireless signal.

According to this invention, in a radio transmission device that divides a spectrum signal, distributes it on the frequency axis, and then transmits a radio signal, even if the number of divisions changes, the radio signal can be transmitted without degrading communication quality.

1 is a block diagram showing a configuration of a wireless transmission device according to an embodiment of the present invention. 1 is a block diagram showing a configuration of a wireless receiving device according to an embodiment of the present invention; 11A and 11B are diagrams illustrating a process of generating a spectrum division synthesis signal in the case of two division in this embodiment. 11A and 11B are diagrams illustrating a process of generating a spectrum division synthesis signal in the case of four divisions in this embodiment. 11A and 11B are diagrams illustrating a generation process of a spectrum division synthesis signal in the case of eight division in this embodiment. 4 is a diagram showing the configuration of a table stored in a storage unit of the wireless transmission device of the present embodiment. FIG. 5 is a flowchart showing a flow of processing by the wireless transmission device of the present embodiment. 5 is a flowchart showing a flow of processing by the wireless receiving device of the present embodiment. 1 is a graph (part 1) for explaining the effect of the present embodiment. 1 is a graph (part 1) showing the process of adjusting an operating point in a wireless transmission device according to the present embodiment. 13 is a graph (part 2) for explaining the effect of the present embodiment. 11 is a graph (part 2) showing the process of adjusting the operating point in the wireless transmission device of the present embodiment. FIG. 2 is a block diagram showing another example of the configuration of the wireless transmission device according to the present embodiment. FIG. 1 is a block diagram (part 1) showing the configuration of a wireless communication system applied to satellite communication or the like. FIG. 2 is a block diagram (part 2) showing the configuration of a wireless communication system applied to satellite communication or the like. 1 is a block diagram showing a configuration of a wireless communication system applied to a cellular system. 1 is a block diagram showing a configuration of a wireless transmitting device that performs transmission using a spectrum division synthesis signal. 18 is a block diagram showing a configuration of a wireless receiving device that receives a wireless signal transmitted by the wireless transmitting device shown in FIG. 17. 18 is a diagram showing a process of generating a spectrum division synthesis signal performed in the wireless transmission device shown in FIG. 17. 19 is a diagram showing a spectrum signal restoration process performed in the wireless receiving device shown in FIG. 18. 1 is a graph showing a change over time in power of a spectrum division synthesis modulated signal. 1 is a graph showing a relationship between the number of divisions and PAPR in a spectrum division synthesis modulated signal. 18 is a graph (part 1) showing the amplification characteristics of the transmission amplifier unit of the wireless transmission device of FIG. 17. 20 is a graph (part 2) showing the amplification characteristics of the transmission amplifier unit of the wireless transmission device of FIG. 17 .

(Configuration of wireless transmitting device)
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a block diagram showing the configuration of a wireless transmission device 1 according to an embodiment of the present invention. The wireless transmission device 1 includes a modulation unit 11, a transmission filter bank unit 12, a transmission amplifier unit 13, an antenna 14, an optimal operating point detection unit 15, and a storage unit 16.

The modulation unit 11 takes in transmission data and modulates the taken-in transmission data with a predetermined modulation method to generate a modulated signal. For example, QPSK is used as the predetermined modulation method.

The transmission filter bank unit 12 includes a time window processing unit 20, a frequency conversion unit 21, a branching processing unit 22, a timer unit 23, a set of two split filter units 24-2-1, 24-2-2, a set of four split filter units 24-4-1 to 24-4-4, a set of eight split filter units 24-8-1 to 24-8-8, a set of two frequency shift units 25-2-1, 25-2-2, a set of four frequency shift units 25-4-1 to 25-4-4, a set of eight frequency shift units 25-8-1 to 25-8-8, adders 26-2, 26-4, 26-8, and an inverse frequency conversion unit 27.

In the following description, when splitting filter units 24-2-1 and 24-2-2 are shown together, they are referred to as splitting filter unit 24-2, when splitting filter units 24-4-1 to 24-4-4 are shown together, they are referred to as splitting filter unit 24-4, and when splitting filter units 24-8-1 to 24-8-8 are shown together, they are referred to as splitting filter unit 24-8. Similarly, when frequency shift units 25-2-1 and 25-2-2 are shown together, they are referred to as frequency shift unit 25-2, when frequency shift units 25-4-1 to 25-4-4 are shown together, they are referred to as frequency shift unit 25-4, and when frequency shift units 25-8-1 to 25-8-8 are shown together, they are referred to as frequency shift unit 25-8.

The time window processing unit 20 applies a time window function with a predetermined roll-off rate to the modulated signal output by the modulation unit 11 to cut out a portion of the modulated signal. The time window processing unit 20 repeatedly cuts out a portion of the modulated signal while shifting the position. The length of the modulated signal cut out by the time window function is predetermined to match the size of the FFT (Fast Fourier Transform) performed by the frequency conversion unit 21.

The frequency conversion unit 21 converts the modulated signal extracted by the time window processing unit 20 into the frequency domain to generate a spectrum signal. The calculation applied to the conversion into the frequency domain is, for example, FFT, but DFT (Discrete Fourier Transform) may also be applied.

The timing unit 23 is, for example, a clock, and continuously outputs information indicating the time to the branch processing unit 22.

The branching processing unit 22 stores in advance in an internal storage area schedule information indicating how many subspectrum signals the spectrum signal is to be divided into for each time. Here, the number of divisions is either 2, 4, or 8, and the schedule information defines information such as, for example, 2 divisions from 0:00 to 0:10, 4 divisions from 0:10 to 0:20, and 8 divisions from 0:20 to 0:30. Note that the time interval at which the number of divisions is changed does not have to be periodic as described above.

The branching processing unit 22 determines the number of divisions at the time output by the clock unit 23 based on information indicating the time output by the clock unit 23 and schedule information. The branching processing unit 22 branches and outputs the spectrum signal according to the determined number of divisions. The branching processing unit 22 also outputs the determined number of divisions to the optimal operating point detection unit 15.

The configuration of each of the split filter units 24-2, 24-4, and 24-8 and each of the frequency shift units 25-2, 25-4, and 25-8 will be described with reference to Figures 3 to 5. Note that the solid lines in Figures 3(a), 4(a), and 5(a) indicate the spectrum signals generated by the frequency conversion unit 21.

Each of the split filter units 24-2-1, 24-2-2 has a bandpass filter with the same bandwidth shape as shown by the dashed line in FIG. 3(a), but with different center frequencies f2-1, f2-2. The bandwidth of the spectrum signal needs to be adequately covered by the two bandpass filters provided in each of the split filter units 24-2-1, 24-2-2. For this reason, the center frequencies f2-1, f2-2 and the bandwidths of the two bandpass filters are determined in advance so that the bands of the two bandpass filters overlap in part. Each of the split filter units 24-2-1, 24-2-2 applies its respective bandpass filter to the spectrum signal to generate the two subspectrum signals shown in FIG. 3(b).

Each of the split filter units 24-4-1 to 24-4-4 includes bandpass filters having the same bandwidth shape as shown by the dashed line in FIG. 4(a), but with different center frequencies f4-1 to f4-4. The four bandpass filters included in each of the split filter units 24-4-1 to 24-4-4 must adequately cover the bandwidth of the spectrum signal. For this reason, the center frequencies f4-1 to f4-4 and the bandwidths of the four bandpass filters are predetermined so that adjacent bandpass filters among the four bandpass filters partially overlap. Each of the split filter units 24-4-1 to 24-4-4 applies its respective bandpass filter to the spectrum signal to generate the four subspectrum signals shown in FIG. 4(b).

Each of the split filter units 24-8-1 to 24-8-8 includes bandpass filters having the same bandwidth shape as shown by the dashed line in FIG. 5(a), but with different center frequencies f8-1 to f8-8. The eight bandpass filters included in each of the split filter units 24-8-1 to 24-8-4 must adequately cover the bandwidth of the spectrum signal. For this reason, the center frequencies f8-1 to f8-8 and the bandwidths of the eight bandpass filters are predetermined so that adjacent bandpass filters among the eight bandpass filters partially overlap. Each of the split filter units 24-8-1 to 24-8-8 applies its respective bandpass filter to the spectrum signal to generate the eight subspectrum signals shown in FIG. 5(b).

The position where the bandpass filters cross when their bands overlap is, for example, the 3 dB attenuation point.

Each of the frequency shift units 25-2-1 and 25-2-2 takes in the subspectrum signals output by the split filter units 24-2-1 and 24-2-2 connected to them, and shifts and distributes the subspectrum signals so that the bands of the subspectrum signals do not overlap on the frequency axis, as shown in FIG. 3(c). In FIG. 3(c), the center frequencies of the subspectrum signals after shifting are shown as fs2-1 and fs2-2.

Each of the frequency shift units 25-4-1 to 25-4-4 takes in the subspectrum signals output by the division filter units 24-4-1 to 24-4-4 to which it is connected, and shifts and distributes the subspectrum signals so that the bands of the subspectrum signals do not overlap on the frequency axis, as shown in FIG. 4(c). In FIG. 4(c), the center frequencies of the subspectrum signals after shifting are shown as fs4-1 to fs4-4.

Each of the frequency shift units 25-8-1 to 25-8-8 takes in the subspectrum signals output by the division filter units 24-8-1 to 24-8-8 to which it is connected, and shifts and distributes the subspectrum signals so that the bands of the subspectrum signals do not overlap on the frequency axis, as shown in FIG. 5(c). In FIG. 5(c), the center frequencies of the subspectrum signals after shifting are shown as fs8-1 to fs8-8.

The amount of shift for each of the frequency shift units 25-2-1, 25-2-2, 25-4-1 to 25-4-4, and 25-8-1 to 25-8-8 is determined in advance so that the bands of the subspectrum signals after shifting do not overlap on the frequency axis and fall within the frequency band allocated for wireless communication.

The adder 26-2 adds, i.e., synthesizes, the two subspectrum signals shifted by the frequency shifters 25-2-1 and 25-2-2 to generate a spectrum division synthesis signal. The adder 26-4 synthesizes the four subspectrum signals shifted by the frequency shifters 25-4-1 to 25-4-4 to generate a spectrum division synthesis signal. The adder 26-8 synthesizes the eight subspectrum signals shifted by the frequency shifters 25-8-1 to 25-8-8 to generate a spectrum division synthesis signal.

The inverse frequency conversion unit 27 converts the spectrum division synthesis signals output by the addition units 26-2, 26-4, and 26-8 into the time domain to generate a spectrum division synthesis modulated signal. The calculation applied to the conversion into the time domain is, for example, an inverse fast Fourier transform (IFFT), but an inverse discrete Fourier transform (IDFT) may also be applied.

The storage unit 16 stores, for example, a table shown in FIG. 6. The table shown in FIG. 6 has the items "Division number" and "PAPR". In the "Division number", a numerical value of "2", "4", or "8" corresponding to the division number specified by the branching processing unit 22 is written. In the "PAPR" item, for example, the PAPR value of the spectrum division synthesis modulated signal for each division number measured in advance as shown in FIG. 22 is written in units of "dB (decibels)". The PAPR value is in the power dimension.

The optimal operating point detection unit 15 detects the optimal operating point (effective operating point) of the transmission amplifier unit 13 corresponding to the division number specified by the branching processing unit 22, and operates the transmission amplifier unit 13 at the detected operating point. Specifically, the optimal operating point detection unit 15 reads out the PAPR value corresponding to the division number specified by the branching processing unit 22 from the table stored in the memory unit 16. The optimal operating point detection unit 15 outputs the read out PAPR value to the transmission amplifier unit 13.

The transmission amplifier unit 13 sets the operating point to an optimal position based on the PAPR value output by the optimal operating point detection unit 15, and then amplifies the spectrum division synthesis modulated signal output by the inverse frequency conversion unit 27. The antenna 14 transmits the amplified spectrum division synthesis modulated signal by radiating it into the air as a radio signal.

(Configuration of wireless receiving device)
2 is a block diagram showing a configuration of a wireless receiving device 2 according to an embodiment of the present invention. The wireless receiving device 2 includes an antenna 31, a receiving amplifier unit 32, a receiving filter bank unit 33, and a demodulator unit 34. The antenna 31 outputs a received signal obtained by receiving a wireless signal transmitted by the wireless transmitting device 1. The receiving amplifier unit 32 amplifies the received signal.

The receiving filter bank unit 33 includes a time window processing unit 40, a frequency conversion unit 41, a branching processing unit 42, a timer unit 43, a set of two extraction filter units 44-2-1, 44-2-2, a set of four extraction filter units 44-4-1 to 44-4-4, a set of eight extraction filter units 44-8-1 to 44-8-8, a set of two frequency shift units 45-2-1, 45-2-2, a set of four frequency shift units 45-4-1 to 45-4-4, a set of eight frequency shift units 45-8-1 to 45-8-8, adders 46-2, 46-4, 46-8, and an inverse frequency conversion unit 47.

In the following description, when the extraction filter units 44-2-1 and 44-2-2 are shown together, they are referred to as extraction filter unit 44-2, when the extraction filter units 44-4-1 to 44-4-4 are shown together, they are referred to as extraction filter unit 44-4, and when the extraction filter units 44-8-1 to 44-8-8 are shown together, they are referred to as extraction filter unit 44-8. Similarly, when the frequency shift units 45-2-1 and 45-2-2 are shown together, they are referred to as frequency shift unit 45-2, when the frequency shift units 45-4-1 to 45-4-4 are shown together, they are referred to as frequency shift unit 45-4, and when the frequency shift units 45-8-1 to 45-8-8 are shown together, they are referred to as frequency shift unit 45-8.

The time window processing unit 40 applies a time window function with a predetermined roll-off rate to the received signal amplified by the receiving amplifier unit 32 to cut out a portion of the received signal. The time window processing unit 40 repeatedly cuts out a portion of the received signal while shifting the position. The length of the received signal cut out by the time window function is predetermined to match the size of the FFT performed by the frequency conversion unit 41.

The frequency converter 41 converts the received signal extracted by the time window processor 40 into the frequency domain. By converting into the frequency domain, the spectrum division synthesis signal before being converted into the time domain by the inverse frequency converter 27 of the wireless transmission device 1 is obtained. Note that the calculation applied to the conversion into the frequency domain is, for example, FFT, but DFT may also be applied.

The timing unit 43 is, for example, a clock, and is synchronized with the time of the timing unit 23 of the wireless transmission device 1, and continuously outputs information indicating the time to the branch processing unit 42.

The branching processing unit 42 pre-stores in its internal storage area schedule information that is the same as the schedule information that the branching processing unit 22 of the wireless transmission device 1 stores in its internal storage area.

Based on the information indicating the time output by the timer 43 and the schedule information, the branching processing unit 42 determines the number of divisions at the time output by the timer 43. The branching processing unit 42 branches the spectrum division synthesis signal according to the determined number of divisions, and outputs the signal to extraction filter unit 44-2 in the case of division into two, to extraction filter unit 44-4 in the case of division into four, and to extraction filter unit 44-8 in the case of division into eight.

Each of the extraction filter units 44-2-1, 44-2-2 has a bandpass filter with the same bandwidth shape but different center frequencies fs2-1, fs2-2, and applies the bandpass filter to the spectrum division synthesis signal to extract two subspectrum signals. The shape and bandwidth of the bandpass filter provided in each of the extraction filter units 44-2-1, 44-2-2 may be any shape and bandwidth that can extract each of the two shifted subspectrum signals shown in FIG. 3(c), and the shape and bandwidth are determined in advance so that the bandwidths do not overlap with each other.

Each of the extraction filter units 44-4-1 to 44-4-4 has a bandpass filter with the same bandwidth shape but different center frequencies fs4-1 to fs4-4, and applies the bandpass filter to the spectrum division synthesis signal to extract four subspectrum signals. The shape and bandwidth of the bandpass filter provided in each of the extraction filter units 44-4-1 to 44-4-4 may be any shape and bandwidth that can extract each of the four shifted subspectrum signals shown in FIG. 4(c), and the shape and bandwidth are determined in advance so that the bandwidths do not overlap with each other.

Each of the extraction filter units 44-8-1 to 44-8-8 has a bandpass filter with the same bandwidth shape but different center frequencies fs8-1 to fs8-8, and applies the bandpass filter to the spectrum division synthesis signal to extract eight subspectrum signals. The shape and bandwidth of the bandpass filter provided in each of the extraction filter units 44-8-1 to 44-8-8 may be any shape and bandwidth that can extract each of the eight shifted subspectrum signals shown in FIG. 5(c), and the shape and bandwidth are determined in advance so that the bandwidths do not overlap with each other.

Each of the frequency shift units 45-2-1, 45-2-2 applies the shift amount applied by each of the frequency shift units 25-2-1, 25-2-2 of the wireless transmission device 1 in the opposite direction to the subspectrum signals extracted by the extraction filter units 44-2-1, 44-2-2 connected to each of them, shifting them on the frequency axis. As a result, the positions of the center frequencies of the subspectrum signals extracted by each of the extraction filter units 44-2-1, 44-2-2 become f2-1, f2-2, respectively, and the two subspectrum signals shown in FIG. 3(b) are obtained.

Each of the frequency shift units 45-4-1 to 45-4-4 applies the shift amount applied by each of the frequency shift units 25-4-1 to 25-4-4 of the wireless transmission device 1 in the opposite direction to the subspectrum signals extracted by the extraction filter units 44-4-1 to 44-4-4 connected to it, shifting them on the frequency axis. As a result, the positions of the center frequencies of the subspectrum signals extracted by each of the extraction filter units 44-4-1 to 44-4-4 become f4-1 to f4-4, respectively, and the four subspectrum signals shown in FIG. 4(b) are obtained.

Each of the frequency shift units 45-8-1 to 45-8-8 applies the shift amount applied by each of the frequency shift units 25-8-1 to 25-8-8 of the wireless transmission device 1 in the opposite direction to the subspectrum signals extracted by the extraction filter units 44-8-1 to 44-8-8 connected to it, shifting them on the frequency axis. As a result, the positions of the center frequencies of the subspectrum signals extracted by each of the extraction filter units 44-8-1 to 44-8-4 become f8-1 to f8-8, respectively, and the eight subspectrum signals shown in FIG. 5(b) are obtained.

The amount of shift for each of the frequency shift units 45-2, 45-4, and 45-8 is predetermined to be the amount of shift in the opposite direction to the amount of shift for each of the frequency shift units 25-2, 25-4, and 25-8 when the amount of shift for each of the frequency shift units 25-2, 25-4, and 25-8 of the wireless transmission device 1 is predetermined.

The adder 46-2 adds, i.e., synthesizes, the subspectrum signals shifted by the frequency shifters 45-2-1 and 45-2-2 to generate a spectrum signal. The adder 46-4 synthesizes the subspectrum signals shifted by the frequency shifters 45-4-1 to 45-4-4 to generate a spectrum signal. The adder 46-8 synthesizes the subspectrum signals shifted by the frequency shifters 45-8-1 to 45-8-8 to generate a spectrum signal.

The inverse frequency conversion unit 47 converts the spectrum signals output by the addition units 46-2, 46-4, and 46-8 into the time domain to generate a modulated signal. The calculation applied to the conversion into the time domain is, for example, IFFT, but IDFT may also be applied.

The demodulation unit 34 applies a demodulation method corresponding to the modulation method applied by the modulation unit 11 of the wireless transmission device 1 to the modulated signal generated by the inverse frequency conversion unit 47 to demodulate the received data.

(Radio transmission device processing)
7 is a flowchart showing a flow of processing by the wireless transmission device 1. The modulation unit 11 takes in transmission data, modulates the taken-in transmission data with a predetermined modulation method to generate and output a modulated signal (step St1). The time window processing unit 20 takes in the modulated signal output by the modulation unit 11, and applies a time window function with a predetermined roll-off rate to the taken-in modulated signal to cut out and output a part of the modulated signal (step St2).

The frequency conversion unit 21 captures the modulated signal extracted by the time window processing unit 20, converts the captured modulated signal into the frequency domain to generate a spectrum signal, and outputs the generated spectrum signal (step St3). The branching processing unit 22 determines the number of divisions at the time output by the clock unit 23 based on information indicating the time output by the clock unit 23 and schedule information stored in an internal storage area. The branching processing unit 22 outputs the determined number of divisions to the optimal operating point detection unit 15 (step St4).

When the optimal operating point detection unit 15 receives the division number output by the branch processing unit 22, it reads out the PAPR value written in the "PAPR" item of the table in the storage unit 16 that corresponds to the received division number. The optimal operating point detection unit 15 outputs the read PAPR value to the transmission amplifier unit 13 (step St20).

The branching processing unit 22 takes in the spectrum signal output by the frequency conversion unit 21 and branches the taken-in spectrum signal according to the specified division number. If the specified division number is "2", the branching processing unit 22 branches the spectrum signal into two and outputs them to each of the division filter units 24-2-1 and 24-2-2. If the specified division number is "4", the branching processing unit 22 branches the spectrum signal into four and outputs them to each of the division filter units 24-4-1 to 24-4-4. If the specified division number is "8", the branching processing unit 22 branches the spectrum signal into eight and outputs them to each of the division filter units 24-8-1 to 24-8-8 (step St5).

Each of the splitting filter units 24-2, 24-4, and 24-8 filters the spectrum signal output by the branching processing unit 22 using its own bandpass filter, and outputs a subspectrum signal obtained by filtering (step St6). Note that for the splitting filter units 24-2, 24-4, and 24-8 to which no spectrum signal is provided from the branching processing unit 22, there is no spectrum signal to be filtered, and therefore no signal is output.

Each of the frequency shift units 25-2, 25-4, and 25-8 receives the subspectrum signal output by the division filter units 24-2, 24-4, and 24-8 connected thereto, and shifts the received subspectrum signal on the frequency axis based on a predetermined shift amount (step St7). Note that for the frequency shift units 25-2, 25-4, and 25-8 to which no subspectrum signal is provided from the division filter units 24-2, 24-4, and 24-8, there is no subspectrum signal to be shifted, and therefore no signal is output.

Each of the addition units 26-2, 26-4, and 26-8 generates a spectrum division synthesis signal by synthesizing the shifted subspectrum signals output by the frequency shift units 25-2, 25-4, and 25-8 connected to the addition units 26-2, 26-4, and 26-8, and outputs the generated spectrum division synthesis signal to the inverse frequency conversion unit 27 (step St8). Note that since one of the frequency shift units 25-2, 25-4, and 25-8 outputs a shifted subspectrum signal, one of the addition units 26-2, 26-4, and 26-8 generates a spectrum division synthesis signal and outputs it to the inverse frequency conversion unit 27.

The inverse frequency conversion unit 27 converts the spectrum division synthesis signal output by one of the addition units 26-2, 26-4, and 26-8 into the time domain to generate a spectrum division synthesis modulated signal (step St9).

The transmitting amplifier unit 13 captures the PAPR value output by the optimal operating point detection unit 15, adjusts the position of the operating point based on the captured PAPR value, and amplifies the spectrum division synthesis modulated signal output by the inverse frequency conversion unit 27 (step St10). The antenna 14 transmits the amplified spectrum division synthesis modulated signal by radiating it into the air as a radio signal (step St11). Since the transmitting amplifier unit 13 adjusts the position of the operating point based on the PAPR value output by the optimal operating point detection unit 15, it amplifies in the linear region even when the input power value peaks, and further amplifies the spectrum division synthesis modulated signal so that the output power value is the maximum for all input power values.

The process of step St20 by the optimal operating point detection unit 15 is executed in parallel with the processes of steps St5 to St9, and before the process of step St10 is executed, the transmission amplifier unit 13 completes the process of adjusting the position of the operating point based on the PAPR value received from the optimal operating point detection unit 15.

(Radio receiving device processing)
8 is a flowchart showing the flow of processing by the wireless receiving device 2. The antenna 31 receives a wireless signal transmitted by the wireless transmitting device 1 and outputs the received signal to the receiving amplifier section 32. The receiving amplifier section 32 amplifies and outputs the received signal (step Sr1).

The time window processing unit 40 captures the amplified received signal output by the receiving amplifier unit 32, and applies a time window function with a predetermined roll-off rate to the captured amplified received signal to extract and output a portion of the amplified received signal (step Sr2).

The frequency conversion unit 41 takes in the amplified received signal extracted by the time window processing unit 40, converts the taken in amplified received signal into the frequency domain to generate a spectrum division synthesis signal, and outputs the generated spectrum division synthesis signal (step Sr3). The branching processing unit 42 identifies the number of divisions at the time output by the timer unit 43 based on information indicating the time output by the timer unit 43 and schedule information stored in an internal memory area (step Sr4).

The branching processing unit 42 takes in the spectrum division synthesis signal output by the frequency conversion unit 41 and branches the taken in spectrum division synthesis signal according to the specified division number. If the specified division number is "2", the branching processing unit 42 branches the spectrum division synthesis signal into two and outputs them to each of the extraction filter units 44-2-1 and 44-2-2. If the specified division number is "4", the branching processing unit 42 branches the spectrum division synthesis signal into four and outputs them to each of the extraction filter units 44-4-1 to 44-4-4. If the specified division number is "8", the branching processing unit 42 branches the spectrum signal into eight and outputs them to each of the extraction filter units 44-8-1 to 44-8-8 (step Sr5).

Each of the extraction filter units 44-2, 44-4, and 44-8 filters the spectrum division synthesis signal output by the branching processing unit 42 using its own bandpass filter, and outputs a subspectrum signal obtained by filtering (step Sr6). Note that for the extraction filter units 44-2, 44-4, and 44-8 to which no spectrum signal is provided from the branching processing unit 42, there is no spectrum division synthesis signal to be filtered, and therefore no signal is output.

Each of the frequency shift units 45-2, 45-4, and 45-8 takes in the subspectrum signal output by the extraction filter units 44-2, 44-4, and 44-8 connected thereto, and shifts the taken-in subspectrum signal on the frequency axis based on a predetermined shift amount (step Sr7). Note that for frequency shift units 45-2, 45-4, and 45-8 to which no subspectrum signal is provided from the extraction filter units 44-2, 44-4, and 44-8, there is no subspectrum signal to be shifted, and therefore no signal is output.

Each of the addition units 46-2, 46-4, and 46-8 generates a spectrum signal by synthesizing the shifted subspectrum signals output by the frequency shift units 45-2, 45-4, and 45-8 connected to it, and outputs the generated spectrum signal to the inverse frequency conversion unit 47 (step Sr8). Note that since one of the frequency shift units 45-2, 45-4, and 45-8 outputs a shifted subspectrum signal, one of the addition units 46-2, 46-4, and 46-8 outputs a spectrum signal to the inverse frequency conversion unit 47.

The inverse frequency conversion unit 47 converts the spectrum signal output by one of the addition units 46-2, 46-4, and 46-8 into the time domain to generate a modulated signal, and outputs the generated modulated signal (step Sr9). The demodulation unit 34 takes in the modulated signal output by the inverse frequency conversion unit 47 and demodulates the taken-in modulated signal. The demodulation unit 34 outputs the received data obtained by demodulation (step Sr10).

(Effects of the configuration of this embodiment)
Next, the effects of this embodiment will be described with reference to FIGS.
The horizontal axis of the graph in Fig. 9 is time, and the vertical axis is the input power value of the transmission amplifier unit 13. The vertical axis indicates a linear region where amplification is possible linearly according to the amplification characteristics of the transmission amplifier unit 13, and a nonlinear region where amplification is nonlinear. The graph in Fig. 9 shows the results when the schedule information stored in the internal storage area of the branching processing unit 22 defines information such that times t0 to t1 are divided into 2, times t1 to t2 are divided into 4, times t2 to t3 are divided into 8, times t3 to t4 are divided into 2, and times t4 to t5 are divided into 8.

In FIG. 9, the dashed line graph shows the peak input power value when the operating point of the transmission amplifier unit 13 is fixed so as to be the optimal operating point for the division number of 2 without using the optimal operating point detection unit 15 in the wireless transmission device 1. In FIG. 9, since the operating point of the transmission amplifier unit 13 is fixed so as to be the optimal operating point for the division number of 2, when the input power value peaks in the case of division number of 2, the operating point is located at the boundary between the linear region and the nonlinear region. Since the PAPR increases as the division number increases, when the input power value peaks in the cases of division number of 4 and division number of 8, the operating point exists in the nonlinear region. In addition, in FIG. 9, the solid line graph shows the average power value of the input power value. Since the operating point of the transmission amplifier unit 13 is fixed so as to be the optimal operating point for the division number of 2, the average power value of the input power value is the same value as in the case of division number of 2 even in the cases of division number of 4 and division number of 8.

Figure 10 is a graph showing the amplification characteristics indicating the relationship between the input power value of the transmission amplifier unit 13 and the output power value after amplification. When the operating point of the transmission amplifier unit 13 is fixed so as to be the optimal operating point when the number of divisions is 2, the operating point when divided into two in the graph of Figure 10 will be located at the boundary position between the linear region and the nonlinear region indicated by the reference symbol 60. The position indicated by the reference symbol 61 indicates the position of the operating point when divided into four, and the position indicated by the reference symbol 62 indicates the position of the operating point when divided into eight. The positions indicated by the reference symbols 61 and 62 are both located in the nonlinear region.

In the wireless transmission device 1 of this embodiment, the optimal operating point detection unit 15 reads out the PAPR value corresponding to each division number from the table in the storage unit 16 and applies it to the transmission amplifier unit 13. When the PAPR value is applied, the transmission amplifier unit 13 automatically determines the optimal operating point according to the PAPR value, so that in the case of a division number of 4, the input power value is reduced based on the PAPR value as shown by reference number 71, and in the case of a division number of 8, the input power value is reduced based on the PAPR value as shown by reference number 72. Therefore, in the cases of division number 4 and division number 8, it is possible to change the operating point to the position shown by reference number 60 in FIG. 10. When this is shown in FIG. 9, the input power value at the peak is changed to the position of the graph shown by the dotted line, making it possible to amplify in the linear region.

The horizontal axis of the graph in FIG. 11 is time, and the vertical axis is the output power value of the transmission amplifier unit 13. As in FIG. 9, the vertical axis indicates a linear region where amplification is possible linearly according to the amplification characteristics of the transmission amplifier unit 13, and a nonlinear region where amplification is nonlinear. As in the graph in FIG. 9, the graph in FIG. 11 shows the results when the schedule information stored in the internal storage area of the branching processing unit 22 defines information such that times t0 to t1 are divided into 2, times t1 to t2 into 4, times t2 to t3 into 8, times t3 to t4 into 2, and times t4 to t5 into 8.

In FIG. 11, the dashed line graph shows the peak output power value when the operating point of the transmission amplifier unit 13 is fixed so as to be the optimal operating point when the number of divisions is 8, without using the optimal operating point detection unit 15 in the wireless transmission device 1. Since the operating point of the transmission amplifier unit 13 is fixed so as to be the optimal operating point when the number of divisions is 8, in all cases of the number of divisions 2, 4, and 8, the operating point is located at the boundary between the linear region and the nonlinear region when the output power value peaks. Also, in FIG. 11, the solid line graph is a graph showing the average power value of the output power value. Since the operating point of the transmission amplifier unit 13 is fixed so as to be the optimal operating point when the number of divisions is 8, in the cases of the number of divisions 2 and 4, the average power value of the output power value is the same as in the case of the number of divisions 8 due to the decrease in PAPR caused by the decrease in the number of divisions. In FIG. 11, the dashed line graph shows the average power value of the output power value when the operating point of the transmission amplifier unit 13 is fixed so as to be the optimal operating point in each of the cases of the number of divisions 2 and 4. In other words, if the operating point of the transmission amplifier unit 13 is fixed so that it is the optimal operating point when the division number is 8, the average power value of the output power value will decrease when the division number is 2 and when the division number is 4, as shown by the dashed arrow.

As in FIG. 10, FIG. 12 is a graph showing the amplification characteristics showing the relationship between the input power value of the transmission amplifier unit 13 and the output power value after amplification. When the operating point of the transmission amplifier unit 13 is fixed so as to be the optimal operating point when the division number is 8, the operating point at peak power when the division number is 8 in the graph of FIG. 12 will be at the boundary position indicated by the reference numeral 60 between the linear region and the nonlinear region. In this case, the operating point at average power when the division number is 8 will be the position indicated by the reference numeral 65. The position indicated by the reference numeral 63 indicates the position of the operating point at average power when the operating point of the transmission amplifier unit 13 is fixed so as to be the optimal operating point when the division number is 2, and the position indicated by the reference numeral 64 indicates the position of the operating point at average power when the operating point of the transmission amplifier unit 13 is fixed so as to be the optimal operating point when the division number is 4. If the operating point of the transmission amplifier unit 13 is fixed so that it is the optimal operating point when the division number is 8, as explained with reference to FIG. 11, the average power value of the output power value will be at the position indicated by the symbol 65 even when the division number is 2 and 4, resulting in a decrease from the output power value that would normally be obtained.

In the wireless transmission device 1 of this embodiment, the optimal operating point detection unit 15 reads out the PAPR value corresponding to each division number from the table in the storage unit 16 and applies it to the transmission amplifier unit 13. When the PAPR value is applied, the transmission amplifier unit 13 automatically determines the optimal operating point according to the PAPR value, so that in the case of division number 4, the input power value increases based on the PAPR value as shown by reference symbol 73, and in the case of division number 8, the input power value increases based on the PAPR value as shown by reference symbol 74. Therefore, in the cases of division number 4 and division number 8, it is possible to change the operating point at the time of average power to the position shown by reference symbol 63. As a result, it is possible to increase the output power value in the cases of division number 4 and division number 8 by the amount shown by reference symbols 83 and 84, respectively. As shown in FIG. 11, in all cases of division number 2, division number 4, and division number 8, it is possible to set the average power value of the output power value when the operating point of the transmission amplifier unit 13 is fixed so as to be the optimal operating point in the case of division number 2 shown by the dotted line, and accordingly it is possible to increase the power of the wireless signal.

(Another configuration example of this embodiment)
Fig. 13 is a block diagram showing the configuration of a wireless transmission device 1a according to another configuration example of this embodiment. In the wireless transmission device 1a in Fig. 13, the same components as those in the wireless transmission device 1 in Fig. 1 are denoted by the same reference numerals, and different components will be described below.

The wireless transmission device 1a includes a modulation unit 11, a transmission filter bank unit 12a, a transmission amplifier unit 13, an antenna 14, an optimal operating point detection unit 15, and a memory unit 16.

The transmission filter bank section 12 of the wireless transmission device 1 shown in Figure 1 includes a 2-division division filter section 24-2 and a frequency shift section 25-2, a 4-division division filter section 24-4 and a frequency shift section 25-4, and an 8-division division filter section 24-8 and a frequency shift section 25-8. In contrast, the wireless transmission device 1a shown in Figure 13 includes a configuration in which the upper limit of the number of divisions is 8, and the number of divisions can be flexibly changed.

In FIG. 13, the transmission filter bank unit 12a includes a time window processing unit 20, a frequency conversion unit 21, a branching processing unit 22a, a timing unit 23, division filter units 24a-1 to 24a-8, frequency shift units 25a-1 to 25a-8, an adder unit 26, and an inverse frequency conversion unit 27.

Each of the split filter units 24a-1 to 24a-8 can arbitrarily change the center frequency, bandwidth, and shape of the bandpass filter. Each of the split filter units 24a-1 to 24a-8 forms a bandpass filter having a center frequency, bandwidth, and shape specified by the split processing unit 22a, and applies the formed bandpass filter to the spectrum signal output by the split processing unit 22a to generate a subspectrum signal.

Each of the frequency shift units 25a-1 to 25a-8 is capable of changing the amount of shift when shifting a signal on the frequency axis. Each of the frequency shift units 25a-1 to 25a-8 shifts the subspectrum signals output by the splitting filter units 24a-1 to 24a-8 connected to each of them on the frequency axis according to the amount of shift specified by the branching processing unit 22a.

The adder 26 adds, i.e., synthesizes, the shifted subspectrum signals output by the frequency shifters 25a-1 to 25a-8 to generate a spectrum division synthesis signal, and outputs the generated spectrum division synthesis signal to the inverse frequency converter 27.

Similar to the branching processing unit 22, the branching processing unit 22a pre-stores in an internal memory area schedule information indicating how many subspectrum signals the spectrum signal is to be divided into for each time.

The branch processing unit 22a determines the number of divisions at the time output by the clock unit 23 based on the information indicating the time output by the clock unit 23 and the schedule information. The branch processing unit 22a outputs the determined number of divisions to the optimal operating point detection unit 15.

The branching processing unit 22a also stores in advance in an internal storage area the following information for each division number: information specifying the combination of the division filter units 24a-1 to 24a-8 and the frequency shift units 25a-1 to 25a-8 to be used; information indicating the center frequency, bandwidth, and shape of the bandpass filter to be applied to each of the division filter units 24a-1 to 24a-8 to be used; and the shift amount to be applied to each of the frequency shift units 25a-1 to 25a-8 to be used.

The branching processing unit 22a is connected to each of the division filter units 24a-1 to 24a-8 and each of the frequency shift units 25a-1 to 25a-8 via a control line indicated by a dashed connection line. When the branching processing unit 22a specifies the number of divisions, it outputs information indicating the center frequency, bandwidth, and shape of the bandpass filter corresponding to the specified number of divisions to each of the division filter units 24a-1 to 24a-8 to be used. In addition, the branching processing unit 22a outputs the shift amount corresponding to the specified number of divisions to each of the frequency shift units 25a-1 to 25a-8 to be used.

For example, when the number of divisions is "2", the branching processing unit 22a stores the following information in an internal storage area. As combinations to be used, the division filter units 24a-1 and 24a-2 and the frequency shift units 25a-1 and 25a-2 are stored, and as information on the bandpass filters to be applied to each of the division filter units 24a-1 and 24a-2, information indicating the center frequency, bandwidth, and shape of each of the bandpass filters of the division filter units 24-2-1 and 24-2-2 of the wireless transmission device 1 is stored. In addition, as the shift amount to be applied to each of the frequency shift units 25a-1 and 25a-2, the shift amount of each of the frequency shift units 25-2-1 and 25-2-2 of the wireless transmission device 1 is stored.

When the number of divisions is "4", the branching processing unit 22a stores the following information in an internal storage area. As combinations to be used, the division filter units 24a-1 to 24a-4 and the frequency shift units 25a-1 to 25a-4 are stored, and as information on the bandpass filters to be applied to each of the division filter units 24a-1 to 24a-4, information indicating the center frequency, bandwidth, and shape of each of the bandpass filters of the division filter units 24-4-1 to 24-4-4 of the wireless transmission device 1 is stored. In addition, as the shift amount to be applied to each of the frequency shift units 25a-1 to 25a-4, the shift amount of each of the frequency shift units 25-4-1 to 25-4-4 of the wireless transmission device 1 is stored.

When the number of divisions is "8", the branching processing unit 22a stores the following information in an internal storage area. As combinations to be used, the division filter units 24a-1 to 24a-8 and the frequency shift units 25a-1 to 25a-8 are stored, and as information on the bandpass filters to be applied to each of the division filter units 24a-1 to 24a-8, information indicating the center frequency, bandwidth, and shape of each of the bandpass filters of the division filter units 24-8-1 to 24-8-8 of the wireless transmission device 1 is stored. In addition, as the shift amount to be applied to each of the frequency shift units 25a-1 to 25a-8, the shift amount of each of the frequency shift units 25-8-1 to 25-8-8 of the wireless transmission device 1 is stored.

In the process by the wireless transmission device 1a, in the flowchart shown in FIG. 7, the branch processing unit 22a performs the process of identifying the number of divisions in step St4, and the following processes are performed in steps St5, St6, and St7.

When the specified division number is "2", the branching processing unit 22a reads from an internal storage area information indicating the center frequency, bandwidth, and shape of the bandpass filter corresponding to each of the division filter units 24a-1, 24a-2 associated with the division number "2", and the shift amount corresponding to the frequency filter units 25a-1, 25a-2. The branching processing unit 22a outputs the read information indicating the center frequency, bandwidth, and shape of the bandpass filter to each of the division filter units 24a-1, 24a-2, and outputs the read shift amount to each of the frequency filter units 25a-1, 25a-2.

The branching processing unit 22a branches the spectrum signal into two and outputs them to the division filter units 24a-1 and 24a-2. The division filter units 24a-1 and 24a-2 and the frequency shift units 25a-1 and 25a-2 generate two subspectrum signals through the processing steps shown in FIG. 3.

When the specified division number is "4", the branching processing unit 22a reads from an internal storage area information indicating the center frequency, bandwidth, and shape of the bandpass filter corresponding to each of the division filter units 24a-1 to 24a-4 associated with the division number "4", and the shift amount corresponding to the frequency filter units 25a-1 to 25a-4. The branching processing unit 22a outputs the read information indicating the center frequency, bandwidth, and shape of the bandpass filter to each of the division filter units 24a-1 to 24a-4, and outputs the read shift amount to each of the frequency filter units 25a-1 to 25a-4.

The branching processing unit 22a branches the spectrum signal into four and outputs them to the division filter units 24a-1 to 24a-4. The division filter units 24a-1 to 24a-4 and the frequency shift units 25a-1 to 25a-4 generate four subspectrum signals through the processing steps shown in FIG. 4.

When the specified division number is "8", the branching processing unit 22a reads from an internal storage area information indicating the center frequency, bandwidth, and shape of the bandpass filter corresponding to each of the division filter units 24a-1 to 24a-8 associated with the division number "8", and the shift amount corresponding to the frequency filter units 25a-1 to 25a-8. The branching processing unit 22a outputs the read information indicating the center frequency, bandwidth, and shape of the bandpass filter to each of the division filter units 24a-1 to 24a-8, and outputs the read shift amount to each of the frequency filter units 25a-1 to 25a-8.

The branching processing unit 22a branches the spectrum signal into eight signals and outputs them to the division filter units 24a-1 to 24a-8. The division filter units 24a-1 to 24a-8 and the frequency shift units 25a-1 to 25a-8 generate eight subspectrum signals through the processing steps shown in FIG. 5.

In step St8, the adder 26 combines the shifted subspectrum signals output by the frequency shifters 25a-1 to 25a-8 to generate a spectrum division synthesis signal, and outputs the generated spectrum division synthesis signal to the inverse frequency converter 27. For the other steps St1 to St3, St9 to St11, and St20, the same processing as in the case of the wireless transmission device 1 is performed.

For example, if the number of divisions is "2," "4," and "8," the wireless transmission device 1 shown in FIG. 1 requires 14 division filter units 24-2, 24-4, and 24-8 and 14 frequency shift units 25-2, 25-4, and 25-8. In contrast, the wireless transmission device 1a shown in FIG. 13 only requires eight division filter units 24a-1 to 24a-8 and eight frequency shift units 25a-1 to 25a-8.

As described above, the wireless transmission device 1a allows the number of divisions to be changed more flexibly, making it possible to reduce the number of parts compared to the wireless transmission device 1. However, when increasing the number of division options, it is necessary to increase the number of records for each number of divisions stored in the table of the storage unit 16, and the wireless reception device 2 must be configured to include an extraction filter unit that can change the bandpass filter and a frequency shift unit that can change the shift amount, like the wireless transmission device 1a.

In addition, the shapes of the bandpass filters provided in the split filter units 24-2, 24-4, and 24-8 of the wireless transmission device 1 and the split filter units 24a-1 to 24a-8 of the wireless transmission device 1a are shown as curved shapes as shown in Figures 3 to 5, but they may also be rectangular shapes specified by a center frequency and a bandwidth. In this case, the branching processing unit 22a of the wireless transmission device 1a simply stores information indicating the center frequency and bandwidth of the bandpass filters in an internal memory area.

In the above embodiment and other configuration examples of the wireless transmission device 1, 1a, the transmission filter bank unit 12, 12a converts the modulated signal obtained by modulating the transmission data into the frequency domain to generate a spectrum signal, filters the generated spectrum signal with a number of bandpass filters corresponding to a predetermined division number, in which the bands of adjacent bandpass filters on the frequency axis partially overlap, generates a predetermined number of subspectrum signals by distributing the subspectrum signals on the frequency axis so that the bands of the generated subspectrum signals do not overlap, and generates a spectrum division synthesis modulated signal by synthesizing the distributed subspectrum signals and converting them into the time domain. The transmission amplifier unit 13 amplifies the spectrum division synthesis modulated signal. The optimal operating point detection unit 15 operates the transmission amplifier unit 13 at the position of the effective operating point of the transmission amplifier unit 13 obtained based on the peak-to-average power ratio of the spectrum division synthesis modulated signal for each predetermined division number and the amplification characteristics of the transmission amplifier unit 13. As a result, by determining in advance the peak-to-average power ratio of the spectrum division synthesis modulated signal corresponding to the division number by measuring in advance, even if the predetermined division number is changed at any timing, the operating point of the transmission amplifier unit 13 can be adjusted to an appropriate position with the optimal input back-off for the division number at that time based on the relationship between the division number and the peak-to-average power ratio of the spectrum division synthesis modulated signal. Therefore, in the wireless transmission device 1, 1a that divides the spectrum signal and distributes it on the frequency axis before transmitting the wireless signal, even if the division number changes, the wireless signal can be transmitted without degrading the communication quality.

Note that the transmit filter bank units 12, 12a and the receive filter bank unit 33 in the above-described embodiment and other configuration examples may be realized by electronic circuits such as ICs (Integrated Circuits).

In addition, in the above-described embodiment and other configuration examples, the branching processing unit 22, 22a varies the number of divisions over time according to the schedule information, but the user of the wireless transmission device 1, 1a may change the number of divisions at any timing.

The wireless transmitting device 1, 1a and the wireless receiving device 2 in the above-mentioned embodiment may be realized by a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed to realize the function. Note that the term "computer system" here includes hardware such as an OS and peripheral devices. Furthermore, the term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into a computer system. Furthermore, the term "computer-readable recording medium" may include a medium that dynamically holds a program for a short period of time, such as a communication line when a program is transmitted via a network such as the Internet or a communication line such as a telephone line, and a medium that holds a program for a certain period of time, such as a volatile memory inside a computer system that is a server or client in such a case. Furthermore, the above-mentioned program may be a program for realizing a part of the above-mentioned function, or may be a program that can realize the above-mentioned function in combination with a program already recorded in the computer system, or may be a program that is realized using a programmable logic device such as an FPGA (Field Programmable Gate Array).

The above describes an embodiment of the present invention in detail with reference to the drawings, but the specific configuration is not limited to this embodiment and includes designs that do not deviate from the gist of the present invention.

1...radio transmitter, 11...modulation section, 12...transmission filter bank transmission section, 13...transmission amplifier section, 14...antenna, 15...optimum operating point detection section, 16...storage section, 20...time window processing section, 21...frequency conversion section, 22...branching processing section, 23...time counter section, 24-2-1, 24-2-2, 24-4-1 to 24-4-4, 24-8-1 to 24-8-8...division filter section, 25-2-1, 25-2-2, 25-4-1 to 25-4-4, 25-8-1 to 25-8-8...frequency shift section, 26-2, 26-4, 26-8...addition section, 27...inverse frequency conversion section

Claims (5)

a transmission filter bank section which generates a spectrum signal by converting a modulated signal obtained by modulating transmission data into a frequency domain, and filters the spectrum signal using a number of bandpass filters corresponding to a predetermined division number, the bandpass filters having bands partially overlapping with each other, to generate a plurality of subspectrum signals, distributes and allocates each of the subspectrum signals on a frequency axis so that the bands of the subspectrum signals do not overlap, and generates a spectrum division synthesis modulated signal by synthesizing and converting the distributed subspectrum signals into a time domain;
A transmission amplifier unit that amplifies the spectrum division synthesis modulated signal;
an antenna that transmits the spectrum division synthesis modulated signal amplified by the transmission amplifier unit as a radio signal;
an optimal operating point detection unit that operates the transmission amplifier unit at an effective operating point of the transmission amplifier unit obtained based on the peak-to-average power ratio of the spectrum division synthesis modulated signal for each of the predetermined division numbers and the amplification characteristic of the transmission amplifier unit;
Equipped with
the optimal operating point detection unit refers to a table in which the number of divisions corresponds to the value of the peak-to-average power ratio, obtains the value of the peak-to-average power ratio corresponding to the predetermined number of divisions, and operates the transmission amplifier unit at an effective operating point of the transmission amplifier unit based on the obtained value of the peak-to-average power ratio . The position of the effective operating point of the transmission amplifier unit is a position where the transmission amplifier unit performs amplification in a linear region.
2. The wireless transmission device according to claim 1. The position of the effective operating point of the transmission amplifier unit is a position where a maximum output power value is obtained with respect to an input power value of the transmission amplifier unit.
3. The wireless transmission device according to claim 2. The predetermined number of divisions changes over time or at any timing.
The wireless transmission device according to claim 1 . a spectrum signal generated by converting a modulated signal obtained by modulating transmission data into a frequency domain is filtered by a plurality of bandpass filters, the number of which corresponds to a predetermined division number, the bandpass filters having bands which partially overlap with each other to generate a plurality of subspectrum signals, the subspectrum signals are distributed on a frequency axis so that the bands of the subspectrum signals do not overlap with each other, and the distributed subspectrum signals are synthesized and converted into a time domain to generate a spectrum division synthesis modulated signal;
Refer to a table in which the number of divisions corresponds to a value of the peak -to-average power ratio, and obtain a value of the peak-to-average power ratio corresponding to the predetermined number of divisions among the peak-to-average power ratios of the spectrum division combined modulated signal for each predetermined number of divisions ;
operating the transmission amplifier unit at an effective operating point of the transmission amplifier unit obtained based on the acquired value of the peak-to-average power ratio and an amplification characteristic of the transmission amplifier unit ;
amplifying the spectrum division synthesis modulated signal;
The spectrum division synthesis modulated signal amplified by the transmission amplifier unit is transmitted as a radio signal.
Wireless transmission method.

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