JP6461881B2 - Receiver - Google Patents

Description

  The present invention relates to a digital communication system used for wireless communication or wired communication, which can receive a frequency multiplexed signal transmitted using a plurality of carriers distributed on the frequency axis and process the received signal with a demodulator. The present invention relates to a receiving apparatus that performs frequency conversion to a frequency band such as a band and performs power adjustment.

  In a receiving apparatus of a digital communication system, a received signal is frequency converted into a frequency band such as a baseband that can be processed by a demodulator using a frequency converting apparatus, and a carrier to be demodulated is extracted by a filter and demodulated.

  When signals of various frequency bands such as unlicensed bands and license bands are densely arranged, base stations such as optical fiber radio (ROF), satellite communications, and terrestrial radio relay networks that transmit these signals through optical fibers When the receiver receives not only the carrier to be received but also the return signal of the transmission carrier, in the wavelength division multiplexing transmission (WDM) in the optical fiber, the received signal of the receiving apparatus includes a large number of carriers other than the demodulation target. Therefore, only the signal in the frequency band to be demodulated is extracted by a filter and demodulated.

The frequency band used in the digital communication system may be scattered depending on the condition of the transmission path. For example, the following situations occur in the frequency band used in wireless communication.
(1) In the license band, when acquiring a radio station license, there is no continuous unallocated band for the total bandwidth to be allocated.
(2) When operating with multiple frequency bands assigned in the license band, but high-speed communication is required, and multiple bands are used together.

(3) When borrowing the bandwidth of a wireless repeater owned by another operator, there is no continuous unused bandwidth for the required bandwidth.
(4) When an unlicensed band is used by selecting a vacant band because of the dense frequency environment.

  As described above, a plurality of carriers may be arranged in a plurality of different frequency bands and transmitted / received at the same time, or may be selected and received from a plurality of carriers as necessary.

  FIG. 5 shows a configuration example of a conventional receiving apparatus that performs multicarrier transmission (Non-Patent Document 1). In FIG. 5, the receiving apparatus includes a frequency conversion unit 100 and a demodulation unit 200. The frequency conversion unit 100 and the demodulation unit 200 correspond to the IF-CONV (IF converter) and modem module in Non-Patent Document 1.

  The demodulator 200 includes a band pass filter (BPF) 21, an attenuator 22, an amplifier 23, an automatic gain control circuit (AGC) 24 that automatically controls a predetermined output power according to the reception level for each carrier, and a demodulator 25. Is done. The demodulator 25 has a configuration having a plurality of demodulators to demodulate a plurality of carriers, or operates the demodulator at a speed higher than the symbol rate, and demodulates the plurality of carriers using one demodulator in time division. Any of the configurations may be used. The configuration of FIG. 5 assumes a configuration used in time division.

  The frequency converter 100 includes a bandpass filter (BPF) 11 that performs band limitation of the received signal, an attenuator 12, an amplifier 13, and a demodulator so that the input power of the demodulator 25 falls within the input power range defined by the demodulator 25. When the input frequency band and the reception frequency band (RF) of the device 25 are different, a frequency conversion circuit 14 that converts the frequency of the received signal is provided.

  The frequency conversion circuit 14 uses a local oscillator and a multiplier and has a configuration that can flexibly cope with the change of the oscillation frequency of the local oscillator used for frequency conversion even when the transmission band to be used is changed. The configuration of the frequency conversion circuit 14 is an example, and a configuration in which a plurality of frequency conversion circuits 14 are provided to convert from RF to a desired frequency band via an intermediate frequency (IF) is common.

Yamashita, Abe, Kobayashi, “Development and performance evaluation of VPFDM modem module for polarization-free tracking satellite communication”, IEICE Technical Report SAT, Satellite Communication 108 (149), 7-12, 2008-07-17

  As shown in FIG. 5 (2), when carriers to be demodulated are scattered at a plurality of locations, carriers existing in the adjacent band of the carrier to be demodulated are also included in the pass band of the BPF 11, so The received power is also input to the demodulator 200. In particular, when frequencies are used densely, the power in the adjacent band increases, so the input power to the demodulator 200 increases, the amplifier of the demodulator 200 saturates, and transmission characteristics may deteriorate.

  Further, when the transmitters of the respective carriers are different, or when the transmission path has frequency characteristics, the reception level differs for each carrier as shown in FIG. 5 (2). The AGC 24 that automatically adjusts the power for each carrier in the demodulator 200 is provided. However, when the carrier within the adjustment range of the AGC 24 and the carrier outside the adjustment range coexist, the output power is adjusted by the frequency converter 100. However, when a carrier that exceeds the upper limit of the adjustment range of the AGC 24 and a carrier that is lower than the lower limit of the adjustment range coexist, adjustment cannot be performed, and reception characteristics deteriorate.

  An object of the present invention is to provide a receiving apparatus capable of flexibly adjusting the power of a plurality of carriers to be demodulated as a whole or for each carrier in consideration of the AGC adjustment range.

  A first invention includes a frequency conversion unit including a frequency conversion circuit that receives frequency-multiplexed signals of a plurality of carriers distributed on the frequency axis and converts the frequency-multiplexed signals into a frequency band processed by a demodulator, In a receiving apparatus comprising a demodulation unit including an automatic gain control circuit that adjusts power according to the reception level of each carrier of the frequency-multiplexed frequency-converted signal and inputs it to the demodulator, the frequency conversion unit receives the frequency-multiplexed signal An overall power adjustment circuit that adjusts the power collectively is provided, and the reception level value of each carrier detected by the automatic gain control circuit exceeds the upper limit of the adjustment range of the automatic gain control circuit, or within the adjustment range or the lower limit of the adjustment range. Control means is provided for outputting a first control signal for collectively controlling the power of the frequency-multiplexed signal to the overall power adjustment circuit in accordance with a determination result indicating that the frequency is below.

  A second invention includes a frequency conversion unit including a frequency conversion circuit that receives frequency-multiplexed signals of a plurality of carriers dispersedly arranged on the frequency axis and converts the frequency-multiplexed signals into a frequency band processed by a demodulator, In a receiving apparatus comprising a demodulation unit including an automatic gain control circuit that adjusts power according to the reception level of each carrier of the frequency-multiplexed frequency-converted signal and inputs it to the demodulator, the frequency conversion unit receives the frequency-multiplexed signal Carrier power adjustment means for individually adjusting the power of each carrier is provided, and the reception level value of each carrier detected by the automatic gain control circuit exceeds the upper limit of the adjustment range of the automatic gain control circuit, or within the adjustment range or within the adjustment range. Control means for outputting a second control signal for individually controlling the power of each carrier to the carrier power adjusting means according to the determination result indicating that the value is below the lower limit. Provided.

  A third invention includes a frequency conversion unit including a frequency conversion circuit that receives frequency multiplexed signals of a plurality of carriers distributed on the frequency axis and converts the frequency multiplexed signals into a frequency band processed by a demodulator; In a receiving apparatus comprising a demodulation unit including an automatic gain control circuit that adjusts power according to the reception level of each carrier of the frequency-multiplexed frequency-converted signal and inputs it to the demodulator, the frequency conversion unit receives the frequency-multiplexed signal An overall power adjustment circuit that collectively adjusts power and carrier power adjustment means that individually adjusts the power of each carrier of the frequency multiplexed signal, and the reception level value of each carrier detected by the automatic gain control circuit is automatically Depending on the determination result indicating that the upper limit of the adjustment range of the gain control circuit is exceeded, or that it is within the adjustment range or less than the lower limit of the adjustment range, the frequency adjustment Outputs a first control signal for controlling the power of signals collectively comprises control means for outputting a second control signal for individually controlling the power of each carrier with respect to the carrier power adjusting means.

  In the receiving apparatus of the first or third invention, the control means performs control to collectively increase the power of the frequency multiplexed signal from the specified value when at least one reception level value of each carrier is below the lower limit of the adjustment range. The first control signal to be performed is output. The control means also includes a carrier in which at least one reception level value of each carrier exceeds the upper limit of the adjustment range, or a carrier whose reception level value of each carrier is lower than the lower limit of the adjustment range and a carrier that exceeds the upper limit of the adjustment range. In this case, a first control signal is output for performing control to reduce the power of the frequency multiplexed signal from the specified value all at once.

  In the receiving apparatus of the second or third invention, the control means performs control to increase the power of the carrier below the lower limit of the adjustment range from the specified value among the reception level values of each carrier, and sets the carrier power exceeding the upper limit of the adjustment range. A second control signal for performing control to reduce the electric power from the specified value is output.

  In the receiving apparatus of the second or third invention, the carrier power adjusting means selects a carrier to be demodulated in the demodulator using a filter from the frequency multiplexed signal, performs power adjustment for each of the selected carriers, and adds them. It is a configuration.

  In the receiving apparatus of the second or third invention, the carrier power adjusting means performs Fourier transform on the frequency-multiplexed signal, and uses the filter coefficient corresponding to the second control signal to select the carrier to be demodulated and the power. In this configuration, adjustment is performed, addition is performed, and inverse Fourier transform is performed for output.

  According to the present invention, power can be adjusted flexibly for the whole of a plurality of carriers to be demodulated or for each extracted carrier, so that reception characteristics can be improved.

It is a figure which shows the structural example of the receiver of Example 1 of this invention. It is a figure which shows the pass band of a carrier filter. It is a figure which shows the structural example of the receiver of Example 2 of this invention. It is a figure which shows the frequency shift example of the carrier in an extraction filter. It is a figure which shows the structural example of the conventional receiver.

Example 1
FIG. 1 shows a configuration example of a receiving apparatus according to the first embodiment of the present invention.
In FIG. 1, the receiving apparatus includes a frequency conversion unit 10 and a demodulation unit 20. The frequency converting unit 10 selects a carrier wave to be demodulated by selecting a band-pass filter (BPF) 11, an overall power adjusting circuit 15 including a variable attenuator and an amplifier, a frequency converting circuit 14 including a local oscillator and a multiplier, and a carrier to be demodulated. Carrier power adjustment circuits 16-1 to 16-n, carrier filters 17-1 to 17-n, a signal passing circuit 18, and a selective addition circuit 19 that selectively adds and outputs the carriers to be demodulated.

  Note that the carrier power adjustment circuits 16-1 to 16-n and the carrier filters 17-1 to 17-n are configured to extract and adjust power for each carrier to be demodulated as shown in FIG. As shown in 2 (2), there is a configuration in which a plurality of carriers to be demodulated are collectively extracted and the power is adjusted. A circuit configuration may be employed in which carrier power adjustment circuits 16-1 to 16-n are arranged downstream of the carrier filters 17-1 to 17-n.

  The demodulator 20 corresponds to the reception level value of each carrier to be demodulated detected by the band pass filter (BPF) 21, the attenuator 22, the amplifier 23, the automatic gain control circuit (AGC) 24, the demodulator 25, and the AGC 24. The control signal generation circuit 26 generates a control signal. The control signal generated by the control signal generation circuit 26 is fed back to the overall power adjustment circuit 15 of the frequency conversion unit 10 and further fed back to the carrier power adjustment circuits 16-1 to 16-n to adjust the AGC 24 in the demodulation unit 20. Power adjustment is performed for carriers that are above the upper limit of the range or carriers that are below the lower limit of the adjustment range. The demodulator 25 has a configuration having a plurality of demodulators to demodulate a plurality of carriers, or operates the demodulator at a speed higher than the symbol rate, and demodulates the plurality of carriers using one demodulator in time division. Any of the configurations may be used. The configuration in FIG. 1 assumes a configuration used in time division.

  The AGC 24 determines whether or not the reception level value is within the adjustment range for each carrier. For example, if the reception level value is below the lower limit of the adjustment range (1, 0), and within the adjustment range (0, 0). If the upper limit of the adjustment range is exceeded, (0, 1) is output. The control signal generation circuit 26 calculates the logical sum (OR) of the 2-bit decision output for the reception level value of each carrier.

(1) When the OR result is (1, 0), the reception level value of each carrier is below the lower limit of the adjustment range (1, 0) or within the adjustment range (0, 0). That is, if at least one of the reception level values of each carrier falls below the lower limit of the adjustment range, a control signal for increasing the output power of the overall power adjustment circuit 15 from the specified value is generated.
(2) When the OR result is (0, 1), the reception level value of each carrier exceeds the upper limit of the adjustment range (0, 1) or is within the adjustment range (0, 0). That is, when at least one of the reception level values of each carrier exceeds the upper limit of the adjustment range, a control signal for reducing the output power of the overall power adjustment circuit 15 from the specified value is generated.

(3) When the OR result is (0, 0), since the reception level value of each carrier is within the adjustment range (0, 0), the output power of the overall power adjustment circuit 15 remains at the specified value. A control signal is generated. However, a control signal that lowers the output power of the overall power adjustment circuit 15 from a specified value may be generated in order to provide a margin for the amplification range of the AGC 24 of the demodulator 20.
(4) When the OR result is (1, 1), the reception level value of each carrier is below the lower limit of the adjustment range (1, 0), within the adjustment range (0, 0), and the upper limit of the adjustment range. More than (0, 1) is mixed. Here, if there is a carrier that exceeds the upper limit of the adjustment range, there is a possibility that the control of the AGC 24 may be saturated, and thus a control signal for reducing the output power of the overall power adjustment circuit 15 from the specified value is generated.

  In accordance with such a control signal of the control signal generation circuit 26, the overall power adjustment circuit 15 of the frequency conversion unit 10 adjusts the power, and the AGC 24 detects the reception level value of each carrier and re-adjusts it. The power adjustment value of the output power in the overall power adjustment circuit 15 becomes the loop gain of the feedback circuit. When the power adjustment value is variable (has a range of 0.1 dB to 1 dB), the convergence speed of the feedback circuit can be adjusted. In addition, when there is no need to variably control the overall power adjustment circuit 15 based on external settings or line allocation information, the power adjustment value may be fixed.

  The carrier power adjustment circuits 16-1 to 16-n and the carrier filters 17-1 to 17-n extract each carrier to be demodulated, adjust the level, and output. As a result, only the carrier to be demodulated or the part of the carrier that is close to the demodulator leaks due to the characteristics of the carrier filter, and the input power to the demodulator 20 can be limited. .

  The carrier power adjustment circuits 16-1 to 16-n are controlled from the control signal generation circuit 26 by the reception level detection output for each carrier of the AGC 24, line allocation information, and manual setting, like the overall power adjustment circuit 15. The line allocation information includes pre-assignment that specifies a band to be used in advance and demand assignment that dynamically changes the band to be used. If it is known in advance that the received power is too high or too low in the corresponding band, the power may be set manually.

Examples of carrier power control of the carrier power adjustment circuits 16-1 to 16-n are shown below.
(1) A carrier power adjustment circuit 16-in front of a carrier filter 17-i that passes this carrier i for a carrier i whose reception level value detected by the AGC 24 falls below (1,0) the lower limit of the adjustment range. Control to increase the output power from the specified value at i.
(2) A carrier power adjustment circuit 16- preceding the carrier filter 17-j that passes the carrier j for a carrier j whose reception level value detected by the AGC 24 exceeds the upper limit of the adjustment range (0, 1). Control is performed to reduce the output power from the specified value at j.
(3) For a carrier k whose reception level value detected by the AGC 24 is within the adjustment range (0, 0), output by the carrier power adjustment circuit 16-k before the carrier filter 17-k that passes this carrier k. Do not adjust power.

  As with the overall power adjustment circuit 15, feedback control is performed on the reception level value of each carrier by the control signal of the control signal generation circuit 26. As with the overall power adjustment circuit 15, the adjustment value of the output power of each carrier is variable or fixed, and this value becomes the loop gain of the feedback circuit. In the case of variable, the convergence speed can be adjusted.

  The adjustment value may be fixed when it is not necessary to change the setting according to external settings or line allocation information. Further, instead of 0/1, intermediate values such as 0.2 and 0.7 may be provided, and flexible adjustment may be performed by control that multiplies the output power adjustment value.

  For the carrier x that is not subject to demodulation, if the power of the carrier power adjustment circuit 16-x is set to “0”, the output of the signal in the band of the corresponding carrier filter 17-x can be limited. Alternatively, the same operation may be performed by selecting and adding only the carrier to be demodulated by the selective addition circuit 19.

  Further, when adjusting the power of the carrier to be demodulated, the selection adding circuit 19 does not select the output of the signal passing circuit 18. On the other hand, when the power of the carrier to be demodulated is not adjusted and only the function of the overall power adjustment circuit 15 is used, the selection addition circuit 19 inputs the signal from the overall power adjustment circuit 15 and the frequency conversion circuit 14 to the signal passing circuit 18. Select and output the signal. In this case, it is possible to replace the overall power adjustment circuit 15 by adding a power adjustment function to the signal passing circuit 18.

(Example 2)
FIG. 3 shows a configuration example of a receiving apparatus according to the second embodiment of the present invention.
The characteristics of the second embodiment are the carrier power adjustment circuits 16-1 to 16-n and carrier filters 17-1 to 17-n of the first embodiment, and a Fourier transformer (FFT) 31 instead of the signal passing circuit 18. Using the extraction filters 32-1 to 32-n and 33, the selective addition circuit 34, and the inverse Fourier transformer (IFFT) 35, the reception signal converted into the signal on the frequency axis by Fourier transformation is processed. The control signal output from the control signal generation circuit 26 is input to the extraction filter coefficient generation circuit 36, and the filter coefficients of the extraction filters 32-1 to 32-n and 33 are generated. Other configurations are the same as those of the first embodiment.

  The extraction filter coefficient generation circuit 36 generates a filter coefficient for extracting a carrier in accordance with the control signal of the control signal generation circuit 26 and multiplies the received signal on the frequency axis by the carrier filter 17-of the first embodiment. A function equivalent to 1-17-n is obtained.

  Further, power adjustment can be performed by multiplying the entire filter coefficient by a times. The multiple “a” is the same as the adjustment value of the carrier power adjustment circuits 16-1 to 16-n of the first embodiment, and the convergence speed of the feedback control can be adjusted by making the adjustment value variable.

  Furthermore, by setting the entire band or the band in which the carrier exists to “1” as the filter coefficient of the extraction filter 33, a function equivalent to the signal passing circuit 18 of the first embodiment can be realized. In addition, when the power is adjusted by the extraction filter 33, an appropriate value of the filter coefficient other than “1” may be set.

  Further, when the processing bandwidth of the frequency converter 10 is wider than the processing bandwidth of the demodulator 20, a carrier arranged in a range exceeding the processing bandwidth of the demodulator 20 is extracted and demodulated as shown in FIG. It is also possible to add by shifting the frequency of the carriers by the extraction filters 32-1 to 32-n so as to be within the processing bandwidth of the unit 20.

  Further, the part from the Fourier transform to the inverse Fourier transform may have a configuration of overlap addition.

10,100 Frequency converter 11 Band pass filter (BPF)
DESCRIPTION OF SYMBOLS 12 Attenuator 13 Amplifier 14 Frequency conversion circuit 15 Overall power adjustment circuit 16 Carrier power adjustment circuit 17 Carrier filter 18 Signal passing circuit 19 Selection addition circuit 20,200 Demodulator 21 Band pass filter (BPF)
22 Attenuator 23 Amplifier 24 Automatic gain control circuit (AGC)
25 Demodulator 26 Control Signal Generation Circuit 31 Fourier Transformer (FFT)
32, 33 Extraction filter 34 Selective addition circuit 35 Inverse Fourier transformer (IFFT)
36 Extraction filter coefficient generation circuit

Claims (8)

A frequency conversion unit including a frequency conversion circuit that receives frequency-multiplexed signals of a plurality of carriers distributed on the frequency axis and converts the frequency-multiplexed signals into a frequency band processed by a demodulator;
A demodulation unit including an automatic gain control circuit that adjusts power according to the reception level of each carrier of the frequency-multiplexed frequency-converted signal and inputs it to the demodulator;
The frequency converter comprises an overall power adjustment circuit that collectively adjusts the power of the frequency multiplexed signal,
In accordance with a determination result indicating that the reception level value of each carrier detected by the automatic gain control circuit exceeds the upper limit of the adjustment range of the automatic gain control circuit or falls below the lower limit of the adjustment range. A receiving apparatus comprising: a control unit that outputs a first control signal that collectively controls power of the frequency-multiplexed signal to an overall power adjustment circuit. A frequency conversion unit including a frequency conversion circuit that receives frequency-multiplexed signals of a plurality of carriers distributed on the frequency axis and converts the frequency-multiplexed signals into a frequency band processed by a demodulator;
A demodulation unit including an automatic gain control circuit that adjusts power according to the reception level of each carrier of the frequency-multiplexed frequency-converted signal and inputs it to the demodulator;
The frequency converter comprises carrier power adjustment means for individually adjusting the power of each carrier of the frequency multiplexed signal,
In accordance with a determination result indicating that the reception level value of each carrier detected by the automatic gain control circuit exceeds the upper limit of the adjustment range of the automatic gain control circuit or falls below the lower limit of the adjustment range. A receiving apparatus comprising: a control unit that outputs a second control signal for individually controlling the power of each carrier to a carrier power adjusting unit. A frequency conversion unit including a frequency conversion circuit that receives frequency-multiplexed signals of a plurality of carriers distributed on the frequency axis and converts the frequency-multiplexed signals into a frequency band processed by a demodulator;
A demodulation unit including an automatic gain control circuit that adjusts power according to the reception level of each carrier of the frequency-multiplexed frequency-converted signal and inputs it to the demodulator;
The frequency converter comprises an overall power adjustment circuit that collectively adjusts the power of the frequency multiplex signal, and carrier power adjustment means that individually adjusts the power of each carrier of the frequency multiplex signal,
In accordance with a determination result indicating that the reception level value of each carrier detected by the automatic gain control circuit exceeds the upper limit of the adjustment range of the automatic gain control circuit or falls below the lower limit of the adjustment range. A second control for outputting a first control signal for collectively controlling the power of the frequency-multiplexed signal to an overall power adjustment circuit and for individually controlling the power of each carrier to the carrier power adjustment means. A receiving device comprising control means for outputting a signal. The receiving apparatus according to claim 1 or 3,
The control means includes the first control signal for performing control to collectively raise the power of the frequency multiplexed signal from a specified value when at least one reception level value of each carrier is below a lower limit of the adjustment range. A receiving device characterized by outputting. The receiving apparatus according to claim 1 or 3,
The control means is configured such that at least one reception level value of each carrier exceeds an upper limit of the adjustment range, or a reception level value of each carrier exceeds a lower limit of the adjustment range and an upper limit of the adjustment range. The receiving apparatus that outputs the first control signal that performs control to collectively reduce the power of the frequency-multiplexed signal from a specified value when carriers are mixed. The receiving apparatus according to claim 2 or 3,
The control means performs control to increase the power of a carrier that is below the lower limit of the adjustment range from the specified value among the reception level values of the carriers, and performs control to decrease the power of the carrier that exceeds the upper limit of the adjustment range from the specified value. The receiving apparatus that outputs the second control signal to be performed. The receiving apparatus according to claim 2 or 3,
The carrier power adjustment means is configured to select a carrier to be demodulated in the demodulator using a filter from the frequency multiplex signal, perform power adjustment for each selected carrier, and add. apparatus. The receiving apparatus according to claim 2 or 3,
The carrier power adjusting means performs Fourier transform on the frequency-multiplexed signal, selects a carrier to be demodulated in the demodulator using a filter coefficient corresponding to the second control signal, performs power adjustment, and adds them. A receiving apparatus characterized by being configured to output after Fourier transform.

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