JP2944606B2 - Peak clipping device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission peak power of a transmitting apparatus in a mobile communication system such as an FDMA (Frequency Division Multiple Access) and CDMA (Code Division Multiple Access) system for multiplexing a plurality of communication channels in a frequency band. The present invention relates to a peak clipping device that performs amplitude limitation (limitation) on a baseband signal in order to reduce the noise.

[0002]

2. Description of the Related Art Conventionally, in a mobile communication system of this type of FDMA and CDMA systems, when amplifying a signal after multiplexing a plurality of communication channels, if the number of signals to be multiplexed increases, the signal peak after the multiplexing increases. The value increases. In addition,
The same applies to the case of amplifying a signal obtained by combining a plurality of carrier waves in the multiplex communication system of TDMA (time division multiplex connection). This amplification requires non-generation of peak distortion. That is, it is necessary to prevent the spread of the spectrum due to the occurrence of the distortion and to prevent the generation of the interference wave in the adjacent communication channel and the deterioration of the modulation accuracy.

As a measure for preventing the generation of the interference wave and the deterioration of the modulation accuracy, it is necessary to increase the maximum amplitude output. In this case, the device scale of the amplifier increases and its power consumption also increases. In addition, when a band-limiting filter attenuates leakage power to an adjacent channel, a band-limiting filter having a steep characteristic is required.

[0004] In other words, it is extremely difficult to attenuate the leakage power of the adjacent channel with respect to the distorted amplified output signal. In a modulation method in which modulation is performed after multiplexing with a baseband signal, a process of limiting the amplitude of a peak of a modulated wave is performed on the baseband signal in advance. In this case, even if the modulation accuracy at the moment when the amplitude is limited is slightly deteriorated and distortion occurs, the distortion component is removed by a band-limiting filter at the subsequent stage.

Japanese Patent Laid-Open Publication No. Hei 9-18451, "CDMA Base Station Transmitter" discloses a technique for limiting the amplitude of a modulated wave.
There is a conventional example. In this conventional example, a limiter (peak clipping circuit) is constituted by a ROM, and a combined baseband signal in-phase component and a combined baseband signal quadrature component are read out from the ROM as addresses, and the amplitude-limited combined baseband of the amplitude-limited data is read out. The signal in-phase component and the amplitude-limited combined baseband signal quadrature component are output.

[0006] In this way, after performing the amplitude control of the combined baseband signal, the signal is passed through a roll-off filter to remove the spectrum distortion and suppress the transmission peak voltage. In this case, if the combined baseband signal in-phase component and the combined baseband signal quadrature component are each represented by 8 bits, the number of addresses = 256 (= 2 to the eighth power) and the data width is 8
The number of bits becomes 2, so that the amplitude limiting process can be realized with a ROM of 1 megabit capacity. As a result, the dynamic range and linearity conditions for the analog baseband unit, the modulation unit, and the transmission power amplification unit are greatly relaxed,
The CDMA base station transmitting apparatus having the simple configuration is realized.

[0007]

However, in the conventional example of Japanese Patent Laid-Open No. Hei 9-18451, when the limiter (peak clipping circuit) is constituted by a ROM, when the number of signals to be multiplexed increases, the combined baseband signal in-phase component and The combined baseband signal orthogonal components cannot be represented by about 10 bits each. In other words, RO with a large capacity
M is required, and the connection configuration when mounting the ROM on the circuit board is complicated, and the cost is increased.

The present invention is to solve such a problem in the prior art. In a mobile communication system such as an FDMA or CDMA system, the present invention relates to an amplitude limiting process when the number of multiplexed signals increases. It is possible to suppress the increase in equipment scale and the deterioration of transmission quality,
It is an object of the present invention to provide a peak clipping device capable of reducing the cost.

[0009]

In order to achieve the above object, a peak clipping device according to the present invention is a peak clipping device for selectively limiting the amplitude of a combined baseband signal in-phase component and a combined baseband signal quadrature component.
And according to a control signal for performing the amplitude limitation,
As each address the upper bits of the composite baseband signal in-phase component and combining the baseband signals quadrature components of a plurality of bits is input, the amplitude limiting synthetic baseband signal phase component and amplitude limitation synthesis of a plurality of bits read from the storage unit selects and outputs the baseband signal quadrature component in accordance with a control signal indicating not to perform amplitude limiting, before
It is configured to include processing means for selecting and outputting the in-phase component and the composite baseband signal quadrature component of the plurality of bits of the combined baseband signal.

[0010] The peak clipping device of the present invention, said processing means, each of the several upper bits of the composite baseband signal in-phase component and combining the baseband signals quadrature components of a plurality of bits which is input as an address, a plurality of bits Storage means for reading out an in- phase component and an amplitude-limited synthesized baseband signal quadrature component of an amplitude-limited synthesized baseband signal, and determining whether or not the input synthesized baseband signal in-phase component and synthesized baseband signal quadrature component do not limit the amplitude an amplitude value calculating means for sending a control signal to,
From the amplitude value calculating means , when a control signal indicating that the amplitude is not limited is input , the combined baseband signal in-phase component and the combined baseband signal quadrature component are selected and output,
Further, when the input control signal to the effect that amplitude limiting, a configuration and a selection means for selecting the amplitude limit synthesized baseband signal phase component and amplitude limitation synthesized baseband signal quadrature component from the storage means is there.

Further, the two multipliers an amplitude value calculating means, for squaring each of the input synthesized baseband signal phase component and combining the baseband signal quadrature component here,
An adder for outputting the squared value of the amplitude obtained by adding the value from the multiplier, the value from the adder, the amplitude performing restriction 2
Is compared with the threshold value of the squared value, it is a control signal corresponding to the greater and smaller than the threshold value as a structure including a comparator to be transmitted to said selection means.

Furthermore, peak clipping device of the present invention, said processing means, each of the several upper bits of the composite baseband signal in-phase component and combining the baseband signals quadrature components of a plurality of bits which is input as an address, a plurality of bits Storage means for reading out an in-phase component of a certain amplitude-limited combined baseband signal and a quadrature component of the amplitude-limited combined baseband signal, and reading and outputting predetermined data for a combined baseband signal in-phase component and a combined baseband signal quadrature component which are not subjected to the amplitude limitation; From the storage means
Comparison means for sending a control signal when data is detected
And a control signal indicating that the amplitude is not to be limited from the comparing means.
When you enter, the composite baseband signal in-phase component and to select the composite baseband signal quadrature component output, and, when a control signal is input to the effect that amplitude limiting, amplitude limiting synthetic base from said storage means Selecting means for selecting and outputting the in-phase component of the band signal and the quadrature component of the amplitude-limited combined baseband signal.

Here, the comparing means comprises a plurality of Es to which data of the in-phase component of the amplitude-limited combined baseband signal and the data of the quadrature component of the amplitude-limited combined baseband signal are input.
And EX-OR unit having a X-OR gates, the EX-O
A predetermined data generating unit for transmitting predetermined data to each EX-OR gate of the R unit; and an O for outputting a control signal obtained by performing an OR process on the EX-OR value from the EX-OR gate circuit.
The configuration includes an R gate. Further, the predetermined data is set to “00” indicating that the data is not amplitude-limited.
000000 0000,0000 0000 000
0 ".

Further, the peak clipping device of the present invention uses a ROM as the storage means, and further uses a multiplexer as the selection means. The input plural bits are 12 bits, and the upper several bits are 4 bits. Furthermore, these configurations are arranged to reduce the transmission peak power of a transmission device in a mobile communication system that multiplexes a plurality of communication channels in a frequency band, and further includes a band limiting filter for noise removal after the device. There is a configuration.

The peak clipping device of the present invention having such a configuration outputs the input plural-bit synthesized baseband signal in-phase component and the synthesized baseband signal quadrature component as they are when the amplitude limitation is not performed, thereby limiting the amplitude limitation. Do
Sometimes , an amplitude-limited combined baseband signal in-phase component and an amplitude-limited combined baseband signal quadrature component, which are a plurality of bits similar to the above, which are read out using the upper few bits as an address, are output.

As a result, in a mobile communication system such as the FDMA and CDMA systems, it is possible to suppress an increase in the device scale and deterioration in transmission quality in amplitude limiting processing when the number of signals to be multiplexed increases. And the cost can be reduced.

For example, when the upper 4 bits of each of the 12-bit combined baseband signal in-phase component and the combined baseband signal quadrature component are read out as addresses, the number of addresses = 256 (= 2 to the eighth power) and the data width is 12 bits ×
2, the amplitude limit processing can be performed with a ROM having a small capacity of 6 kilobits. When there is no amplitude limitation, the original combined baseband signal in-phase component I and the combined baseband signal quadrature component Q are output, so that the transmission quality does not deteriorate.

When an in-phase component of the amplitude-limited synthesized baseband signal and an orthogonal component of the amplitude-limited synthesized baseband signal whose amplitude is limited are selected and output, a phase error occurs, but the probability of occurrence is small. , The deterioration of the transmission quality can be suppressed.

[0019]

Next, an embodiment of a peak clipping device according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a communication system to which the peak clipping device according to the first embodiment of the present invention is applied. This communication system is a modulation system in which a baseband signal is multiplexed and then modulated at a time, and the amplitude of a peak of a modulated wave is previously limited by the baseband signal. In other words, the modulation accuracy at the moment of performing the amplitude limiting process is degraded, but the distortion generated when the modulation accuracy is somewhat sacrificed is removed by the subsequent band limiting filter.

In FIG. 1, the communication system includes a baseband signal generator 11 to generate a baseband signal.
1n, an addition / synthesis unit 12 that adds and synthesizes the baseband signals from the baseband signal generation units 11 to 1n, a peak clipping circuit 13 that performs an amplitude limiting process on the synthesized baseband signal, A band limiting filter (BPF) 14 for performing band limiting. The communication system further includes a D / A converter 15 that converts a band-limited digital baseband signal into an analog baseband signal, and transmits the analog baseband signal from the D / A converter 15 to a transmission radio frequency ( It has a frequency conversion unit 16 for converting the RF signal into an RF signal, and a transmission power amplification unit 17 for amplifying the RF signal and transmitting it from the antenna Ant.

FIG. 2 shows the peak clipping circuit 1 shown in FIG.
FIG. 3 is a block diagram showing a configuration of No. 3. The peak clipping circuit 13 receives several tens of bits (for example, 1
Upper bits (for example, 4 bits) of the combined baseband signal (baseband signal) in-phase component I (I signal) and the combined baseband signal (baseband signal) quadrature component Q (Q signal) expressed by 2 bits). ) Is input as an address, and has a ROM 21 for reading out and outputting an amplitude-limited synthesized baseband signal in-phase component Ia and an amplitude-limited synthesized baseband signal quadrature component Qa of amplitude-limited 12-bit data.

Further, the peak clipping circuit 13
And an amplitude value calculation circuit 22 to which a combined baseband signal in-phase component I and a combined baseband signal quadrature component Q are inputted and which sends out a control signal “0, 1” based on the calculation of the amplitude value as described later. The control signal "0,1" output from the amplitude value calculating circuit 22 uses the combination (I signal, Q signal) of the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q, or the amplitude-limited combined base. A switching circuit 23 for selecting and outputting any one of a combination (Ia signal, Qa signal) of the band signal in-phase component Ia and the amplitude-limited combined baseband signal quadrature component Qa.

FIG. 3 is a block diagram showing a detailed configuration of the amplitude value calculating circuit 22 in FIG. This amplitude value calculation circuit 2
Reference numeral 2 denotes multipliers 25a and 25b for squaring each of the input in-phase component I and the quadrature component Q of the synthesized baseband signal to be input, and values obtained from the multipliers 25a and 25b are added to obtain an amplitude 2 An adder 26 for outputting a multiplied value, and comparing the value from the adder 26 with a square value (threshold value Vref) of the amplitude to be limited, and controlling when the value is smaller than the threshold value Vref. A comparator 27 for sending a signal "0" to the switch circuit 23 and sending a control signal "1" to the switch circuit 23 when the square of the amplitude value is larger than the limited squared value of the amplitude. doing. Note that a general-purpose multiplexer or the like may be used for the switch circuit 23 in FIG.

FIG. 4 is a diagram showing a memory map of the ROM 21 in FIG. In the ROM 21, the upper four bits of each of the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q shown in FIG. The data having the upper 4 bits of each of the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q for which the amplitude is to be limited are the amplitude-limited combined baseband signal in-phase component Ia and the amplitude-limited data. The restricted combined baseband signal orthogonal component Qa is written as data. The amplitude-limited combined baseband signal in-phase component Ia and the amplitude-limited combined baseband signal quadrature component Qa of the amplitude-limited data are each 1
It is represented by 2 bits.

In the ROM 21, the combined baseband signal in-phase component I in which data having the upper 4 bits of each of the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q which are not limited in amplitude are represented by 12 bits.
And the lower 8 of the combined baseband signal quadrature component Q
Write data with the bit set to 0. For example, R
In the OM 21, “000001” of the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q respectively.
01 0001,0000 0001 0111 "as data having the address" 0000 0000 "in the ROM 21 as" 0000 0000 0000,
0000 0000 0000 ”.

The combined baseband signal in-phase component I and the combined baseband signal quadrature component Q are stored in the ROM 21 as "0000 0101 0001,0001 0".
001 0111 ”, then“ 0000 ”in the ROM 21
"0001" as data with an address of "0000"
0000 0000,0001 0000 000
Write "0".

Further, the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q are stored in the ROM 21 as "0110 0101 0001, 0110 0".
001 0111 ”,“ 0110 ”in the ROM 21
“0001” as data with address “0001”
0000 0000,0001 0000 000
Write "0".

The combined baseband signal in-phase component I and the combined baseband signal quadrature component Q are stored in the ROM 21 as "0111 0101 0001, 0111".
0001 0111 ”,“ 011 ”in the ROM 21
“000” as data with the address “101111”
1 0000 0000,0001 0000 000
Write "0".

Next, the operation of the first embodiment will be described. In the communication system shown in FIG. 1, baseband signal generation sections 11 to 1n respectively generate baseband signals and send them to addition / synthesis section 12. The adder / synthesizer 12 adds and synthesizes the baseband signals to generate a peak clipping circuit 1.
3 The peak clipping circuit 13 performs a peak clipping process on the synthesized baseband signal as described later in detail.

The peak-clipped amplitude-limited synthesized baseband signal is band-limited by the band-limiting filter 14. The digital baseband signal band-limited by the band-limiting filter 14 is converted into an analog baseband signal by the D / A converter 11 and transmitted to the frequency converter 16. The frequency converter 16 converts an analog baseband signal into a transmission radio frequency (RF) signal,
The signal is power-amplified by the transmission power amplifier 17 and the antenna An
Wireless transmission is performed from t.

Next, the peak clipping circuit 1 shown in FIG.
Operation 3 will be described. 2 to 4, in the peak clipping circuit 13, a combined baseband signal in-phase component I and a combined baseband signal quadrature component Q expressed by 12 bits are input to the switch circuit 23 and the ROM 21. The upper four bits of the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q are input to the ROM 21 as addresses. ROM2
1 reads the upper 4 bits of each of the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q as an address of the ROM 21 as shown in FIG.

In FIG. 4, the combination of the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q for limiting the amplitude is indicated by hatched portions. Data using the upper 4 bits of the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q for performing the amplitude limitation as the address,
The amplitude-limited combined baseband signal in-phase component Ia and the amplitude-limited combined baseband signal quadrature component Qa of the amplitude-limited data are written as data. The in-phase component Ia of the amplitude-limited combined baseband signal and the quadrature component Qa of the amplitude-limited combined baseband signal output from the ROM 21 are each represented by 12 bits.

In FIG. 4, the combination of the in- phase component I of the synthesized baseband signal and the quadrature component Q of the synthesized baseband signal, for which the amplitude limitation is not performed , is indicated by the portion without oblique lines. The data having the upper 4 bits as the address of each of the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q that does not perform the amplitude limitation is the combined baseband signal in-phase component I and the combined base The lower 8 bits of each of the quadrature components Q of the band signal are written as 0 data.

In the amplitude value calculating circuit 22 shown in FIG. 3, the input composite baseband signal in-phase component I and the composite baseband signal quadrature component Q are squared by multipliers 25a and 25a. 26 are added by an adder 26 to calculate a square value of the amplitude.
7 is compared with the square value of the amplitude (threshold value Vref) for limiting. That is, it is determined whether the threshold value is larger or smaller than Vref. As a result of this determination, for example, when the square value (addition value) of the amplitude value is smaller than the square value of the limited amplitude (threshold value Vref), the control signal “0” is set.
To the switch circuit 23. In addition, the square value of the amplitude (threshold value Vre) at which the square value (addition value) of the amplitude value is limited
f) If the control signal “1” is larger than the switch circuit 2
3

The switch circuit 23 selects and outputs a combination of the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q when the control signal "0" is transmitted from the amplitude value calculating circuit 22. When the control signal “1” is transmitted from the amplitude value calculation circuit 22, a combination of the amplitude-limited combined baseband signal in-phase component Ia and the amplitude-limited combined baseband signal quadrature component Q is selected and output.

As a result, in the first embodiment, for example, the amplitude limiting process performed by reading the upper 4 bits of each of the in-phase component I of the combined baseband signal and the quadrature component Q of the combined baseband signal as an address is performed by the following method.
256 (= 2 to the power of 8), data width 12 bits x 2 and 6
This is possible with a ROM of a small capacity of kilobits. Also,
When there is no amplitude limitation, a combination of the original combined baseband signal in-phase component I and the combined baseband signal quadrature component Q is output, and as a result, transmission quality does not deteriorate.

When a combination of the amplitude-limited combined baseband signal in-phase component Ia and the amplitude-limited combined baseband signal quadrature component Qa is selected and output, the original combined baseband signal in-phase component Ia is output. In addition, the amplitude of the combination of the orthogonal component Q and the combined baseband signal is limited to generate a phase error, but the occurrence probability is small. Therefore, deterioration of transmission quality can be suppressed.

Next, a second embodiment will be described. FIG. 5 is a block diagram showing a configuration of the peak clipping circuit 13a according to the second embodiment. The peak clipping circuit 13a receives a composite baseband signal in-phase component I (I signal) and a composite baseband signal quadrature component Q (Q signal) expressed by several tens of bits (for example, 12 bits). The upper-order several bits (for example, 4 bits) of each of the band signal in-phase component I and the synthesized baseband signal quadrature component Q are input as an address, and the amplitude-limited synthesized baseband signal in-phase component Ia and amplitude of 12-bit data whose amplitude is limited. It has a ROM 31 that outputs a restricted combined baseband signal quadrature component Qa.

Further, as the unique data stored in the ROM 31, the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q without amplitude limitation can be clearly discriminated, for example, "0000 0000 0000,0
A data string such as “000 0000 0000” is appropriate.

Further, the peak clipping device 13a
Is a comparator 32 for transmitting a control signal "0, 1" which compares the amplitude-limited combined baseband signal in-phase component Ia and the amplitude-limited combined baseband signal quadrature component Qa with unique data.
And the control signal “0, 1” output from the comparator 32
A combination of the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q (I signal, Q signal), or
A switch circuit 33 for selecting and outputting any one of a combination (Ia signal, Qa signal) of the amplitude-limited combined baseband signal in-phase component Ia and the amplitude-limited combined baseband signal quadrature component Qa.

FIG. 6 is a block diagram showing a detailed configuration of the comparator 32. The comparator 32 outputs an amplitude-limited combined baseband signal in-phase component Ia (12 bits) and an amplitude-limited combined baseband signal quadrature component Qa output from the ROM 31.
The EX-OR gate circuit 40 to which each of the (12-bit) 24-bit data is input, and the EX-OR gate of the EX-OR gate circuit 40 supplies the 24-bit unique data “0000 0000 0000,000,000 0000 000”.
Unique data generation unit 41 for sending out “0000”
OR gate 42 that outputs the EX-OR value from X-OR gate circuit 40 as an OR value (control signal “0, 1”)
And Note that a general-purpose multiplexer or the like may be used for the switch circuit 33 in FIG.

FIG. 7 is a diagram showing a memory map of the ROM 31 in FIG. In FIG. 7, the ROM 31 reads the upper 4 bits of each of the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q as an address. In-phase component I of synthesized baseband signal for limiting amplitude
And the amplitude-limited composite baseband signal in-phase component Ia of the amplitude-limited data as data having the upper 4 bits of each of the combined baseband signal quadrature components Q as addresses.
And the amplitude-limited combined baseband signal quadrature component Qa is written as data. The amplitude-limited combined baseband signal in-phase component Ia and the amplitude-limited combined baseband signal quadrature component Qa of the amplitude-limited data are each represented by 12 bits.

The peculiar data generating unit 41 generates peculiar data as data using the upper four bits of each of the in-phase component I and the quadrature component Q of the synthesized baseband signal without amplitude limitation as addresses. For example, each of the in-phase component of the combined baseband signal and the quadrature component of the combined baseband signal is referred to as “0000 0101 0001,
0001 0001 0111 ", the ROM 31
"0000 0001" as data having an address of "0000 0001"
0000 ".

Further, the unique data generating section 41 converts the synthesized baseband signal in-phase component I and the synthesized baseband signal quadrature component Q into “0110 0101 0001,0”.
110 0001 0111 ”, data“ 0000 0001 ”in the ROM 31 as an address“ 0000 0000 0000, 0000 0000 ”
0000 ".

Further, the singular data generation unit 41 converts the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q into “0110 0101 0001,0”.
Assuming that “110 0001 0111”, “0001 0000 0000, 0001 0000” is used as data with the address “0110 0111” in the ROM 31.
0000 ".

Further, the unique data generating section 41 converts the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q into “0111 0101 0001,0”.
Assuming that “111 0001 0111”, “0001 0000 0000, 0001 0000” is used as data with the address “0111 0111” in the ROM 31.
0000 ".

Next, the operation of the peak clipping circuit 13a shown in FIG. 5 will be described. In FIGS. 5 and 7, the peak clipping circuit 13a includes a switch circuit 33 and a ROM for combining a combined baseband signal in-phase component I and a combined baseband signal quadrature component Q expressed by 12 bits.
31 is input. The upper 31 bits of the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q are input to the ROM 31 as addresses. R
The OM 31 reads the upper four bits of each of the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q as an address of the ROM 31, as shown in FIG.

In FIG. 7, the combination of the in-phase component I of the synthesized baseband signal and the quadrature component Q of the synthesized baseband signal for limiting the amplitude is indicated by hatched portions. Data using the upper 4 bits of the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q for performing the amplitude limitation as the address,
The amplitude-limited combined baseband signal in-phase component Ia and the amplitude-limited combined baseband signal quadrature component Qa of the amplitude-limited data are written as data. The in-phase component Ia of the amplitude-limited synthesized baseband signal and the quadrature component Qa of the amplitude-limited synthesized baseband signal output from the ROM 31 are each represented by 12 bits.

In FIG. 7, the combination of the in-phase component I of the synthesized baseband signal and the quadrature component Q of the synthesized baseband signal, for which no amplitude limitation is performed, is shown as a portion without oblique lines . The data using the upper 4 bits of each of the in-phase component I and the quadrature component Q of the synthesized baseband signal without amplitude limitation as unique addresses, for example, “0000 0000 0000, 0000 00”
00 0000 ”is written in the ROM 31.

In the comparator 32 shown in FIG. 6, the data of the in-phase component I of the amplitude-limited synthesized baseband signal and the quadrature component Q of the amplitude-limited synthesized baseband signal are converted into singular data "for example, 0
000 0000 0000, 0000 0000 0
000 ”is determined. When the data of the in-phase component I of the amplitude-limited combined baseband signal and the quadrature component Q of the amplitude-limited combined baseband signal are singular data in this comparison determination, the control signal “0” is sent to the switch circuit 33. If the data is not unique data, the control signal is "1".
To the switch circuit 33.

The switch circuit 33 selects and outputs a combination of the combined baseband signal in-phase component I and the combined baseband signal quadrature component Q when the control signal "0" is transmitted from the amplitude value calculating circuit 22. When the control signal "1" is transmitted from the amplitude value calculating circuit 22, a combination of the amplitude-limited combined baseband signal in-phase component Ia and the amplitude-limited combined baseband signal quadrature component Qa is selected and output.

As a result, in the second embodiment, as in the first embodiment, the amplitude limiting process of reading out the upper 4 bits of each of the combined baseband signal in-phase component and the combined baseband signal quadrature component as an address is performed. Number of addresses = 256 (= 2 to the eighth power), data width 12 bits × 2
This is possible with a ROM having a small capacity of 6 kilobits.
Further, when there is no amplitude limitation, the combination of the original combined baseband signal in-phase component I and the combined baseband signal quadrature component Q is output, so that the transmission quality does not deteriorate.

It should be noted that even when a combination of the in-phase component Ia of the amplitude-limited synthesized baseband signal and the quadrature component Qa of the amplitude-limited synthesized baseband signal subjected to the amplitude limitation is selected and output, the first case is also obtained.
As in the embodiment, for the combination of the original combined baseband signal in-phase component and the combined baseband signal quadrature component,
Although the phase error occurs due to the amplitude limitation, the probability of occurrence is small, so that the deterioration of the transmission quality can be suppressed.

In the communication system such as the CDMA base station transmitter shown in FIG. 1 to which the peak clipping circuits 13 and 13a of the first and second embodiments are applied, the transmission peak voltage is effectively suppressed, The conditions of the dynamic range and the linearity for the baseband section, the modulation section, and the transmission power amplification section can be greatly relaxed, and the configuration can be simplified.

[0055]

As is apparent from the above description, according to the peak clipping device of the present invention, when the amplitude limitation is not performed, the in-phase component of the input multi-bit composite baseband signal and the quadrature composite baseband signal are input. The component is output as it is, and a plurality of bits of the in-phase component of the amplitude-limited combined baseband signal and the quadrature component of the amplitude-limited combined baseband signal which are read out using the upper few bits as an address when performing the amplitude limitation are output.

As a result, for example, the amplitude limiting process of reading out the upper 4 bits of each of the 12-bit combined baseband signal in-phase component and the combined baseband signal quadrature component as an address is performed by the number of addresses = 256 (= 2 = 2/8).
This is possible with a ROM having a small capacity of 6 kilobits with a data width of 12 bits × 2. Further, when there is no amplitude limitation, the combination of the original combined baseband signal in-phase component I and the combined baseband signal quadrature component Q is output, so that the transmission quality does not deteriorate.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a communication system including a peak clipping device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a peak clipping circuit in FIG.

FIG. 3 is a block diagram illustrating a detailed configuration of an amplitude value calculation circuit in FIG. 2;

FIG. 4 is a diagram showing a memory map of a ROM in FIG. 2;

FIG. 5 is a block diagram illustrating a configuration of an amplitude limiting circuit according to a second embodiment.

FIG. 6 is a block diagram showing a detailed configuration of a comparator in FIG.

FIG. 7 is a diagram showing a memory map of a ROM in FIG. 5;

[Explanation of symbols]

 11 to 1n Baseband signal generation unit 12 Addition and synthesis unit 13, 13a Peak clipping circuit 14 Band limiting filter 21, 31 ROM 22 Amplitude value calculation circuit 23, 33 Switch circuit 25a, 25a Multiplier 26 Adder 27, 32 Comparator 40 EX-OR gate circuit 42 OR gate

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) H04J 1/00 H04J 13/00 H04L 27/00

Claims (10)

(57) [Claims] 1. A peak clipping device for selectively limiting an amplitude of an in-phase component of a combined baseband signal and a quadrature component of a combined baseband signal, the peak clipping device being input according to a control signal for limiting the amplitude. Also , using the upper several bits of each of the multi-bit composite baseband signal in-phase component and the composite baseband signal quadrature component as an address, the amplitude-limited composite baseband signal in-phase component and amplitude, which are a plurality of bits read from the storage unit. limiting synthesized baseband signal quadrature component selects and outputs, in accordance with the control signal indicating not to perform amplitude limiting, the multiple
A peak clipping device comprising a processing means for selecting and outputting an in-phase component and a composite baseband signal quadrature component of a combined baseband signal of several bits . Wherein said processing means, as the address of each of the upper bits of the composite baseband signal in-phase component and combining the baseband signals quadrature components of a plurality of bits is input, the amplitude limiting synthetic baseband signal phase of a plurality of bits amplitude sending component and a storage means for reading the amplitude limitation synthesized baseband signal quadrature component, the input synthesized baseband signal phase component and combining the baseband signal quadrature component to determine whether or not those not amplitude limited control signal value calculation means, from the amplitude value calculating means, when was inputs a control signal to the effect that no amplitude limitation <br/>, and outputs the synthesized baseband signal phase component and select the synthetic baseband signal quadrature component Further, when the input control signal to the effect that amplitude limiting, amplitude limiting synthetic baseband signal phase component from the storage means Fine amplitude limitation synthesized baseband signal selection means for selecting and outputting the quadrature component, the peak clipping device according to claim 1, characterized in that it comprises a. Amplitude wherein the amplitude value calculating means, which adds the two multiplier for squaring each of the inputted synthesized baseband signal phase component and combining the baseband signal quadrature component, the value from the multiplier an adder for outputting a square value of the values from the adder is compared with the threshold value of the square value of the amplitude for performing the limit control signals corresponding to the greater and smaller than the threshold value 3. A peak clipping device according to claim 2, further comprising: a comparator that sends a signal to the selection unit. Wherein said processing means, as the address of each of the upper bits of the composite baseband signal in-phase component and combining the baseband signals quadrature components of a plurality of bits is input, the amplitude limiting synthetic baseband signal phase of a plurality of bits Storage means for reading out the component and amplitude-limited composite baseband signal quadrature component, and reading and outputting predetermined data for the combined baseband signal in-phase component and the synthesized baseband signal quadrature component which are not amplitude-limited; and predetermined data from the storage means. Is detected
Comparison means for sending a control signal to, from the comparing means, when you enter <br/> a control signal indicating that no amplitude limitation, by selecting the composite baseband signal in-phase component and combining the baseband signal quadrature component Output, and
Characterized in that it comprises when a control signal is input to the effect that amplitude limiting, and selection means for selecting the amplitude limit synthesized baseband signal phase component and amplitude limitation synthesized baseband signal quadrature component from the storage means, the The peak clipping device according to claim 1, wherein Wherein said comparing means, said amplitude limiting synthesized baseband signal phase component and EX-OR having a plurality of EX-OR gates, each input data amplitude limiting synthetic baseband signal quadrature component
Parts and, OR gate for outputting a predetermined data generator for sending predetermined data to each of the EX-OR gate of the EX-OR unit, a control signal OR processing EX-OR value from the EX-OR gate circuit The peak clipping device according to claim 4, comprising: 6. "0000" indicating that the predetermined data is data whose amplitude is not limited.
0000 0000, 0000 0000 0000 "
The peak clipping device according to claim 4, wherein 7. The peak clipping device according to claim 2, wherein a ROM is used as the storage unit. 8. The peak clipping device according to claim 2, wherein a multiplexer is used as said selecting means. 9. The peak clipping device according to claim 1, wherein the plurality of input bits are 12 bits, and the upper several bits are 4 bits. 10. The apparatus according to claim 1, wherein the apparatus is arranged to reduce a transmission peak power of a transmission apparatus in a mobile communication system that multiplexes a plurality of communication channels in a frequency band, And a band clipping filter for removing a distortion component after the apparatus.