JP2004349941A - Transmitting device, wireless base station, and clipping method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmitting device, a wireless base station, and a clipping method that can maintain an excellent communication state by preventing the wireless base station from stopping operating owing to breakage of a power sending amplifier or a protecting function of a breaker and also deterring EVM deterioration due to clipping from increasing. <P>SOLUTION: The transmitting device is provided with a clipping part which outputs a base band signal generated by limiting the amplitude value of a base band signal with a specified amplitude limit value, a variable attenuator which attenuates the level of a transmit signal according to a control signal, and a comparison control part which generates the control signal to be supplied to the variable attenuator according to the output signal of a detector so that the mean value of output electric power of the power sending amplifier does not exceed maximum sending electric power and generates clipping information for controlling the amplitude limit value so that the difference between the amplitude limit value used by the clipping part and a clipping base band signal becomes constant when the amplitude of the base band signal exceeds a threshold corresponding to the maximum sending electric power. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a transmission device used in a radio base station of a CDMA (Code Division Multiple Access) system, and in particular, limits an input level of a transmission power amplifier so that the output power of the transmission power amplifier does not exceed a predetermined instantaneous maximum power. The present invention relates to a transmission device, a radio base station, and a clipping method.
[0002]
[Prior art]
FIG. 9 is a block diagram showing a cell configuration of a CDMA mobile communication system.
[0003]
As shown in FIG. 9, in a CDMA mobile communication system, one cell is provided with one radio base station 1, and the radio base station 1 performs radio communication with a mobile station 5 in its own cell. It provides a call and data communication service to the user who owns the mobile station 5.
[0004]
In the CDMA system, the radio base station 1 allocates a common frequency band (carrier) to a plurality of mobile stations 5, so that transmission quality between the radio base station 1 and each mobile station 5 is ensured while moving by another user. Transmission power control is performed to suppress unnecessary interference power to the station 5.
[0005]
For example, in downlink transmission (data transmission from the radio base station 1 to the mobile station 5), the mobile station 5 reduces the transmission power to the radio base station 1 if the reception quality exceeds a desired value. If it is less than the above, the wireless base station 1 is instructed to increase the transmission power. The radio base station 1 increases / decreases transmission power according to an instruction from each mobile station 5 and transmits a signal at an optimum transmission power for each mobile station 5.
[0006]
By the way, since the dynamic range of the transmission power amplifier provided in the radio base station 1 and amplifying the signal to the power required for transmission has a limit, the number of mobile stations 5 that simultaneously perform radio communication increases, the output power increases, and the transmission power increases. If the transmission power exceeds the maximum possible transmission power, the operation of the radio base station 1 may be stopped due to the protection function such as the destruction of the transmission power amplifier or the breaker. For this reason, the wireless base station 1 regulates the number of communication channels allocated to one carrier so as not to perform wireless communication with a certain number or more of the mobile stations 5.
[0007]
However, in the CDMA system, the transmission power to each mobile station 5 is different due to the above-described transmission power control. Therefore, simply regulating the number of communication channels may exceed the maximum transmission power. If the number of communication channels per carrier is limited in consideration of the maximum value of the transmission power for each mobile station 5, the system will have a smaller traffic capacity.
[0008]
Therefore, as a conventional method for preventing the output power of the transmission power amplifier from exceeding a predetermined maximum transmission power, for example, Patent Document 1 proposes a configuration for suppressing the input power of the transmission power amplifier. In Patent Literature 1, an average value of output power is detected, an attenuation amount of a variable attenuator provided upstream of the transmission power amplifier is adjusted according to the detected value, and an average level of input power supplied to the transmission power amplifier is determined. By keeping it below the value, destruction of the transmission power amplifier is prevented.
[0009]
[Patent Document 1]
JP-A-2001-44929
[Problems to be solved by the invention]
In a CDMA mobile communication system, a large instantaneous power is usually generated at the time of transmission. Therefore, the transmission power amplifier is very high so that the spread of the transmission spectrum due to nonlinear distortion is suppressed and the adjacent channel leakage power is reduced. A configuration having linearity up to the output level is desirable. However, a transmission power amplifier having good linearity up to a very large output level has a large circuit scale, is expensive, and has high power consumption.
[0011]
In the conventional mobile communication system described in Patent Document 1, since only the attenuation of the variable attenuator is controlled based on the average value of the output power of the transmission power amplifier, the output power is equal to the instantaneous maximum power (peak). Level), it is necessary to clip the input power of the transmission power amplifier. The clipping process is an indispensable technique for suppressing an increase in the circuit scale of the transmission power amplifier and realizing it at low cost.
[0012]
However, if the input power supplied to the transmission power amplifier is clipped, the signal waveform is distorted, and the EVM (Error Vector Magnitude) is significantly deteriorated, so that a problem occurs in that a good communication state cannot be maintained.
[0013]
The clipping process is usually performed by a digital circuit that processes a baseband signal provided before the variable attenuator in order to reduce a variation in clipping value due to the device. For this reason, if excessive clipping is performed on a baseband signal that increases linearly, signal distortion increases and EVM is significantly degraded.
[0014]
The present invention has been made in order to solve the problems of the conventional technology as described above, and prevents the operation of the radio base station from being stopped by a protection function such as a destruction of a transmission power amplifier or a breaker, and also by clipping. An object of the present invention is to provide a transmission device, a radio base station, and a clipping method that can maintain a good communication state by suppressing an increase in EVM deterioration.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, a transmitting apparatus of the present invention generates a transmission signal to be supplied to a transmission power amplifier from a baseband signal obtained by combining a plurality of transmission data, and outputs a predetermined instantaneous output power of the transmission power amplifier. A transmission device for limiting a level of the transmission signal so as not to exceed a maximum power,
A clipping unit that limits the amplitude value of the baseband signal according to a predetermined amplitude limit value, and outputs a clipping baseband signal that is the signal after the amplitude limit,
A detector for detecting the level of the transmission signal;
Attenuating the level of the transmission signal, a variable attenuator whose attenuation can be changed according to a predetermined control signal,
Generating the control signal to be supplied to the variable attenuator based on the output signal of the detector so that the average value of the output power of the transmission power amplifier does not exceed the maximum transmission power, the amplitude of the baseband signal is Clipping for controlling the amplitude limit value so that the difference between the amplitude limit value used in the clipping unit and the clipping baseband signal is constant when a predetermined threshold value corresponding to the maximum transmission power is exceeded. A comparison control unit for generating information;
It is a structure which has.
[0016]
Further, the wireless base station of the present invention, the transmitting device,
A power amplifier that amplifies the transmission signal to a power required for transmission,
It is a structure which has.
[0017]
On the other hand, in the clipping method of the present invention, the level of a transmission signal to be supplied to a transmission power amplifier generated from a baseband signal obtained by combining a plurality of transmission data is determined by changing the output power of the transmission power amplifier to a predetermined instantaneous maximum power. Is a clipping method for restricting not to exceed
Detecting the level of the transmission signal,
Based on the detection result of the level of the transmission signal, so that the average value of the output power of the transmission power amplifier does not exceed a preset maximum transmission power, attenuate the level of the transmission signal using a variable attenuator,
The amplitude value of the baseband signal is limited according to a predetermined amplitude limit value, and when the amplitude of the baseband signal exceeds a predetermined threshold value corresponding to the maximum transmission power, the amplitude limit value and the base value are set. In this method, the amplitude limit value is set so that a difference between the band signal and a clipping baseband signal which is a signal after the amplitude limit is constant.
[0018]
(Action)
In the transmission device, the radio base station, and the clipping method as described above, the clipping unit limits the amplitude value of the baseband signal according to a predetermined amplitude limit value, and outputs the clipped baseband signal that is the signal after the limitation. Then, the comparison control unit generates a control signal to be supplied to the variable attenuator based on the output signal of the detector so that the average value of the output power of the transmission power amplifier does not exceed the maximum transmission power. When the amplitude exceeds a predetermined threshold value corresponding to the maximum transmission power, clipping information for controlling the amplitude limit value so that the difference between the amplitude limit value used in the clipping unit and the clipping baseband signal is constant. By generating the baseband signal, only the instantaneous peak is clipped, so that the distortion of the transmission signal is reduced.
[0019]
Further, the attenuation of the variable attenuator is controlled based on the output signal of the detector so that the average value of the output power of the transmission power amplifier does not exceed the preset maximum transmission power. It is suppressed below the maximum transmission power.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described with reference to the drawings.
[0021]
FIG. 1 is a block diagram illustrating a configuration example of a wireless base station, and FIG. 2 is a block diagram illustrating a configuration example of a transmission device according to the present invention.
[0022]
As shown in FIG. 1, a radio base station 1 includes a transmitting device 2 that combines and modulates transmission data S1 to be transmitted to a mobile station 5, and a transmission device that amplifies an output signal S6 of the transmitting device 2 to power required for transmission. The configuration includes a power amplifier 3 and an antenna 4 for transmitting the transmission output S20 amplified by the transmission power amplifier 3 to the mobile station 5.
[0023]
It should be noted that the radio base station 1 shown in FIG. 1 shows only components necessary for downlink transmission. The actual radio base station 1 has, in addition to the configuration shown in FIG. 1, a receiving device that receives a signal from the mobile station 5 and reproduces received data for each mobile station 5 from a received signal, and a communication state for each mobile station 5. A communication interface, which is an interface with a radio network controller that manages the position of each mobile station 5 and relays communication between the mobile station 5 and the network via a plurality of radio base stations 1 It is equipped with devices and the like.
[0024]
As shown in FIG. 2, the transmission device 2 has a configuration including a baseband unit 6 that performs digital signal processing and an RF unit 7 that performs analog signal processing.
[0025]
The baseband unit 6 receives, as an input, an addition / synthesis unit 8 that synthesizes a plurality of transmission data S1 such as a pilot channel, a control channel, and a communication channel, and a baseband signal S2 output from the addition / synthesis unit 8. Is limited in accordance with clipping information S12 supplied from a comparison control unit 17 described later, a clipping baseband signal S3 which is a signal after the restriction, and a baseband amplitude indicating the amplitude value of the clipping baseband signal S3. A clipping unit 9 for outputting data S10, a modulation unit 10 for modulating the clipping baseband signal S3, and a modulation signal S4 output from the modulation unit 10 are converted into analog signals and output to the RF unit 7 as radio signals S5. D / A unit 11 and the level of the transmitter output S6 detected by the RF unit 7 (A / D unit 16) which receives the detection voltage S7 indicating the power, and converts the detection voltage S7 into transmission power data S8 which is a digital signal, and the average output power of the transmission power amplifier 3 does not exceed the maximum transmission power. The control voltage S9 to be supplied to the variable attenuator 12 described later is generated as described above, and when the amplitude of the baseband signal S2 exceeds the value corresponding to the maximum transmission power of the transmission power amplifier 3, the amplitude limit value used in the clipping unit 9 is used. And a comparison control unit 17 that generates clipping information S12 for controlling the amplitude limit value so that the difference between the signal and the clipping baseband signal S3 is constant. The threshold value S11 set in advance is supplied to the comparison control unit 17 as a value corresponding to the maximum transmission power (average value) of the transmission power amplifier 3.
[0026]
Further, the RF unit 7 attenuates the amplitude of the radio signal S5 output from the baseband unit 6 according to the control voltage S9 supplied from the comparison control unit 17, and outputs the output signal of the variable attenuator 12 to the variable attenuator 12. Amplifying section 13 for amplifying, detector 15 for detecting the level of transmitting apparatus output S6 output from amplifying section 13 to transmission power amplifier 3, and coupler for distributing a part of transmitting apparatus output S6 to detector 15 14.
[0027]
Next, among the components of the baseband unit 6 shown in FIG. 2, the configurations of the addition / synthesis unit 8, the clipping unit 9, and the comparison control unit 17 will be described with reference to FIGS. Note that the modulator 10, the D / A unit 11, the A / D unit 16, and the RF unit 7 may use well-known configurations, and a description of these configurations will be omitted here.
[0028]
FIG. 3 is a block diagram illustrating a configuration example of the addition / synthesis unit illustrated in FIG. 2, and FIG. 4 is a block diagram illustrating a configuration example of the clipping unit illustrated in FIG. FIG. 5 is a block diagram showing a configuration example of the comparison control unit shown in FIG.
[0029]
As shown in FIG. 3, the addition / synthesis unit 8 includes a plurality of adders 81 that respectively add a plurality of transmission data S1 such as a pilot channel, a control channel, and a communication channel. The band signal S2 is output.
[0030]
As shown in FIG. 4, the clipping unit 9 includes a limiter unit 91 that outputs a clipped baseband signal S3 after the amplitude limitation based on a clipping value S17 that is an amplitude limitation value of the baseband signal S2; A control unit 92 that supplies a clipping value S17 to a limiter unit 91 based on the supplied clipping information S12, and an amplitude of a clipping baseband signal S3 output from the limiter unit 91 is detected and compared as baseband amplitude data S10. And an amplitude data detection unit 93 that outputs the data to the unit 17.
[0031]
As shown in FIG. 5, the comparison control unit 17 calculates an average value of the baseband amplitude data S10 supplied from the clipping unit 9 during a predetermined period, and outputs average baseband power data S14 obtained by converting the average value into power. The baseband average value unit 178 compares the average baseband power data S14 with a threshold value S11 which is a value corresponding to the maximum transmission power of the transmission power amplifier 3, and outputs comparison data S19 indicating the difference between them. And generating clipping information S12 for controlling the clipping value S17 based on the comparison data S19 so that the difference between the clipping value S17 used in the clipping unit and the clipping baseband signal S3 is constant. If the band power data S14 is equal to or smaller than the threshold value S11, the average base band A control unit 177 that outputs the value of the power data S14 as the baseband data S16, and outputs the threshold S11 as the baseband data S16 when the average baseband power data S14 is larger than the threshold S11; An average value of transmission power data S8 output from / D unit 16 in a predetermined period is obtained, and transmission power average value unit 173 that outputs the average value as average transmission power data S15, and a baseband output from control unit 177. An operation for outputting control data S18 based on the difference between baseband data S16 and average transmission power data S15 so that the difference between data S16 and average transmission power data S15 output from amplitude power conversion section 172 is minimized. Unit 175 to convert the control data S18, which is a digital signal, into the control voltage S9, which is an analog signal A structure having a D / A unit 176 for conversion. The baseband average value unit 178 calculates an average value of the baseband amplitude data S10 output from the clipping unit 9 during a predetermined period, and outputs an average value unit 171 that outputs the average value as average baseband amplitude data S13; And an amplitude power conversion unit 172 that outputs average baseband power data S14 obtained by converting the average baseband amplitude data S13 output from the unit 171 into power.
[0032]
In such a configuration, the clipping method of the present invention will be described next with reference to FIGS.
[0033]
FIG. 6 is a flowchart showing a processing procedure of the clipping method of the present invention. 7A and 7B are diagrams for explaining the difference between the conventional clipping method and the clipping method of the present invention. FIG. 7A is a graph showing the conventional clipping method, and FIG. 7B is a graph showing the clipping method of the present invention. It is. FIG. 8 is a graph showing the difference between the conventional clipping method and the EVM according to the clipping method of the present invention.
[0034]
As shown in FIG. 6, the baseband unit 6 first averages the amplitude value of the baseband amplitude data S10 output from the clipping unit 9 by the comparison control unit 17, and converts the average value to the power value. The band power data S14 is compared with a preset threshold value S11 by the comparator 174 (step F1).
[0035]
When it is determined that the average baseband power data S14 is equal to or smaller than the threshold value S11 as a result of the processing in step F1, the baseband unit 6 sets the average baseband power data S14 and the threshold value S11 obtained in the processing in step F1. The control unit 177 sets a predetermined initial value in the clipping information S12 based on the comparison data S19, which is the comparison result, and outputs the initial value to the clipping unit 9 as the clipping information S12 (step F2). The initial value is a value set so that the EVM satisfies a predetermined standard at the time of transmission at the maximum output power of the transmission power amplifier 3, and is a value determined by an experiment, a simulation, or the like.
[0036]
Next, the baseband unit 6 outputs the value of the average baseband power data S14 to the arithmetic unit 175 as the baseband data S16 by the control unit 177 based on the comparison data S19 obtained in the process of step F1 (step F3). ).
[0037]
The arithmetic unit 175 compares the value of the baseband data S16 with the value of the average transmission power data S15, and minimizes the difference between them (for example, it is proportional to the difference between the baseband data S16 and the average transmission power data S15). ) Generate control data S18 (step F4).
[0038]
The control data S18 generated by the arithmetic unit 175 is converted to a control voltage S9 by the D / A unit 176 and output to the variable attenuator 12 (step F5).
[0039]
Then, returning to the process of step F1, the processes of steps F1 to F5 are repeated until the value of the baseband data S16 matches the value of the average transmission power data S15.
[0040]
Here, since the value of the average baseband power data S14 is output to the calculation unit 175 as the baseband data S16 by the processing of step F3, the baseband unit 6 determines the amplitude of the clipping baseband signal S3 and the transmission device. Control is performed so that the level of the output S6 matches.
[0041]
On the other hand, when it is determined that the average baseband power data S14 is larger than the threshold value 11 as a result of the process of Step F1, the baseband unit 6 proceeds to the process of Step F6, and is obtained by the process of Step F1. The clipping information S12 is calculated by the control unit 177 based on the comparison data S19, which is the comparison result between the average baseband power data S14 and the threshold value 11 (step F6).
[0042]
The control unit 177 converts the clipping information S12 into
S12 = initial value + (S14-S11)
And outputs the calculated clipping information S12 to the clipping unit 9 (step F7).
[0043]
Next, the baseband unit 6 outputs the threshold value S11 to the calculation unit 175 as baseband data S16 by the control unit 177 based on the comparison data S19 obtained in the process of step F1 (step F8).
[0044]
Subsequently, the arithmetic unit 175 compares the value of the baseband data S16 with the value of the average transmission power data S15, and minimizes the difference between them (for example, the difference between the baseband data S16 and the average transmission power data S15). Is generated (step F4).
[0045]
The control data S18 generated by the arithmetic unit 175 is converted to a control voltage S9 by the D / A unit 176 and output to the variable attenuator 12 (step F5).
[0046]
Then, returning to the process of step F1, the processes of steps F1, F6 to F8, F4, and F5 are repeated until the value of the baseband data S16 matches the value of the average transmission power data S15.
[0047]
Here, since the threshold value S11 corresponding to the maximum transmission power of the transmission power amplifier 3 is output to the calculation unit 175 as the baseband data S16 by the processing of step F8, the baseband unit 6 outputs the transmission device output S6 Is controlled so as to match the level corresponding to the maximum transmission power of the transmission power amplifier 3.
[0048]
FIG. 7 shows a conventional clipping method and a clipping method of the present invention, respectively. FIG. 8 is a diagram showing a difference between the conventional clipping method and the clipping method of the present invention in EVM degradation.
[0049]
7A and 7B, the horizontal axis represents the amplitude of the baseband signal S2, and the vertical axis represents the level of the clipping baseband signal S3 and the output S6 of the transmitting device, respectively.
[0050]
As shown in FIG. 7A, in the conventional clipping method, when the baseband signal S2 is equal to or higher than the threshold value S11 (point B), the output S6 of the transmitting apparatus does not exceed the threshold value S11. Control is performed so that the power amplifier 3 does not exceed the maximum transmission power. At this time, since the amplitude of the clipping baseband signal S3 is conventionally limited only by a predetermined clipping value, when the clipping reverse band signal S3 approaches the clipping value S17, not only the instantaneous peak but also the baseband signal S2 is clipped. Distortion occurs, and the EVM deteriorates.
[0051]
On the other hand, as shown in FIG. 7B, according to the clipping method of the present invention, when the baseband signal S2 exceeds the threshold value S11 (point D), the output S6 of the transmitting apparatus does not exceed the threshold value S11. The variable attenuator 12 controls the clipping value S17 so that the difference (C) between the clipping value S17 at the threshold value S11 (point D) and the clipping baseband signal S3 is kept constant. For this reason, since only the instantaneous peak is clipped in the baseband signal S2, generation of distortion is suppressed, and deterioration of the EVM does not increase.
[0052]
As shown in FIG. 8, in the conventional clipping method, the EVM deteriorates as the power of the transmitter output S6 increases, and becomes out of specification at a power exceeding the threshold value S11. On the other hand, according to the clipping method of the present invention, the difference (C) between the clipping value S17 and the clipping inverse band signal S3 is constant even if the threshold value S11 is exceeded, so that the EVM is independent of the level of the transmitter output S6. It is constant, and the amount of EVM deterioration does not increase.
[0053]
Therefore, according to the clipping method of the present invention, the transmission power can be limited to the instantaneous maximum power (peak level) or less, and the distortion of the transmission signal can be reduced to prevent the EVM from deteriorating. Therefore, a good communication state can be maintained without increasing the EVM deterioration. Furthermore, in the present invention, the value of the baseband data S16 is set to the threshold value S11 corresponding to the maximum transmission power of the transmission power amplifier 3 in the processing of step F8, so that the bases compared in the processing of step F4 The value of the band data S16 becomes the threshold value S11, and the average transmission power data S15 is controlled so as not to exceed the threshold value S11. That is, since the average value of the output power of the transmission power amplifier 3 is suppressed to the maximum transmission power or less, the destruction of the transmission power amplifier and the operation stop of the radio base station due to a protection function such as a breaker are prevented.
[0054]
【The invention's effect】
Since the present invention is configured as described above, the following effects can be obtained.
[0055]
The clipping unit limits the amplitude value of the baseband signal according to a predetermined amplitude limit value, outputs a clipped baseband signal that is the signal after the limitation, and the comparison control unit outputs the output power of the transmission power amplifier. A control signal to be supplied to the variable attenuator is generated based on the output signal of the detector so that the average value does not exceed the maximum transmission power, and the amplitude of the baseband signal exceeds a predetermined threshold value corresponding to the maximum transmission power. In this case, by generating clipping information for controlling the amplitude limit value so that the difference between the amplitude limit value used in the clipping unit and the clipping baseband signal is constant, only the instantaneous peak of the baseband signal is clipped. Therefore, the distortion of the transmission signal is reduced.
[0056]
Therefore, the transmission power of the power amplifier can be limited to the instantaneous maximum power or less, the error vector magnitude can be prevented from deteriorating, and a good communication state can be maintained.
[0057]
Further, the attenuation of the variable attenuator is controlled based on the output signal of the detector so that the average value of the output power of the transmission power amplifier does not exceed the preset maximum transmission power. The transmission power is suppressed to be equal to or less than the maximum transmission power, and the operation stop of the radio base station due to the protection function such as the destruction of the transmission power amplifier and the breaker is prevented.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration example of a wireless base station.
FIG. 2 is a block diagram illustrating a configuration example of a transmission device according to the present invention.
FIG. 3 is a block diagram illustrating a configuration example of an addition / synthesis unit illustrated in FIG. 2;
FIG. 4 is a block diagram illustrating a configuration example of a clipping unit illustrated in FIG. 2;
FIG. 5 is a block diagram illustrating a configuration example of a comparison control unit illustrated in FIG. 2;
FIG. 6 is a flowchart showing a processing procedure of the clipping method of the present invention.
7A and 7B are diagrams for explaining the difference between the conventional clipping method and the clipping method of the present invention. FIG. 7A is a graph showing the conventional clipping method, and FIG. 7B is a diagram showing the clipping method of the present invention. It is a graph.
FIG. 8 is a graph showing a difference between an EVM according to a conventional clipping method and a clipping method according to the present invention.
FIG. 9 is a block diagram showing a cell configuration of a CDMA mobile communication system.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 radio base station 2 transmission device 3 transmission power amplifier 4 antenna 5 mobile station 6 baseband unit 7 RF unit 8 addition and synthesis unit 81 adder 9 clipping unit 91 limiter units 92 and 177 control unit 93 amplitude data detection unit 10 modulation unit 11 , 176 D / A unit 12 Variable attenuator 13 Amplifying unit 14 Coupler 15 Detector 16 A / D unit 17 Comparison control unit 171 Average value unit 172 Amplitude power conversion unit 173 Transmission power average value unit 174 Comparator 175 Operation unit 178 Base Band average value part

Claims (7)

A transmission signal to be supplied to a transmission power amplifier is generated from a baseband signal obtained by combining a plurality of transmission data, and the level of the transmission signal is adjusted so that the output power of the transmission power amplifier does not exceed a predetermined instantaneous maximum power. A transmitting device to be restricted,
A clipping unit that limits the amplitude value of the baseband signal according to a predetermined amplitude limit value, and outputs a clipping baseband signal that is the signal after the amplitude limit,
A detector for detecting the level of the transmission signal;
Attenuating the level of the transmission signal, a variable attenuator whose attenuation can be changed according to a predetermined control signal,
Generating the control signal to be supplied to the variable attenuator based on the output signal of the detector so that the average value of the output power of the transmission power amplifier does not exceed the maximum transmission power, the amplitude of the baseband signal is Clipping for controlling the amplitude limit value so that the difference between the amplitude limit value used in the clipping unit and the clipping baseband signal is constant when a predetermined threshold value corresponding to the maximum transmission power is exceeded. A comparison control unit for generating information;
A transmission device having: The clipping unit,
An amplitude data detection unit that outputs baseband amplitude data indicating an amplitude value of the clipping baseband signal,
The comparison control unit includes:
A baseband average value section that calculates an average value of the baseband amplitude data in a predetermined period and outputs average baseband power data obtained by converting the average value into power,
A comparator that compares the average baseband power data with a threshold value corresponding to the maximum transmission power, and outputs comparison data indicating a difference between the two.
Generating the clipping information for controlling the amplitude limit value such that a difference between the amplitude limit value used in the clipping unit and the clipping baseband signal is constant based on the comparison data; When the power data is equal to or less than the threshold value, the value of the average baseband power data is output as baseband data, and when the average baseband power data is greater than the threshold value, the threshold value is set to the base value. A control unit for outputting as band data,
A transmission power average value section that calculates an average value of transmission power data indicating a level of the transmission signal detected by the detector during a predetermined period, and outputs the average value as average transmission power data,
An arithmetic unit that outputs the control signal based on a difference between the baseband data and the average transmission power data so that a difference between the baseband data and the average transmission power data is minimized.
The transmitting device according to claim 1, further comprising: The control unit includes:
When the average baseband power data is equal to or less than the threshold value, an initial value set so that an error vector magnitude satisfies a predetermined standard at the time of maximum power transmission is output as the clipping information, and the average baseband power data is output. The transmitting apparatus according to claim 2, wherein when the band power data is larger than the threshold, the threshold is subtracted from the average baseband power data, and a value added to the initial value is output as the clipping information. . A transmission device according to any one of claims 1 to 3,
A power amplifier that amplifies the transmission signal to a power required for transmission,
A wireless base station having A transmission signal to be supplied to a transmission power amplifier generated from a baseband signal obtained by synthesizing a plurality of transmission data, so as to limit the output power of the transmission power amplifier so as not to exceed a predetermined instantaneous maximum power. A clipping method,
Detecting the level of the transmission signal,
Based on the detection result of the level of the transmission signal, so that the average value of the output power of the transmission power amplifier does not exceed a preset maximum transmission power, attenuate the level of the transmission signal using a variable attenuator,
The amplitude value of the baseband signal is limited according to a predetermined amplitude limit value, and when the amplitude of the baseband signal exceeds a predetermined threshold value corresponding to the maximum transmission power, the amplitude limit value and the base value are set. A clipping method for setting the amplitude limit value such that a difference between the band signal and a clipped baseband signal which is a signal after the amplitude limit is constant. Detecting the amplitude value of the clipping baseband signal, generating baseband amplitude data indicating the amplitude value,
An average value of the baseband amplitude data in a predetermined period is obtained, and average baseband power data obtained by converting the average value into power is generated.
Comparing the average baseband power data and a threshold value corresponding to the maximum transmission power, generating comparison data indicating a difference therebetween,
While setting the amplitude limit value so that the difference between the amplitude limit value and the clipping baseband signal is constant based on the comparison data, and when the average baseband power data is equal to or less than the threshold value, Output the value of the average baseband power data as baseband data, and output the threshold as the baseband data when the average baseband power data is larger than the threshold.
An average value of transmission power data indicating a level of the transmission signal detected by the detector is determined for a predetermined period, and average transmission power data indicating the average value is generated.
The clipping method according to claim 5, wherein the control signal is generated based on a difference between the baseband data and the average transmission power data so that a difference between the baseband data and the average transmission power data is minimized. When the average baseband power data is equal to or less than the threshold value, an initial value set such that an error vector magnitude satisfies a predetermined standard at the time of maximum power transmission is output as the clipping information, and the average baseband power is output. 7. The clipping method according to claim 6, wherein when the band power data is larger than the threshold, the threshold is subtracted from the average baseband power data, and a value added to the initial value is output as the clipping information. .

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