JP2012227811A - Digital radio equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means that corrects a deviation of a transmission output generated by a deviation of data to be transmitted and always keeps average power constant.SOLUTION: A modulation base band section 104 determines whether or not a present time slot is a control physical channel on transmission side. When the slot is the control physical channel on transmission side, the modulation base band section 104 notifies a gain adjuster 103 as such. The gain adjuster 103 adjusts an amplitude of a signal input into a quadrature modulator 906 to a fixed level by changing a multiplication coefficient at the control physical channel.

Description

  The present invention relates to a power amplifier using a linear digital modulation system, and more particularly to a wireless transmitter compatible with a communication protocol in which the amplitude of an output signal varies greatly due to a data symbol bias.

  Municipal digital communication system ARIB STD-T86 (Non-patent Document 1) is a radio equipment of a fixed station that performs radio communication of municipal disaster prevention radio communication using radio waves of a frequency of 60 MHz specified in Article 58-2-12 of the Radio Equipment Regulations. Is specified.

  This specification employs the TDMA / TDD system and the modulation system is defined as 16QAM. One frame of this specification is 80 ms, and 10 frames constitute one superframe. One slot includes three uplink slots (ST # 0, ST # 1, ST # 2) and three downlink slots (ST # 3, ST # 4, ST # 5). Of these, ST # 0 and ST # 3 are control physical channels, and ST # 1, ST # 2, ST # 4, and ST # 5 are communication physical channels. FIG. 1 is a frame configuration diagram showing the configuration of one frame of Non-Patent Document 1.

  In a power amplifier using a linear digital modulation system such as 16QAM or π / 4 shift QPSK, nonlinear distortion compensation of the power amplifier is indispensable. In order to realize nonlinear distortion compensation, various nonlinear distortion compensation methods (linearizers) have been proposed. Among them, the Cartesian loop negative feedback type linearizer has been used for a long time. A radio transmitter equipped with a Cartesian loop negative feedback system performs negative feedback control by dividing the transmission baseband signal into an in-phase signal and a quadrature signal.

  As a means for solving the problem of non-linear distortion compensation, JP 2009-159520 A (Patent Document 1) can be cited.

JP 2009-159520 A

ARIB STD-T86

  However, problems arise in actual operation.

  FIG. 2 shows the signal format of the control physical channel, and FIG. 3 shows the signal format of the communication physical channel. Abbreviations in each figure correspond to the following.

  In the control physical channel, the AGC preamble (AP) occupies the first half and the control signal (CAC) occupies the second half. On the other hand, in the communication physical channel, the traffic channel (TCH) is dominant in both the first and second half.

  Here, the problem is the bias of data derived from AP = 10A800080A (hexadecimal) defined in Chapter 4 of Non-Patent Document 1 (Non-Patent Document 1 FIG. 4.1.6.1-1). ). FIG. 4 is an IQ plan view for explaining the bias of the average power during transmission.

  As is clear from the figure, AP uses only symbols 0, 2, 8, and A which are the outermost symbols on the IQ plane. Therefore, the maximum output is obtained at the AP output (dashed line in FIG. 4). On the other hand, TCH which is a random signal takes an average value of all symbols (solid line in FIG. 4). As a result, the amplitude when the control physical channel is output is about 1.34 times (= 3 / √5) the amplitude when the communication physical channel is output.

  That is, when only the control channel is transmitted (when waiting for the master station, answering back from the slave station to the master station, etc.), the transmission output increases compared to the random signal. In response, the increased power is detected and the output is suppressed by APC control (automatic output control).

  In addition, when the transmission of the physical channel for communication including the TCH shifts to the control physical channel, the transmission output suddenly increases, and in some cases, it may be possible to deviate from the legal output limit before the output is detected and corrected. .

  That is, there is a problem that the deviation of the transmission output caused by the deviation of the data to be transmitted affects the power control.

  An object of the present invention is to provide means for correcting a bias in transmission output caused by a bias in data to be transmitted and keeping the average power constant at all times.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  The digital radio apparatus according to the representative embodiment of the present invention uses a modulation method having information meaning in the phase angle and amplitude amount of the symbol and data to be handled as data in which the amplitude amount of the symbol exists in each data slot. A data slot corresponding to the format includes a control unit, a modulation baseband unit, and a quadrature modulator, and a multiplier is provided for each electrical path through which the I component and Q component of the baseband transmission output signal are input to the quadrature modulator. The control unit changes the multiplication coefficient of each multiplier according to the above.

  In this digital wireless device, the multiplication coefficient changed by the control unit may be determined by a ratio between the deviation of the amplitude of the symbol and the average amplitude.

  By using the digital radio apparatus according to the present invention, it is possible to keep the average output power constant by adjusting the amplitude of the modulated wave signal of each IQ component according to the transmission channel.

It is a frame block diagram showing the structure of 1 frame of a nonpatent literature 1. This is the signal format of the control physical channel. It is a signal format of a physical channel for communication. It is IQ top view for demonstrating about the deviation of the average electric power at the time of transmission. It is a block diagram showing the structure of the transmission part of the digital radio | wireless apparatus using the negative feedback linearizer system of a fundamental Cartesian system. It is a block diagram showing the structure of the transmission part of the digital radio | wireless apparatus using the negative feedback linearizer system of the Cartesian system concerning this invention.

  In the following embodiment, when it is necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments. However, unless otherwise specified, it is not irrelevant to one another, and one is related to some or all of the other, details, supplementary explanations, and the like. Also, in the following embodiments, when referring to the number of elements (including the number, numerical value, quantity, range, etc.), especially when clearly indicated and when clearly limited to a specific number in principle, etc. Except for the specific number, the number may be more than or less than the specified number.

  Further, in the following embodiments, it is needless to say that the constituent elements are not necessarily essential unless particularly specified and apparently essential in principle.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Basic embodiment)
FIG. 5 is a block diagram illustrating a configuration of a transmission unit of a digital wireless device using a basic Cartesian negative feedback linearizer method.

  A digital radio using this negative feedback linearizer system includes a modulation baseband unit 901, adders 904 and 905, a quadrature modulator 906, an amplifier 907, a directional coupler 908, an antenna 909, a frequency synthesizer 910, and a phase shift circuit 911. A variable attenuator 912, a quadrature demodulator 913, a level detector 914, a phase shift advance / delay detector 921, a rotation direction detector 922, and a phase controller 923.

  The modulation baseband unit 901 is a module that performs modulation from a digital signal to an analog signal. In this figure, it is assumed that the component is separated into an I component and a Q component at the stage of the modulation baseband unit 901. Therefore, the output of the modulation baseband unit 901 includes an I component output and a Q component output.

  The outputs of these modulation baseband units 901 are the I component output and the Q component output, which are input to the adders 904 and 905 and the rotation direction detector 922. As an input signal to the modulation baseband unit 901, the output of the level detector 914 is raised. With reference to this, the control signal for the variable attenuator 912 is determined.

  The adder 904 is an analog adder for adding the correction output of the quadrature demodulator 913 to the I component output of the modulation baseband unit 901. The adder 905 is an analog adder for adding the correction output of the quadrature demodulator 913 to the Q component output of the modulation baseband unit 901.

  The quadrature modulator 906 is a quadrature modulator that mixes the output of the frequency synthesizer 910 and the outputs of the adders 904 and 905 with an internal mixer, removes a necessary signal component by a filter, and then combines and outputs the IQ component. .

  The amplifier 907 is an amplifier that amplifies the amplitude of the output signal of the quadrature modulator 906.

  A directional coupler (coupler) 908 is a distributor for using a single antenna 909 for transmission and reception. One of the outputs of the directional coupler 908 is input to the variable attenuator 912 and the level detector 914.

  Since the present invention focuses on feedback control of the output signal, the present specification focuses only on the distribution (extraction) of the directional coupler (coupler) 908 with respect to the modulated wave signal. In the actual configuration of the transceiver, transmission / reception distribution may be necessary, but is not particularly described in this specification.

  The antenna 909 is an antenna element that radiates radio waves into space or converts radio waves in space into high frequency energy.

  The frequency synthesizer 910 is a PLL (phase lock loop) circuit for synthesizing arbitrary frequencies and outputting them as a local oscillation frequency to a quadrature modulator or the like.

  The phase shift circuit 911 is a phase shift circuit for shifting the local oscillation frequency output from the frequency synthesizer 910 by 90 degrees and inputting it to the quadrature demodulator 913. The phase shift circuit 911 receives an output from a phase controller 923, which will be described later, so that the shift amount can be finely adjusted.

  Further, since the present invention assumes that the output signal is fed back, the quadrature demodulator 913 receives a signal having a phase opposite to that of the signal input to the quadrature modulator 906. Therefore, the phase shift circuit 911 also generates signals having the same frequency and opposite phases.

  The variable attenuator 912 is an attenuator for attenuating the signal to an appropriate amplitude amount before inputting the output of the directional coupler 908 to the quadrature demodulator 913 according to the control signal from the modulation baseband unit 901.

  The orthogonal demodulator 913 is a demodulator for separating and extracting the I component and the Q component from the input signal and confirming orthogonality. The quadrature demodulator 913 returns the output of the directional coupler 908 attenuated by the attenuator 912 to baseband.

  The signals (I component feedback signal and Q component feedback signal) returned to the baseband by the quadrature demodulator 913 are output to the adders 904 and 905. These I component feedback signal and Q component feedback signal are added by each adder, and the transmission baseband signal after the addition is input to the quadrature modulator 906.

  The level detector 914 is a level detector for detecting the level of the modulated wave signal extracted by the directional coupler 908.

  The detection result of the level detector 914 is input to the modulation baseband unit 901. The CPU of the modulation baseband unit 901 outputs a control signal in order to finely adjust the attenuation rate of the variable attenuator 913 with reference to these.

  The modulation baseband unit 901 also detects an output power abnormality by looking at the output level that is the detection result of the level detector 914.

  The phase shift advance / delay detector 921 detects the phase of the Q component output output from the modulation baseband unit 901 and the phase of the Q component output after addition by the adder 905, respectively. Detect late.

  The rotation direction detector 922 confirms whether the I component output and Q component output output from the modulation baseband unit 901 maintain orthogonality.

  The phase controller 923 is a circuit that adjusts the phase shift amount of the phase shift circuit 911 with reference to the outputs of the phase shift advance / delay detector 921 and the rotation direction detector 922. As an output of the phase controller 923, a control signal for the phase shift circuit 911 is also output. A control unit such as a CPU is also included in the phase controller 923 for controlling the control signal.

  In such negative feedback, in order to stabilize the system, the I component output of the adder 904 and the input signal of the adder 905, the Q component output, the I component feedback signal for the feedback signal, and the phase of the Q component feedback signal are in phase. Need to be. The phase shift circuit 911 performs fine adjustment of the phase based on the control signal of the phase controller 923.

(Embodiment of the present invention)
FIG. 6 is a block diagram showing a configuration of a transmission unit of a digital wireless device using the Cartesian negative feedback linearizer method according to the present invention.

  The present embodiment is characterized in that it includes multipliers 101 and 102 and a gain adjuster 103 in addition to the configuration of FIG. Further, the modulation baseband unit 901 is replaced with the modulation baseband unit 104.

  Note that the phase shift advance / delay detector 921, the rotation direction detector 922, and the phase controller 923 illustrated in FIG. 5 are provided in the modulation baseband unit 901, and control lines are provided in the modulation baseband unit 901 for control. It is also possible to control the line from the modulation baseband unit 901. In FIG. 6, in order to clarify the features of the present invention in consideration of the above, it is assumed that a phase shift advance / delay detector 921, a rotation direction detector 922, and a phase controller 923 are provided in the modulation baseband unit. The description related to these was simplified.

  The multipliers 101 and 102 are analog multiplier circuits that are electrically disposed between the modulation baseband unit 104 (input side) and the adders 904 and 905 (output side). Further, the input terminals of the multipliers 101 and 102 are connected to the gain adjuster 103, respectively.

  The gain adjuster 103 receives a control signal from the modulation baseband unit 104 and outputs a predetermined voltage to the multipliers 101 and 102. A voltage applied from the gain adjuster 103 to the multipliers 101 and 102 becomes a multiplication coefficient.

  The modulation baseband unit 104 according to the present invention has a function of determining whether or not the current slot in the frame is a control physical channel (specifically, # 3 in FIG. 1) at the time of transmission. As a means at this time, the recognition may be performed by an input from a module that controls an upper communication layer. Further, the modulation baseband unit 104 may voluntarily determine a slot by managing input / output slots and time.

  At this time, the slot control signal input from the modulation baseband unit 104 to the gain adjuster 103 is slot information indicating whether the control physical channel is currently being transmitted. The transmission output is changed accordingly. The specific method of change is as follows.

  As already described, during transmission of the control physical channel, the average power output from the antenna 909 increases compared to the communication physical channel due to the fixed value of the AGC preamble (AP).

  In order to avoid this, when the slot information (= slot control signal) from the modulation baseband unit 104 indicates that the control physical channel is being transmitted, the gain adjuster 103 sets the amplitude of the output signal to the communication physical channel. It is reduced to about 0.75 times (= √5 / 3) from the amplitude at the time. In order to execute this, the gain adjuster 103 can realize this by reducing the voltage output to the multipliers 101 and 102 by about 0.75 times.

  By taking these measures, the output power from the antenna 909 can be kept constant.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

  For example, in the above description, it has been described that the amplitude of the output of the antenna 909 increases during transmission of the control physical channel. On the other hand, the present invention can be applied even when the amplitude of the output of the antenna 909 becomes small during transmission of a specific channel. In this case, the output voltage of the gain adjuster 103 is increased during transmission of the specific channel. Such a case is also included in the range of the present invention.

  Further, in the above description, slot # 3 in FIG. 1 is searched for considering application in a mobile station. However, the present invention may be applied to the base station side, and in this case, it is necessary to search for slot # 0 in FIG.

  In the above description, the gain adjuster 103 is provided for the purpose of explanation, and the input voltage of the multipliers 101 and 102 is determined. However, it goes without saying that including the gain adjuster 103 in the modulation baseband unit 104 and including the multipliers 101 and 102 in the modulation baseband unit 104 are also included in the range of the present invention.

  Furthermore, in the above description, the description has been made as an improvement of the transmission unit of the digital radio using the negative feedback linearizer system. However, the range of the present invention includes changing the coefficient at the time of amplification for each data slot without performing correction by negative feedback.

  Furthermore, the circuit configuration may be performed by using the control CPU included in the modulation baseband unit 104 as an independent module “control unit”.

  In the above, the invention has been described in a form specialized for ARIB STD-T86. However, the present invention is not limited to this, and the present invention can be applied to any communication system in which power is increased (or decreased) by biasing data symbols of transmission data.

101, 102 ... multiplier, 103 ... gain adjuster,
104, 901 ... modulation baseband unit, 904, 905 ... adder, 906 ... quadrature modulator,
907 ... Amplifier, 908 ... Directional coupler, 909 ... Antenna,
910 ... Frequency synthesizer, 911 ... Phase shift circuit, 912 ... Variable attenuator,
913: Quadrature demodulator, 914: Level detector.

Claims (2)

The modulation method having information meaning in the phase angle and amplitude amount of the symbol and the data to be handled correspond to the data format in which the amplitude amount of the symbol exists in each data slot, and the control unit, the modulation baseband unit and the quadrature modulator In digital radio including
A multiplier is provided for each electrical path through which the I component and Q component of the baseband transmission output signal are input to the quadrature modulator,
The digital radio device, wherein the control unit changes a multiplication coefficient of each multiplier according to the data slot. 2. The digital radio according to claim 1, wherein the multiplication coefficient changed by the control unit is determined by a ratio between a bias of an amplitude amount of the symbol and an average amplitude amount.

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