JP2008205858A - Distortion compensating device of power amplifier and distortion compensating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a distortion compensating device of a power amplifier capable of compensating a distortion characteristic in a power amplifier with high accuracy after simplifying a circuit. <P>SOLUTION: A distortion detecting part C acquires an input RF signal and an output RF signal of an amplifying part 3, detects an amplitude difference, a phase difference between the both signals and a distortion component are detected, and the distortion component is inputted to a digital part A. The digital part A sequentially selects a compensation amount corresponding to an amplitude value of the input RF signal of the amplifying part 3 among compensation amounts registered in a lookup table 24, and a distortion compensating part B compensates the input RF signal with the compensation amount and outputs the input RF signal to the amplifying part 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a distortion compensation apparatus and a distortion compensation method for a power amplifier that are used in, for example, a transmission apparatus of a digital wireless communication / broadcasting system and compensate for nonlinear distortion generated in the power amplifier of the transmission apparatus.

Terrestrial digital repeaters are sequentially placed at each transmitting station. By the way, the transmission signal transmitted from each transmitting station is influenced by nonlinear distortion by the power amplifier. Accordingly, a predistortion type distortion compensation method that suppresses this nonlinear distortion by providing a compensator that detects and corrects the nonlinear distortion at each transmitting station has been considered (for example, Patent Document 1). .
JP-A-2005-12419.

  By the way, the compensator requires a reference signal inside, requires a plurality of analog BPFs (band-pass filters), requires a digital high-speed device, and has a problem of high performance, low price, It is difficult to achieve high efficiency at the same time.

  Each transmitting station requires regular maintenance in order to maintain high accuracy of the compensation processing. This maintenance work is performed, for example, by adjusting a local oscillator that generates a reference signal for each channel.

  However, since the maintenance person goes to each transmitting station and manually adjusts the adjustment work, the maintenance takes a lot of time and effort.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a power amplifier distortion compensating apparatus and a distortion compensating method capable of compensating for distortion characteristics in a power amplifier with high accuracy while simplifying a circuit.

In order to achieve the above object, a distortion compensating apparatus for a power amplifier according to the present invention comprises a phase error and an amplitude error in the amplifier from an input RF (Radio Frequency) signal and an output RF signal of the power amplifier for which distortion compensation is required. And a distortion correction unit that generates a distortion compensation amount from the distortion component detected by the distortion detection unit and compensates an input RF signal of the power amplifier with the distortion compensation amount. It is what I did.

  The distortion correction means includes a compensation amount table for registering the distortion compensation amount in association with the amplitude information of the input RF signal of the power amplifier. From this compensation amount table, the distortion compensation amount corresponding to the amplitude information of the input RF signal is obtained. It is characterized in that it is read out and the input RF signal of the power amplifier is compensated with the distortion compensation amount.

  According to this configuration, the input RF signal and output RF signal of the power amplifier are taken in, and the amplitude error and phase error of both signals are detected as distortion components, so the distortion correction unit is shared by multiple channels. In this distortion correction unit, the compensation amount corresponding to the amplitude information of the input RF signal is sequentially selected from the compensation amounts registered in the compensation table, and the input RF signal is compensated with this compensation amount. As a result, the RF signal can be input to the power amplifier with a characteristic opposite to the distortion characteristic of the power amplifier, and the distortion component of the RF output can be compensated.

  Therefore, the distortion characteristic in the power amplifier can be compensated with high accuracy while simplifying the circuit.

  As described above in detail, according to the present invention, it is possible to provide a distortion compensation device and a distortion compensation method for a power amplifier that can compensate for distortion characteristics in the power amplifier with high accuracy while simplifying the circuit. .

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a configuration of a transmission apparatus applied to the present invention. An analog RF signal input to an input terminal 1 is amplified in power by an amplifier 3 via a distortion compensator 2 according to the present invention. A transmission signal is output via the output terminal 4.

  In the distortion compensator 2, the analog RF signal input to the input terminal 1 is distributed into two by the distributor 21, one is supplied to the delay adjustment unit (delay line) 22, and the other is A of the digital unit A. After being converted into a digital amplitude value by a / D (analog / digital) converter 23, it is supplied to a lookup table 24. The delay adjusting unit 22 delays the analog RF signal for a predetermined time. The analog RF signal delayed by the delay adjusting unit 22 is distributed to two by the distributor 25, one is supplied to the distortion compensator B, and the other is distributed to two by the distributor 26, and then the distortion detecting unit. C is supplied.

  Also, the distortion detection unit C is supplied with an RF signal obtained by distributing the RF output of the amplification unit 3 into two by the distributor 27. As shown in FIG. 2, the distortion detector C takes the analog RF signal from the distributor 26 and the analog RF signal from the distributor 27 into the log amplifiers 41 and 42, respectively, and then uses the phase detector 43 to While obtaining the phase error, the gain detector 44 obtains both amplitude errors. The amplitude error ΔG and the phase error Δθ obtained here are supplied to the digital unit A.

  The digital unit A converts the amplitude error ΔG and the phase error Δθ from the distortion detection unit C into digital values by the A / D converters 28 and 29, respectively, and registers the digital values in the lookup table 24 as distortion compensation amounts. Keep it. An example of the lookup table 24 is shown in FIG. FIG. 3 shows a characteristic diagram of the compensation amounts G and θ stored in the lookup table 24.

  On the other hand, the digital unit A converts the analog RF signal from the distributor 21 into a digital value by the A / D converter 23, and then calculates the distortion compensation amount (ΔG, Δθ) corresponding to the value of R in the lookup table 24. And the compensation amount is converted into an analog signal by the D / A converters 30 and 31, respectively, and then output to the distortion compensator B.

  The distortion compensation unit B includes an amplitude compensation unit 32 and a phase compensation unit 33. Then, the analog RF signal from the distributor 25 is compensated by the distortion compensation amount from the digital part A and output to the amplifying part 3.

Next, operation in the above configuration will be described.
Previously, the transmission apparatus shown in FIG. 4 was considered. In FIG. 4, the same parts as those in FIG.

  That is, in the previous transmission device, the input RF signal and output RF signal of the amplifying unit 3 are converted into IF signals using the reference signal of the local oscillator 53 by the frequency converting units 51 and 52, respectively, and then the bandpass filters 54 and 55 are used. To the digital part A.

  In this case, it is necessary to drop the signal to the baseband using the reference signal, and the circuit scale is large and the price cannot be reduced.

  In addition, adjustment for each channel of the local oscillator 53 and the bandpass filters 54 and 55 must be performed.

  Therefore, in the present embodiment, the distortion detector C detects the amplitude error and the phase error between the input RF signal and the output RF signal of the amplifier 3, so that a local oscillator and a bandpass filter are not required. .

  As described above, in the above-described embodiment, the distortion detection unit C takes in the input RF signal and output RF signal of the amplification unit 3, detects the amplitude error and phase error of both signals, and detects the distortion component. Is input to the digital part A. The digital unit A sequentially selects a compensation amount corresponding to the amplitude value of the input RF signal of the amplification unit 3 from the compensation amounts registered in the lookup table 24, and the distortion compensation unit B uses this compensation amount for the input RF signal. Is output to the amplifying unit 3. Thereby, the RF signal can be input to the amplifying unit 3 with a characteristic opposite to the distortion characteristic of the amplifying unit 3, and the distortion component of the RF output can be compensated.

  Therefore, it is possible to compensate the distortion characteristics in the amplifying unit 3 with high accuracy while simplifying the circuit.

  Although the present invention has been described based on the embodiments, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, although the distortion compensator 2 has been described with a hardware configuration in the above-described embodiment, it can be realized with a software configuration.

The block diagram which shows the structure of the transmitter applied to this invention. The circuit block diagram which shows the specific structure of the distortion detection part shown in FIG. FIG. 4 is a characteristic diagram of compensation amounts stored in the lookup table shown in FIG. 1. The block diagram which shows the structure of the transmitter considered before.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Input terminal, 2 ... Distortion compensator, 3 ... Amplification part, 4 ... Output terminal, 21, 25, 26, 27 ... Distributor, 22 ... Delay adjustment part, 23, 28, 29 ... A / D converter, 24 ... Look-up table, 30, 31 ... D / A converter, 32 ... Amplitude compensator, 33 ... Phase compensator, A ... Digital part, B ... Distortion compensator, C ... Distortion detector.

Claims (3)

Distortion detecting means for detecting a distortion component of a phase error and an amplitude error in the power amplifier from an input RF (Radio Frequency) signal and an output RF signal of the power amplifier for which distortion compensation is required;
Distortion compensation for a power amplifier, comprising distortion compensation means for generating a distortion compensation amount from the distortion component detected by the distortion detection means, and compensating the input RF signal of the power amplifier with the distortion compensation amount. apparatus. The distortion correction means includes a compensation amount table for registering the distortion compensation amount in association with amplitude information and phase information of the input RF signal of the power amplifier. From the compensation amount table, amplitude information and phase information of the input RF signal are registered. The distortion compensation apparatus for a power amplifier according to claim 1, wherein the distortion compensation amount corresponding to is read and the input RF signal of the power amplifier is compensated with the distortion compensation amount. Applied to a distortion compensation device that performs distortion compensation of a power amplifier,
A distortion detecting step of detecting a distortion component of a phase error and an amplitude error in the power amplifier from an input RF (Radio Frequency) signal and an output RF signal of the power amplifier;
A distortion compensation method, comprising: generating a distortion compensation amount from the distortion component detected in the distortion detection step; and compensating the input RF signal of the power amplifier with the distortion compensation amount.

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