JP4576221B2 - Power series predistorter for multi-frequency band - Google Patents

Description

  The present invention relates to a predistorter that compensates for distortion of a power amplifier that amplifies a high-frequency signal, and more particularly to a power series predistorter for a multi-frequency band that can realize distortion compensation for a plurality of high-frequency signals in a plurality of bands.

One of the nonlinear distortion compensation methods for microwave power amplifiers is a predistortion method using digital signal processing (hereinafter referred to as digital predistortion method) (for example, Patent Document 1). A feature of the digital predistortion method is that a complicated analog circuit is not required by enabling a predistorter configuration by digital signal processing.
To date, digital predistorters have been known to have a look-up table having a table for previously linearizing the nonlinear characteristics of an amplifier (for example, Non-Patent Document 1 and Patent Document 2). A digital predistorter having a look-up table feeds back an amplifier output signal and updates a set value of the look-up table so that a distortion component becomes a design value or less. In this manner, it is known that distortion compensation can be performed by digital signal processing. It is known that the distortion compensation amount is about 15 dB or less (Non-Patent Document 2).

There is a predistorter based on a power series model. So far, it has been realized by an analog circuit, and the distortion improvement amount has reached 30 dB or more (Non-Patent Document 3). It is known that the power series model accurately models the nonlinear characteristics of an amplifier (for example, Non-Patent Document 4). In a distortion compensation method in a digital predistorter using a power series model, it is necessary to extract a signal for correcting each order coefficient from an amplifier output signal. So far, in Patent Document 1, the correction signal is extracted by removing the fundamental wave and each distortion component from the transmission signal. As a method of extracting a correction signal for a power series model more simply, there is a method of using two equal level output waves as pilot signals (Non-patent Document 3).
British Patent Application No. 2,335,812 Special Table 2002-522989 H. Girard, and K. Feher, “A new baseband linearizer for mre efficient utilization of earth station amplifiers used for QPSK transmission”, IEEE J. Select. Areas Commun. SAC-1, No. 1, 1983. Ishikawa, Hase, Kubo, Tozawa, Kanno, “Development of Adaptive Distortion Compensator for W-CDMA Base Station”, Society Conference of IEICE, C-2-31, 2002.09. T.Nojima, and T.Knno, “Cuber predistortion linearizer for relay equipment in 800MHz band land mobile telephone system”, IEEE Trans. Vech. Tech., Vol. VT-34, No. 4, pp.169-177, 1985 11. Tri T. Ha, Solid-State Microwave amplifier Design, Chapter 6, Krieger Publishing Company, 1991.

  In a method of simultaneously serving mobile radio in a plurality of discrete frequency bands, a predistorter adapted to each frequency band is required. However, in the configuration of the conventional predistorter mentioned in the background section, the frequency range that can be adjusted is about 20 MHz, centering on the carrier frequency, and the 800 MHz band and the 1.5 MHz like PDC (Personal Digital Cellular). Predetermined distortion compensation could not be achieved while simultaneously performing distortion compensation on transmission signals in a plurality of GHz bands. Conventional predistorters do not include a distortion generation path that collectively performs distortion compensation in accordance with each transmission frequency band. For this reason, it has not been possible to adjust to achieve a sufficient amount of distortion compensation in a plurality of frequency bands. If predistortion processing of a plurality of frequency bands can be performed at once, the apparatus can be simplified, reduced in power consumption, and reduced in size.

  In addition, there is a method of configuring a power series predistorter having distortion generating means corresponding to a plurality of frequency bands by using a common delay line of a power series predistorter. In such a method in which a plurality of power series predistorters are configured in parallel, transmission signals of a plurality of frequency bands are input to the respective distortion generating means. Each distortion generator adjusts the amplitude and phase of the input transmission signal so as to perform distortion compensation for each frequency band. However, when the transmission signal input to the distortion generating means is a transmission signal in a plurality of frequency bands, the optimum amplitude and phase cannot be adjusted for the transmission signals in each frequency band. For example, if the transmission signal is 800 MHz and 1.5 GHz, the distortion generator can set the optimum amplitude and phase for the 800 MHz band, but the optimum amplitude for the 1.5 GHz band with a difference frequency of 700 MHz. To set the phase, an amplitude and phase setting means capable of high-speed operation that follows the difference frequency of 700 MHz is required. However, there is no such high-speed amplitude / phase setting means. As described above, even if a plurality of series predistorters that should operate in the respective frequency bands are used, a series predistorter that should operate in a plurality of frequency bands cannot be configured.

According to the present invention, there is provided a distortion generation path having a band signal extractor configured by a band rejection filter that extracts a signal of each frequency band, and a distortion generator that generates an odd-order component of the extracted signal. Provided corresponding to multiple frequency bands, distributes input signal to linear signal path and these multiple distortion generation paths, and synthesizes the outputs of those paths to output power series predistorter for multi-frequency band . In this way, a predistorter that independently performs distortion compensation in a plurality of frequency bands is configured.

According to the power series predistorter according to the present invention, a plurality of band signals are frequency-separated for each band, odd-order distortion is generated for each frequency band, and distortion components generated in the power amplifier are suppressed by the distortion components. As described above, the frequency band is adjusted for each frequency band, combined with the transmission signal, and input to the power amplifier. As a result, odd-order distortion components in each frequency band on the output side of the power amplifier are removed.
That is, the amount of distortion compensation can be adjusted independently for each frequency band, and the amount of distortion compensation in a plurality of frequency bands can be processed collectively. Therefore, according to the present invention, it is possible to simplify the apparatus, reduce power consumption, and reduce the size.

First Embodiment FIG. 1 shows the best mode for carrying out the present invention. The predistorter includes a controller 31 and predistortion circuit 100, predistortion circuit 100, a linear signal transfer path P _L, a first third-order distortion generating path P _D1 for frequency band, a second frequency A band third-order distortion generation path _PD2 and combiners 14A and 14B for combining output signals of these paths are included. The predistorter shown in FIG. 1 is realized by digital signal processing, and corresponds to first and second frequency bands (represented by center frequencies f1 and f2). If applied to mobile radio, f1 can be set to, for example, the 800 MHz band, and f2 can be set to, for example, the 1.5 GHz band. As another example, f1 may be a 1.5 GHz band and f2 may be a 2 GHz band. Furthermore, the number of frequency bands is not limited to two, and any number of two or more can be applied. Further, a fifth-order or higher-order distortion generator may be added to the distortion generation path of each frequency band.

Transmission signal S _T is distributed to the linear signal transfer path P _L and the first and second distortion generating path P corresponding to two frequency bands _D1, P _D2. The first distortion generating path P _D1 and band signal extractors 11-1 of the first frequency band, a third-order distortion generator X3-1, is constituted by cascade connection of the vector adjuster V3-1. The second distortion generating path P _D2 and the band signal extractors 11-2 of the second frequency band, a third-order distortion generator X3-2, is constituted by cascade connection of the vector adjuster V3-2. Outputs of the first and second distortion generating paths are combined by combiner 14B, the combined result is combined with the output of the linear signal transfer path P _L at the combiner 14A. Here, the delay circuit 10D of the linear signal transmission path P _L can be constituted by a memory such as a shift register, and in the case of an analog predistorter described later, can be constituted by a delay line. The two band signal extractors 11-1 and 11-2 may be configured with a band pass filter or a band rejection filter.

The band signal having the center frequency f1 extracted by the band signal extractor 11-1 is supplied to the third-order distortion generator X3-1. The third-order distortion generator X3-1 generates third-order distortion of the transmission signal in the band of the center frequency f1. The vector adjuster V3-1 is composed of a cascade circuit of a variable attenuator VA-1 and a variable phase shifter VP-1, and the level of the third-order distortion signal generated by the third-order distortion generator X3-1 is the output of the predistorter. The controller 31 performs initial setting so that the amplitude coincides with the third-order distortion component generated in a power amplifier (not shown) connected to the side, and the phase is opposite, and the controller 31 maintains the initial setting state. Control.
Similarly, the band signal of the center frequency f2 extracted by the band signal extractor 11-2 is supplied to the third-order distortion generator X3-2 to generate the third-order distortion component of the transmission signal of the frequency band f2. This third-order distortion component is also equal in amplitude to the third-order distortion component in the band f2 generated in the power amplifier by the vector adjuster V3-2 configured by cascading the variable attenuator VA-2 and the variable phase shifter VP-2. Initial setting is performed so that the phase is reversed, and control is performed by the controller 31 so as to maintain the set state.

The distortion components generated in the first and second distortion generation paths P _D1 and P _D2 are synthesized by the synthesizer 14B, and synthesized by the synthesizer 14A with the delayed transmission signal from the linear signal transmission path P _L. The analog signal is converted into an analog signal by an analog converter (DAC) 21, and the analog signal is output as an output signal of a digital predistorter. Although not specifically shown, this analog signal is amplified by a power amplifier and radiated as a radio wave from a transmitting antenna.
A part of the transmission signal amplified by the power amplifier is extracted by, for example, a directional coupler, the distortion component of the transmission signal is detected by the signal detector 28, and converted into a digital signal by the analog / digital converter (ADC) 29. The digital signal is converted and input to the controller 31.

The controller 31 controls the vector adjusters V3-1 and V3-2, and adjusts the vector so that the third-order distortion components of the frequency bands f1 and f2 of the transmission signal fed back through the analog / digital converter 29 are minimized. Controls V3-1 and V3-2. For this purpose, the signal detector 28 includes a band signal extractor for extracting the frequency bands f1 and f2.
The characteristics of the band signal extractors 11-1 and 11-2 have desired bandwidths whose center frequencies are f1 and f2, respectively, and extract signals of the first and second frequency bands, respectively. Each such band signal extractor may be constituted by, for example, a band pass filter (band bus filter: BPF), or may be constituted by a band rejection filter (band elimination filter: BEF). In the embodiment of FIG. 1, the case where third-order distortion is generated in the distortion generation paths P _D1 and P _D2 is shown as the case where third-order distortion of the power amplifier is compensated. It is configured to generate the same odd-order distortion as the second-order distortion.

FIG. 2 conceptually shows the frequency vs. attenuation characteristics in the case where the band signal extractors 11-1 and 11-2 are constituted by bandpass filters, respectively, as a solid line and a broken line. It is necessary that the attenuation increases sharply outside the frequency bands of the center frequencies f1 and f2, respectively, and that the separation between the frequency bands is sufficient. Such characteristics can generally be obtained by cascading a plurality of band-pass filters.
FIG. 3 shows frequency vs. attenuation characteristics when, for example, the frequency band extractor 11-1 is configured by a band rejection filter. However, this example is applied to the first band signal extractor 11-1 in the case where the third and fourth distortion generation paths having center frequencies f3 and f4 are further added to the predistorter of FIG. It conceptually shows the required properties. As apparent from FIG. 3, this characteristic is obtained by three band rejection filters BEF1, BEF2, which respectively block the second, third, and fourth frequency bands f2, f3, f4 other than the first frequency band f1. BEF3 can be formed by cascade connection as shown in FIG. Each band rejection filter is configured to have a sufficient band rejection characteristic in the band and a sufficiently low loss pass characteristic in the other band. Each such band rejection filter can be constituted by a notch filter, for example. As the notch filter, a band rejection filter using a dielectric resonator, a filter using a stub by a microstrip line, or the like can be applied. Although not shown in the figure, similarly, the characteristics of the second band signal extractor 11-2 are formed by cascading three band rejection filters that respectively block the other first, third, and fourth frequency bands. Can do. The same applies to band signal extractors of third and fourth frequencies not shown.

When each frequency band extractor is composed of a band pass filter, there are advantages that it is easy to extract the periphery of the center frequency band and that it is relatively easy to isolate from the center frequency. However, since the center frequency is the resonance frequency of the bandpass filter, the signal delay increases. Therefore, it is necessary to increase the delay amount of the delay circuit 10D constituting the linear signal path in FIG. 1 in accordance with the delay amount, thereby reducing the stability of the predistorter. In particular, when the predistorter is configured by an analog circuit as will be described later, the delay line constituting the delay circuit 10D of the linear signal transmission path P _L becomes longer, and the signal attenuation increases. When each frequency band extractor is composed of a band rejection filter, the signal is sufficiently separated from the center frequency in the frequency band to be extracted, so that the delay is small. Therefore, the line length of the linear signal path 10 is short, and there is an advantage of low loss. Furthermore, the design of the band rejection filter is easy.

Also in all the following embodiments, each band signal extractor may be configured by a band pass filter or a band rejection filter.
Second Embodiment FIG. 5 shows a second embodiment of the predistorter according to the present invention. In this embodiment, a predistorter is constituted by an analog circuit and intermediate frequency signals S _T1 and S _T2 having center frequencies f1 and f2 are input from transmitters T-1 and T-. It is assumed that the center frequencies f1 and f2 of the transmission signals S _T1 and S _T2 are separated from each other by several hundred MHz, which is sufficiently larger than the bandwidth of each band. Further, in this embodiment, in order to compensate the third-order distortion and fifth-order distortion of the power amplifier 25, the distortion generation paths P _D1 and P _D2 of the frequency bands f1 and f2 generate third-order distortion and fifth-order distortion. It is configured.

The distributor 10A at the input of the analog predistortion circuit 100 is composed of a directional coupler or power distributor having a wide band (more than the bandwidth of the input signal). The distortion generation path P _D1 is provided with a band signal extractor 11-1 for extracting a signal of the frequency band f1, a distributor 12-1 for distributing the extracted signal into two, and one of the two distributions, and the third-order distortion. The third-order distortion generator X3-1 is generated, the other of the two distributions is given, the fifth-order distortion generator X5-1 that generates the fifth-order distortion, and the outputs of these distortion generators X3-1 and X5-1 Vector adjusters V3-1 and V5-1 that adjust the phase and amplitude, and a combiner 13-1 that combines the outputs of the vector adjusters V3-1 and V5-1 are included.

Similarly, the distortion generation path P _D2 is provided with a band signal extractor 11-2 that extracts a signal of the frequency band f2, a distributor 12-2 that distributes the extracted signal into two, and one of the two distributions. A third-order distortion generator X3-2 that generates the third-order distortion of the transmission signal in band f2 and a fifth-order distortion generator X5- that generates the fifth-order distortion of the transmission signal in frequency band f2 given the other of the two distributions. 2, vector adjusters V3-2, V5-2 for adjusting the phase and amplitude of the third-order distortion and fifth-order distortion components of the outputs of the distortion generators X3-2, X5-2, and their vector adjusters And a synthesizer 13-2 that synthesizes the outputs of V3-2 and V5-2. The output of the combiner 13-1 and 13-2 are combined by combiner 14B, synthesis result is combined with the output of the linear signal transfer path P _L. As a result, the third-order distortion and the fifth-order distortion generated in the respective frequency bands are added as predistortions to the transmission signals in the frequency bands f1, f2 transmitted through the linear signal transmission path.

These vector adjusters V3-1, V5-1, and V3-2, V5-2 also have distortion components generated by the distortion generators X3-1, X5-1, X3-2, and X5-2 in each frequency band. It is provided for initial setting so that the amplitude matches the third-order distortion component and the fifth-order distortion component generated by the power amplifier 25 at f1 and f2, and the phase is opposite. This initial setting state is maintained by the control operation of the controller 31.
The output signal of the analog predistortion circuit 100 is frequency-converted to a predetermined transmission frequency band by the carrier signal from the local oscillator 24 by the frequency converter 23 and is given to the power amplifier 25. The output of the power amplifier 25 is sent to a transmission / reception duplexer (not shown), and a part of the output is distributed by a distributor 26 as a signal extracting means and supplied to a signal detector 28. The signal detector 28 detects third-order and fifth-order distortions generated by the power amplifier 25 related to the transmission signals S _T1 and S _T2 and supplies them to the controller 31. The controller 31 adjusts the vector adjusters V3-1, V5-1, V3-2, and V5-2 so that the detected third-order and fifth-order distortions are minimized. As a result, the predistortion added by the analog predistortion circuit 100 for each frequency band cancels the distortion generated when the power amplifier 25 amplifies transmission signals of different frequency bands.

Intermodulation distortion caused by transmission signals in a plurality of transmission frequency bands occurs at each frequency interval. Even if such intermodulation distortion occurs, it can be easily performed by a duplexer or a band-pass filter at the output of the power amplifier 25. Can be removed. The band signal extractors 11-1 and 11-2 in the second embodiment may be realized by a combination of directional couplers.
In this embodiment, a case where third-order distortion and fifth-order distortion are generated in each frequency band f1, f2 is shown, but the distortion to be generated also depends on the characteristics of the power amplifier 25 to be compensated, and is 7 as necessary. A second distortion component is also generated, or a combination of distortions other than the above-described third and fifth orders is generated. Such a configuration can be easily developed from FIG. Furthermore, in the present embodiment, the number of frequency bands is two, f1 and f2, but the above configuration can be easily expanded to further increase the frequency bands. These also apply to other embodiments described later.
Third Embodiment FIG. 6 shows a third embodiment of the predistorter according to the present invention. In this embodiment, the analog predistorter of FIG. 5 is realized by digital signal processing, and each signal system is constituted by a pair of an in-phase signal (I signal) and a quadrature signal (Q signal). . Also in this embodiment, the predistortion circuit 100 extracts a band signal by a distributor 10A for distributing an input signal, a linear signal transmission path P _L constituted by a delay circuit 10D, and digital signal processing for extracting a signal in the frequency band f1. 11-1, a band signal extractor 11-2 by digital signal processing for extracting a signal in frequency band f2, and third and fifth order distortions for generating third and fifth order distortions in frequency bands f1 and f2, respectively. Generators X3-1, X5-1 and X3-2, X5-2, and vector adjusters V3-1, V5-1, V3-2, and V5-2 are provided.

Each synthesizer 13-1, 13-2, 14A, 14B in FIG. 5 is constituted by an adder in FIG. The signal detector detects the pilot signal and outputs an in-phase component (I signal) and a quadrature component (Q signal). These signals are converted into digital signals by the analog / digital converters 29I and 29Q, respectively, and supplied to the controller 31. The controller 31 adjusts the vector adjusters V3-1, V5-1 and V3-2, V5-2 so that the detected distortion detection level is minimized.
It is assumed that the center frequencies f1 and f2 of the input signal are separated from each other by several hundred MHz, which is sufficiently larger than the bandwidth of each band. The distributor 10A at the input of the digital predistorter is configured by a combination of bandpass filters based on digital signal processing. Band signal extractors 11-1 and 11-2 extract only signals in frequency bands f1 and f2, respectively. In this example, the signal of the frequency band f1 extracted by the band signal extractor 11-1 is supplied to odd-order distortion generators X3-1 and X5-1 that generate third-order and fifth-order distortion signals, respectively. Third and fifth order distortions are generated. The amplitude and phase of these third-order and fifth-order distortions are adjusted by the controller 31 as described above in the vector adjusters V3-1 and V5-1 using the variable phase shifter and variable attenuator.

Similarly, the signal in the frequency band f2 extracted by the band signal extractor 11-2 is supplied to odd-order distortion generators X3-2 and X5-2 that generate third-order and fifth-order distortion signals, respectively. Second and fifth order distortions are generated. The third-order and fifth-order distortions are adjusted by the controller 31 in amplitude and phase in vector adjusters V3-2 and V5-2 using a variable phase shifter and variable attenuator.
The third-order and fifth-order distortion signals generated by the distortion generation paths P _D1 and P _D2 in the frequency bands f1 and f2 in this way are synthesized by the adders 13-1, 13-2, 14B, and the adder 14A It is synthesized with the transmission signal of the linear signal transmission path P _L. The synthesized signal is converted into an analog signal by digital / analog converters 21-1 and 21-2. The analog signal is orthogonally modulated by the vector modulator 22, frequency-converted to a predetermined transmission frequency band by the frequency converter 23 using the carrier signal having the frequency f _C from the local oscillator 24, and amplified by the power amplifier 25. At this time, the third-order and fifth-order distortion signals added by the digital predistortion circuit 100 for each frequency band are canceled with the distortion components generated by the power amplifier 25. In addition, intermodulation distortion occurs at each frequency interval due to the transmission signals of multiple transmission frequency bands f1 and f2, but even if such intermodulation distortion occurs, it is outside the transmission signal frequency band, and the power amplifier output Can be easily removed with a duplexer or a band-pass filter.

In this embodiment, the number of frequency bands of the transmission signal is 2, but the number of frequency bands of 2 or more can be easily expanded using the above configuration.
Fourth Embodiment FIG. 7 shows a fourth embodiment of the predistorter according to the present invention. This embodiment is an embodiment of the analog predistorter shown in FIG. 5, which enables automatic adjustment of the vector adjusters V3-1, V5-1, V3-2, and V5-2 using a pilot signal. It is. In this embodiment, the signal generator 32-1 as a signal generating means for generating a pilot signal S _P1, S _P2 of the respective frequency bands f1, f2, and 32-2 pilot signals of two frequency bands S _P1, As a synthesizer 33 for synthesizing S _P2 , a synthesizer 8 for adding the synthesized pilot signal to the transmission signal and injecting it into the predistortion circuit 100, and a signal extraction means for distributing a part of the output of the power amplifier 25 Distributor 26, distributor 27 that distributes the distributed signal into two systems, and signal detection as a signal detection means that detects the distortion components of the pilot signals of frequency bands f1 and f2 from the two distributed signals, respectively. Devices 28-1 and 28-2 have been added. The distortion components detected by the signal detectors 28-1 and 28-2 are separately supplied to the two controllers 31-1 and 31-2 constituting the control means.

Signal generators 32-1 and 32-2 generate pilot signals S _P1 and S _P2 of frequency bands f1 and f2. The generated pilot signals S _P1 and S _P2 are synthesized by the synthesizer 33 and further injected into the input of the predistortion circuit 100 via the synthesizer 8. The output of the predistortion circuit 100 is frequency-converted by the frequency converter 23 using the carrier wave having the frequency f _C from the local oscillator 24 and is supplied to the power amplifier 25.
First, the configuration and control operation in the frequency band of the center frequency f1 will be described first.
The pilot signal S _P1, e.g. narrowband CW (tone signal) a frequency of about interval 1kHz using a two-wave. Its frequency interval may be sufficiently narrower than the frequency bandwidth of the transmission signal S _T1. The pilot signal S _P1 is combined with the transmission signal by the combiner 8 and input to the power series predistortion circuit 100 similar to that described with reference to FIG. The band signal extractors 11-1 for extracting a frequency band of the center frequency f1, are extracted pilot signal S _P1 and the transmission signal S _T1 in the frequency band f1 is, third-order distortion generator X3-1 and fifth-order distortion generator X5 Distributed to -1. These distortion generator generates a third-order distortion component and the fifth-order distortion component of each pilot signal S _P1 and the transmission signal S _T1. The amplitude and phase of these third-order distortion components and fifth-order distortion components are adjusted by vector adjusters V3-1 and V5-1, respectively.

A pilot signal component is extracted by the distributor 26 at the output of the power amplifier 25. The distributor 26 includes a directional coupler or a power combiner, and BPF or BEF which is a band extracting unit provided at the output thereof, and extracts a desired band. From the extracted pilot signal component, to detect the intermodulation distortion component of the signal detector CW2 wave other than the pilot signal S _P1 generated by the signal generator 32-1 by 28-1. For example, the detected distortion component is a third-order distortion component generated next to the outside (high-frequency side and low-frequency side) of the pilot signal of the CW2 wave, and a fifth-order distortion component generated further outside the third-order distortion component. It is. Specifically, for example, when the center frequency of the CW two-wave pilot signal S _P1 for the frequency band f1 is f _P1 and the frequency interval of two waves is f ₀ , the third order distortion is applied to the pilot signal of the frequency f _P1 ± f _0. The frequency of the component is f _P1 ± 3f ₀ and the frequency of the fifth-order distortion component is f _P1 ± 5f ₀ .

Controller 31-1 controls the vector adjuster V3-1 the third-order distortion generating path of the center frequency f1 so as to minimize the third-order distortion component related to the pilot signal S _P1. Similarly the controller 31-1 controls the vector adjusters V5-1 of fifth-order distortion generating path of the center frequency f1 so as to minimize the fifth-order distortion component related to the pilot signal S _P1. In this way, the power series predistorter having the center frequency f1 is operated.
Controller 31-1 changes the setting of the center frequency of the pilot signal S _P1 of the signal generator 32-1 as necessary. Vector adjuster V3-1 using different pilot signals S _P1 center frequencies, by controlling the V5-1, it is possible to perform distortion compensation over a wide band. Further, by changing the setting of the frequency interval of the pilot signal S _P1 of the CW2 wave, the non-linear characteristic with memory characteristics of the power amplifier 25 can be compensated. Further, by changing the setting of the amplitude of the pilot signal S _P1, it allows the change of the power combining ratio of the transmission signal S _T1 and the pilot signal S _P1. As a result, power efficiency deterioration due to the injection of the pilot signal _SP1 can be reduced.

Similarly, the signal generator 32-2 vector adjuster V3-2 of the center frequency f2, and generates a pilot signal S _P2 for controlling the V5-2. The point that the controller 31-2 controls the vector adjusters V3-2 and V5-2 so that the third-order and fifth-order distortion components related to the injection of the pilot signal S _P2 and the detected pilot signal S _P2 is minimized. This is the same as in the case of the pilot signal _SP1 , and the description is omitted.
In this embodiment, the vector adjusters V3-1 and V5-1 having the center frequency f1 are controlled by the controller 31-1 for the center frequency f1, and the vector adjusters V3-2 and V5-2 having the center frequency f2 are controlled by the center frequency. Controlled by the f2 controller 31-2, the controllers 31-1, 31-2 operate independently. Thereby, the distortion compensation can be adjusted simultaneously in the two frequency bands f1 and f2.

For pilot signals S _P1 and S _P2 , an example of a CW2 wave is shown, but a narrowband modulated wave may be used. Further, the controllers 31-1 and 31-2 of this embodiment can also control the vector adjuster without using the pilot signals S _P1 and S _P2 . That is, the distributor 26 is configured by a directional coupler or a power distributor, and extracts the transmission signal S _T1 or S _T2 of the transmitter T-1 or the transmitter T-2. Signal detector 28-1 detects the intermodulation distortion component from the transmission signal S _T1 of the transmitter T1 or transmitter T-2. The controller 31-1 controls the vector adjusters V3-1 and V5-1 of the distortion generation path in the frequency band f1 so as to minimize the detected intermodulation distortion component. On the other hand, the signal detector 28 detects the intermodulation distortion component from the transmission signal S _T2 of the transmitter T2. In this way, it is possible to configure a series predistorter that should be capable of compensating for distortion in a plurality of frequency bands without using the signal generators 32-1 and 32-2.

It has been stated that the controllers 31-1, 31-2 are controlled to minimize the detected signal. If there is a specified out-of-band leakage power ratio, the controller controls the vector adjuster so that it is below the specified value. That is, it is obvious that the control is not necessarily required to be minimized.
The signal detectors 28-1 and 28-2 are composed of level detectors when the pilot signals S _P1 and S _P2 are pilot signals of tone signals (CW signals), respectively, and are pilot signals of modulated signals, It can be composed of a correlation detector or a synchronous detector. The same applies to the embodiments described later.
Fifth Embodiment FIG. 8 shows a fifth embodiment of the present invention. In this embodiment, all the vector adjusters are controlled by using one controller 31 as a control means instead of the two controllers 31-1, 31-2 in the embodiment of FIG. is there.

In the fifth embodiment, the vector adjusters V3-1 and V5-1 having the center frequency f1 and the vector adjusters V3-2 and V5-2 having the center frequency f2 are simultaneously controlled by the single controller 31. When the isolation between the distortion generation paths in the two frequency bands f1 and f2 is not sufficient, the vector adjustment of the center frequency f1 and the center frequency f2 depends on each other according to the isolation amount of the two distortion generation paths. That is, if the vector adjusters V3-1 and V5-1 at the center frequency f1 are adjusted, the adjustment of the vector adjusters V3-2 and V5-2 at the center frequency f2 is affected. Even when the adjustment of the center frequency f1 is optimal, the adjustment of the center frequency f1 is not optimal by controlling the vector adjusters V3-2 and V5-2 of the center frequency f2. In the fifth embodiment, in order to solve such a phenomenon, signal detectors 28-1, 28 using the intermodulation distortion components of pilot signals S _P1 , S _P2 of center frequency f1 and center frequency f2 as signal detection means. -2 is detected at the same time. The controller 31 controls the vector adjusters V3-1, V5-1, V3-2, and V5-2 of the center frequency f1 and the center frequency f2 at the same time so as to minimize the detected intermodulation distortion. As a result, it is possible to configure a series predistorter that should perform distortion compensation simultaneously in the two frequency bands f1 and f2. Further, the controller may be controlled by alternately switching the vector adjusters V3-1, V5-1, V3-2, and V5-2.

For pilot signals S _P1 and S _P2 , an example of a CW2 wave is shown, but a narrowband modulated wave may be used. Further, as described in the fourth embodiment of FIG. 7, the controller 31 can also control the vector adjuster without using a pilot signal.
Sixth Embodiment FIG. 9 shows a sixth embodiment of the present invention. This embodiment is different from the embodiment shown in FIG. 8 in that the pilot signals S _P1 and S _{P2 are} transmitted by one signal generator 32 instead of the two signal generators 32-1 and 32-2 for the two frequency bands f1 and f2. And one signal detector 28 is used instead of the two signal detectors 28-1 and 28-2. The controller 31 gives an instruction to generate one of the pilot signal S _P1, S _P2 to the signal generator 32 switches the intermodulation distortion component of the pilot signal S _P1, S _P2 of the center frequency f1 and the center frequency f2 Then, the controller 31 alternately controls the vector adjusters of the center frequency f1 and the center frequency f2 so as to minimize the detected intermodulation distortion. As a result, a series predistorter that should perform distortion compensation in two frequency bands can be configured. Similarly, the controller may control the vector adjuster simultaneously.

As for the pilot signal, an example of a CW2 wave has been shown. However, a narrowband modulated wave may be used in the same manner as described in the previous embodiment, or the vector adjuster may be controlled without using a pilot signal. It can also be done.
Seventh Embodiment FIG. 10 shows a seventh embodiment of the present invention. In this embodiment, the IF band analog predistorter shown in FIG. 7 is implemented by digital signal processing. This embodiment is also configured such that the vector adjuster is automatically adjusted using the pilot signals in the respective frequency bands as compared with the embodiment of FIG. However, here, two signal generators 32-1 and 32-2 are provided corresponding to the two frequency bands, and a part of the transmission signal from the distributor 26 is divided into two by the distributor 27. The signal detectors 28-1 and 28-2 are subjected to detection as distortion component I and Q signals. These distortion detection results are converted into digital signals by analog / digital converters 29I-1, 29Q-1, 29I-2, 29Q-2, and are supplied to controllers 31-1, 31-2.

The configuration and operation of the predistortion circuit 100 are the same as those in FIG. 6, and the vector adjusters V3-1, V5-1, V3-2 by the controllers 31-1, 31-2 using the pilot signals SP1, SP2 are used. , V5-2 control is the same as in the embodiment of FIG.
Eighth Embodiment FIG. 11 shows an eighth embodiment of the present invention. In this embodiment, the IF band analog predistorter of the embodiment shown in FIG. 8 is configured as a power series predistorter by digital signal processing. The configuration of the predistorter shown in FIG. 11 is the same as that of the configuration shown in FIG. 10 in which two controllers 31-1, 31-2 are replaced with one controller 31. The control of the vector adjusters V3-1 and V5-1 for the frequency band f1 and the vector adjusters V3-2 and V5-2 for the frequency band f2 by the controller 31 using the pilot signals S _P1 and S _P2 is shown in FIG. This is the same as the embodiment in FIG.
Ninth Embodiment FIG. 12 shows a ninth embodiment of the present invention. In this embodiment, the analog predistorter of the embodiment using one signal generator 32 shown in FIG. 9 is configured as a power series predistorter by digital signal processing. The control of the vector adjuster for the frequency bands f1 and f2 by the controller 31 is the same as in the embodiment of FIG.

  In the embodiment of the digital predistorter shown in FIGS. 1, 10, 11, and 12 described above, the digital signal processing may be performed by a computer according to a program.

  The power series predistorter for a multi-frequency band according to the present invention can be used for a mobile communication base station that transmits signals of a plurality of frequency bands.

1 is a block diagram for explaining a first embodiment of a multi-frequency power series predistorter according to the present invention; FIG. The conceptual diagram for demonstrating the characteristic of the filter in the case of comprising the band signal extractor for frequency bands f1, f2 in the predistorter of this invention by a band pass filter. The conceptual diagram for demonstrating the characteristic of the filter in the case of comprising the band signal extractor for frequency band f1 in the predistorter of this invention by a band rejection filter. The block diagram which shows the structural example of the band signal extractor for frequency band f1 by a band rejection filter. The block diagram for demonstrating 2nd Example of this invention. The block diagram for demonstrating 3rd Example of this invention. The block diagram for demonstrating 4th Example of this invention. The block diagram for demonstrating 5th Example of this invention. The block diagram for demonstrating 6th Example of this invention. The block diagram for demonstrating 7th Example of this invention. The block diagram for demonstrating 8th Example of this invention. The block diagram for demonstrating 9th Example of this invention.

Claims (17)

It is a power series predistorter for multi-frequency bands to compensate for power amplifier distortion,
Distributing means for distributing input signals of a plurality of frequency bands to a linear signal transmission path and a plurality of distortion generating paths for the frequency bands;
Combining means for combining the output of the linear signal transmission path and the output of the plurality of frequency band distortion generation paths,
A delay circuit provided in the linear signal transmission path;
Including
Each of the frequency band distortion generation paths includes a band signal extractor configured by a band rejection filter that extracts a signal of the corresponding frequency band from the distributed input signal;
A distortion generator that is provided with the extracted signal, generates at least one odd-order distortion component of the signal, and outputs the distortion generation path for the frequency band;
And a power series predistorter for multi-frequency bands.   2. The predistorter according to claim 1, wherein the phase and amplitude of the odd-order distortion are adjusted on the output side of the distortion generator in each of the frequency-band distortion generation paths, and the adjusted odd-order distortion is applied to the frequency band. A power series predistorter for a multi-frequency band, characterized in that a vector adjuster is provided as an output of a distortion generation path for use.   3. The predistorter according to claim 2, wherein each of the frequency band distortion generation paths is provided with the extracted signal and generates a plurality of different odd-order distortion components, and each distortion generation. A plurality of vector adjusters for adjusting the amplitude and phase of the output signal of the combiner, and a second combiner that combines the adjusted vector adjuster output and outputs the output of the frequency band distortion generation path. A power series predistorter for multi-frequency bands. In predistorter according to any one of claims 2 to 3, each of the vector adjuster variable attenuator and a variable phase shifter power series should for multi-band, characterized in that it is constituted by cascade connection of Puridisu Tota. The power series predistorter should for multi-band, wherein the predistorter according to any one of claims 1 to 3 has been implemented with digital signal processing. The power series predistorter should for multi-band, wherein the predistorter according to any one of claims 1 to 3, which is realized by analog signal processing. In predistorter according to claim 2 or 3, wherein the signal detecting means for detecting a distortion component of the plurality of frequency bands from an output signal of the power amplifier, a frequency band corresponding based on the distortion components of said plurality of frequency bands And a control means for controlling the vector adjuster. A power series predistorter for a multi-frequency band. 8. The predistorter according to claim 7, wherein the signal detection means includes a plurality of signal detectors that respectively detect signal components of the plurality of frequency bands from an output signal of the power amplifier, and the control means includes the plurality of frequencies. A power series predistorter for a multi-frequency band, comprising: a plurality of controllers that respectively control the vector adjusters corresponding to the plurality of frequency bands based on band signal components. 8. The predistorter according to claim 7, wherein the signal detection means includes one signal detector for detecting signal components of the plurality of frequency bands from an output signal of the power amplifier, and the control means includes the plurality of frequency bands. A power series predistorter for multi-frequency bands, comprising: one controller for controlling each of the vector adjusters corresponding to the plurality of frequency bands based on the signal components. 8. The predistorter according to claim 7, wherein the signal detection means includes a plurality of signal detectors that respectively detect signal components of the plurality of frequency bands from an output signal of the power amplifier, and the control means includes the plurality of frequencies. A power series predistorter for a multi-frequency band, comprising one controller for controlling each of the vector adjusters corresponding to the plurality of frequency bands based on band signal components. 8. The predistorter according to claim 7 , further comprising: signal generating means for generating a plurality of pilot signals in the plurality of frequency bands; and signal injection means for inputting the plurality of pilot signals to the distributor. A power series predistorter for multi-frequency bands. 12. The predistorter according to claim 11, wherein the signal generating means generates two CW signals having different frequencies, and the signal detecting means detects two CW signals having different frequencies generated by the signal generating means. A power series predistorter for multi-frequency bands. 12. The predistorter according to claim 11, wherein the signal generating means generates a modulated signal, and the signal detecting means detects the modulated signal generated by the signal generating means. Type predistorter. 8. The power series predistorter according to claim 7, wherein the signal detecting means detects a distortion component of the transmission signal. 8. The predistorter according to claim 7, wherein the control means controls the vector adjuster for the plurality of frequency bands so as to minimize the output of the signal detection means. Predistorter. 8. The predistorter according to claim 7, wherein the control means simultaneously controls the vector adjusters of the plurality of frequency bands so as to minimize the output of the signal detection means. Type predistorter. 8. The predistorter according to claim 7, wherein the control means switches and controls the vector adjusters of the plurality of frequency bands so as to minimize the output of the signal detection means. Series predistorter.

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