JP4328339B2 - Multi-frequency feedforward amplifier - Google Patents

Description

  The present invention relates to a transmission amplifier for wireless communication that adaptively changes a plurality of frequency bands. In particular, the present invention relates to a multi-frequency band feedforward amplifier that collectively amplifies a plurality of frequency bands.

  FIG. 1 shows a basic configuration of a conventionally used feedforward amplifier. The feedforward amplifier includes two signal processing circuits. One is a distortion detection circuit 150, and the other is a distortion removal circuit 151. The distortion detection circuit 150 includes a main amplifier signal path 153 and a linear signal path 154. The distortion removal circuit 151 includes a main signal path 158 and a distortion injection path 159. The main amplifier signal path 153 (also referred to as a vector adjustment path) includes a vector adjuster 155 and a main amplifier 156. The vector adjuster 155 includes a variable phase shifter 155a and a variable attenuator 155b. The linear signal path 154 includes a delay line. The main signal path 158 is configured by a delay line. The distortion injection path 159 (also referred to as a vector adjustment path) includes a vector adjuster 200 and an auxiliary amplifier 201. The vector adjuster 200 includes a variable phase shifter 200a and a variable attenuator 200b. Here, distributor 152, power combiner / distributor 157, and combiner 202 are simple lossless power distributors and power combiners configured by a transformer circuit, a hybrid circuit, and the like.

  First, the basic operation of the feedforward amplifier will be described. The signal input to the feedforward amplifier is distributed by the distributor 152 to the main amplifier signal path 153 and the linear signal path 154. At this time, the variable phase shifter 155a and the variable attenuator 155b of the main amplifier signal path 153 are adjusted so that the signals of the main amplifier signal path 153 and the linear signal path 154 have equal amplitude and opposite phase. As a method of making the phase opposite, there is a method in which the distributor 152 or the power combiner / distributor 157 appropriately sets the phase shift amount between the input and output terminals, a method in which the main amplifier 156 inverts the phase, and the like.

  Since the distortion detection circuit 150 is configured in this way, the power combiner / distributor 157 can output the difference component between the signal that has passed through the main amplifier signal path 153 and the signal that has passed through the linear signal path 154. This difference component is exactly the distortion component generated in the main amplifier 156. Therefore, the blocks from the distributor 152 to the power combiner / distributor 157 shown in FIG. 1 are called distortion detection circuits.

  Next, the distortion removal circuit 151 will be described. The output of the distortion detection circuit 150 is distributed to the main signal path 158 and the distortion injection path 159 via the power combiner / distributor 157. The main signal path 158 receives the output of the main amplifier 156 of the main amplifier signal path 153 (the signal that has passed through the main amplifier signal path 153). Further, the distortion component of the main amplifier 156 detected by the distortion detection circuit 150 (the difference component between the signal passing through the main amplifier signal path 153 and the signal passing through the linear signal path 154) is input to the distortion injection path 159. . The variable phase shifter 200a and variable attenuator 200b of the distortion injection path 159 are adjusted so that the distortion component of the signal passing through the main signal path 158 and the signal passing through the distortion injection path 159 have equal amplitude and opposite phase. The By adjusting in this way, the synthesizer 202 can synthesize the distortion component of the main amplifier 156 having the same amplitude and the opposite phase with the signal that has passed through the main amplifier signal path 153. Then, the synthesizer 202 outputs a signal that cancels out the distortion components of the entire amplifier circuit. As is well known, a linear amplifier is used as the auxiliary amplifier in order to remove distortion components generated in the main amplifier used in the feedforward amplifier. The above is the operation of an ideal feedforward amplifier. Actually, it is not easy to completely maintain the balance of the distortion detection circuit and the distortion removal circuit. Even if the initial setting is complete, the characteristics of the amplifier change due to fluctuations in the ambient temperature, power supply, etc., and it is extremely difficult to maintain good balance with time stability.

  As a method for maintaining the balance of the distortion detection circuit and distortion removal circuit of the feedforward amplifier with high accuracy, an automatic adjustment method using a pilot signal is known. For example, there is Patent Document 1. Non-Patent Document 1 is known as a device that puts these to practical use. These feedforward amplifiers are put into practical use in the 800 MHz band and 1.5 GHz band of the PDC (Personal Digital Cellular) system. Such a feedforward amplifier is generally designed and adjusted for each frequency band to be amplified.

  The feedforward amplifiers in Patent Document 2 and Patent Document 3 subdivide a single transmission band, for example, 20 MHz in a 2 GHz band by a plurality of bandpass filters, and amplify the signal extracted by subdividing. The feedforward amplifier compensates for amplitude deviation and phase deviation generated in the amplifier for each subdivided frequency, and improves distortion compensation accuracy.

  Conventional wireless systems have used a single system that complies with any standard such as PDC, GSM (Global System for Mobile Communications), or IMT-2000 (International Mobile Telecommunication 2000). On the other hand, there is a technique for softwareizing a radio so that a single hardware can support a plurality of radio systems. If a single hardware can support a plurality of wireless systems, the user can use the mobile communication environment without being aware of the wireless system and the core network behind it. However, in reality, a single hardware corresponding to a plurality of wireless systems has not been realized.

  In addition, the services provided by the wireless system will be different for each region or operator, and the wireless system will be diversified. For this reason, in the future, it will be necessary to mix optimal radio systems for each purpose at the same time and in the same place.

  There is a multiband radio system as a method using these plural radio systems. This wireless system adaptively changes the frequency band or the number of frequency bands used according to the propagation environment and traffic conditions. In order to ensure a predetermined transmission quality or transmission amount, multiband transmission using an unused frequency band is effective. Therefore, in a multiband wireless system, the number of frequency bands is changed in order to ensure transmission quality and transmission amount that the wireless system should guarantee. The same change is made within the same band. Furthermore, when the frequency bands used by multiple operators are mixed, the multiband wireless system uses interference recognition technology, frequency sharing technology, interference cancellation technology, interference reduction avoidance technology, multiband control technology, etc. By performing adaptive control using a vacant frequency band, frequency utilization efficiency can be increased.

  The feedforward amplifier is used as a linear amplifier for a base station corresponding to such a multiband radio system. However, when multiple frequency bands to be amplified are far apart compared to the bandwidth of each frequency band, the electrical length of the delay line for each frequency band is different. The amount of adjustment of the variable phase shifter and variable attenuator for setting the balance to a predetermined range differs depending on the frequency band to be amplified.

  Specifically, when a delay line common to all frequency bands is used, the set value of the vector adjuster must always follow a signal that rotates at the angular speed of the frequency difference due to the frequency difference of the input signals. . However, conventional vector adjusters have not been able to follow such high-speed rotating signals. In addition, conventional vector adjusters have been unable to set optimum amplitude and phase for a plurality of input signals simultaneously due to structural reasons.

  For example, when signals in the 800 MHz band and the 1.5 GHz band are input to the same vector adjuster, optimal vector adjustment can be performed for any frequency band. However, optimal vector adjustment that follows a frequency difference of 700 MHz cannot be performed. Therefore, the conventional feedforward amplifier cannot simultaneously amplify the 800 MHz band signal and the 1.5 GHz band signal below a predetermined distortion compensation amount.

As a method for solving this problem, a non-patent document 2 proposes a dual-band feedforward amplifier. In this configuration, a vector adjuster having a band extracting unit is provided for each frequency band. In other words, this dual-band feedforward amplifier extracts a frequency band signal to be vector-adjusted from two input frequency band signals by means of a filter provided in front of the vector adjuster. Then, vector adjustment is performed for each frequency band. This dual-band feedforward amplifier configuration can compensate for distortion in a plurality of frequency bands. The band to be compensated is fixed by a filter.
JP-A-1-198809 JP 2000-223961 A JP 2001-284975 A Toshio Nojima, Shoichi Takahashi, "Ultra Low Distortion Multi-frequency Common Amplifier for Mobile Communications ---- Self-Adjusting Feedforward Amplifier (SAFF-A) ----", IEICE, Radio Communication Systems Study Group, RCS90 -4, 1990. Suzuki Yuri, Takahashi Shoichi, “Dual-Band Feedforward Amplifier”, 2005 IEICE General Conference, C-2-2, March 2005.

  In a multiband wireless system having a plurality of transmission bands, it is conceivable to change the frequency band depending on the service status of the wireless system, interference with other wireless systems, and the like. However, as described above, the distortion compensation bandwidth of the feedforward amplifier is determined by the adjustment accuracy of each loop of the distortion detection circuit and the distortion removal circuit. Therefore, in the conventional feedforward amplifier, the distortion compensation adjustment cannot be made to correspond to the change of the frequency band. Further, the conventional dual band feedforward amplifier in which the frequency band for distortion compensation is fixed cannot adaptively change the operating frequency. For a feedforward amplifier that is used for a long period of time, a change in the frequency band involves a modification or change of the feedforward amplifier at the base station. Therefore, a great deal of labor and time is required to readjust many feedforward amplifiers. There is a need for a feedforward amplifier configuration that can eliminate this effort and time.

  For example, a dual-band feedforward amplifier that simultaneously compensates for distortion of a signal in the frequency band f1 and a signal in the frequency band f2 is changed from the signal in the frequency band f1 and the signal in the frequency band f3 when the frequency band f2 is changed to f3. Cannot be compensated for at the same time. This is because the operating band of the conventional dual-band feedforward amplifier is fixed, and as described above, loop adjustment cannot be performed due to the frequency difference between f1 and f3.

  Another possible method is to provide a dual-band feedforward amplifier with fixed filters and vector adjusters corresponding to all frequency bands expected to be serviced in the future. However, having a fixed filter and a vector adjuster that can handle all frequency bands also has a fixed filter and a vector adjuster that are not used, which is contrary to the construction of an economical feedforward amplifier. Thus, with the change of the frequency band or the increase / decrease of the carrier wave, there has been a demand for a feedforward amplifier that does not require the replacement of the components and the configuration is not redundant.

  The present invention relates to a feedforward amplifier including a distortion detection circuit and a distortion removal circuit. A first variable frequency band extractor and a first vector adjuster for extracting a specific frequency band are provided in each of the N first vector adjustment paths of the distortion detection circuit. Each of the N second vector adjustment paths of the distortion removal circuit is provided with N second variable frequency band extractors and second vector adjusters that extract a specific frequency band. The frequency bands extracted by the N first variable frequency band extractors and the N second variable frequency band extractors are adaptively controlled by the frequency control unit.

  Furthermore, a feedforward amplifier according to the present invention includes a local oscillator, a local oscillator frequency control unit that controls the frequency of the local oscillator, a mixer that multiplies an input signal from the first distribution unit and a signal from the local oscillator, and a mixer The low-pass filter that passes only the low-frequency component of the output of the output, the local oscillator frequency controller detects the frequency band of the input signal from the signal that controls the local oscillator and the output signal of the low-pass filter, frequency control A band detector having an analysis unit for outputting a control signal to the detector.

  According to the present invention, it is possible to realize a feedforward amplifier that enables adaptive distortion compensation even when a plurality of frequency bands are changed. It is possible to simplify the configuration of the feedforward amplifier that amplifies a plurality of frequency bands at the same time, thereby realizing low power consumption. According to the configuration of the present invention, it is possible to adjust to a predetermined distortion compensation amount for each frequency band regardless of the difference in electrical length of the delay lines constituting the linear signal path. Since the center frequency or bandwidth of the frequency band extractor can be changed, it is possible to adjust to a predetermined distortion compensation amount for each frequency band.

  Thus, the feedforward amplifier of the present invention can linearly amplify the frequency band corresponding to the service status of the wireless system. Therefore, the present invention can eliminate the need for additional equipment associated with a change in frequency band or an increase in carrier waves.

  Further, the present invention uses a variable filter in the feedforward amplifier in order to make changing the frequency band easy and inexpensive. Further, the pass band of the variable filter is controlled so as to match the band to be used. Therefore, even one feedforward amplifier can cope with the frequency change of the wireless system. Further, the feedforward amplifier according to the present invention can switch the operation band by a command to switch the frequency band from the operation center, so that it is not necessary to apply a great deal of effort to the adjustment of the radio system. Furthermore, the feedforward amplifier of the present invention can detect the frequency band of the received signal and automatically switch the frequency band even when the transmitter side changes the frequency band. It can also be changed. In addition, a single feedforward amplifier is more advantageous in terms of device scale and power consumption than configuring a feedforward amplifier for each frequency band.

  FIG. 2 shows the principle of the multi-frequency band signal processing circuit of the feedforward amplifier of the present invention. This multi-frequency band signal processing circuit amplifies the signals of the linear signal path 20 constituted by delay lines, the respective variable frequency band vector adjustment paths 21a and 21b, and the respective variable frequency band vector adjustment paths 21a and 21b. Multi-frequency band amplifying units 22a and 22b, a distribution unit 23 that distributes input signals to the linear signal paths and the respective variable frequency band vector adjustment paths, outputs from the multi-frequency band amplifying units 22a and 22b, and outputs from the linear signal path 20 Is included.

  The first variable frequency band vector adjustment path 21a includes a first variable frequency band extractor 25a that extracts a first frequency band signal having a center frequency f1, and a vector adjuster 26a that adjusts the amplitude and phase of the first frequency band signal. including. The second variable frequency band vector adjustment path 21b includes a second variable frequency band extractor 25b that extracts a second frequency band signal having a center frequency f2, and a vector adjuster 26b that adjusts the amplitude and phase of the second frequency band signal. Including. The outputs of the vector adjusters 26a and 26b are amplified by the multi-band amplifiers 22a and 22b.

  FIG. 2 shows that another variable frequency band vector adjustment path may be provided. Although not shown, each vector adjuster is configured by a serial connection of a variable frequency band extractor, a vector adjuster, and a multi-frequency band amplifying unit, similar to the variable frequency band vector adjustment paths 21a and 21b. The distribution unit 23 distributes the input signal to the linear signal path 20 and the first and second variable frequency band vector adjustment paths 21a, 21b,. The combining unit 24 combines the outputs of those paths. The multi-band signal processing circuit shown in FIG. 2 can be applied to the distortion detection circuit 150 and distortion removal circuit 151 of the feedforward amplifier described in FIG.

  For example, the case where the frequency band f1 corresponds to the 800 MHz band and the frequency band f2 corresponds to the 1.5 GHz band, and further uses the 2 GHz band as the frequency band f3 and the 5 GHz band as the frequency band f4 will be described. These frequency bands are sufficiently separated from the bandwidth of each frequency band, and a variable frequency band extractor is provided for each frequency band. The variable frequency band extractors 25a, 25b, 25c, and 25d extract signals in each frequency band. The vector adjusters 26a, 26b, 26c, and 26d adjust the vectors of the signals in the respective frequency bands. The multi-frequency band amplifying units 22a, 22b, 22c, and 22d amplify signals in each frequency band. The synthesizer 24 synthesizes the outputs from the multiband amplifiers 22a, 22b, 22c, and 22d and the output of the linear signal path 20.

  FIG. 3 conceptually shows distortion compensation when the first and second variable frequency band extractors are configured by variable bandpass filters. The frequency bands whose center frequencies are f1 and f2 are sufficiently separated from each other, and distortion compensation is enabled in each frequency band.

  The first and second variable frequency band extractors 25a and 25b extract the signals of the first frequency band and the second frequency band, respectively, so that the center frequencies have the desired bandwidths at f1 and f2, respectively. Each such variable frequency band extractor may be constituted by, for example, a variable band pass filter (band bus filter: BPF) or a variable band rejection filter (band elimination filter: BEF).

  FIG. 4 shows an example of the frequency characteristic of the attenuation when the first variable frequency band extractor is configured with a variable band rejection filter. This example conceptually shows the characteristics required for the first variable frequency band extractor 25a when the frequency bands f3 and f4 are also added to the multi-frequency band signal processing circuit of FIG. As shown in FIG. 5, this characteristic can be formed by three band rejection filters BEF2, BEF3, and BEF4 that block the second, third, and fourth frequency bands other than the first frequency band. . It is desirable that each band rejection filter has a sufficient band rejection characteristic in that band and a sufficiently low loss pass characteristic in the other band. Such a band rejection filter can be constituted by a notch filter, for example. There are a notch filter using a dielectric resonator and a notch filter using a stub by a microstrip line. Similarly, the second variable frequency band extractor 25b can be formed of three band rejection filters that block the first, third, and fourth frequency bands. The same applies to the third and fourth frequency band extractors. As described above, the multi-frequency band signal processing circuit used in the present invention is not limited to the number of target frequency bands, but in the following, in order to simplify the description, the number of frequency bands is Two cases will be described.

  The advantage of configuring the frequency band extractor with a band-pass filter is that it is easy to extract the band around the center frequency 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 lengthen the delay line constituting the linear signal path 20 of FIG. 2 in accordance with the delay amount, and there is a disadvantage that the attenuation amount becomes large. When the frequency band extractor is configured by a band rejection filter, the frequency band to be extracted is not the center frequency of the band rejection filter. Therefore, the delay in the extracted frequency band is small. Therefore, there is an advantage that the line length of the linear signal path 20 is short and the loss is low. Furthermore, it is easy to design a band rejection filter.

  The center frequency or bandwidth of the variable band pass filter and the variable band rejection filter can be changed. In the case of a notch filter in a microstrip line, there is a method of changing the center length of the resonator length by a switch such as a diode or MEMS. As a method of changing the bandwidth of the bandpass filter, there is a method of switching banks of filter banks having different center frequencies. FIG. 6 shows a configuration example of a filter bank having four filters. The frequency band controller 32 controls the number of filters to be operated by ON / OFF of switches 30 and 31 before and after the filter. FIG. 7 shows the frequency characteristics of the filter bank when only the filter (BPF1) is operated. FIG. 8 shows the frequency characteristics of the filter bank when the filter (BPF1) and the filter (BPF2) are operated. BPF1 and BPF2 are close frequency characteristics, and the frequency characteristics of the filter bank are the combined frequency characteristics of BPF1 and BPF2. Thus, the pass bandwidth can be changed by using the filter bank. As a method of changing the bandwidth of the band rejection filter, there is a method of switching a resonator by a microstrip line with a diode or MEMS.

  The line length of the linear signal path 20 is designed so that the signal delay amount due to the linear signal path 20 and the delay amounts due to the variable frequency band vector adjustment paths 21a and 21b are equal on the input side of the synthesis unit 24. The first vector adjuster 26a includes a first variable frequency band vector so that the component of the first frequency band f1 of the output signal of the linear signal path 20 and the output of the multi-frequency band amplifying unit 22a have equal amplitude and opposite phase. The phase and amplitude of the signal of the adjustment path 21a are controlled. Similarly, the second vector adjuster 26b has a second variable so that the component of the second frequency band f2 of the output signal of the linear signal path 20 and the output of the multi-frequency band amplifying unit 22b have equal amplitude and opposite phase. The phase and amplitude of the signal of the frequency band vector adjustment path 21b are controlled. By this adjustment, the synthesizer 24 can output a difference component and a sum component between the output of the linear signal path 20 and the outputs of the variable frequency band vector adjustment paths 21a and 21b.

  The vector adjusters 26a and 26b of the first and second variable frequency band vector adjustment paths 21a and 21b of the multi-frequency band signal processing circuit of FIG. 2 are adjusted based on the linear signal path 20, respectively. Thereby, vector adjustment can be performed independently with respect to the frequency band f1 and the frequency band f2.

  Hereinafter, a more specific example of the multi-frequency band signal processing circuit will be described. In the following description, it is needless to say that the portion referred to as a vessel can be configured by a physical circuit, and can also be realized by an arithmetic processing unit and software.

  FIG. 9 is a specific first configuration example of the multi-frequency band signal processing circuit shown in FIG. In the first configuration example, the multi-frequency band amplifying unit 22 in FIG. 2 is combined with the individual amplifiers 80a and 80b for the respective frequency bands and the outputs of these amplifiers to be output from the multi-frequency band amplifying unit. A synthesizer 81 is used. The distributor 82 includes a distributor 82a and a distributor 82b. The distributor 82a distributes the input signal into two, one is distributed to the linear signal path 20, and the other is distributed to the distributor 82b. The distributor 82b further distributes the signal distributed from the distributor 82a for each variable frequency band vector adjustment path. The signal vector adjustment by the vector adjustment path of each variable frequency band and the difference component and the sum component obtained thereby at the output terminal of the synthesizer 24 are the same as those in FIG. As the combiner 24, a directional coupler, a Wilkinson power combiner, or the like can be used. The frequency band controller 32 controls the variable bandpass filters 25a and 25b by a control signal from the operation center or the band detector.

  FIG. 10 shows a second configuration example of the multi-frequency band signal processing circuit. The difference between FIG. 10 and FIG. 9 is that the outputs of the vector adjusters 26 a and 26 b are combined by the combiner 90 and then amplified by the common amplifier 91. The other parts are the same as the corresponding parts in FIG.

  For example, when the frequency band is changed from the frequency band f1 to f2, the frequency band controller 32 changes the pass band of the variable band pass filter 25a from f1 to f2 by a control signal from the operation center or the band detector. To do. At this time, the variable passband filter 25a changes the center frequency by changing the resonator structure. In this way, the operating band of the transmission amplifier once installed can be adaptively changed. That is, the transmission amplifier configuration of the present invention can eliminate the need for new equipment investment associated with the change of the frequency band.

  A base station corresponding to a plurality of radio systems includes a transmitter and a receiver corresponding to the plurality of radio systems. The output signals of the plurality of transmitters are power amplified by the multiband feedforward amplifier of the present invention. When cell interference increases in an area where a base station provides mobile communication services, for example, due to an increase in subscribers, the operation center that monitors the base station changes some radio systems. Commands are given to the base station.

  As the number of carriers used in the frequency band f1 increases or decreases, the frequency band controller 32 increases the pass bandwidth of the variable bandpass filters 25a and 25b based on the control signal from the operation center or band detector. Or decrease. Such increase / decrease of the pass bandwidth can be realized by changing the number of filter banks of the variable pass band filters 25a and 25b as shown in FIG. As described above, even when the number of carriers is increased or decreased according to fluctuations in communication traffic, it is possible to minimize cell interference caused by the increased number of carriers.

[First Embodiment]
FIG. 11 shows a first embodiment of a feedforward amplifier according to the present invention. In all the following embodiments, in order to simplify the drawings and description, the number of used frequency bands is assumed to be 2, but in general, two or more frequency bands may be used.
In the following description, 1- is added to the head of the reference code of the multi-band signal processing circuit forming the distortion detection circuit, and 2- is added to the head of the reference code of the multi-band signal processing circuit forming the distortion removing circuit. However, in the case of a unique number, it is not indicated.

  The multiband signal processing circuit synthesizer 1-24 constituting the distortion detection circuit 150 functions as the synthesizer / distributor 100 together with the multifrequency band signal processing circuit divider 2-23 constituting the distortion removal circuit 151. Further, the multi-frequency band amplifying unit constituted by the individual amplifiers 1-80a and 1-80b of the distortion detection circuit 150 constitutes a main amplifier 1-156 in the feedforward amplifier. Each individual amplifier 1-80a, 1-80b is a power amplifier. The multi-frequency band amplifying unit of the distortion removing circuit 151 constitutes the auxiliary amplifier 101 of the feedforward amplifier. The individual amplifiers 2-80a and 2-80b are linear amplifiers.

  The combiner / distributor 100 obtains the difference component between the output of the linear signal path 1-20 and the combined output of the vector adjustment path 1-21 at the output terminal, and outputs the difference component to the distributor 102 of the distortion removal circuit 151. The synthesizer / distributor 100 obtains the sum component of the output of the linear signal path 1-20 and the output of the synthesizer 1-24, and outputs the sum component to the linear signal path 2-20 of the distortion removal circuit 151. Since the main amplifier 1-156 composed of the individual amplifiers 1-80a and 1-80b generates intermodulation distortion at the time of signal amplification, the difference component output from the combiner / distributor 100 to the distributor 102 side is the individual amplifier 1 The distortion component generated by −80a and 1-80b. On the other hand, the sum component output from the combiner / distributor 100 to the linear signal path 2-20 (main signal path) side is a combined signal of the input signal of the multi-frequency band and the output signal of the individual amplifier.

The synthesizer 104 of the distortion removal circuit 151 outputs a difference component between the output of the linear signal path 2-20 and the combined output of the vector adjustment path of each frequency band. Therefore, the distortion component generated by the main amplifier included in the output of the linear signal path is canceled with the combined output of the vector adjustment paths 2-26a and 2-26b, and the signal component of the multi-frequency band is output to the terminal.
In order to realize such a distortion removal amount in the distortion removal circuit 151, the distortion detection circuit 150 and the distortion removal circuit 151 may perform vector adjustment by the multiband signal processing circuit described in FIG.

  The feedforward amplifier of the first embodiment uses a vector adjuster for each frequency band. Therefore, distortion compensation can be performed independently for each frequency band. The vector adjuster adjusts the amplitude and phase of the signal passing through each vector adjuster so that the delay lines of the distortion detection circuit 150 and the distortion removal circuit 151 have equal amplitude, opposite phase, and equal delay.

  The distortion compensation amount when signals in two frequency bands are amplified by the feedforward amplifier of FIG. 11 has the characteristics shown in FIG. In the feedforward amplifier according to the present invention, distortion is generated for each frequency band so that the distortion components of the main amplifier included in the signals of the amplified center frequencies f1 and f2 are equal to or less than a predetermined value (target value). The vector adjusters of the detection circuit 150 and the distortion removal circuit 151 are adjusted. If each vector adjustment path is sufficiently isolated, adjusting the vector adjuster of one frequency band does not affect the vector adjuster of the other frequency band. That is, the vector adjusters for a plurality of frequency bands can be adjusted independently. Further, by adding the vector adjustment path, it is possible to flexibly add a frequency band for compensating for distortion of the feedforward amplifier.

  One of the first variable frequency band extracting means 1-25a and 2-25a and the second variable frequency band extracting means 1-25b and 2-25b of the feedforward amplifier shown in the first embodiment is variable frequency extracted. The other may be frequency extraction means that does not change the frequency.

  The first and second variable frequency band extracting means 1-25a, 1-25b, 2-25a, 2-25b change the center frequency or the pass band width according to an instruction from the frequency band controller 32. The frequency controller 32 changes the center frequency or bandwidth of the frequency band to be amplified by the feedforward amplifier according to the control signal from the operation center. These control periods or control speeds differ depending on each wireless system. Since the initial pull-in operation related to distortion compensation of the feedforward amplifier is high-speed, the first and second variable frequency band extracting means in the first embodiment have a control period or control speed at least equal to or greater than the initial pull-in operation time. You can change the settings.

[Second Embodiment]
FIG. 12 shows a second embodiment. In the second embodiment, the multiband signal processing circuit shown in FIG. 10 is applied as the distortion removing circuit 151. Also in the feedforward amplifier of the second embodiment, vector adjustment is performed using the vector adjusters 1-26a, 1-26b, 2-26a, 2-26b for each frequency band. If there is sufficient isolation between the vector adjustment paths, adjustment of the vector adjuster of one frequency band does not affect the vector adjuster of the other frequency band. Therefore, distortion compensation can be performed independently for each frequency band. Moreover, if a vector adjustment path is added, a frequency band for distortion compensation can be flexibly added.
The auxiliary amplifier 2-156 of the distortion removing circuit has one common amplifier 2-91 that simultaneously amplifies a plurality of frequency bands as shown in FIG. Therefore, it is possible to simplify the device configuration by reducing the number of amplifiers used, and to expect low power consumption.

[Third Embodiment]
FIG. 13 shows a third embodiment. The third embodiment is an example in which the multiband signal processing circuit shown in FIG. 10 is used as the distortion detection circuit 150. The feedforward amplifier of the third embodiment also performs vector adjustment using the vector adjusters 1-26a, 1-26b, 2-26a, and 2-26b for each frequency band. If there is sufficient isolation between the vector adjustment paths, adjustment of the vector adjuster of one frequency band does not affect the vector adjuster of the other frequency band. Therefore, distortion compensation can be performed independently for each frequency band. Moreover, if a vector adjustment path is added, a frequency band for distortion compensation can be flexibly added.
The main amplifier 1-156 of the distortion detection circuit has one common amplifier 1-91 that simultaneously amplifies a plurality of frequency bands as shown in FIG. Therefore, it is possible to simplify the device configuration by reducing the number of amplifiers used, and to expect low power consumption.

[Fourth Embodiment]
FIG. 14 shows a fourth embodiment. In the fourth embodiment, the multi-frequency band signal processing circuit of FIG. 10 is applied to both the distortion detection circuit 150 and the distortion removal circuit 151. The main amplifier 1-156 of the distortion detection circuit 150 is composed of one common amplifier 1-91 that simultaneously amplifies a plurality of frequency bands, and the auxiliary amplifier 2-156 of the distortion removal circuit 151 also amplifies a plurality of frequency bands simultaneously. One common amplifier 2-91. Therefore, it is possible to simplify the apparatus by reducing the number of amplifiers used, and lower power consumption can be expected.

[Fifth Embodiment]
FIG. 15 shows a fifth embodiment. In the fifth embodiment, a band detector 33 is added to the configuration of FIG. In the case of this configuration, the distributor 1-82a also distributes a part of the input signal to the band detector 33. The band detector 33 detects the frequency band of the input signal by the method shown below and outputs a control signal to the frequency band controller 32. The operation of the other components is the same as in the first embodiment.

  FIG. 16 shows a functional configuration example of the band detector 33. The band detector 33 includes a local oscillator frequency control unit 331, a local oscillator 332, a mixer 333, a low-pass filter 334, and an analysis unit 335. The local oscillator frequency control unit 331 controls the local oscillator 332 so as to continuously sweep the frequency from the lower limit frequency to the upper limit frequency of the input signal. The local oscillator 332 oscillates according to an instruction from the local oscillator frequency control unit 331. The mixer 333 multiplies the input signal distributed from the distributor 1-82 a by the signal from the local oscillator 332. The output signal from the mixer 333 includes the frequency component of the difference between the frequency of the input signal and the frequency of the signal from the local oscillator 332. That is, when the frequency of the input signal and the frequency of the signal from the local oscillator 332 are very close, the output from the mixer 333 includes a component near DC (low frequency component). The low pass filter 334 passes only the low frequency component of the output from the mixer 333. Therefore, the band detector output signal is obtained from the low-pass filter 334 only when the frequency of the input signal and the frequency of the signal from the local oscillator 332 are very close. The analysis unit 335 compares the frequency sweep signal from the local oscillator frequency control unit 331 with the band detector output signal from the low-pass filter 334, detects the frequency band of the input signal, and controls the frequency band controller 32. Output a signal.

  FIG. 17 shows an example of the spectrum of the input signal of the feedforward amplifier. The center frequency of the first frequency band is f1, the lower limit frequency is f1L, and the upper limit frequency is f1H. The center frequency of the second frequency band is f2, the lower limit frequency is f2L, and the upper limit frequency is f2H. FIG. 18 shows the relationship between the sweep frequency and the frequency of the input signal. The horizontal axis is the sweep frequency, and the vertical axis is the frequency of the input signal. This figure shows that a signal in the vicinity of DC is output from the low-pass filter 334 when the sweep frequency is from the frequency f1L to the frequency f1H and from the frequency f2L to the frequency f2H. FIG. 19 shows a temporal change in the signal output from the local oscillator 332. The horizontal axis is time, and the vertical axis is the output from the local oscillator 332. FIG. 20 shows a temporal change in the output from the low-pass filter 334. The horizontal axis is time, and the vertical axis is the output from the low-pass filter 334. As shown in FIG. 20, when the frequency of the output from the local oscillator 332 corresponds to the frequency f1L to the frequency f1H and the frequency f2L to the frequency f2H, the output from the low-pass filter 334 is obtained.

Note that when a threshold is set for the output from the low-pass filter 334, the bandwidth of the frequency band is narrowed as shown in FIG. Therefore, the analysis unit 335 may correct each frequency by multiplying the obtained lower limit frequencies f1L and f2L and the upper limit frequencies f1H and f2H by a predetermined coefficient.
Further, the local oscillator frequency control unit 331 and the analysis unit 335 can be realized by an analog / digital converter and a microprocessor. As the local oscillator 332, a generally used signal oscillator or the like may be used. The mixer 333 and the low-pass filter 334 can be realized by an active filter using an LC filter or an operational amplifier.

  Since the band detector 33 operates in this way, the feedforward amplifier can adaptively cope with the case where the input signal is dynamically changed. The time required to change the frequency band processed by the feedforward amplifier depends on the period of the signal swept by the local oscillator 332. When the frequency change at high speed is necessary, the period of the signal swept by the local oscillator 332 may be shortened.

[Sixth Embodiment]
FIG. 22 shows a sixth embodiment. In the sixth embodiment, a band detector 33 is added to the configuration of FIG. The configuration and operation of the band detector 33 are the same as those in the fifth embodiment, and the others are the same as those in the second embodiment.

[Seventh Embodiment]
FIG. 23 shows a seventh embodiment. In the seventh embodiment, a band detector 33 is added to the configuration of FIG. The configuration and operation of the band detector 33 are the same as those in the fifth embodiment, and the others are the same as those in the third embodiment.

[Eighth Embodiment]
FIG. 24 shows an eighth embodiment. In the eighth embodiment, a band detector 33 is added to the configuration of FIG. The configuration and operation of the band detector 33 are the same as those of the fifth embodiment, and the others are the same as those of the fourth embodiment.

  The multi-frequency band feedforward amplifier using the multi-frequency band signal processing circuit of the present invention can be used as a mobile communication transmission amplifier that simultaneously transmits signals of a plurality of frequency bands.

It is a figure which shows the basic composition of the conventional feedforward amplifier. It is a figure which shows the structural example of the multiband signal processing circuit used for the feedforward amplifier of this invention. It is a figure which shows the conceptual diagram of distortion compensation at the time of comprising a variable frequency band extractor with a variable bandpass filter. It is a figure which shows the example of the frequency characteristic of the attenuation amount at the time of comprising a variable frequency band extractor with a variable band rejection filter. It is a figure which shows the cascade connection of a band-stop filter. It is a figure which shows the example of a filter bank structure by four filters. It is a figure which shows the frequency characteristic of a filter bank. It is a figure which shows the frequency characteristic of a filter bank. It is a figure which shows the specific structural example of a multiband signal processing circuit. It is a figure which shows the 2nd structural example of a multiband signal processing circuit. 1 is a diagram illustrating a first embodiment of a feedforward amplifier according to the present invention. FIG. It is a figure which shows 2nd Embodiment of the feedforward amplifier by this invention. FIG. 4 is a diagram showing a third embodiment of a feedforward amplifier according to the present invention. FIG. 6 is a diagram showing a fourth embodiment of a feedforward amplifier according to the present invention. FIG. 7 is a diagram showing a fifth embodiment of a feedforward amplifier according to the present invention. It is a figure which shows the function structural example of a band detector. It is a figure which shows the example of the spectrum of the input signal of a feedforward amplifier. It is a figure which shows the relationship between a sweep frequency and the frequency of an input signal. It is a figure which shows the time change of the signal output from a local oscillator. It is a figure which shows the time change of the signal output from a low-pass filter. It is the figure which showed that the bandwidth of the frequency band detected becomes narrow when a threshold value is set to the output from a low-pass filter. FIG. 7 shows a sixth embodiment of a feedforward amplifier according to the present invention. FIG. 9 is a diagram showing a seventh embodiment of the feedforward amplifier according to the present invention. It is a figure which shows 8th Embodiment of the feedforward amplifier by this invention.

Claims (9)

A feedforward amplifier having a distortion detection circuit and a distortion removal circuit,
N is an integer greater than or equal to 2,
It also has a frequency band controller and a band detector,
The distortion detection circuit includes:
A first linear signal path constituted by first delay means;
N first vector adjustment paths;
A first distributor for distributing an input signal to the first linear signal path, the N first vector adjustment paths, and the band detector ;
N first variable frequency band extractors that are provided for each of the first vector adjustment paths and extract signals in discrete frequency bands;
N first vector adjusters that are provided for each of the first vector adjustment paths and adjust the phase and amplitude;
A first multi-band amplifier for amplifying the output of each first vector adjuster in the first vector adjustment path;
A synthesizer / distributor that outputs a sum component and a difference component of the output of the first linear signal path and the output of the first multiband amplifier;
The distortion removal circuit includes:
A second linear signal path configured by second delay means and receiving the sum component;
N second vector adjustment paths through which the difference component is input;
N second variable frequency band extractors provided for each of the second vector adjustment paths and extracting signals in the same frequency band as the N first variable frequency band extractors, and for each of the second vector adjustment paths N second vector adjusters for adjusting phase and amplitude,
A second multi-band amplifier for amplifying the output of the second vector adjuster of the second vector adjustment path;
A second synthesis unit that synthesizes and outputs the output of the second linear signal path and the output of the second multiband amplification unit;
The band detector is
A local oscillator,
A local oscillator frequency control unit for controlling the frequency of the local oscillator;
A mixer for multiplying an input signal from the first distribution unit by a signal from the local oscillator;
A low-pass filter that passes only low-frequency components of the output of the mixer;
The local oscillator frequency control unit includes a signal that controls the local oscillator and an analysis unit that detects a frequency band of the input signal from the output signal of the low-pass filter and outputs a control signal to the frequency band controller. ,
Said frequency band controller, that controls the N first variable frequency band extractors and said N second variable frequency band extractors
Multi-frequency band for the feed-forward amplifier, wherein a call. The feed forward amplifier according to claim 1.
The first multi-band amplifier includes N first amplifiers for individually amplifying outputs of the first vector adjusters of the N first vector adjustment paths, and N first amplifiers. A first output synthesizer that combines outputs and outputs the first multi-frequency band amplifying unit;
The second multi-band amplification unit includes N second amplifiers for individually amplifying outputs of the second vector adjusters of the N second vector adjustment paths, and N second amplifiers. A multi-frequency band feedforward amplifier comprising: a second output synthesizer that synthesizes outputs and outputs the output of the second multi-band amplifier. The feed forward amplifier according to claim 1.
A first output synthesizer that synthesizes the outputs of the first vector adjusters of the N first vector adjustment paths; and amplifies the output of the first output synthesizer; A common first amplifier as an output of the first multiband amplifier,
The second multi-band amplification unit includes N second amplifiers for individually amplifying outputs of the second vector adjusters of the N second vector adjustment paths, and N second amplifiers. A multi-frequency band feedforward amplifier comprising: a second output synthesizer that synthesizes outputs and outputs the output of the second multi-band amplifier. The feed forward amplifier according to claim 1.
The first multi-band amplifier includes N first amplifiers for individually amplifying outputs of the first vector adjusters of the N first vector adjustment paths, and N first amplifiers. A first output synthesizer that combines outputs and outputs the first multi-frequency band amplifying unit;
A second output synthesizer that synthesizes outputs of the second vector adjusters of the N second vector adjustment paths; and amplifies the output of the second output synthesizer; A multi-frequency band feedforward amplifier comprising a common second amplifier serving as an output of the second multi-frequency band amplifier. The feed forward amplifier according to claim 1.
A first output synthesizer that synthesizes the outputs of the first vector adjusters of the N first vector adjustment paths; and amplifies the output of the first output synthesizer; A common first amplifier as an output of the first multiband amplifier,
A second output synthesizer that synthesizes outputs of the second vector adjusters of the N second vector adjustment paths; and amplifies the output of the second output synthesizer; A multi-frequency band feedforward amplifier comprising a common second amplifier serving as an output of the second multi-frequency band amplifier. The feedforward amplifier according to any one of claims 1 to 5 ,
Each of the N first variable frequency band extractors is N-1 cascaded first variable blocks that respectively block the extraction frequency bands of the remaining N-1 first variable frequency band extractors. It consists of a bandstop filter,
Each of the N second variable frequency band extractors includes N-1 cascaded second variable blocks that respectively block the extraction frequency bands of the remaining N-1 second variable frequency band extractors. A multi-frequency band feedforward amplifier comprising a band rejection filter. The feedforward amplifier according to any one of claims 1 to 5 ,
The N first variable frequency band extractors are configured by first variable band pass filters whose center frequencies are the center frequencies of the respective extraction frequency bands,
The N second variable frequency band extractors are configured by a second variable band pass filter whose center frequency is the center frequency of each extraction frequency band. A multi-frequency band feedforward amplifier. The feedforward amplifier according to any one of claims 1 to 5 ,
Each of the N first variable frequency band extractors or each of the N second variable frequency band extractors has a center frequency controlled by the frequency band controller. Feed forward amplifier. The feedforward amplifier according to any one of claims 1 to 5 ,
Each of the N first variable frequency band extractors or each of the N second variable frequency band extractors has a bandwidth controlled by the frequency band controller. Feed forward amplifier.

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