WO2016084650A1

WO2016084650A1 - Active antenna system

Info

Publication number: WO2016084650A1
Application number: PCT/JP2015/082226
Authority: WO
Inventors: 雄介八幡
Original assignee: 住友電気工業株式会社
Priority date: 2014-11-25
Filing date: 2015-11-17
Publication date: 2016-06-02
Also published as: JP2016100835A

Abstract

An active antenna system 3 is provided with: a plurality of couplers 31 which acquire transmission signals from a plurality of power amplifiers 16; a consolidating unit 32 to which a plurality of first signal lines 33 extending from each of the plurality of couplers 31 are connected, and which consolidates a plurality of transmission signals supplied respectively from the plurality of couplers 31, via the plurality of first signal lines 33, into a prescribed number of consolidated signals, less than the number of said plurality of transmission signals; and a distortion compensating unit 40 which performs distortion compensation for the plurality of power amplifiers 16 on the basis of feedback signals obtained by feeding back the transmission signals from the plurality of power amplifiers 16. The consolidating unit 32 supplies the prescribed number of consolidated signals to the distortion compensating unit 40 as the feedback signals, via a second signal line 34 connected between the consolidating unit 32 and a digital signal processing unit 10, the second signal line 34 consisting of a number of lines corresponding to the prescribed number of consolidated signals.

Description

Active antenna system

The present invention relates to an active antenna system used for a base station apparatus or the like of a radio communication system.

In recent years, in wireless communication systems used for mobile phones and the like, the demand for expansion of communication areas and expansion of communication capacity has increased due to the spread of smartphones and the like. Therefore, use of an active antenna system including a plurality of antenna elements and a plurality of amplifiers provided corresponding to the plurality of antenna elements to amplify transmission / reception signals for a base station apparatus is being studied (for example, patents). Reference 1).

Special table 2009-544205

Here, in an amplifier used for transmission / reception of a radio signal, distortion compensation is generally performed in order to improve distortion characteristics.
For this reason, it is conceivable to perform distortion compensation for each of the plurality of amplifiers included in the active antenna system as described above.

FIG. 6 is a diagram illustrating an example of a case where a function for performing distortion compensation is provided for a plurality of amplifiers that amplify transmission signals included in the active antenna system.
As shown in the figure, this active antenna system includes a digital signal processing unit 100 to which a transmission signal of a digital signal is given, a plurality of amplifiers 101 to which a transmission signal is given through the digital signal processing unit 100, and a plurality of amplifiers 101. And a plurality of antenna elements 102 connected to the output side.

The output signal of each amplifier 101 is given to the digital signal processing unit 100 as a feedback signal. The digital signal processing unit 100 obtains a distortion characteristic of each amplifier 101 by comparing the given feedback signal and the input signal, and predistorts the transmission signal given to each amplifier 101 based on the obtained distortion characteristic. It has a function to perform compensation.

Here, the active antenna system of FIG. 6 is connected between each amplifier 101 and the antenna element 102 in order to provide the digital signal processing unit 100 with the output signal of each amplifier 101 as a feedback signal. A coupler 103 to be obtained and a signal line 104 connecting the coupler 103 and the digital signal processing unit 100 are provided.
The digital signal processing unit 100 acquires a feedback signal from each amplifier 101 fed back through the signal line 104.

As described above, in order to perform distortion compensation of the amplifier 101, the output signal of the amplifier 101 is required as a feedback signal. However, in the active antenna system, a plurality of amplifiers 101 corresponding to each of the plurality of antenna elements 102 is used. Therefore, it is necessary to provide the number of signal lines 104 corresponding to the number of amplifiers 101.
For this reason, as the number of amplifiers 101 increases, the number of signal lines 104 required also increases, and the area (physical area) necessary for providing the signal lines 104 increases.

That is, the digital signal processing unit 100, the amplifier 101, and the signal line 104 included in the active antenna system are mounted on the wiring board. However, as the number of the amplifiers 101 increases, the number of signal lines 104 required increases. The area on the board necessary for mounting increases. As a result, the substrate size is increased, which makes it difficult to reduce the size of the entire system.

The present invention has been made in view of such circumstances, and an object thereof is to provide an active antenna system that can be further downsized.

An active antenna system according to an embodiment is an active antenna system including a plurality of antenna elements and a plurality of amplifiers provided corresponding to each of the plurality of antenna elements, and an output signal of the plurality of amplifiers And a plurality of first signal lines extending from each of the plurality of acquisition units, and the plurality of outputs given from each of the plurality of acquisition units via the plurality of first signal lines. An aggregating unit that aggregates signals into a predetermined number of aggregated signals smaller than the plurality of output signals, and a distortion compensating unit that performs distortion compensation of the plurality of amplifiers based on feedback signals obtained by feeding back the output signals of the plurality of amplifiers The aggregation unit includes the predetermined number of aggregate signals as the feedback signal via a second signal line connecting the aggregation unit and the distortion compensation unit. The applied distortion compensation unit, the second signal line is composed of a number of lines corresponding to the aggregate signal of the predetermined number of Te.

According to the active antenna system of the present invention, further downsizing is possible.

It is a figure which shows a part of base station apparatus provided with the active antenna system which concerns on one Embodiment. It is the block diagram which showed the structure of the antenna system which concerns on 1st Embodiment. It is a block diagram which shows the distortion compensation part which a digital signal processing part has. It is a block diagram of the antenna system which concerns on the modification of 1st Embodiment. It is the block diagram which showed the structure of the antenna system which concerns on 2nd Embodiment. It is a figure which shows an example at the time of providing the function for performing distortion compensation with respect to the several amplifier which amplifies the transmission signal with which an active antenna system is provided.

[Description of Embodiment]

First, the contents of the embodiment will be listed and described.
(1) An active antenna system according to an embodiment is an active antenna system including a plurality of antenna elements and a plurality of amplifiers provided corresponding to each of the plurality of antenna elements. And a plurality of first signal lines extending from each of the plurality of acquisition units, and a plurality of units provided from the plurality of acquisition units via the plurality of first signal lines. An aggregating unit for aggregating the output signals into a predetermined number of aggregating signals smaller than the plurality of output signals, and performing distortion compensation of the plurality of amplifiers based on feedback signals obtained by feeding back the output signals of the plurality of amplifiers A distortion compensation unit, and the aggregation unit sends the predetermined number of aggregate signals to the feedback signal via a second signal line connecting the aggregation unit and the distortion compensation unit. The applied distortion compensation unit, the second signal line is composed of a number of lines corresponding to the aggregate signal of the predetermined number as.

According to the active antenna system configured as described above, since the second signal line is configured with the number of lines corresponding to a predetermined number of aggregate signals, the number of lines of the second signal line is equal to the number of amplifiers. Can be less. As a result, the number of second signal lines can be reduced as compared to the case where the number of signal lines for returning feedback signals is set to the number corresponding to the number of amplifiers as in the conventional example. it can. As a result, an area necessary for providing the second signal line can be suppressed, and the entire system can be further downsized.

(2) In the active antenna system, the aggregation unit is connected between the plurality of acquisition units and the distortion compensation unit in a state of being arranged closer to the acquisition unit than the distortion compensation unit. Preferably, in this case, the length of the second signal line relative to the first signal line can be made relatively longer than in the case where the aggregation part is arranged at a position close to the distortion compensation part. Thereby, the area | region suppressed by providing a 2nd signal line can be made wider by lengthening the length of the 2nd signal line which can reduce the number of lines.

(3) In the active antenna system, it is preferable that the aggregation unit selects a predetermined number of output signals as the predetermined number of aggregate signals from the plurality of output signals.
(4) In this case, the aggregation unit may select the predetermined number of output signals from the plurality of output signals according to a predetermined order.
As a result, the aggregating unit can select each output signal output from the plurality of amplifiers evenly, and can provide it to the distortion compensating unit as a feedback signal.

(5) In the active antenna system, a plurality of the distortion compensators may be provided corresponding to each of the plurality of amplifiers, and the distortion compensation may be performed for each of the plurality of amplifiers.
In this case, since distortion compensation is performed for each of the plurality of amplifiers, distortion compensation can be performed with higher accuracy according to the characteristics of each amplifier.

(6) In the active antenna system, the aggregation unit is connected between the plurality of distortion compensation units and the predetermined number of aggregation signals are output from any of the plurality of power amplifiers. It is preferable that a distribution unit is further provided for identifying whether the output signal is an output signal and distributing the predetermined number of aggregate signals to the distortion compensation unit corresponding to the identified amplifier.
In this case, the predetermined number of aggregate signals selected by the aggregation unit can be appropriately given to the corresponding distortion compensation unit.

(7) In the active antenna system, the aggregation unit multiplexes the plurality of output signals so that the number of signals is smaller than that of the plurality of output signals. It is preferable to aggregate into a number of aggregate signals.
In this case, the characteristics of each amplifier can be reflected in the aggregate signal with a simple configuration.

[Details of the embodiment]
Hereinafter, preferred embodiments will be described with reference to the drawings.
[Overall configuration of base station equipment with active antenna system]
FIG. 1 is a diagram illustrating a part of a base station apparatus including an active antenna system according to an embodiment. In the figure, a base station apparatus 1 is used as a base station apparatus in a wireless communication system for a mobile phone to which LTE (Long Term Evolution) is applied, for example, and is a mobile terminal such as a mobile phone (not shown). It has a function of performing wireless communication.
As shown in the figure, the base station device 1 includes a baseband unit (BBU) 2 and an active antenna system 3.

The baseband unit 2 is connected to an active antenna system 3 (hereinafter also simply referred to as an antenna system 3) by a signal transmission path (optical transmission path or electrical transmission path) 4 extending from the baseband unit 2.

The baseband unit 2 has a function of generating a transmission baseband signal (I / Q signal), which is a digital signal, by performing digital modulation processing on transmission data given from an upper network (not shown).
The baseband unit 2 gives a transmission baseband signal obtained by modulating transmission data to the antenna system 3 via the signal transmission path 4.

Further, the baseband unit 2 acquires a reception baseband signal (I / Q signal) which is a digital signal given from the antenna system 3 via the signal transmission path 4, and performs digital demodulation processing on the reception baseband signal. To generate received data.
The baseband unit 2 gives the received data obtained by demodulating the received baseband signal to the upper network.

As described above, the baseband unit 2 has a function of performing processing such as digital modulation / demodulation processing on data and baseband signals transmitted and received by wireless communication.

The antenna system 3 includes a plurality of antenna elements 5 for transmitting and receiving radio frequency signals in the housing 3a, and an amplifier for amplifying transmission / reception signals for each of the plurality of antenna elements 5. When the station device 1 performs wireless communication with a mobile terminal, the station device 1 has a function of transmitting and receiving a wireless signal related to the wireless communication.

The plurality of antenna elements 5 are arranged at a predetermined interval to constitute an array antenna.

[Configuration of Antenna System According to First Embodiment]
FIG. 2 is a block diagram showing a configuration of the antenna system 3 according to the first embodiment.
The antenna system 3 includes a digital signal processing unit 10, a transmission unit 11, and a reception unit 9 connected to the baseband unit 2.

The digital signal processing unit 10 performs digital signal processing on the transmission baseband signal given from the baseband unit 2 as necessary, and then gives the transmission baseband signal to the transmission unit 11. The digital signal processing unit 10 also performs baseband signal processing in the receiving unit 9 as described later.
The digital signal processing unit 10 has a function of performing predistortion compensation (distortion compensation processing) on the power amplifier included in the antenna system 3. The function of performing this predistortion compensation will be described in detail later.

The transmission unit 11 converts the transmission baseband signal given from the baseband unit 2 into a radio frequency transmission signal, amplifies the converted radio frequency transmission signal, and gives it to each of the plurality of antenna elements 5.

The transmission unit 11 includes a digital-to-analog converter (DAC: Digital to Analog Converter) 12, a processing unit 13, and a distributor 14, and is configured to perform signal processing on an analog signal.

The digital-analog converter 12 has a function of converting a transmission baseband signal, which is a digital signal given from the digital signal processing unit 10, into an analog signal.
The digital-analog converter 12 gives the transmission baseband signal converted into the analog signal to the processing unit 13 connected to the subsequent stage of the digital-analog converter 12.
The processing unit 13 orthogonally modulates the transmission baseband signal composed of the I signal and the Q signal supplied from the digital-analog converter 12, and multiplies the signal after the orthogonal modulation by the radio frequency local signal to thereby generate a radio frequency signal. Is converted into a transmission signal.

The processing unit 13 gives the transmission signal obtained by converting the transmission baseband signal to the distributor 14 connected to the subsequent stage of the processing unit 13.
The distributor 14 distributes the transmission signal into a plurality of parts corresponding to the plurality of antenna elements 5.

The transmitter 11 further includes a plurality of first phase shifters 15 and a plurality of power amplifiers 16.
The first phase shifter 15 and the power amplifier 16 are provided between the distributor 14 and each antenna element 5, and a plurality of first phase shifters 15 and power amplifiers 16 are provided corresponding to the plurality of antenna elements 5.
Therefore, the plurality of transmission signals distributed by the distributor 14 are provided to the antenna elements 5 through the first phase shifter 15, the power amplifier 16, and the antenna duplexer 17, respectively.

The plurality of first phase shifters 15 connected to the subsequent stage of the distributor 14 adjusts the phase of the transmission signal distributed by the distributor 14. The 1st phase shifter 15 is comprised so that the setting regarding the phase adjustment can be controlled from the outside. For example, a control command for controlling the plurality of first phase shifters 15 is given to the antenna system 3 through the signal transmission path 4, and the digital signal processing unit 10 of the antenna system 3 receives a plurality of first commands based on the given control command. One phase shifter 15 can be configured to be controlled.

The plurality of first phase shifters 15 adjust the phase of each transmission signal distributed by the distributor 14 so that the transmission signal is transmitted as a radio signal from each of the plurality of antenna elements 5 as described later. The tilt angle can be adjusted.
The tilt angle is an angle with respect to the horizontal direction of a beam formed by radio signals transmitted from a plurality of antenna elements 5 constituting the array antenna.

Each first phase shifter 15 provides the transmission signal subjected to phase adjustment to a power amplifier 16 connected to the subsequent stage of the first phase shifter 15.
Each power amplifier 16 amplifies the transmission signal given from the first phase shifter 15. Each power amplifier 16 applies the amplified transmission signal to the antenna duplexer 17 connected to the subsequent stage of the power amplifier 16.

Each antenna duplexer 17 is connected to an antenna element 5, a transmission unit 11, and a reception unit 9. The antenna duplexer 17 is configured by, for example, a circulator, a duplexer, or the like, and has a function for sharing the antenna element 5 between the transmitter 11 and the receiver 9.

The antenna duplexer 17 has a function of giving a signal given from the power amplifier 16 to the antenna element 5 and giving a signal given from the antenna element 5 to the receiving unit 9. Therefore, the antenna duplexer 17 gives the transmission signal to the antenna element 5 when the amplified transmission signal is given from the power amplifier 16.
The transmission signal given to each antenna element 5 from each antenna duplexer 17 is radiated from each antenna element 5 to the space and transmitted as a radio signal.

As described above, the transmission baseband signal which is a digital signal given from the baseband unit 2 is converted into a transmission signal which is an analog signal by the digital-analog converter 12 and the processing unit 13. Further, the transmission signal is distributed by the distributor 14, phase-adjusted by the first phase shifter 15, amplified by the power amplifier 16, and given to each antenna element 5.

The receiving unit 9 converts a received signal received by each of the plurality of antenna elements 5 into a baseband signal, and provides the baseband unit 2 through the digital signal processing unit 10.

The receiving unit 9 includes a plurality of low noise amplifiers 20, a plurality of second phase shifters 21, a synthesizer 22, a processing unit 23, and an analog-to-digital converter (ADC: Analog to Digital Converter) 24. It is configured to perform signal processing on analog signals.

The low noise amplifier 20 is connected to the antenna duplexer 17 (FIG. 2). Each antenna duplexer 17 provides each low-noise amplifier 20 with a radio frequency reception signal that is an analog signal received by each antenna element 5.
The low noise amplifier 20 amplifies the received signal and gives it to the second phase shifter 21 connected to the subsequent stage of the low noise amplifier 20.

The second phase shifter 21 adjusts the phase of the received signal amplified by the low noise amplifier 20. The second phase shifter 21 is configured so that settings relating to the phase adjustment can be controlled from the outside. For example, a control command for controlling the plurality of second phase shifters 21 is given to the antenna system 3 through the signal transmission path 4, and the digital signal processing unit 10 of the antenna system 3 receives a plurality of first commands based on the given control command. The two phase shifters 21 can be controlled.

The plurality of second phase shifters 21 adjust the tilt angle when the reception signals are received by the plurality of antenna elements 5 by performing phase adjustment of the plurality of reception signals amplified by the plurality of low noise amplifiers 20. can do.

Each second phase shifter 21 provides the received signal, which has been subjected to phase adjustment, to a synthesizer 22 connected to the subsequent stage of the second phase shifter 21.
The synthesizer 22 synthesizes the received signals given from the second phase shifters 21 and outputs a synthesized signal (received signal).

The synthesized signal output from the synthesizer 22 is given to the processing unit 23 connected to the subsequent stage of the synthesizer 22.
The processing unit 23 multiplies the synthesized signal supplied from the synthesizer 22 by a local signal having a baseband frequency to convert the synthesized signal into an intermediate frequency signal and performs orthogonal demodulation on the intermediate frequency signal. Convert to band signal (receive baseband signal).

The processing unit 23 gives the received baseband signal obtained by converting the combined signal to the analog-digital converter 24 connected to the subsequent stage of the processing unit 23.

The analog-digital converter 24 has a function of converting a received baseband signal, which is an analog signal supplied from the processing unit 23, into a digital signal.
The analog-to-digital converter 24 gives the received baseband signal converted into a digital signal to the digital signal processing unit 10.

The digital signal processing unit 10 performs digital signal processing on the received baseband signal given from the analog-digital converter 24 as necessary, and then gives the received baseband signal to the baseband unit 2.

As described above, the received signals, which are analog signals received by the plurality of antenna elements 5, are amplified by the respective low noise amplifiers 20, adjusted in phase by the respective second phase shifters 21, and synthesized by the synthesizer 22. Is done. Further, the combined received signal is converted into a received baseband signal which is a digital signal by the processing unit 23 and the analog-digital converter 24 and is given to the baseband unit 2.

The antenna system 3 also includes a signal feedback unit 30 that feeds back a feedback signal used for distortion compensation processing performed for each power amplifier 16 described later to the digital signal processing unit 10.
The signal feedback unit 30 includes a plurality of couplers 31 provided on the line 18 that connects the output ends of the power amplifiers 16 and the antenna duplexers 17, and an aggregation unit 32 that aggregates signals provided from the plurality of couplers 31. It has.

The coupler 31 is configured by a directional coupler or the like, and has a function of acquiring a transmission signal given to the antenna duplexer 17 through the line 18 from the output end of the power amplifier 16. That is, the plurality of couplers 31 constitute an acquisition unit that acquires transmission signals that are output signals output from the output terminals of the plurality of amplifiers 16.
Each coupler 31 and the consolidating unit 32 are connected to each other by a first signal line 33 extending from each coupler 31.
Each coupler 31 provides a transmission signal to the aggregation unit 32 via a first signal line 33 extending from each coupler 31.

The aggregating unit 32 has a function of aggregating a plurality of transmission signals given from the respective couplers 31 into a predetermined number of aggregation signals smaller than the number of the plurality of transmission signals.
The aggregation unit 32 is configured by a switch or the like that switches signal lines, and selects a predetermined number of transmission signals from among a plurality of transmission signals as an aggregation signal by switching the signal lines. In the present embodiment, the predetermined number is set to “1”, and the aggregation unit 32 is configured to select one transmission signal from a plurality of transmission signals.
Thus, the aggregating unit 32 selects a predetermined number of transmission signals from among the plurality of transmission signals as the predetermined number of aggregation signals, so that the plurality of transmission signals are smaller than the number of the plurality of transmission signals. Aggregate to the aggregate signal.

In addition, when the aggregation unit 32 outputs the selected transmission signals as a predetermined number of aggregation signals for a certain period, the aggregation unit 32 reselects the transmission signals in accordance with a predetermined order from the plurality of transmission signals. The aggregating unit 32 outputs the reselected transmission signal for a certain period. As described above, the aggregating unit 32 selects a transmission signal in a predetermined order from a plurality of transmission signals every predetermined period, and switches transmission signals to be selected as a predetermined number of aggregated signals.
Thereby, the aggregating unit 32 selects the plurality of transmission signals output from the plurality of power amplifiers 16 as a predetermined number of aggregated signals.

The aggregation unit 32 and the digital signal processing unit 10 are connected by a second signal line 34.
The aggregation unit 32 provides a predetermined number of aggregate signals to the digital signal processing unit 10 via the second signal line 34.

The second signal line 34 includes a processing unit 35 and an analog / digital converter 36. The processing unit 35 and the analog-digital converter 36 are connected between the aggregation unit 32 and the digital signal processing unit 10, and are necessary for a predetermined number of aggregation signals that are analog signals and radio frequency signals. Processing is performed, and a predetermined number of aggregate signals after processing are provided to the digital signal processing unit 10.
The processing unit 35 multiplies a predetermined number of aggregate signals given from the aggregation unit 32 by a baseband frequency local signal to convert the aggregate signal into an intermediate frequency signal and orthogonally demodulates the intermediate frequency signal. To convert it to a baseband signal.

The processing unit 35 provides a predetermined number of aggregate signals converted into baseband signals to an analog-digital converter 36 connected to the subsequent stage of the processing unit 35.

The analog-digital converter 36 converts a predetermined number of aggregate signals converted into analog baseband signals given from the processing unit 35 into digital signals, and gives them to the digital signal processing unit 10.

Here, the second signal line 34 is configured by the number of lines corresponding to a predetermined number of aggregate signals. That is, the second signal line 34 includes the same number of lines as the number of aggregate signals in order to transmit a predetermined number of aggregate signals in parallel.
In the present embodiment, since the predetermined number is “1”, the second signal line 34 is configured by one line corresponding to one aggregated signal. If the predetermined number is “2”, the second signal line 34 is composed of two lines. If the predetermined number is “3”, the second signal line 34 is composed of three lines. .

The aggregation unit 32 is connected between each coupler 31 and the digital signal processing unit 10. The aggregation unit 32 is arranged at a position closer to each coupler 31 than the digital signal processing unit 10. Therefore, the length of the second signal line 34 is relatively longer than the length of the first signal line 33.

As described above, the signal feedback unit 30 (the aggregation unit 32 thereof) provides a predetermined number of aggregate signals to the digital signal processing unit 10 via the second signal line 34.
The predetermined number of aggregate signals given to the digital signal processing unit 10 are given to the distortion compensation processing unit included in the digital signal processing unit 10 and used for distortion compensation of the plurality of power amplifiers 16.
In other words, the aggregating unit 32 uses the predetermined number of aggregated signals as feedback signals via the second signal line 34 connecting the aggregating unit 32 and the digital signal processing unit 10 (distortion compensation unit) to the digital signal processing unit 10. (Distortion compensation unit).

[Distortion compensation section]
FIG. 3 is a block diagram illustrating a distortion compensation unit included in the digital signal processing unit 10.
The digital signal processing unit 10 is configured by a computer including a CPU, a storage unit, and the like. Each functional unit included in the digital signal processing unit 10 described below by reading a program stored in the storage unit and the like is described below. And a function of executing various processes.

As shown in the figure, the digital signal processing unit 10 functionally includes a distortion compensation unit 40.
The distortion compensation unit 40 receives a predetermined number of aggregate signals given from the aggregation unit 32 as feedback signals, and performs distortion compensation for the plurality of power amplifiers 16 based on the predetermined number of aggregate signals.

The distortion compensation unit 40 includes a calculation unit 41 for obtaining a distortion compensation coefficient used for performing distortion compensation, a LUT (Look Up Table) 42 for registering the distortion compensation coefficient obtained by the calculation unit 41, and a baseband unit. 2, a compensation processing unit 43 that performs predistortion processing on the signal x, which is a transmission baseband signal given from 2.

A predetermined number of aggregate signals received as feedback signals are given to the calculation unit 41.
In addition to a predetermined number of aggregate signals, the calculation unit 41 is given a signal x via a branch path 44 branched at the preceding stage of the compensation processing unit 43. Note that the signal x to be compared with the predetermined number of aggregate signals is a transmission baseband signal corresponding to the predetermined number of aggregate signals, and the timing of the signals is adjusted by a delay adjustment unit (not shown) and is given to the calculation unit 41.

The calculation unit 41 has a function of estimating an inverse model indicating an inverse characteristic of the input / output characteristic of the power amplifier 16 based on a predetermined number of aggregate signals and the signal x. However, the model of the power amplifier 16 estimated by the calculation unit 41 is not necessarily an inverse model, and may be a forward model.

A model indicating the input / output characteristics of the power amplifier 16 can be expressed by, for example, a power series.
The calculation unit 41 of the present embodiment obtains an error signal between a predetermined number of aggregate signals and the signal x, and estimates an inverse model of the power amplifier 16 that can minimize the error signal as a power series.
The calculation unit 41 obtains each power series coefficient indicating the estimated inverse model as a distortion compensation coefficient for compensating for distortion of the power amplifier 16.
The calculation unit 41 provides the LUT 42 with the obtained distortion compensation coefficient, which is the next-order coefficient.

The LUT 42 is configured to be able to register a distortion compensation coefficient given from the calculation unit 41.
Further, when a new distortion compensation coefficient is given from the calculation unit 41 when a distortion compensation coefficient has already been registered, the LUT 42 discards the already registered distortion compensation coefficient and updates it with a new distortion compensation coefficient. sign up.

The compensation processing unit 43 performs distortion compensation processing on the signal x based on the distortion compensation coefficient obtained by the computing unit 41, and outputs a compensation signal u after distortion compensation.
As described above, the distortion compensation coefficient represents an inverse model of the power amplifier 16 that can minimize the error signal. Therefore, a reverse characteristic capable of minimizing an error signal between a predetermined number of aggregate signals and the signal x is added to the compensation signal u after distortion compensation.
The compensation processing unit 43 can cause the power amplifier 16 to output a transmission signal in which the distortion is suppressed by providing the power amplifier 16 with the compensation signal u compensated with a characteristic opposite to the distortion characteristic of the power amplifier 16.

The compensation processing unit 43 refers to the LUT 42 and acquires a distortion compensation coefficient registered in the LUT 42. The compensation processing unit 43 performs distortion compensation processing on the signal x, which is a transmission baseband signal, based on the acquired distortion compensation coefficient, and outputs a compensation signal u, which is a transmission baseband signal after distortion compensation.

A compensation signal u that is a transmission baseband signal output from the compensation processing unit 43 is converted into a transmission signal through the digital-analog converter 12 and the processing unit 13, and is then supplied to the distributor 14.
The compensation signal u converted into the transmission signal is distributed by the distributor 14 and supplied to the power amplifier 16 (see FIG. 1).

Here, the calculation unit 41 estimates an inverse model of the power amplifier 16 using a predetermined number of aggregate signals as feedback signals. The predetermined number of aggregate signals are selected by the aggregation unit 32 from among a plurality of transmission signals output from the plurality of power amplifiers 16.
For this reason, the distortion characteristic of the power amplifier 16 that has output the transmission signals not selected as the predetermined number of aggregate signals is not reflected in the inverse model based on the predetermined number of aggregate signals.

In this regard, as described above, the aggregating unit 32 selects a transmission signal according to a predetermined order from a plurality of transmission signals every predetermined period, and switches transmission signals to be selected as a predetermined number of aggregated signals.
Therefore, the aggregating unit 32 can select a plurality of transmission signals output from the plurality of power amplifiers 16 as a predetermined number of aggregated signals, and can provide the selected signal to the distortion compensating unit 40.

The calculation unit 41 estimates an inverse model based on the switched aggregate signal every time the aggregation unit 32 switches selection of a predetermined number of aggregate signals. As a result, the calculation unit 41 sequentially reflects the distortion characteristics of the power amplifiers 16 in the inverse model, and registers them in the LUT 42 as distortion compensation coefficients.
As a result, the compensation processing unit 43 that performs distortion compensation based on the distortion compensation coefficient registered in the LUT 42 can sequentially reflect the distortion characteristics of each power amplifier 16 in the compensation signal u.

The compensation processing unit 43 can perform distortion compensation processing according to the current input / output characteristics by performing distortion compensation based on the distortion compensation coefficient of the LUT 42 updated by the calculation unit 41.

A plurality of power amplifiers 16 are selected and used in advance whose distortion characteristics are close to each other.
For this reason, the compensation processing unit 43 can perform distortion compensation with high accuracy even if the distortion characteristics of the power amplifiers 16 are sequentially reflected in the compensation signal u.

As described above, the distortion compensator 40 receives a predetermined number of aggregate signals given from the aggregation unit 32 as feedback signals, and performs distortion compensation of the plurality of power amplifiers 16 based on the predetermined number of aggregate signals.

[Effect]
In the antenna system 3 having the above-described configuration, a plurality of couplers 31 serving as a plurality of acquisition units that acquire transmission signals as output signals of the plurality of power amplifiers 16 and a plurality of first signal lines 33 extending from each of the plurality of couplers 31 are connected. An aggregating unit 32 for aggregating a plurality of transmission signals given from the plurality of couplers 31 via the plurality of first signal lines 33 into a predetermined number of aggregation signals smaller than the plurality of transmission signals, and a plurality of power amplifiers 16. And a distortion compensator 40 that performs distortion compensation of the plurality of power amplifiers 16 based on a feedback signal obtained by feeding back the transmission signal. The aggregating unit 32 includes the aggregating unit 32 and the distortion compensating unit 40 (digital signal processing unit 10). ) To the distortion compensator 40 as a feedback signal through a second signal line 34 that connects between the second signal line 34 and the second signal line 3. It is composed of a number of lines corresponding to a predetermined number of aggregate signal.

Here, the digital signal processing unit 10, the power amplifier 16, the first signal line 33, the second signal line 34, and the like included in the antenna system 3 are mounted on the wiring board. However, as the number of the power amplifiers 16 increases, The required number of

lines

33 and 34 also increases, and the area on the substrate necessary for mounting each

signal line

33 and 34 increases. As a result, the size of the wiring board may have to be increased.

In this regard, according to the antenna system 3 configured as described above, since the second signal line 34 is configured with the number of lines corresponding to a predetermined number of aggregate signals, the number of lines of the second signal line 34 is changed to a plurality of power amplifiers. The number can be less than 16. As a result, the number of second signal lines 34 can be reduced as compared to the case where the number of signal lines for returning feedback signals is set to the number corresponding to the number of amplifiers as in the conventional example. Can do. As a result, an area necessary for providing the second signal line 34 can be suppressed, and the antenna system 3 as a whole can be further downsized.

Further, since the aggregation unit 32 is disposed closer to each coupler 31 than the digital signal processing unit 10 (distortion compensation unit 40) and is connected between each coupler 31 and the distortion compensation unit 40, the aggregation unit 32 The length of the second signal line 34 relative to the first signal line 33 can be made relatively long compared to the case where 32 is disposed at a position close to the distortion compensation unit 40. Thereby, the area | region suppressed by providing the 2nd signal track | line 34 can be made wider by lengthening the length of the 2nd signal track | line 34 which can reduce the number of track | lines.

[Modification]
In the above-described embodiment, the predetermined number selected as the aggregate signal by the aggregation unit 32 from the plurality of transmission signals given from the respective couplers 31 is set to “1”, and the number of the second signal lines 34 is also one. And the case where the 2nd signal track | line 34 was made into the number of lines corresponding to an aggregate signal was shown.
However, the aggregating unit 32 is configured to aggregate a predetermined number of aggregated signals by selecting a larger number of transmission signals within a range of a smaller number than the plurality of transmission signals provided by the first signal line 33. Also good.

FIG. 4 is a block diagram of an antenna system 3 according to a modification of the first embodiment.
In this modification, the second signal line 34 is composed of two lines.
In this case, the aggregating unit 32 is configured to select two transmission signals from a plurality of transmission signals given from the respective couplers 31 and aggregate them into a predetermined number of aggregation signals. That is, in this modification, the predetermined number is set to “2”.
Also in this case, the aggregating unit 32 selects a transmission signal according to a predetermined order from a plurality of transmission signals every predetermined period, and switches transmission signals to be selected as a predetermined number (two) of the aggregated signals.

The aggregating unit 32 transmits two aggregated signals in parallel via the two second signal lines 34, and gives them to the distortion compensation unit 40 of the digital signal processing unit 10.
The calculation unit 41 of the distortion compensator 40 to which the two aggregated signals are given multiplexes the two aggregated signals, and obtains a distortion compensation coefficient based on the combined signal and the signal x.
Thus, when a plurality of aggregate signals are given as a predetermined number of aggregate signals via the plurality of second signal lines 34, the calculation unit 41 of the distortion compensation unit 40 combines the plurality of aggregate signals. The distortion compensation coefficient can be obtained based on the above.

In the first embodiment, the aggregation unit 32 is configured by a switch or the like that switches the signal line, and selects a predetermined number of transmission signals as a predetermined number of aggregation signals from the plurality of transmission signals. A case where the transmission signals are aggregated into a predetermined number of aggregation signals smaller than the plurality of transmission signals has been shown.
However, the aggregating unit 32 is configured by a multiplexer that combines a plurality of output signals so that the number of signals is smaller than that of the plurality of output signals, and the plurality of output signals are combined by combining the plurality of output signals. May be aggregated into a predetermined number of aggregate signals.

For example, when the aggregating unit 32 is configured by a multiplexer that multiplexes all of the plurality of output signals output from the power amplifiers 16, the aggregating unit 32 outputs the plurality of output signals output from the power amplifiers 16. The combined signal can be applied to the distortion compensator 40 of the digital signal processor 10 via the second signal line 34 (FIG. 2).
According to this configuration, a simple configuration can be achieved by using the aggregation unit 32 as a multiplexer, and the characteristics of each power amplifier 16 can be reflected in the aggregate signal provided to the distortion compensation unit 40 with a simple configuration.

The calculation unit 41 of the distortion compensation unit 40 obtains a distortion compensation coefficient based on the aggregate signal reflecting the characteristics of each power amplifier 16.
As a result, the compensation processing unit 43 that performs distortion compensation based on the distortion compensation coefficient registered in the LUT 42 can reflect the distortion characteristics of each power amplifier 16 in the compensation signal u.

Furthermore, in the first embodiment, the aggregation unit 32 selects a transmission signal in a predetermined order from a plurality of transmission signals every predetermined period, and switches the transmission signals to be selected as a predetermined number of aggregation signals. It was.
However, when a plurality of power amplifiers 16 are selected and used in advance whose distortion characteristics are close to each other, the aggregating unit 32 selects the transmission signal from the plurality of transmission signals, and selects the transmission signal. The transmission signal may be provided to the digital signal processing unit 10 as a predetermined number of aggregate signals without changing the transmission signals as a predetermined number of aggregate signals.

In this case, if the distortion characteristics of some of the plurality of power amplifiers 16 are grasped, it can be estimated that the distortion characteristics of other power amplifiers 16 are also approximated to the grasped distortion characteristics.

[About the second embodiment]
FIG. 5 is a block diagram showing the configuration of the antenna system 3 according to the second embodiment.
The antenna system 3 includes a digital signal processing unit 10 connected to the baseband unit 2 and a transmission unit 11. In FIG. 5, the receiving unit is omitted for easy understanding.

In the antenna system 3 of the present embodiment, the digital signal processing unit 10 is configured to output a plurality of transmission baseband signals corresponding to each power amplifier 16, and the transmission unit 11 includes each power amplifier. The difference from the first embodiment is that each 16 includes a digital-analog converter 12 and a processing unit 13.

Further, in the antenna system 3 of the present embodiment, the digital signal processing unit 10 includes a plurality of distortion compensation units 40 for each power amplifier 16, and a predetermined number of aggregate signals are respectively transmitted to the plurality of distortion compensation units 40. The second embodiment is also different from the first embodiment in that a distribution unit 45 for distributing the image to the image is provided.
Other configurations are the same as those of the first embodiment except for the portions specifically described below.

In the present embodiment, the plurality of distortion compensation units 40 are provided corresponding to each of the plurality of power amplifiers 16, and are configured to perform distortion compensation for each of the plurality of power amplifiers 16.

In addition, a predetermined number of aggregate signals aggregated by the aggregation unit 32 are provided to the distribution unit 45 of the digital signal processing unit 10.
The distribution unit 45 is connected between the aggregation unit 32 and the plurality of distortion compensation units 40. The distribution unit 45 specifies which power amplifier 16 of the plurality of power amplifiers 16 is the predetermined number of aggregate signals, and corresponds to the power amplifier 16 that has output the specified output signal. A predetermined number of aggregate signals are distributed to the distortion compensator 40.

Here, the distribution unit 45 and the aggregation unit 32 are connected by a signal line 37 for exchanging information with each other.
The aggregating unit 32 presents information indicating which power amplifier 16 of the plurality of power amplifiers 16 is the transmission signal output from the power amplifier 16 to the distributing unit 45 at the present time. Is configured to give.

Based on the information given from the aggregating unit 32, the distributing unit 45 determines which power amplifier 16 of the plurality of power amplifiers 16 is a predetermined number of aggregated signals that are currently given. Is identified. The distribution unit 45 distributes a predetermined number of aggregate signals to the distortion compensation unit 40 that performs distortion compensation of the power amplifier 16 that is the output source of the identified output signal.
Thereby, the predetermined number of aggregate signals selected by the aggregation unit 32 can be appropriately given to the corresponding distortion compensation unit 40.

According to the present embodiment, a plurality of distortion compensation units 40 are provided corresponding to each of the plurality of power amplifiers 16, and are configured to perform distortion compensation for each of the plurality of power amplifiers 16. The distortion compensation can be performed every 16 and the distortion compensation can be performed more accurately according to the characteristics of each power amplifier 16.

[Others]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Base station apparatus 2 Baseband unit 3 Active antenna system 3a Case 4 Signal transmission path 5 Antenna element 10 Digital signal processing part 11 Transmission part 12 Reception part 12 Digital analog converter 13 Processing part 14 Divider 15 1st phase shifter Reference Signs List 16 power amplifier 17 antenna duplexer 18 line 20 low noise amplifier 21 second phase shifter 22 combiner 23 processing unit 24 analog to digital converter 30 signal feedback unit 31 coupler 32 aggregation unit 33 first signal line 34 second signal line 35 Processing unit 36 Analog-digital converter 37 Signal line 40 Distortion compensation unit 41 Calculation unit 42 LUT
43 Compensation processing unit 44 Branch path 45 Distribution unit x signal u Compensation signal

Claims

An active antenna system comprising a plurality of antenna elements and a plurality of amplifiers provided corresponding to each of the plurality of antenna elements,
A plurality of acquisition units for acquiring output signals of the plurality of amplifiers;
A plurality of first signal lines extending from each of the plurality of acquisition units are connected, and a plurality of the output signals given from the plurality of acquisition units via the plurality of first signal lines are received from the plurality of the output signals. An aggregating unit that aggregates a predetermined number of aggregated signals,
A distortion compensation unit that performs distortion compensation of the plurality of amplifiers based on feedback signals obtained by feeding back the output signals of the plurality of amplifiers, and
The aggregation unit gives the predetermined number of aggregate signals as the feedback signal to the distortion compensation unit via a second signal line connecting the aggregation unit and the distortion compensation unit,
The second antenna is an active antenna system configured with a number of lines corresponding to the predetermined number of aggregate signals.
2. The active antenna system according to claim 1, wherein the aggregation unit is connected between the plurality of acquisition units and the distortion compensation unit in a state of being arranged closer to the acquisition unit than the distortion compensation unit. .
The active antenna system according to claim 1 or 2, wherein the aggregation unit selects a predetermined number of output signals from the plurality of output signals as the predetermined number of aggregate signals.
The active antenna system according to claim 3, wherein the aggregation unit selects the predetermined number of output signals from the plurality of output signals according to a predetermined order.
5. The active antenna system according to claim 3, wherein a plurality of the distortion compensators are provided corresponding to each of the plurality of amplifiers and configured to perform distortion compensation for each of the plurality of amplifiers.
It is connected between the aggregation unit and the plurality of distortion compensation units, and specifies which power amplifier among the plurality of power amplifiers is the output signal from which the predetermined number of aggregation signals are output The active antenna system according to claim 5, further comprising a distribution unit that distributes the predetermined number of aggregate signals to the distortion compensation unit corresponding to the identified amplifier.
The aggregation unit aggregates the plurality of output signals into the predetermined number of aggregation signals by combining the plurality of output signals so that the number of signals is smaller than that of the plurality of output signals. 2. The active antenna system according to 2.