CN100407822C - Automatic gain control method and device for time division duplex system array antenna base station - Google Patents

Abstract

The invention discloses an automatic gain control method and device for an array antenna base station of a time-division duplex system. The method includes: completing the control function of a variable gain amplifier by a digital down-conversion chip and a numerically controlled attenuator in a receiving branch; The digital down-conversion chip completes the recovery of the input digital signal, and bypasses the automatic gain control function of the digital down-conversion chip itself; the digital signal processing chip on the channel board completes the synchronous control of the array channel automatic gain control to ensure signal The data bit width is dynamically reduced, thereby reducing the burden of subsequent signal processing; and the automatic gain control of each receiving branch is performed synchronously to maintain the original characteristics of the array signal. The invention can guarantee the spatial characteristic of the array receiving signal, and guarantee the realization of the intelligent antenna algorithm.

Description

Automatic gain control method and device for time division duplex system array antenna base station

technical field

The invention relates to a mobile base station system using an intelligent antenna, in particular to an automatic gain control method and device for a base station using an intelligent antenna in a time division duplex system.

Background technique

Smart antenna is a hot technology in the field of communication in recent years. Among the three major standards of third-generation mobile communication technology that have been adopted, the TD-SCDMA (Time Division Synchronous Code Division Multiple Access) standard submitted by my country clearly includes smart As one of the necessary technologies to improve system capacity and coverage, the antenna adopts a frame format that is particularly conducive to the use of smart antenna technology. At the same time, WCDMA (Wideband Code Division Multiple Access) and CDMA2000 (Qualcomm's Code Division Multiple Access standard) provide convenience for the application of smart antenna technology (such as auxiliary pilots), making smart antennas one of the optional technologies. one. The industry's research on the future fourth-generation mobile communication technology shows that smart antennas will become a must in 4G (fourth-generation mobile communication technology).

Automatic gain control (AGC) is an effective technology to improve the dynamic range of the receiver, which can ensure that the amplitude of the signal input to the A/D converter is basically constant when the input signal changes within a large range. In the current popular base station digital IF receiver, the AGC loop is placed between the analog and digital circuits, the gain control algorithm is implemented in the digital part, and the appropriate gain setting is fed back to the analog variable gain amplifier (VGA) or digitally controlled attenuator , so a large receiver dynamic range can be obtained. However, in the digital intermediate frequency solutions provided by various manufacturers, the realization of AGC adopts the self-closed loop method of the channel. For systems using array antennas like TD-SCDMA base stations, the AGC synchronous joint control of each channel of the array is required. The above AGC scheme based on the self-closed loop of each channel will destroy the spatial characteristics of the array received signals, affect the realization of the smart antenna algorithm, and reduce the base station transceiver performance.

Chinese patent "multi-channel digital automatic gain control method and control device" with application number 01132482.1 (publication number: 1350365) and Chinese patent "multi-channel combined fast numerical control of multi-channel receiver" with application number 97229202.0 (publication number: 2353093) AGC device" provides a multi-channel digital AGC method and a control device. The former is used in phased array radar, sonar and other fields. The article does not state that the FFT algorithm used in it is processed in the time domain or air domain. The superficial understanding is that the AGC of each channel is still carried out independently; the latter is applied to multi-channel direction-finding receivers , use the output of some channels as the basis to control the gain of all channels, and its purpose has nothing to do with the array signal processing. The descriptions of the two patents are very simple, and both are combined with relatively old receiver implementation schemes, which are not suitable for the current popular digital down-conversion receivers. At the same time, due to different fields, it is not a solution for the array base station AGC, so it cannot be applied to the field of mobile communication.

Contents of the invention

The technical problem to be solved by the present invention is to provide an automatic gain control method and device for a time-division duplex system array antenna base station, which solves the problem that the existing technology cannot guarantee the spatial characteristics of the array received signal, which affects the realization of the smart antenna algorithm and reduces the transceiver performance of the base station And other issues.

In order to achieve the above object, the present invention provides an automatic gain control method for a time division duplex system array antenna base station, each element of the array antenna is respectively connected to a front end in the base station, and each front end is respectively connected to the base station array channel A receiving branch and a transmitting branch, each receiving branch and transmitting branch are connected to the channel board, and the main control unit controls the channel board, receiving branch and transmitting branch, and the method is characterized in that the method includes The steps are as follows: step 1, set a digital down-conversion chip and a digital control attenuator in the receiving branch to complete the control function of the variable gain amplifier, and ensure that when the signal input by the antenna port changes in a large range, it is input to the receiving branch. The signal amplitude of the A/D converter in the branch remains within a suitable range, so as to avoid saturation overflow; Step 2, utilize the digital down-conversion chip to complete the down-conversion and amplitude recovery of the input digital signal, so that the baseband digital signal has wider bit width, and bypass the automatic gain control function of the digital down-conversion chip itself; Step 3, complete the synchronous control of the array channel automatic gain control by a digital signal processing chip on the channel board, to ensure The dynamics of the signal and reduce the data bit width, thereby reducing the burden of subsequent signal processing; and the automatic gain control of each receiving branch is performed synchronously to maintain the original characteristics of the array signal.

The automatic gain control method of the above-mentioned time-division duplex system array antenna base station is characterized in that, in the first step, the digital down-conversion chip evaluates the data after A/D conversion, and according to the peak value of the input data, The average value of the power and the set corresponding threshold value generate a control signal to control the attenuation of the digitally controlled attenuator, so that the signal input to the A/D converter avoids saturation overflow.

The automatic gain control method of the above-mentioned time division duplex system array antenna base station is characterized in that, in the second step, the input digital data is restored by the joint action of the control signal and the output data of the A/D converter. The amplitude of the signal, and the control of the variable gain amplifiers of each of the receiving branches is performed independently.

The above automatic gain control method for the array antenna base station of the time division duplex system is characterized in that the bit width of the input digital signal is set to 24Bit, 16Bit or 8Bit according to system requirements, and the control signal is 3-5Bit.

The automatic gain control method of the above-mentioned time division duplex system array antenna base station is characterized in that, in the third step, the digital signal processing chip on the channel board calculates the amplitude of the input digital signal of each receiving branch and average the amplitude average of each channel, compare the average value with an expected average value to obtain an automatic gain control factor, and perform automatic gain control compensation for all receiving branches according to the factor, so that the large input The signal reduction ensures that the baseband algorithm such as joint detection will not be saturated and overflowed when the baseband algorithm is implemented, and also amplifies the input small signal to avoid the decrease in algorithm performance due to subsequent truncation.

The automatic gain control method of the above-mentioned time-division duplex system array antenna base station is characterized in that the expected mean value is realized according to the data bit width required by the digital signal processing chip, the peak-to-average ratio of the time-division duplex system signal and the baseband algorithm The specific performance requirements at the time are determined by compromise.

The automatic gain control method of the above-mentioned time division duplex system array antenna base station is characterized in that the power of the input digital signal of each receiving branch is calculated by I ² +Q ² , and the amplitude is calculated by $\mathrm{MAX}\left(\right|I|,|Q\left|\right)+\frac{1}{2}\mathrm{MIN}\left(\right|I|,|Q\left|\right)$ Calculate, wherein I, Q are the real and imaginary parts of the input digital signal; the average value after the amplitude of each channel is averaged is: $\mathrm{mean}=\frac{1}{K\·L}\underset{k=1}{\overset{K}{\mathrm{\Σ}}}\underset{l=1}{\overset{L}{\mathrm{\Σ}}}(\max (I_{l,k},Q_{l,k})+\frac{1}{2}\min (I_{l,k},Q_{l,k})),$ The average value after averaging the power of each channel is: $\mathrm{mean}=\frac{1}{K\&Center\; Dot;L}\underset{k=1}{\overset{K}{\mathrm{\Σ}}}\underset{l=1}{\overset{L}{\mathrm{\Σ}}}(I_{l,k}^2+Q_{l,k}^2),$ Among them, mean is the average value, K is the actual number of effective channels, L is the evaluation window length of the received signal, 1 is the sample number, k is the actual effective channel number, I _lk and Q _lk are the kth channel respectively The real and imaginary part values of the first sample point of the channel.

In order to better realize the purpose of the present invention, the present invention also provides an automatic gain control device for a time division duplex system array antenna base station, each element of the array antenna is connected to a front end in the base station, and each front end Respectively connect a receiving branch and a transmitting branch of the base station array channel, each receiving branch and transmitting branch are connected to the channel board, the main control unit controls the channel board, receiving branch and transmitting branch, its characteristics In that, the receiving branch includes a sequentially connected amplification and filtering circuit, a digitally controlled attenuator, an A/D converter, and a digital down-conversion chip, and the control function of the variable gain amplifier is completed by the digitally down-converted chip and the digitally controlled attenuator, Ensure that the signal amplitude input to the A/D converter in the receiving branch remains within an appropriate range to avoid saturation overflow; the automatic gain control circuit of the digital down-conversion chip itself is bypassed to complete the input digital The frequency of the signal is down-converted and the signal amplitude is restored; the channel board has a digital signal processing chip, which is used to complete the synchronous control of the automatic gain control of the array channel and maintain the original characteristics of the array signal.

The above-mentioned device is characterized in that the digital down-conversion chip includes multiple parallel down-conversion paths, and each down-conversion path includes sequentially connected VGA control modules, digital mixers, CIC filters, half-band filters and FIR filter.

The above device is characterized in that the digital signal processing chip includes a sequentially connected receiving amplitude estimation module, factor generation module and compensation module; the receiving amplitude estimation module is used to calculate the input digital signal of each receiving branch The average value of the received amplitude is averaged on all antennas; the factor generating module is used for comparing the average value with an expected average value to obtain an automatic gain control factor; the compensation module is used for all receiving support according to the factor circuit for automatic gain control compensation.

Technical effect of the present invention is: the automatic gain control method and device for TDD (time division duplex) system array antenna base station provided by the present invention have the following advantages:

1) Combined with the digital IF chip and implemented in the baseband part, it provides a complete automatic gain solution for the TDD communication system using array antennas;

2) The synchronous control of the gain of each channel ensures that the array space characteristics of the received signal are not destroyed, and there are applications using smart antenna technology;

3) Received signals in different time slots, gain independent control;

4) The performance of the baseband algorithm (such as joint detection) under input signals of different sizes is guaranteed.

Description of drawings

Fig. 1 is a flow chart of the steps of the inventive method;

Fig. 2 is a schematic diagram of the composition of the TDD system array antenna base station taking TD-SCDMA as an example in the present invention;

Fig. 3 is the receiving branch composition and VGA control realization schematic diagram of the present invention taking single channel as example;

Fig. 4 is a schematic diagram of the principle of a digital down-conversion chip in the present invention;

Fig. 5 is a schematic diagram of the composition of the AGC unit in the DSP of the present invention;

Fig. 6 is a program flow chart of the AGC processing unit in the DSP of the present invention.

Detailed ways

The specific implementation of the present invention will be described below by taking the TD-SCDMA system as an example.

Fig. 1 is the step flowchart of the inventive method; The present invention comprises the following steps:

Step 100, the VGA control function is completed by the digital down-conversion chip and the numerically controlled attenuator in the receiving branch, to ensure that when the signal input by the antenna port changes in a large range, the A/D input to the receiving branch The signal amplitude of the converter is kept within an appropriate range to avoid saturation overflow;

Step 200, the digital down-conversion chip completes the down-conversion and amplitude recovery of the input data, so that the baseband digital signal has a wider bit width, and bypasses the automatic gain control function of the digital down-conversion chip itself;

Step 300, the digital signal processing chip on the channel board completes the synchronous control of the automatic gain control of the array channel to ensure the dynamics of the signal and reduce the data bit width, thereby reducing the burden of subsequent signal processing; reducing the input large signal, It ensures that baseband algorithms such as joint detection will not be saturated and overflowed; the input small signal is amplified so that the performance of the algorithm will not be reduced due to subsequent truncation; at the same time, since the automatic gain control of each receiving branch is carried out synchronously, maintaining The original characteristics of the array signal.

In the time slot format of TD-SCDMA, a 10ms radio frame is divided into two 5ms subframes, and each subframe contains 7 regular time slots (TS0~TS6) and 3 special time slots (DwPTS, GP, UpPTS). Because it is a time-division system, the number of users contained in each time slot and the fading characteristics may be different, so the AGC of each time slot is performed independently. The specific implementation will be described below.

Fig. 2 is a schematic diagram of the composition of the TDD system array antenna base station taking TD-SCDMA as an example in the present invention; the automatic gain control method for the TDD system array antenna base station of the present invention, as shown in Fig. 2, said base station consists of array antennas 11~ 1N, receiving front end 21~2N, receiving branch 31~3N, transmitting branch 41~4N, channel board 51~5M, main control unit 6, etc. The receiving branch completes the down-conversion, filtering, amplification, VGA control, A/D conversion, digital down-conversion, shaping filtering and other processing of the received signal of the array, wherein the digital down-conversion is completed by a dedicated digital down-conversion chip, and Bypass the AGC function in the digital down-conversion chip, that is, the digital down-conversion dedicated chip performs digital down-conversion, VGA control and recovery of signal amplitude, and shaping filtering. The transmitting branch completes functions such as shaping filtering, digital up-conversion, and power amplification. The channel board includes an interface unit 511 , an AGC processing unit 512 , an uplink baseband processing unit 513 , a downlink baseband processing unit 514 , and a communication processor 515 . The interface unit 511 is implemented by FPGA (Field Programmable Gate Array), and the AGC processing unit 512, uplink baseband processing unit 513, and downlink baseband processing unit 514 are implemented in DSP (Digital Signal Processing Chip). The interface unit completes the demultiplexing of the uplink baseband signal and writes the data stream into the buffer of the DSP, and reads the downlink baseband signal from the buffer of the DSP and multiplexes it. In regular time slots, the uplink baseband processing unit completes functions such as joint detection, decoding, power control, and uplink synchronization control of uplink received signals, and the downlink baseband processing unit completes downlink signal encoding, physical frame formation, modulation, beamforming, and power weighting and other functions. In GP and uplink pilot time slots, the uplink baseband processing unit completes functions such as synchronization establishment and channel correction.

Fig. 3 is the receiving branch circuit composition and the VGA control realization schematic diagram of the present invention taking single channel as example, the content of primary frequency conversion aspect is ignored in the figure; The inventive method is jointly completed by the AGC processing unit in the receiving branch circuit and DSP. The receiving branch includes an amplification filter circuit 311, a digitally controlled attenuator 312, an A/D converter 313, and a digital down-conversion chip 314, wherein the digitally controlled attenuator has a digital control interface of 3 to 5 Bit, and is controlled by the digitally down-converted chip , can reach a control range of 48dB with a step size of 6dB. The A/D converter is a high-speed A/D conversion device with a width of 12Bit to 14Bit. Each receive branch has a separate digitally controlled attenuator and A/D converter.

FIG. 4 is a schematic diagram of the principle of the digital down-conversion chip in the present invention; its own AGC function module is not shown in the figure. In the method of the present invention, the AGC function inside the digital down-conversion chip is set to a fixed gain state. The digital down-conversion chip includes 4 to 6 parallel down-conversion channels, each channel includes VGA control 3141, digital mixer 3142, CIC filter 3143, half-band filter 3144, FIR filter 3145, etc. The digital down-conversion chip evaluates the data after A/D conversion, and generates a 3~5Bit control signal to control the attenuation of the digital control attenuator according to the peak value of the input data, the average power value and the corresponding threshold value set, so as to ensure The input A/D converter signal will not saturate and overflow. At the same time, the control signal of 3~5Bit is sent to the follow-up processing part in the chip as the index, and the output of the A/D converter is used as the base number part. After digital mixing, the base part and the exponent part work together to restore the amplitude of the input digital I/Q signal. In the array channel AGC of the present invention, the digital AGC circuit inside the digital down-conversion chip needs to be bypassed so that the output is in a fixed gain mode. The I/Q data bit width output by the digital chip can be set to 24Bit, 16Bit, 8Bit, etc. according to system requirements. The VGA control of each receiving branch is carried out independently.

5 is a schematic diagram of the composition of the AGC unit in the DSP in the present invention; the AGC processing unit is implemented in the DSP by software and consists of a receiving amplitude estimation module 5121, an AGC factor generation module 5122, and an AGC compensation module 5123. Assuming that the array received signal input to the AGC module is expressed as: I ₁ , Q ₁ , I ₂ , Q ₂ , ..., I _N , Q _N (wherein N is the number of array channels), the received amplitude estimation module calculates the amplitude or The power value, in order to reduce the amount of computation, can be calculated on the data in a window with a length of L in a time slot. According to the needs of the system, L is 64, 128, etc. The calculation of power can be I ² +Q ² , the calculation of magnitude can be $\mathrm{MAX}\left(\right|I|,|Q\left|\right)+\frac{1}{2}\mathrm{MIN}\left(\right|I|,|Q\left|\right).$ The received amplitude estimation module calculates the average value of the received power or the average value of the amplitude of each channel and averages the average value of each channel, namely:

$\mathrm{<span\; class="notranslate">\; mean</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; L</span>}}\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; K</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\underset{\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>$

or $\mathrm{mean}=\frac{1}{K\&Center\; Dot;L}\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}(\max (I_{l,k},Q_{l,k})+\frac{1}{2}\min (I_{l,k},Q_{l,k}))$

Among them, mean represents the average value of the received signal amplitude (or power), K is the actual number of effective channels (K is less than or equal to N), and L is the length of the received signal evaluation window.

The expected mean _des of the received signal is determined based on the data bit width required by the DSP, the peak-to-average ratio of the TD-SCDMA signal, and the specific performance requirements when the joint detection algorithm is implemented. When the AGC output is required to be 16B1t and the number of antennas is 8 , the value of mean _des is generally between 2 ⁸ and 2 ¹¹ .

The AGC factor generation module compares the size of mean and mean _des to obtain the AGC factor, namely:

$\mathrm{<span\; class="notranslate">\; agcfact</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; mean</span>}}_{\mathrm{<span\; class="notranslate">\; des</span>}}}{\mathrm{<span\; class="notranslate">\; mean</span>}}$

For the convenience of implementation, the agcfact of the above linear representation is expressed as a power of base 2, namely:

表示向下取整。in

Indicates rounding down.

The AGC compensation module performs AGC compensation according to the sign of agcfact, that is, if agcfact ≥ 0, the current time slot data received by all K active channels (including the two data fields before and after, the midamble offset code in the middle, and the 16 data behind the next block of data) GP interval of chips) shifts the agcfact bit to the left; if agcfact<0, shifts the current time slot data received by all K active channels to the right - the agcfact bit. It must be noted that, for the data of all active channels in the same time slot, there is only one agcfact, which ensures the synchronous control of the AGC of the array channels, thereby protecting the spatial characteristics of the array received signals.

Fig. 6 is a program flow chart of the AGC processing unit in the DSP of the present invention. Specifically include:

Step 601, make channel counter k=0;

Step 602, calculating the amplitude or power mean value of the received data of the kth channel;

Step 603, making k=k+1;

Step 604, judge whether k is less than the predetermined value K, and execute step 605, otherwise return to 602;

Step 605, calculating the amplitude or power mean value of data received by all K activated channels;

Step 606, seeking the AGC factor;

Step 607, perform AGC compensation on the data received by all activated channels, and write back to the original storage space, and end.

Although the method described in the present invention takes the TD-SCDMA system as an example, the method is not limited to the TD-SCDMA system, and its basic idea can be applied to other TDD systems or even FDD systems.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the implementation scope of the present invention; all equivalent changes and modifications made according to the present invention are covered by the patent scope of the present invention.

Claims (9)

1. an automatic gain control method for a time division duplex system array antenna base station, each array element of the array antenna is connected to a front end in the base station respectively, and each front end is connected to a receiving branch and a receiving branch of the base station array channel respectively The transmitting branch, each receiving branch and transmitting branch are connected to the channel board, and the main control unit controls the channel board, receiving branch and transmitting branch, and it is characterized in that the method includes the following steps: Step 1: Set a digital down-conversion chip and a digitally controlled attenuator in the receiving branch to complete the control function of the variable gain amplifier, so as to ensure that when the signal input by the antenna port changes within a large range, it is input into the receiving branch The signal amplitude of the A/D converter is kept in an appropriate range to avoid saturation overflow; Step 2, using the digital down-conversion chip to complete the down-conversion and amplitude recovery of the input digital signal, so that the baseband digital signal has a wider bit width, and bypass the automatic gain control function of the digital down-conversion chip itself; Step 3, calculating the amplitude or power mean value of the input digital signal of each receiving branch by a digital signal processing chip on the channel board and averaging the amplitude mean value or power mean value of each channel, and combining the mean value with a Comparing the expected mean value to obtain an automatic gain control factor, and performing automatic gain control compensation for all receiving branches according to the factor, completing the synchronous control of the array channel automatic gain control, ensuring the dynamics of the signal and reducing the data bit width , thereby reducing the burden of subsequent signal processing; and the automatic gain control of each receiving branch is performed synchronously to maintain the original characteristics of the array signal. 2. the automatic gain control method of time division duplex system array antenna base station according to claim 1, it is characterized in that, in described step 1, described digital down-conversion chip evaluates the data after A/D conversion , generating a control signal to control the attenuation of the numerically controlled attenuator according to the peak value of the input data, the average power value and the corresponding threshold value set, so that the signal input to the A/D converter avoids saturation overflow. 3. the automatic gain control method of time division duplex system array antenna base station according to claim 2, it is characterized in that, in described step 2, by the output data of described control signal and described A/D converter common The function restores the amplitude of the input digital signal, and the control of the variable gain amplifiers of each of the receiving branches is performed independently. 4. the automatic gain control method of time division duplex system array antenna base station according to claim 3, it is characterized in that, the bit width of described input digital signal is set to 24Bit, 16Bit or 8Bit according to system requirement, and described control signal is 3~5Bit. 5. the automatic gain control method of time division duplex system array antenna base station according to claim 3, it is characterized in that, in described step 3, by completing the synchronous control of described array channel automatic gain control, thereby make the input The reduction of the large signal ensures that the baseband algorithm of the joint detection will not be saturated and overflowed, and also amplifies the input small signal to avoid the decrease in algorithm performance due to subsequent truncation. 6. the automatic gain control method of time-division duplex system array antenna base station according to claim 5, it is characterized in that, the power of the described input digital signal of each receiving branch is with I ² + ^Q Calculation, amplitude is with $\mathrm{MAX}\left(\right|I|,|Q\left|\right)+\frac{1}{2}\mathrm{MIN}\left(\right|I|,|Q\left|\right)$ Calculate, wherein I, Q are the real and imaginary parts of the input digital signal; the average value after the amplitude of each channel is averaged is: $\mathrm{mean}=\frac{1}{K\&CenterDot;L}\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}(\max (I_{l,k},Q_{l,k})+\frac{1}{2}\min (I_{l,k},Q_{l,k})),$ The average value after averaging the power of each channel is: $\mathrm{mean}=\frac{1}{K\&Center\; Dot;L}\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}(I_{l,k}^2+Q_{l,k}^2),$ Among them, mean is the average value, K is the actual effective number of channels, L is the evaluation window length of the received signal, l is the sample number, k is the actual effective channel number, I _lk and Q _lk are the kth The real and imaginary part values of the input digital signal at the lth sample point of the channel. 7. the automatic gain control method of time division duplex system array antenna base station according to claim 5, it is characterized in that, described expected mean value is the peak value of time division duplex system according to the data bit width of described digital signal processing chip demand The specific performance requirements of the average ratio and the baseband algorithm are determined by compromise. 8. An automatic gain control device for a time-division duplex system array antenna base station, each array element of the array antenna is connected to a front end in the base station, and each front end is respectively connected to a receiving branch and a transmitting branch of the base station array channel Branches, each receiving branch and transmitting branch are connected to the channel board, the main control unit controls the channel board, receiving branch and transmitting branch, it is characterized in that the receiving branch includes sequentially connected amplification and filtering circuit, a digitally controlled attenuator, an A/D converter and a digital down-conversion chip, and the control function of the variable gain amplifier is completed by the digitally down-converted chip and the digitally controlled attenuator to ensure that the A/D frequency input to the receiving branch is The signal amplitude of the converter is kept in an appropriate range to avoid saturation overflow; the automatic gain control circuit of the digital down-conversion chip itself is bypassed to complete the recovery of the input digital signal; the channel board has a digital signal processing chip , used to complete the synchronous control of the automatic gain control of the array channel and keep the original characteristics of the array signal, the digital signal processing chip includes a sequentially connected receiving amplitude estimation module, factor generation module and compensation module; the receiving amplitude estimation module is used for Calculate the average value of the received amplitude of the input digital signal of each receiving branch and perform the average of multiple branches; the factor generation module is used to compare the average value with an expected average value to obtain an automatic gain control factor; the The compensation module is used to perform automatic gain control compensation on all receiving branches according to the factor. 9. the automatic gain control device of time division duplex system array antenna base station according to claim 8, it is characterized in that, described digital down-conversion chip comprises the down-conversion path of multi-channel parallel, and each down-conversion path comprises sequentially connected VGA control block, digital mixer, CIC filter, half-band filter and FIR filter.

Images