CN102136860A - Channel correction system and method for transmission digital beam forming technology - Google Patents

Abstract

A transmission channel error correction system and method for transmitting digital beamforming technology, the system includes a transmission channel, a weight control unit, a digital beamforming unit, a synthesis unit, a vector network analyzer, a receiving processing unit, a correction calculation unit and a storage unit. The method of the present invention comprises: 1. Obtaining internal correction coefficients, system correction coefficients, and external correction coefficients; 2. judging whether the correction coefficients need to be updated, if so, turning to step 3; otherwise, turning to step 5; 3. updating the internal correction coefficients; 4. Update the system calibration coefficient; 5. Calibrate the transmission channel; 6. Determine whether to stop the calibration, if yes, end the calibration; otherwise, go to step 2. The method of the present invention greatly simplifies the amount of calculation and reduces the use of equipment; fully utilizes the beamforming weight in the transmitting digital multi-beamforming technology, flexibly controls the output of the transmitting channel, and ensures the consistency of the correction signal characteristic parameters in each transmitting channel, and more Efficiently forms the desired beam.

Description

Channel Correction System and Method for Transmit Digital Beamforming Techniques

technical field

The present invention relates to the technical field of radar measurement and control communication, and further relates to a system and method for correcting channel errors in the transmission digital beamforming technology, which is used to solve the problem of inconsistent amplitude and phase responses of multiple antennas and multiple transmission channels in the transmission digital beamforming system question.

Background technique

At present, in the field of radar measurement and control communication technology at home and abroad, there are two main methods for correcting the amplitude and phase errors of the transmitting digital beam system: injection reference correction and blind correction.

Ye Siqing et al. disclosed an injection reference correction method in their patent application document "A Method and System for Transmitting Channel Calibration" (publication number CN101304276A, application number 200810029111, filing date 2008.6.30). The method injects a channel correction signal into each transmission channel, receives the channel correction signal passed through each transmission channel, and calculates the correction coefficient of each transmission channel according to the received channel correction signal. This method can only correct the channel from the baseband to the transmitting antenna port, but cannot correct the entire transmitting channel including the transmitting antenna. When injecting correction signals, it is necessary to inject them in turn among each transmitting channel, and it is difficult to ensure the consistency of the characteristic parameters of the correction signals in each transmitting channel.

S.Kobayakawa, M.Tsutsui and Y.Tanaka et al. in the literature "A Blind Calibration Method for an Adaptive Array Antena in DS-CDMA System Using an MMSE Algorithm" (VTC2000-Spring Tokyo.2000IEEE 51st, Vol 1, page 21) A blind calibration device is disclosed in . The device uses the NLMS adaptive algorithm to iteratively calculate the reference signal directly coupled from the transmitting antenna channel and the sampling signal passing through each radio frequency channel of the transmitting antenna, so as to obtain the correction weight of each transmitting channel. The blind calibration method has strict requirements on the applied environment and the collected signal data. It requires that the reference signal data obtained by the direct coupling of the transmitting antenna channel and the sampling data passing through the radio frequency channels of the transmitting antenna be strictly synchronized, otherwise the adaptive iterative algorithm will diverge and fail to achieve the purpose of correction. However, in the actual communication environment, it is difficult to achieve strict synchronization between the reference signal data obtained by the direct coupling of the transmitting antenna channel and the sampling data passing through the radio frequency channels of the transmitting antenna, so the blind calibration method is difficult to directly apply in the transmitting digital beamforming technology.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, and propose a correction system based on the transmit digital beamforming technology, and a method for correcting the amplitude and phase errors of the transmit channel by using this system, so that each transmit channel in the transmit digital beamforming technique can The magnitude and phase responses of the channels are consistent.

The channel error correction system of the present invention includes a transmission channel, a weight control unit, a digital beam forming (Digital Beam Forming, DBF) unit, a synthesis unit, a vector network analyzer, a receiving processing unit, a correction calculation unit and a storage unit. The transmit channels include multiple transmitter and transmit antenna channels. The weight control unit is connected with the DBF unit through the bus, the DBF unit is connected with the transmitter through the coaxial cable, and the output end of the transmitter is connected with the transmitting antenna through the coaxial cable. The input end of the synthesis unit is connected to the transmitter through a coupler, and the output end is connected to the VNA analyzer through a coaxial cable. The output terminal of the receiving unit is connected with the correction calculation unit through the bus. The storage unit is connected with the correction calculation unit and the weight control unit through the bus.

The steps of using the amplitude and phase error correction system of the present invention to realize the amplitude and phase error correction for N transmission channels in the transmit digital beamforming technology are as follows:

(1) Obtain the internal correction coefficient.

1a) Choose one of the N emission channels as the standard channel, and set the correction coefficient in the standard channel to 1; choose one of the N-1 emission channels except the standard channel as the channel to be measured.

1b) The weight control unit outputs a set of beamforming weights to the DBF unit. The beamforming weights set the weights of the standard channel and the channel to be tested to 1, and set the weights of the remaining N-2 channels to 0.

1c) Input the correction signal to the DBF unit, and the DBF unit preprocesses the received correction signal and multiplies the beamforming weight to obtain N-channel baseband digital complex signals, and obtains N-channel intermediate frequency analog real signals through up-conversion and sends them to the transmitter .

1d) The synthesis unit couples out N channels of radio frequency signals through the transmitter, and directly sends the radio frequency signals of the standard channels to the VNA analyzer as standard signals, and synthesizes the radio frequency signals of the remaining N-1 channels and sends them to the VNA analyzer as a standby signal. test signal.

1e) Read the phase difference and amplitude difference of the signal under test relative to the standard signal from the VNA, and express the phase difference and amplitude difference in complex numbers as the internal correction coefficient of the channel under test.

1f) judge whether all emission channels have been measured, if so, store the correction coefficients in all emission channels, and end the operation; otherwise, choose one of the emission channels other than the standard channel and the measured channel as the channel to be measured, and Repeat steps 1b), 1c), 1d), 1e), 1f).

(2) Obtain the system correction coefficient.

2a) Select one of the N transmitting channels as the channel to be tested;

2b) The weight control unit outputs a set of beamforming weights to the DBF unit. The beamforming weights set the weights of the channels to be tested to 1, and the weights of the remaining N-1 channels are set to 0.

2c) Input the correction signal to the DBF unit, and the DBF unit preprocesses the received correction signal and multiplies the beamforming weight to obtain N-channel baseband digital complex signals, and obtains N-channel intermediate frequency analog real signals through up-conversion and sends them to the transmitter , the N-way radio frequency signals output by the transmitter are transmitted through the antenna; the DBF unit sends the baseband digital complex signal of the channel to be tested selected in step 2a) to the calibration calculation unit as a standard signal.

2d) The receiving processing unit preprocesses the received radio frequency signal to obtain a baseband digital complex signal, and sends it to the calibration calculation unit as the signal to be tested.

2e) The correction calculation unit extracts the characteristic parameters of the received standard signal and the signal to be measured, and compares them to obtain the system correction coefficient of the channel to be measured.

2f) Determine whether all emission channels have been measured, if yes, store the system correction coefficients of all emission channels, and end the operation; otherwise, choose one of the emission channels other than the measured channel as the channel to be measured, and repeat step 2b) , 2c), 2d), 2e), 2f).

(3) Obtain the external correction coefficient. The weight control unit calls the system correction coefficient and the internal correction coefficient of each transmission channel from the storage unit, obtains the external correction coefficient after corresponding division, and stores it in the storage unit.

(4) Determine whether the correction coefficient needs to be updated. If yes, go to step (5); otherwise, go to step (7).

(5) Update the internal correction coefficient. Use the method of step (1) to update the internal correction coefficient.

(6) Update the system correction coefficient. The weight control unit calls the internal and external correction coefficients of each transmission channel from the storage unit, multiplies them accordingly to obtain the system correction coefficients, and stores them in the storage unit.

(7) Calibrate the emission channel. The weight control unit sends the system correction coefficient to the DBF unit, and the DBF unit multiplies the system correction coefficient and the data of the transmission channel correspondingly to realize the correction of the transmission channel.

(8) Determine whether to stop the calibration. If yes, end the calibration; otherwise, go to step (4).

Compared with the prior art, the present invention has the following advantages:

(1) The present invention corrects the transmission channel including the transmission antenna channel, overcomes the deficiency that the existing method does not correct the transmission antenna channel, makes the amplitude and phase responses of each channel more consistent, and can more effectively form the desired beam.

(2) The channel correction method of the present invention makes full use of the beamforming weights in the transmitting digital beamforming technology, flexibly controls the output of multiple transmitting channels, and overcomes the shortcomings of the existing method that the correction signal must be time-divisionally injected into each channel, The consistency of the correction signal characteristic parameters in multiple transmitting channels can be guaranteed, so that the obtained error correction coefficients are more accurate.

(3) The present invention has no strict requirements on the applied environment and correction signal, and has a wider scope of application.

(4) The channel correction method of the present invention divides the complex system correction coefficient acquisition method into repetitive simple internal correction and single The complex external correction can greatly simplify the calculation amount and reduce the use of equipment, which overcomes the cumbersome shortcomings of traditional methods in calculating system correction coefficients.

Description of drawings

Fig. 1 is the block diagram of system of the present invention;

Fig. 2 is a block diagram of the synthesis unit of the present invention;

Fig. 3 is a flow chart of the method of the present invention.

Detailed ways:

The channel error correction system of the present invention will be further described below with reference to FIG. 1 and FIG. 2 .

The system of the invention includes a transmitting channel, a storage unit, a weight control unit, a DBF unit, a synthesis unit, a vector network analyzer, a receiving processing unit and a correction calculation unit. The transmission channels include N transmitter channels and transmission antenna channels, and the number N of channels is selected according to user needs. In this embodiment, the number N of channels is selected as 16. The transmitter and the transmitting antenna are connected through a coaxial cable. The weight control unit implemented by a digital signal processor (Digital Signal Processor, DSP) is connected to the DBF unit and the storage unit through the data bus. The weight control unit realizes three functions: first, it controls the output of the transmission channel. The weight control unit generates a set of beamforming weights and sends them to the DBF unit, and the output of the transmission channel is controlled by the beamforming weights; secondly, the external correction coefficient is calculated. The system correction coefficient and internal correction coefficient of each transmission channel are called from the storage unit, and the corresponding phase division is obtained to obtain the external correction coefficient; thirdly, the system correction coefficient is updated and sent to the DBF unit. The inner and outer correction coefficients of each transmission channel are called from the storage unit, correspondingly multiplied to obtain the system correction coefficients and stored. The DBF unit consists of a high-speed analog-to-digital converter (ADC), a field programmable gate array (Field Programmable Gates Array, FPGA) and 16 digital upconverters (DUC). ADC samples the input signal; FPGA performs digital quadrature interpolation on the sampled digital real signal, and multiplies the baseband digital complex signal after orthogonal interpolation with the beamforming weight to obtain 16 baseband digital complex signals, and acquires the system When correcting coefficients, output the baseband digital complex signal of the channel to be tested to the correction calculation unit; DUC performs digital up-conversion on 16 baseband digital complex signals to obtain 16 intermediate frequency analog signals. The output end of the DUC is connected to the transmitter through a coaxial cable.

The synthesis unit in Figure 2 is composed of 16 couplers and a synthesizer. The coupler couples 16 radio frequency signals from the transmitter channel, and sends the radio frequency signal of the standard channel to the VNA analyzer as a standard signal, and the remaining 15 channels The radio frequency signal is synthesized by the synthesizer and then sent to the vector network analyzer as the signal to be tested. The vector network analyzer compares the amplitude difference and phase difference between the signal to be tested and the standard signal. The receiving processing unit is composed of a receiving antenna, a receiver, an ADC, and an FPGA, which is wirelessly connected to the transmitting antenna and connected to the correction calculation unit through a bus. The receiving antenna receives the RF signal and sends it to the receiver; the receiver down-converts the RF signal to an intermediate frequency; the ADC performs band-pass sampling on the intermediate frequency analog real signal output by the receiver; FPGA performs orthogonal interpolation on the intermediate frequency digital complex signal obtained by ADC sampling, and obtains The baseband digital complex signal is sent to the correction calculation unit. The correction calculation unit is implemented by a piece of DSP, and compares the baseband numbers obtained from the DBF unit and the receiving processing unit to obtain system correction coefficients and store them in the storage unit. The correction calculation unit and the storage unit are connected through a bus. The storage unit adopts a FLASH chip with a capacity of 256M, which is used to store the obtained internal and external correction coefficients and system correction coefficients.

Below in conjunction with accompanying drawing 3, the method for realizing 16 transmit channel error corrections of the present invention is further described, and its specific steps are as follows:

Step 1. Obtain internal correction coefficients.

1a) Select one of the 16 emission channels as the standard channel, set the internal correction coefficient of the standard channel to 1, and select one of the emission channels other than the standard channel as the channel to be measured.

1b) The DSP outputs a set of beamforming weights to the FPGA. The beamforming weights set the weights of the standard channel and the channel to be tested to 1, and set the weights of the remaining 14 channels to 0.

1c) The correction signal is input to the DBF unit, and the ADC in the DBF unit performs digital band-pass sampling on the received correction signal, and sends the sampled digital intermediate frequency signal to the FPGA to realize digital quadrature interpolation. The FPGA multiplies the baseband digital complex signal and the beamforming weight to obtain 16 baseband digital complex signals, and the DUC up-converts to obtain 16 intermediate frequency analog real signals and sends them to the transmitter.

The implementation method of digital orthogonal interpolation in the present invention is: the digital real signal obtained by ADC sampling is divided into two paths, respectively multiplied by two paths of mutually orthogonal digital local oscillators, the intermediate frequency signal is down-converted to baseband, and passed through the low-pass The filter takes out the frequency spectrum in the baseband, and obtains the baseband digital complex signal after 1/2 extraction.

1d) The coupler couples 16 channels of RF signals through the transmitter, and sends the RF signals of the standard channels directly to the VNA analyzer as standard signals, and the RF signals of the remaining 15 channels are synthesized by a synthesizer and sent to the VNA analyzer as a standard signal. signal to be tested.

1e) Read the phase difference and amplitude difference of the signal under test relative to the standard signal from the VNA, and express the phase difference and amplitude difference in complex numbers as the internal correction coefficient of the channel under test.

1f) Determine whether all emission channels have been measured, if yes, store the correction coefficient C _in in all emission channels, and end the operation; otherwise, select one of the emission channels other than the standard channel and the measured channel as the channel to be measured , and repeat steps 1b), 1c), 1d), 1e), 1f).

Step 2. Obtain the system correction coefficient.

2a) Choose one of the 16 emission channels as the channel to be tested.

2b) The DSP outputs a set of beamforming weights to the FPGA. The beamforming weights set the weights of the channel to be tested to 1, and the weights of the remaining N-1 channels are set to 0.

2c) The correction signal is input to the DBF unit, and the ADC in the DBF unit performs digital bandpass sampling on the received correction signal, and sends the sampled digital intermediate frequency signal to the FPGA to realize digital quadrature interpolation to obtain a baseband digital complex signal. The implementation method of digital orthogonal interpolation is the same as the specific steps described in step 1b). The FPGA multiplies the baseband digital complex signal and the beamforming weight to obtain 16 channels, and sends the baseband digital complex signal of the channel to be tested to the calibration calculation unit through the data bus as a standard signal. The DUC up-converts 16 channels of baseband digital complex signals to obtain 16 channels of intermediate frequency analog real signals and sends them to the transmitter.

2d) The receiving antenna converts the received radio frequency signal into an intermediate frequency signal through receiver analog down-conversion, and the ADC performs digital band-pass sampling on it to obtain a digital intermediate frequency signal, and obtains a baseband digital complex signal through FPGA orthogonal interpolation, and sends it to Give the correction calculation unit as the signal to be tested.

2e) The correction calculation unit extracts the characteristic parameters of the received standard signal and the signal to be measured, and compares them to obtain the system correction coefficient of the channel to be measured. The processing process is: the correction calculation unit performs FFT transformation on the standard signal and the reference signal respectively, obtains the spectrum of the standard signal and searches for its spectral peak, assuming that the spectral peak is at the pth position, and the corresponding amplitude is N _p ; find the The amplitude N′ _p of the pth position of the signal spectrum, then the amplitude and phase error correction coefficient of the channel under test is N _p /N′ _p .

2f) Determine whether all emission channels have been measured, if yes, store the system correction coefficient C _sys of all emission channels, and end the operation; otherwise, choose one of the emission channels other than the measured channel as the channel to be measured, and repeat the steps 2b), 2c), 2d), 2e), 2f).

Step 3. Obtain the external correction coefficient. The weight control unit calls the system correction coefficient and internal correction coefficient of each transmission channel from the storage unit, and obtains the external correction coefficient after corresponding division, that is, C _out =C _sys /C _in , wherein C _out is the external correction coefficient, and C _sys is The system correction coefficient, C _in is the internal correction coefficient, and the external correction coefficient is stored in the storage unit.

Step 4. Determine whether the correction coefficient needs to be updated. If yes, go to step 5; otherwise, go to step 7.

Step 5. Use the method in step 1 to update the internal correction coefficient to obtain an updated internal correction coefficient C′ _in .

Step 6. Update the system correction coefficients. The weight control unit calls the inner and outer correction coefficients of each transmission channel from the storage unit, and multiplies them to obtain the system correction coefficient, that is, C′ _sys =C′ _in ·C _out , and stores the updated system correction coefficient into the storage unit.

Step 7. Calibrate the emission channel. The weight control unit sends the system correction coefficient _C′sys to the DBF unit, and the DBF unit multiplies the system correction coefficient and the transmission channel data correspondingly to realize the transmission channel correction.

Step 8. Determine whether to stop the calibration. If yes, end the calibration; otherwise, go to step 4.

Claims (6)

1. A channel correction system for transmitting digital beamforming technology, comprising a transmitting channel, a receiving processing unit, a correction calculation unit, and a storage unit, characterized in that: the transmitting channel includes multiple transmitters and transmitting antenna channels, The weight control unit is connected to the DBF unit through the bus, the DBF unit is connected to the transmitter through a coaxial cable, the output end of the transmitter is connected to the transmitting antenna through a coaxial cable, and the input end of the synthesis unit is connected to the transmitter through a coupler. The output end is connected to the VNA analyzer through a coaxial cable, the output end of the receiving processing unit is connected to the correction calculation unit through a bus, and the storage unit is connected to the correction calculation unit and the weight control unit through a bus. 2 . The channel correction system for transmitting digital beamforming technology according to claim 1 , wherein the transmitting channel includes N channels, and one of them is selected as a standard channel. 3 . 3. A channel correction system for transmitting digital beamforming technology according to claim 1, characterized in that, the synthesis unit is composed of N-way couplers and a combiner, and the coupler is connected to the transmitter channel , the output end of the coupler corresponding to the standard channel is connected to the VNA analyzer through a coaxial cable, and the output end of the coupler corresponding to the remaining N-1 channels is connected to the synthesizer through a coaxial cable, and the output end of the synthesizer is connected through the same The axis cable is connected to the vector network analyzer. 4. A channel correction method for transmitting digital beamforming technology, characterized in that, the steps of implementing amplitude-phase error correction for N transmitting channels in transmitting digital beamforming technology are as follows: (1) Obtain the internal correction coefficient and store it in the storage unit; (2) Obtain the system correction coefficient and store it in the storage unit; (3) Obtaining the external correction coefficient: the weight control unit calls the system correction coefficient and the internal correction coefficient of each transmission channel from the storage unit, obtains the external correction coefficient after corresponding division, and stores it in the storage unit; (4) Judging whether the correction coefficient needs to be updated, if so, turn to step (5); otherwise, turn to step (7); (5) adopt the method of step (1) to update the internal correction coefficient; (6) Update the system correction coefficient: the weight control unit calls the internal and external correction coefficients of each transmission channel from the storage unit, and multiplies them accordingly to obtain the system correction coefficient and stores it in the storage unit; (7) Calibrate the transmission channel: the weight control unit sends the system correction coefficient to the DBF unit, and the DBF unit multiplies the system correction coefficient and the transmission channel data correspondingly to realize the transmission channel correction; (8) Determine whether to stop the calibration, if yes, end the calibration; otherwise, go to step (4). 5. A kind of channel correction method for transmitting digital beamforming technology according to claim 4, is characterized in that, the specific steps of described step (1) are as follows: 1a) Set the correction coefficient in the standard channel to 1, and select one of the N-1 emission channels except the standard channel as the channel to be measured; 1b) The weight control unit outputs a set of beamforming weights to the DBF unit, the beamforming weights set the weights of the standard channel and the channel to be tested to 1, and the weights of the remaining N-2 channels are set to 0; 1c) Input the correction signal to the DBF unit, and the DBF unit preprocesses the received correction signal and multiplies the beamforming weight to obtain N-channel baseband digital complex signals, and obtains N-channel intermediate frequency analog real signals through up-conversion and sends them to the transmitter ; 1d) The synthesis unit couples out N channels of radio frequency signals through the transmitter, and directly sends the radio frequency signals of the standard channels to the VNA analyzer as standard signals, and synthesizes the radio frequency signals of the remaining N-1 channels and sends them to the VNA analyzer as a standby signal. test signal; 1e) read the phase difference and the amplitude difference of the signal to be tested relative to the standard signal from the vector network analyzer, and express the phase difference and the amplitude difference in complex number form as the internal correction coefficient of the channel to be tested; 1f) judge whether all emission channels have been measured, if so, store the correction coefficients in all emission channels, and end the operation; otherwise, choose one of the emission channels other than the standard channel and the measured channel as the channel to be measured, and Repeat steps 1b), 1c), 1d), 1e), 1f). 6. A kind of channel correction method for transmitting digital beamforming technology according to claim 4, is characterized in that, the specific steps of described step (2) are as follows: 2a) Select one of the N transmitting channels as the channel to be tested; 2b) The weight control unit outputs a set of beamforming weights to the DBF unit, the beamforming weights set the weights of the channels to be tested to 1, and the weights of the remaining N-1 channels are set to 0; 2c) Input the correction signal to the DBF unit, and the DBF unit preprocesses the received correction signal and multiplies the beamforming weight to obtain N-channel baseband digital complex signals, and obtains N-channel intermediate frequency analog real signals through up-conversion and sends them to the transmitter , the N road radio frequency signals output by the transmitter are transmitted through the antenna, and the DBF unit sends the baseband digital complex signal of the channel to be measured selected in step 2a) to the calibration calculation unit as a standard signal; 2d) The receiving processing unit preprocesses the received radio frequency signal to obtain a baseband digital complex signal, and sends it to the calibration calculation unit as the signal to be tested; 2e) The correction calculation unit extracts the characteristic parameters of the received standard signal and the signal to be measured, and compares them to obtain the system correction coefficient of the channel to be measured; 2f) Determine whether all emission channels have been measured, if yes, store the system correction coefficients of all emission channels, and end the operation; otherwise, choose one of the emission channels other than the measured channel as the channel to be measured, and repeat step 2b) , 2c), 2d), 2e), 2f).

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