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CN-122026940-A - IQ imbalance calibration method for receiving channel of zero intermediate frequency transceiver

CN122026940ACN 122026940 ACN122026940 ACN 122026940ACN-122026940-A

Abstract

The invention provides a zero intermediate frequency transceiver receiving channel IQ imbalance calibration method, and relates to the field of radio frequency transceiver calibration. The method comprises the steps of generating a single sound signal in a self-calibration process by a single sound calibration signal generator, generating a double sound excitation signal in the self-calibration process by a double sound excitation signal synthesizer, communicating a transmitting channel with a receiving channel by a radio frequency switch in the self-calibration process, enabling the excitation signal transmitted by the transmitting channel to be looped back to the receiving channel, extracting IQ errors by an error extraction unit, calculating compensation coefficients, and compensating link signals by an error compensation unit. The method generates a double-tone test signal from a transmitting channel, extracts IQ imbalance in a receiving channel according to the algorithm provided by the invention, and compensates the IQ imbalance. According to the method, an external device is not required to build a calibration environment, the self calibration of the chip can be realized, and the calibration cost of a single chip can be effectively reduced.

Inventors

  • SHAO JIE
  • CHEN XIAOFEI

Assignees

  • 华中科技大学

Dates

Publication Date
20260512
Application Date
20260127

Claims (10)

  1. 1. A zero intermediate frequency transceiver receiving channel IQ imbalance calibration method is characterized in that the calibration method uses the following modules: The module 1 is a single-tone calibration signal generator, which is positioned in the digital baseband module and is used for generating a single-tone signal in the self-calibration process; the module 2 is a double-tone excitation signal synthesizer, which is positioned at the digital baseband module of the transmission link and is used for generating double-tone excitation signals in the self-calibration process; the module 3, the radio frequency switch, locate at the front end of radio frequency, connect the sending channel and receiving channel in the course of calibrating, the excitation signal that the sending channel sends will loop back to the receiving channel; The module 4, the error extraction unit, the digital baseband module located in receiving link, realize extraction of IQ error and calculation of compensating coefficient; The module 5, the error compensating unit, the digital baseband module located in receiving link, compensates the link signal according to the compensating coefficient calculated by the said module 4; and the module 6 is used for calibrating the control unit, is positioned in the digital baseband part and is responsible for controlling all relevant modules in the calibrating process.
  2. 2. The method according to claim 1, wherein the single tone calibration signal generator in the module 1 comprises a frequency word sequence generator, a frequency word distributor and four digital signal generators which are identical in structure, and the four digital signal generators are respectively named as a digital signal generator TH, a digital signal generator TL, a digital signal generator RH and a digital signal generator RL for convenience of distinguishing.
  3. 3. The IQ imbalance calibration method according to claim 2, wherein the frequency word sequence generator is configured to generate a single tone signal frequency word sequence required for calibration, and the calculating step comprises: step 1.1, calculating a fundamental frequency of frequency analysis: ; Wherein the method comprises the steps of Representing the frequency of the digital baseband portion of the receive channel during calibration, the digital baseband frequency of the transmit channel is also ; Step 1.2, calculating the local oscillator frequency difference of the receiving channel and the transmitting channel Calculating the frequency sequence offset actually transmitted by a transmission channel: ; Wherein the method comprises the steps of Representing the number of samples to be acquired for each frequency point in the IQ imbalance calculation process; Step 1.3, calculating a frequency point sequence expected to be received by a receiving channel, wherein the calculation formula is as follows: ; wherein i has a value of positive integer 1 to 16, i.e., 1,2, 3..16; step 1.4, calculating a frequency point sequence actually transmitted by a transmission channel: ; wherein i has a value of positive integer 1 to 16, i.e., 1,2, 3..16; Step 1.5, calculating a frequency word sequence expected to be received by a receiving channel, wherein the calculation formula is as follows: ; wherein i has a value of positive integer 1 to 16, i.e., 1,2, 3..16, Indicating the bit width of the receive channel NCO, Represent rounding; step 1.6, calculating a frequency word sequence actually transmitted by a transmission channel, wherein the calculation formula is as follows: ; wherein i has a value of positive integer 1 to 16, i.e., 1,2, 3..16, Indicating the bit width of the transmit channel NCO, Representing rounding.
  4. 4. The IQ imbalance calibration method of a receiver channel of a zero intermediate frequency transceiver according to claim 2, wherein the frequency word distributor sequentially transmits the frequency words generated by the frequency word sequence generator to the four digital signal generators eight times at the following transmission time intervals: ; Wherein the method comprises the steps of Representing the number of data points required for a single frequency point calibration, The additional data points are unstable data points in the frequency switching process that can be skipped for subsequent steps; the digital signal generator TH, the digital signal generator TL, the digital signal generator RH and the digital signal generator RL generate orthogonal signal sequences after receiving the frequency words distributed by the frequency word distributor, respectively 、 、 And Wherein i has a value of positive integer 1 to 8, i.e. 1,2,3.
  5. 5. The IQ imbalance calibration method of a receiving channel of a zero intermediate frequency transceiver according to claim 1, wherein the dual-tone excitation signal synthesizer is configured to add signals generated by the digital signal generator TH and the digital signal generator TL according to different weights to synthesize dual-tone signals And the calculation formula is as follows: ; wherein i has a positive integer of 1 to 8, i.e., 1,2,3.
  6. 6. The IQ imbalance calibration method for a receiving channel of a zero intermediate frequency transceiver according to claim 1, wherein the error extraction unit comprises an error extraction unit 1, an error extraction unit 2 and an IDFT module, and the two error extraction units are completely identical in structure; the error extraction unit 1 is used for extracting an error value of each high-frequency component frequency point, and the calculation process comprises the following steps: step 2.1.1, calculating the product of the received actual signal and the received channel digital signal generator RH, with the following formula: ; Wherein i has a value of positive integer 1 to 8, i.e., 1,2, 3..8, wherein Representing the signal sequence actually received by the receiving channel; Step 2.1.2, calculating the product of the received actual signal and the conjugate value of the received channel digital signal generator RH, and the formula is as follows: ; representing the signal sequence actually received by the receiving channel, Representation of Wherein i has a value of positive integer 1 to 8, i.e. 1,2, 3..8; Step 2.1.3, calculating an error value sequence 1 according to the following calculation formula: ; wherein i has a positive integer of 1 to 8, i.e., 1,2,3.
  7. 7. The IQ imbalance calibration method according to claim 6, wherein the error extraction unit 2 is configured to extract an error value of each low-frequency component frequency point, and the calculation process comprises: Step 2.2.1, calculating the product of the received actual signal and the received channel digital signal generator RL, with the following formula: ; Wherein i has a value of positive integer 1 to 8, i.e., 1,2, 3..8, wherein Representing the signal sequence actually received by the receiving channel; Step 2.2.2, calculating the product of the received actual signal and the conjugate value of the digital signal generator RL of the receiving channel, the formula is as follows: ; representing the signal sequence actually received by the receiving channel, Representation of Wherein i has a value of positive integer 1 to 8, i.e. 1,2, 3..8; Step 2.2.3, calculating an error value sequence 2, wherein the calculation formula is as follows: ; wherein i has a positive integer of 1 to 8, i.e., 1,2,3.
  8. 8. The IQ imbalance calibration method according to claim 6, wherein the IDFT module is configured to convert errors calculated by the 2 error extraction units into compensation filter coefficients, and the calculating process comprises: Step 3.1, re-ordering the error sequences extracted in the steps 2.1.3 and 2.2.3, inserting a value of 0 coordinate point in the middle, and processing the sequence: ; renaming the sequence into elements according to new order Wherein i has a value of positive integer 1 to 16, i.e. 1,2, 3..16, i.e.: ; Step 3.2, the sequence generated in step 3.1 is used Performing linear interpolation to calculate a sequence The calculation formula is as follows: ; Step 3.3, pair Performing inverse discrete Fourier transform to calculate compensation coefficient The calculation formula is as follows: ; Where IDFT represents the inverse discrete fourier transform, Representing the left and right halves of the switching vector.
  9. 9. The IQ imbalance calibration method of a receiver channel of a zero intermediate frequency transceiver according to claim 1, wherein the error compensation unit calculates the compensation coefficient of the receiver channel according to the module 3 after the calibration And compensating, wherein the final compensation calculation formula is as follows: ; Where conv represents the convolution and, Representing the original data without compensation, Representation of Is used for the conjugation of (a), Representing at the current clock frequency Delay data after 8 cycles.
  10. 10. The IQ imbalance calibration method for a receiver channel of a zero intermediate frequency transceiver according to claim 1, wherein the calibration control unit is configured to control the start and stop of the entire self-calibration system, and comprises the steps of: step 4.1, turning on the radio frequency switch and starting the single-tone calibration signal generator; step 4.2, starting a double-tone signal excitation synthesizer; Step 4.3, wait for A post-start error extraction unit, wherein Representing propagation delay of the digital excitation signal from the transmit channel digital baseband to the receive channel digital baseband; Step 4.3, wait for After the time, closing the radio frequency switch, the single-tone calibration signal generator, the double-tone excitation signal synthesizer and the error extraction unit, and completing the calibration; And 4.4, starting an error compensation unit to start compensation for the normal working data.

Description

IQ imbalance calibration method for receiving channel of zero intermediate frequency transceiver Technical Field The invention relates to the technical field of transceiver calibration, in particular to a zero intermediate frequency transceiver receiving channel IQ imbalance calibration method. Background Sub-7GHz communication is required for miniaturization, low cost and low power consumption, and the development of transceivers is being promoted. The zero intermediate frequency transceiver has simple structure, low requirement on a transceiver system filter and wide application prospect in a Sub-7GHz communication system. The zero intermediate frequency receiver can realize conversion between the radio frequency signal and the baseband signal through once frequency mixing, and the IQ two paths of signals theoretically have strict 90-degree phase difference. However, due to manufacturing process deviation, it cannot be ensured that the IQ two-way devices are completely consistent. The method is characterized in that two local oscillation orthogonal signals input into the mixer have phase differences, and IQ two signals generated after mixing are also affected by frequency response differences of the baseband filter and delay of the ADC and the transmission line in the transmission process. The process deviation causes that the signal received by the digital baseband cannot guarantee 90 DEG phase difference, and the signal cannot analyze the expected information without calibration. In the traditional IQ imbalance foreground calibration method of the receiver, an external signal source is required to send test excitation to a receiving link, received baseband signals are analyzed outside a chip, errors are calculated, and then a trimming value is written into a nonvolatile memory unit of a circuit. After the chip is powered on again, the trimming value is read from the nonvolatile memory unit, and error compensation is realized while signal transmission is carried out. According to the method, an external device is required to build a calibration environment, and the calibration process is complex, so that the calibration cost of a single chip is high. Disclosure of Invention Aiming at the defects existing in the prior art, the invention aims to provide a zero intermediate frequency transceiver receiving channel IQ imbalance calibration method so as to solve the problems in the background art. According to the method, an external device is not required to build a calibration environment, the self calibration of the chip can be realized, and the calibration cost of a single chip can be effectively reduced. In order to achieve the above purpose, the invention is realized by the following technical scheme that the IQ imbalance calibration method of the receiving channel of the zero intermediate frequency transceiver is used in the calibration method: The module 1 is a single-tone calibration signal generator, which is positioned in the digital baseband module and is used for generating a single-tone signal in the self-calibration process; the module 2 is a double-tone excitation signal synthesizer, which is positioned at the digital baseband module of the transmission link and is used for generating double-tone excitation signals in the self-calibration process; the module 3, the radio frequency switch, locate at the front end of radio frequency, connect the sending channel and receiving channel in the course of calibrating, the excitation signal that the sending channel sends will loop back to the receiving channel; The module 4, the error extraction unit, the digital baseband module located in receiving link, realize extraction of IQ error and calculation of compensating coefficient; The module 5, the error compensating unit, the digital baseband module located in receiving link, compensates the link signal according to the compensating coefficient calculated by the said module 4; and the module 6 is used for calibrating the control unit, is positioned in the digital baseband part and is responsible for controlling all relevant modules in the calibrating process. Further, the single tone calibration signal generator in the module 1 includes a frequency word sequence generator, a frequency word distributor and four digital signal generators having exactly the same structure, which are respectively named as a digital signal generator TH, a digital signal generator TL, a digital signal generator RH and a digital signal generator RL for the convenience of distinguishing. Further, the frequency word sequence generator is configured to generate a single tone signal frequency word sequence required for calibration, and the calculating step includes: step 1.1, calculating a fundamental frequency of frequency analysis: ; Wherein the method comprises the steps of Representing the frequency of the digital baseband portion of the receive channel during calibration, the digital baseband frequency of the transmit channel