Local oscillator signal calibration system for radar signal processing

Abstract

The invention provides a local oscillator signal calibration system for radar signal processing. The local oscillator signal calibration system comprises an antenna assembly, a radio frequency transceiver chip and an FPGA (Field Programmable Gate Array) main control chip, the FPGA main control chip is used for realizing local oscillator signal calibration; the local oscillator signal calibration comprises the following steps: initializing equipment, switching an equipment working mode, operating the equipment, and performing FPGA loopback calibration; the FPGA loopback calibration comprises the steps that the FPGA main control chip obtains an initial calibration coefficient of the radio frequency transceiver chip, and secondary calibration compensation is carried out on the initial calibration coefficient through the FPGA main control chip; secondary calibration compensation and automatic threshold control carry out loop-back calibration adjustment, and an obtained optimal calibration coefficient is written into a calibration coefficient register set corresponding to the radio frequency transceiver chip; according to the invention, after the initial calibration coefficient of the radio frequency transceiver chip is obtained, secondary calibration compensation and automatic threshold control calibration adjustment are carried out through the FPGA, and good relative calibration capability is still maintained under the condition that radar transceivers of different types and frequency bands are matched with channels.

Description

Technical Field

[0001] The invention belongs to the field of radar signal processing, and in particular relates to a local oscillator signal calibration system for radar signal processing. Background Art

[0002] In the fields of radar, communication, medical treatment, etc., it is necessary to calibrate the local oscillator signal in the radar signal.

[0003] In the field of radar signal processing, existing radar signal processing such as Figure 1 As shown in the figure, the signal of the RF SOC is sent to the front-end channel through the transmission channel, and then sent to the radar antenna transceiver component after the channel up-conversion, and there is also a channel dedicated to antenna calibration. The radar signal enters the receiving channel of the channel through the receiving channel, and then the signal is connected to the receiving signal port of the RF SOC through the connector.

[0004] When the RF SOC is initialized, the SOC will generate a calibration signal from within the chip, and perform calibration from the transmit link loopback signal to the receive link within the SOC. Then it enters the normal working process. However, the signal transmission and reception of the RF SOC will generate DC local oscillator leakage.

[0005] This leakage is generally caused by circuit non-ideal factors, mutual interference between the local oscillator and the RF signal, and chip design and layout. Among them, circuit non-ideal factors are caused by I / Q signal imbalance and DC offset error. In the orthogonal modulation and demodulation process of the RF SOC chip, ideally, the I-way (in-phase) and Q-way (orthogonal phase) signals should be completely orthogonal and equal in amplitude. However, in actual circuits, due to manufacturing process deviations, inconsistent device parameters and other reasons, the I / Q-way signals will have amplitude imbalance and phase imbalance. This imbalance will cause part of the energy of the local oscillator signal to leak into the RF signal, resulting in DC local oscillator leakage. The DC offset error is due to the uncalibrated DC bias of the active devices in the circuit. These biases will cause the signal to generate a DC component during transmission, and some passive devices in the RF system may also have leakage, which further increases the DC offset, thereby causing DC local oscillator leakage.

[0006] The mutual interference between the local oscillator signal and the RF signal is due to the fact that the entire RF system is composed of multiple groups of sub-units and multiple connectors connected in series. There may be reasons such as imperfect shielding, signal coupling and low isolation, which may cause the local oscillator signal to leak or couple into the receiving or transmitting RF path, thereby forming or aggravating DC local oscillator leakage.

[0007] Although the leakage will be self-calibrated and suppressed by the SOC chip, the mechanism of the leakage generation mentioned above shows that the external RF link and the radar antenna transceiver link will have a similar principle basis, so that the external RF link and the radar antenna transceiver link will deteriorate the calibration status of the SOC itself, which may cause the SOC itself to complete the calibration, but the leakage of the entire link is still not suppressed or the suppression effect is worse.

[0008] Therefore, a technical solution is needed to optimize the local oscillator signal calibration problem in radar signal processing. Summary of the invention

[0009] To solve the above problems, the technical solution of the present invention is as follows:

[0010] A local oscillator signal calibration system for radar signal processing, comprising: an antenna assembly, a radio frequency transceiver chip and an FPGA main control chip;

[0011] The antenna components include: radar antenna, channel;

[0012] The FPGA master chip is used to realize the local oscillator signal calibration;

[0013] The local oscillator signal calibration comprises the following steps:

[0014] Device initialization;

[0015] Switch the device working mode: adjust the device working mode to the mode for calibrating the local oscillator signal;

[0016] Equipment operation: including operation of antenna components, RF transceiver chips and FPGA main control chips;

[0017] Perform FPGA loopback calibration, including: the FPGA main control chip obtains the initial calibration coefficient of the RF transceiver chip, and performs secondary calibration compensation on the initial calibration coefficient through the FPGA main control chip; the secondary calibration compensation and automatic threshold control perform loopback calibration adjustment, and write the obtained optimal calibration coefficient into the calibration coefficient register group corresponding to the RF transceiver chip.

[0018] The device initialization uses the FPGA main control chip to initialize the RF transceiver chip and the external clock chip through the SPI interface according to the initialization protocol.

[0019] Switching the device working mode includes the following steps:

[0020] Use the FPGA master chip to switch the working mode of the antenna in the antenna assembly to the calibration mode through the SPI channel;

[0021] Use the FPGA master chip to control the RF transceiver chip to switch the working mode to the normal transceiver working mode through the SPI channel with the RF transceiver chip.

[0022] The operation of the equipment includes the following steps:

[0023] The FPGA master chip configures its own DDS to generate a single tone signal with the same frequency as the RF chip during the initialization and calibration process. The FPGA master chip sends the single tone signal to the RF transceiver chip through the LVDS interface.

[0024] The RF transceiver chip performs digital-to-analog conversion on the single-tone signal and sends it to the antenna through the intermediate frequency TX RF interface;

[0025] The antenna feeds back the analog signal obtained through the calibration channel to the receiving link, and completes the analog-to-digital conversion through the RX receiving channel of the RF transceiver chip; the digitized received signal is returned to the FPGA main control chip through the LVDS interface.

[0026] Performing FPGA loopback calibration includes the following steps:

[0027] S1, FPGA master chip reads the complex number of local oscillator calibration coefficients generated in the initialization calibration mode in the RF transceiver chip through SPI;

[0028] S2, the FPGA main control chip performs phase rotation on the complex local oscillator calibration coefficient generated by the RF transceiver chip read in step S1 through an internal calculation unit; and then configures the local oscillator calibration coefficient after phase rotation into the RF transceiver chip through the SPI channel;

[0029] S3, the FPGA main control chip continuously performs spectrum analysis and calculation on the data of the RX channel returned from the RF transceiver chip, determines the amplitude of its zero-frequency local oscillator signal and records it; if the minimum amplitude is obtained, it enters S4, otherwise it jumps back to S2;

[0030] S4, the FPGA main control chip writes the calibration coefficients obtained in S3 to the calibration coefficient register group corresponding to the RF transceiver chip through the SPI channel, completing the local oscillator signal calibration of the whole machine.

[0031] The phase rotation method includes: performing phase rotation on the local oscillator calibration coefficient complex from 0° to 360° at intervals of 1°.

[0032] Judging the zero-frequency local oscillator signal includes: judging the calibration and suppression effect of the calibration coefficient after phase adjustment through a non-fixed zero-frequency local oscillator threshold.

[0033] Determining the amplitude of the zero-frequency local oscillator signal includes: recording the amplitude of the zero-frequency local oscillator signal after all degrees of phase rotation of the local oscillator calibration coefficient, and finding the minimum amplitude of the zero-frequency local oscillator signal and the corresponding local oscillator calibration coefficient by traversal.

[0034] The present invention has the following beneficial effects:

[0035] 1) After obtaining the initial calibration coefficient of the RF transceiver chip, the initial calibration coefficient is phase-shifted and then compensated again. Through the primary calibration of the RF SOC plus the secondary calibration compensation and automatic threshold control calibration adjustment performed by FPGA, good relative calibration capability can be maintained when radar transceivers of different types and frequency bands are matched with channels.

[0036] 2) FPGA adaptively adjusts the phase of the calibration coefficient, adaptively analyzes the spectrum of the RX channel loopback signal, and judges the calibration and suppression effect of the calibration coefficient after phase adjustment through a non-fixed zero-frequency local oscillator threshold, thereby selecting the most suitable calibration coefficient for the hardware running the current program;

[0037] 3) Automatically and adaptively suppress and calibrate the local oscillator leakage of antennas, channels and radio frequency circuits in different product states. The present invention can be used to compensate, calibrate and suppress the local oscillator leakage of the entire machine due to slight differences in different production conditions and production environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a conventional radar signal receiving and transmitting framework diagram;

[0039] Figure 2 A block diagram of the implementation principle provided for an embodiment of the present invention;

[0040] Figure 3 A flowchart of an FPGA loopback calibration provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings.

[0042] Figure 2 The implementation principle block diagram provided for the embodiment of the present invention, as shown in the figure, a local oscillator signal calibration system for radar signal processing includes: an antenna assembly, a radio frequency transceiver chip and an FPGA main control chip;

[0043] The antenna components include: radar antenna, channel;

[0044] The FPGA master chip is used to realize the local oscillator signal calibration;

[0045] The local oscillator signal calibration comprises the following steps:

[0046] 1. Device initialization;

[0047] Furthermore, the device initialization uses the FPGA main control chip to initialize the RF transceiver chip and the external clock chip through the SPI interface according to the initialization protocol.

[0048] 2. Switch the device working mode: adjust the device working mode to the mode for local oscillator signal calibration;

[0049] Furthermore, switching the device working mode includes the following steps:

[0050] Use the FPGA master chip to switch the working mode of the antenna in the antenna assembly to the calibration mode through the SPI channel;

[0051] Use the FPGA master chip to control the RF transceiver chip to switch the working mode to the normal transceiver working mode through the SPI channel with the RF transceiver chip.

[0052] 3. Equipment operation: including operation of antenna components, RF transceiver chips and FPGA main control chips;

[0053] Furthermore, the operation of the device includes the following steps:

[0054] The FPGA master chip configures its own DDS to generate a single tone signal with the same frequency as the RF chip during the initialization and calibration process. The FPGA master chip sends the single tone signal to the RF transceiver chip through the LVDS interface.

[0055] The RF transceiver chip performs digital-to-analog conversion on the single-tone signal and sends it to the antenna through the intermediate frequency TX RF interface;

[0056] The antenna feeds back the analog signal obtained through the calibration channel to the receiving link, and completes the analog-to-digital conversion through the RX receiving channel of the RF transceiver chip; the digitized received signal is returned to the FPGA main control chip through the LVDS interface.

[0057] 4. Perform FPGA loopback calibration, including: the FPGA main control chip obtains the initial calibration coefficient of the RF transceiver chip, and performs secondary calibration compensation on the initial calibration coefficient through the FPGA main control chip; the secondary calibration compensation and automatic threshold control perform loopback calibration adjustment, and write the obtained optimal calibration coefficient into the calibration coefficient register group corresponding to the RF transceiver chip. Automatically adapt to the local oscillator leakage suppression and calibration of antennas, channels and RF circuits in different product states; adaptive calibration frequency and calibration threshold, maintain good relative calibration capability under the condition of matching work of radar transceivers and channels of different types and frequency bands, and the calibration effect is independent of the ability of external use programs.

[0058] Figure 3 The FPGA loopback calibration flow chart provided in the embodiment of the present invention, as shown in the figure, performs the FPGA loopback calibration including the following steps:

[0059] S1, FPGA master chip reads the complex number of local oscillator calibration coefficients generated in the initialization calibration mode in the RF transceiver chip through SPI;

[0060] S2, the FPGA main control chip performs phase rotation on the complex local oscillator calibration coefficient generated by the RF transceiver chip read in step S1 through an internal calculation unit; and then configures the local oscillator calibration coefficient after phase rotation into the RF transceiver chip through the SPI channel;

[0061] The phase rotation method includes: performing phase rotation on the local oscillator calibration coefficient complex from 0° to 360° at intervals of 1°.

[0062] S3, the FPGA main control chip continuously performs spectrum analysis and calculation on the data of the RX channel returned from the RF transceiver chip, determines the amplitude of its zero-frequency local oscillator signal and records it; if the minimum amplitude is obtained, it enters S4, otherwise it jumps back to S2;

[0063] Judging the zero-frequency local oscillator signal includes: judging the calibration and suppression effect of the calibration coefficient after phase adjustment through a non-fixed zero-frequency local oscillator threshold, thereby selecting the most suitable calibration coefficient for the hardware running the current program.

[0064] Determining the amplitude of the zero-frequency local oscillator signal includes: recording the amplitude of the zero-frequency local oscillator signal after all degrees of phase rotation of the local oscillator calibration coefficient, and finding the minimum amplitude of the zero-frequency local oscillator signal and the corresponding local oscillator calibration coefficient by traversal.

[0065] S4, the FPGA main control chip writes the calibration coefficients obtained in S3 to the calibration coefficient register group corresponding to the RF transceiver chip through the SPI channel, completing the local oscillator signal calibration of the whole machine.

[0066] Through the design process and calibration method of the present invention, the same set of software can be used to automatically match the hardware states of antennas, channels and radio frequency links of different manufacturers and production states, and the calibration mode commonly found in antennas and the calibration capability of radio frequency transceiver chips are used to provide and optimize the calibration effect of the whole machine; by using the radio frequency transceiver integrated chip and combining the programmable characteristics of FPGA, the radar transmission / reception link is included in the calibration link, and the front-end sensitive radio frequency channel components are also included. Through the primary calibration of the radio frequency SOC plus the secondary calibration compensation and automatic threshold control calibration adjustment performed by FPGA, the relative calibration capability is still better when the radar transceivers and channels of different types and frequency bands are matched, and the adaptive threshold can improve the reliability of completing the calibration under different temperatures and working conditions; the adaptive calibration frequency and calibration threshold make the calibration effect independent of the external use program capability, so that the calibration software of the present invention method can be integrated into the initialization process of the existing radar signal processing software, which improves the automation capability and degree of equipment calibration, reduces the abnormality and difference of the calibration effect caused by hardware differences, and improves the reliability of the whole machine signal processing software.

[0067] The above disclosures are only several specific embodiments of the present invention; however, the present invention is not limited thereto, and any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A local oscillator signal calibration system for radar signal processing, characterized in that: include: Antenna components, RF transceiver chips and FPGA main control chips; The antenna components include: radar antenna, channel; The FPGA master chip is used to realize the local oscillator signal calibration; The local oscillator signal calibration comprises the following steps: Device initialization; Switch the device working mode: adjust the device working mode to the mode for calibrating the local oscillator signal; Equipment operation: including operation of antenna components, RF transceiver chips and FPGA main control chips; Perform FPGA loopback calibration, including: the FPGA main control chip obtains the initial calibration coefficient of the RF transceiver chip, and performs secondary calibration compensation on the initial calibration coefficient through the FPGA main control chip; the secondary calibration compensation and automatic threshold control perform loopback calibration adjustment, and write the obtained optimal calibration coefficient into the calibration coefficient register group corresponding to the RF transceiver chip.

2. The local oscillator signal calibration system for radar signal processing according to claim 1, characterized in that: The device initialization uses the FPGA main control chip to complete the initialization work on the radio frequency transceiver chip and the external clock chip through the SPI interface according to the initialization protocol.

3. The local oscillator signal calibration system for radar signal processing according to claim 1, characterized in that: The switching device working mode comprises the following steps: Use the FPGA master chip to switch the working mode of the antenna in the antenna assembly to the calibration mode through the SPI channel; Use the FPGA master chip to control the RF transceiver chip to switch the working mode to the normal transceiver working mode through the SPI channel with the RF transceiver chip.

4. The local oscillator signal calibration system for radar signal processing according to claim 1, characterized in that: The operation of the device comprises the following steps: The FPGA master chip configures its own DDS to generate a single tone signal with the same frequency as the RF chip during the initialization and calibration process. The FPGA master chip sends the single tone signal to the RF transceiver chip through the LVDS interface. The RF transceiver chip performs digital-to-analog conversion on the single-tone signal and sends it to the antenna through the intermediate frequency TX RF interface; The antenna feeds back the analog signal obtained through the calibration channel to the receiving link, and completes the analog-to-digital conversion through the RX receiving channel of the RF transceiver chip; the digitized received signal is returned to the FPGA main control chip through the LVDS interface.

5. The local oscillator signal calibration system for radar signal processing according to claim 1, characterized in that: The FPGA loopback calibration comprises the following steps: S1, FPGA master chip reads the complex number of local oscillator calibration coefficients generated in the initialization calibration mode in the RF transceiver chip through SPI; S2, the FPGA main control chip performs phase rotation on the complex local oscillator calibration coefficient generated by the RF transceiver chip read in step S1 through an internal calculation unit; and then configures the local oscillator calibration coefficient after phase rotation into the RF transceiver chip through the SPI channel; S3, the FPGA main control chip continuously performs spectrum analysis and calculation on the data of the RX channel returned from the RF transceiver chip, determines the amplitude of its zero-frequency local oscillator signal and records it; if the minimum amplitude is obtained, it enters S4, otherwise it jumps back to S2; S4, the FPGA main control chip writes the calibration coefficient obtained by S3 to obtain the best calibration effect into the calibration coefficient register group corresponding to the RF transceiver chip through the SPI channel.

6. The local oscillator signal calibration system for radar signal processing according to claim 5, characterized in that The phase rotation method includes: performing phase rotation on the local oscillator calibration coefficient complex from 0° to 360° at intervals of 1°.

7. The local oscillator signal calibration system for radar signal processing according to claim 5, characterized in that: The determining of the zero-frequency local oscillator signal includes: determining the calibration and suppression effect of the calibration coefficient after phase adjustment through a non-fixed zero-frequency local oscillator threshold.

8. The local oscillator signal calibration system for radar signal processing according to claim 5, characterized in that: The determining of the amplitude of the zero-frequency local oscillator signal includes: recording the amplitude of the zero-frequency local oscillator signal after all degrees of phase rotation and the local oscillator calibration coefficient, and finding the minimum amplitude of the zero-frequency local oscillator signal and the corresponding local oscillator calibration coefficient by traversal.

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