Broadband local oscillator circuit and local oscillator signal generation method

Abstract

The present invention discloses a broadband local oscillator circuit and a local oscillator signal generating method. Aiming at the problems of low normalized noise floor, limited VCO frequency range, poor phase-detection leakage and reference leakage suppression of the current frequency synthesizer with single-chip integrated VCO, a frequency synthesizer without VCO and a frequency synthesizer with internal integrated VCO matrix are adopted to form a phase-locked loop structure; a directional coupler, an amplifier and a high-pass filter are adopted in the phase-locked loop to form a feedback path, so that the phase-locked loop has the performances of high phase noise, wide frequency band, high phase-detection leakage suppression, high reference leakage suppression and the like; the local oscillator circuit can be miniaturized well, the demand for miniaturized use is met, and the circuit has good operability and practicality.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a broadband local oscillator circuit and a local oscillator signal generating method. Background Art

[0002] Frequency sources are widely used in many fields such as electronic countermeasures, radar, telemetry and remote control, and communications, and are known as the "heart" of many electronic systems. As an indispensable part of the up- and down-conversion links of the receiver, the performance of the local oscillator, such as output frequency range, phase noise, harmonic suppression, spurious suppression, frequency hopping time, and frequency stability, is crucial to the entire system.

[0003] At present, frequency synthesis technology can be divided into three types, including direct frequency synthesis technology (DS), phase-locked loop frequency synthesis technology (PLL), and direct digital frequency synthesis technology (DDS). Direct frequency synthesis technology can achieve low phase noise and fast frequency hopping, but its output frequency band is narrow, large in size and difficult to integrate. Phase-locked loop frequency synthesis technology can achieve low phase noise, but there is a problem of slow frequency conversion time. Direct digital frequency synthesis technology starts from the phase perspective, adopts Nyquist sampling theorem, and performs frequency synthesis through digital sampling and storage technology. It has short frequency conversion time, continuous phase, high frequency resolution, easy to realize complex signal modulation, easy to control, and high stability. However, there are also problems such as rich spurious components, limited maximum frequency of synthesized signals, and high power consumption.

[0004] The current development trend of frequency synthesizers is to combine technologies such as direct frequency synthesis technology (DS), phase-locked loop frequency synthesis technology (PLL), direct digital frequency synthesis technology (DDS), etc., and use their respective advantages to improve the technical indicators of frequency synthesizers such as phase noise, spurious indicators, frequency hopping time and output frequency range.

[0005] Reference 1, "Research and Implementation of High-Performance Frequency Source Based on DDS+PLL Technology" (Master's thesis of Wang Yi, National University of Defense Technology, November 2004), adopts a direct digital frequency synthesis (DDS)-driven phase-locked loop (PLL) implementation scheme to obtain a 600MHz sampling clock frequency source with high frequency stability, low phase noise, and low spurious.

[0006] Reference 2, "Research on 8-18 GHz Broadband Microwave Frequency Source Module" (Master's thesis of Li Zhanguo, University of Electronic Science and Technology of China, March 2010), uses a DDS direct excitation PLL circuit structure for the L-band frequency source, controls the frequency hopping operation of the frequency source through FPGA, and uses YTO instead of VCO to achieve relatively good 8-18 GHz broadband frequency output comprehensive technical indicators.

[0007] Reference 3, "Research on Ultra-Wideband Microwave Frequency Source Technology" (Li Mingliang, Master's thesis, University of Electronic Science and Technology of China, 2006.4), uses a mixed frequency synthesis scheme of DDS + PLL to achieve the output of low-end frequency 2-4GHz, and then achieves the spread spectrum from 2-4GHz to 2-12GHz through a segmented amplification frequency multiplication link, and the frequency selection output is controlled by a microwave switch. The entire system uses a single-loop phase-locked control VCO to output an ultra-wideband frequency of 2-12GHz, realizing a small-volume, low-cost microwave frequency source.

[0008] Reference 4, "Research and Design of a Low Phase Noise Frequency Source" (Liu Yuankun's master's thesis at UESTC 2018.3), adopts a complex loop sampling phase-locked + DDS + frequency multiplication scheme for design and implementation, achieving a wide-band output of 5.4GHz-10.8GHz frequency signal, low phase noise, and low spurious agile frequency source.

[0009] Reference 5, "Design of Low Spurious Frequency Source Based on Fractional-Number Phase-Locked Loop" (Yan Chong, Wang Qiang, Li Xiaohui, Ma Donglei) uses fractional-number phase-locked loop technology and a phase-locked loop chip with an internal integrated voltage-controlled oscillator to design a frequency source with an output frequency of 1500~2500MHz, a frequency step of 250kHz, a phase noise of -90dBc / Hz@10kHz, a spurious suppression of less than -65dBc, and an output power of +5dBm.

[0010] Reference 6, "Research and Design of Ultra-Wideband Frequency Source Based on PLL" (Tang Hongyu, Master's Thesis of Hunan University, 2017.6), uses a single-loop phase-locked loop to achieve a frequency source output frequency range of 1.7GHz to 3.4GHz, a single-point frequency locking function, and a frequency sweep function within the entire output frequency range.

[0011] Reference 7, "Broadband Low Spurious Agile Frequency Source" (Master's thesis of Southeast University, Chen Fei, 2017.6), adopts a dual phase-locked loop structure to meet the low spurious requirements. The first-stage phase-locked loop is used as a variable reference for the second-stage phase-locked loop to suppress integer boundary spurs; to meet the low phase noise requirements, a low phase noise reference, a loop filter with appropriate bandwidth, optimized configuration parameters such as the charge pump current of the phase-locked loop system, and a separately designed power supply are adopted; to meet the agile requirements, ADC sampling calibration and DAC preset VCO tuning voltage are adopted; to meet the broadband requirements, a double-balanced mixer mixing method is adopted to expand the frequency band, and filter components are used to filter in frequency bands to ensure good harmonic suppression in a wide frequency band. Gain modules and digital step attenuators are used in combination in frequency bands to ensure high output power dynamic range in a wide frequency band; the output frequency range is 1M~6GHz.

[0012] Reference 8, "Research on Phase-locked Frequency Sources of C-band and X-band" (Zhang Xu, Nanjing University of Science and Technology, 2007.6), uses the frequency synthesis chip ADF41O6 plus different VCOs to realize two phase-locked frequency sources of 5.5 GHz and 8.76 GHz.

[0013] Reference 9, "Research on 60MHz~12GHz Broadband Frequency Source" (Wang Zheng, Master's thesis, University of Electronic Science and Technology of China, March 2010) The frequency generation part uses a YTO fractional-N phase-locked loop to generate a baseband signal of 2GHz~6GHz, and then expands this basic signal to cover the entire frequency band by combining down-conversion, frequency division, and frequency multiplication technology. Some functions of the 60MHz~12GHz frequency source prototype are realized.

[0014] Document 10, invention patent CN103312322A discloses a local oscillator circuit and a local oscillator signal generation method, which realizes a second local oscillator circuit with low phase noise by using three-stage low phase noise frequency multiplication and two-stage microwave band extremely narrow-band high-Q surface acoustic wave resonators.

[0015] Document 11, invention patent CN1133340C discloses a radio frequency phase-locked local oscillator source, in which a reference signal source is connected to two different frequency synthesizers, and each channel is connected in series with a two-stage single-pole single-throw switch, and the control characteristics of the two switches are opposite, which can quickly switch the phase-locked local oscillator source with strong stability and low power consumption.

[0016] References 1-4 use DDS+PLL circuits, references 5-8 use classic phase-locked loop circuits, reference 9 uses PLL+DS circuits, and reference 10 uses DS circuit structures to generate signals with different output frequency ranges. Reference 11 achieves channel isolation of two-way signals by adding two-stage single-pole single-throw switches in the two-way links. The above references mainly start from the circuit structure or channel link to improve the signal spectrum quality from one or more aspects, but there are still certain problems. Summary of the invention

[0017] The present invention aims at the technical problems existing in the prior art and provides a broadband local oscillator circuit and a local oscillator signal generating method, so as to realize the local oscillator signal output with high reference leakage suppression, high phase detection leakage suppression, wide bandwidth, high phase noise and high integration.

[0018] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0019] A broadband local oscillator circuit comprises a first frequency synthesis unit, a second frequency synthesis unit, a control unit, a directional coupler, an amplifier, a high-pass filter, a first switch circuit and a second switch circuit;

[0020] The first frequency synthesis unit includes a first R frequency divider, a first N frequency divider, a first phase detector, a first charge pump and a first loop filter, the first R frequency divider and the first N frequency divider are respectively coupled to the input end of the first phase detector, and the first phase detector, the first charge pump and the first loop filter are coupled in sequence;

[0021] The second frequency synthesis unit comprises a second R frequency divider, a second N frequency divider, a second phase detector, a second charge pump, a second loop filter and a VCO matrix unit, the second R frequency divider and the second N frequency divider are respectively coupled to the input end of the second phase detector, the second phase detector, the second charge pump and the second loop filter are coupled in sequence, and the output end of the VCO matrix unit is coupled to the input end of the second N frequency divider;

[0022] The control unit is coupled to the first frequency synthesis unit and the second frequency synthesis unit respectively through a communication interface to achieve information transmission;

[0023] The input end of the first switch circuit is used to connect the reference input, one output end is coupled to the input end of the first R frequency divider, and the other output end is coupled to the input end of the second R frequency divider, and is used for switching control between the reference input and the first frequency synthesis unit and the second frequency synthesis unit;

[0024] The output end of the second switch circuit is coupled to the input end of the VCO matrix unit, and the two input ends thereof are respectively coupled to the output ends of the first loop filter and the second loop filter, and are used for switching control between the VCO matrix unit and the first loop filter and the second loop filter;

[0025] The output end of the VCO matrix unit is coupled to the input end of the directional coupler, and the coupling end of the directional coupler is coupled to the first N frequency divider through an amplifier and a high-pass filter in sequence.

[0026] In the above technical solution, further, the first frequency synthesis unit adopts a frequency synthesizer without VCO, and the second frequency synthesis unit adopts a frequency synthesizer with an internal integrated VCO matrix.

[0027] In the above technical solution, further, the second frequency synthesis unit also includes a VCO calibration unit and a Σ-Δ modulator.

[0028] In the above technical solution, further, the first switch circuit and the second switch circuit are single-pole double-throw switches.

[0029] In the above technical solution, further, the control unit includes an FPGA chip and a FLASH unit mounted thereon.

[0030] The present invention also provides a method for generating a local oscillator signal based on the broadband local oscillator circuit, comprising the following steps:

[0031] S1, switching the first switch circuit so that the reference input is connected to the second R divider;

[0032] S2, switching the second switch circuit to connect the second loop filter to the VCO matrix unit, so that a phase-locked loop is formed inside the second frequency synthesis unit;

[0033] S3, configuring the second frequency synthesis unit to a calibration mode, and configuring register parameters of the second frequency synthesis unit to lock its output frequency;

[0034] S4, reading the parameters of the full frequency coverage and a certain frequency step of the VCO matrix unit in the self-locking mode of the second frequency synthesis unit, and storing them in the FLASH unit for subsequent use;

[0035] S5, switching the first switch circuit so that the reference input is connected to the first R divider;

[0036] S6, switching the second switch circuit to connect the first loop filter to the VCO matrix unit, so that the first frequency synthesis unit, the VCO matrix unit, the directional coupler, the amplifier, and the high-pass filter form a phase-locked loop;

[0037] S7, configuring register parameters of the first frequency synthesis unit, configuring the second frequency synthesis unit to be in manual mode, calling the VCO matrix unit parameters in step S4 according to the output frequency, and locking the output frequency of the phase-locked loop in step S6.

[0038] The beneficial effects of the present invention are:

[0039] Aiming at the problems of low normalized noise floor, limited VCO frequency range, poor suppression of phase-detection leakage and reference leakage of the current frequency synthesizer with monolithic integrated VCO, a frequency synthesizer without VCO and a frequency synthesizer with internal integrated VCO matrix are adopted to form a phase-locked loop structure; a directional coupler, an amplifier and a high-pass filter are adopted to form a feedback path in the phase-locked loop, and the low-frequency reference frequency is suppressed by the isolation index of the directional coupler, the reverse isolation of the amplifier and the amplitude-frequency characteristic of the high-pass filter, so that the frequency synthesizer has the performance of high phase noise, wide bandwidth, high suppression of phase-detection leakage and high suppression of reference leakage.

[0040] The present invention adopts a combination of a frequency synthesizer without a VCO and a frequency synthesizer with an internal integrated VCO matrix, which can well realize the miniaturization of the local oscillator circuit, meet the needs of miniaturized use, and has good operability and practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of broadband local oscillator circuit of the present invention.

[0042] Figure 2 This is a control flow chart of the local oscillator signal generating method of the present invention.

[0043] Figure 3a ) is a measured diagram of phase-locked leakage when the local oscillator output frequency is 8.054 GHz in Example 1 of the present invention.

[0044] Figure 3b ) is a reference leakage measurement diagram of the local oscillator output frequency of 8.054 GHz in Example 1 of the present invention.

[0045] Figure 3c ) is a measured phase noise diagram of the local oscillator output frequency of 8.054 GHz in Example 1 of the present invention.

[0046] Figure 4a ) is a measured diagram of phase-locked leakage when the local oscillator output frequency is 4.368 GHz in Example 2 of the present invention.

[0047] Figure 4b ) is a reference leakage measurement diagram of the local oscillator output frequency of 4.368 GHz in Example 2 of the present invention.

[0048] Figure 4c ) is a measured phase noise diagram of the local oscillator output frequency of 4.368 GHz in Example 2 of the present invention.

[0049] Figure 5a ) is a measured diagram of phase-locked leakage when the local oscillator output frequency is 5.3808 GHz in Example 2 of the present invention.

[0050] Figure 5b ) is a reference leakage measurement diagram of the local oscillator output frequency of 5.3808 GHz in Example 2 of the present invention.

[0051] Figure 5c ) is a measured phase noise diagram of the local oscillator output frequency of 5.3808 GHz in Example 2 of the present invention.

[0052] Figure 6a ) is a measured diagram of phase-locked leakage when the local oscillator output frequency is 11.369 GHz in Example 2 of the present invention.

[0053] Figure 6b ) is a reference leakage measurement diagram of the local oscillator output frequency of 11.369 GHz in Example 2 of the present invention.

[0054] Figure 6c ) is a measured phase noise diagram of the local oscillator output frequency of 11.369 GHz in Example 2 of the present invention.

[0055] In the figure: 100, a first frequency synthesis unit, 101, a first R frequency divider, 102, a first N frequency divider, 103, a first phase detector, 104, a first charge pump, 105, a first loop filter;

[0056] 200, a second frequency synthesis unit, 201, a second R frequency divider, 202, a second N frequency divider, 203, a second phase detector, 204, a second charge pump, 205, a second loop filter, 206, a VCO matrix unit, 207, a VCO calibration unit, 208, a Σ-Λ modulator;

[0057] 300. FPGA chip, 400. directional coupler, 500. amplifier, 600. high-pass filter, 700. FLASH unit, 800. first switch circuit, 900. second switch circuit. DETAILED DESCRIPTION

[0058] like Figure 1 The broadband local oscillator circuit shown includes a first frequency synthesis unit 100 , a second frequency synthesis unit 200 , a control unit, a directional coupler 400 , an amplifier 500 , a high-pass filter 600 , a first switch circuit 800 and a second switch circuit 900 .

[0059] Among them, the first frequency synthesis unit 100 adopts a frequency synthesizer without VCO, including a first R frequency divider 101, a first N frequency divider 102, a first phase detector 103, a first charge pump 104 and a first loop filter 105, the first R frequency divider 101 and the first N frequency divider 102 are respectively coupled to the input end of the first phase detector 103, and the first phase detector 103, the first charge pump 104 and the first loop filter 105 are coupled in sequence.

[0060] The second frequency synthesis unit 200 adopts a frequency synthesizer with an internal integrated VCO matrix, including a second R frequency divider 201, a second N frequency divider 202, a second phase detector 203, a second charge pump 204, a second loop filter 205 and a VCO matrix unit 206. The second R frequency divider 201 and the second N frequency divider 202 are respectively coupled to the input end of the second phase detector 203, the second phase detector 203, the second charge pump 204 and the second loop filter 205 are coupled in sequence, and the output end of the VCO matrix unit 206 is coupled to the input end of the second N frequency divider 202.

[0061] The control unit includes an FPGA chip 300 and a FLASH unit 700 mounted thereon. The control unit is coupled to the SPI interfaces of the frequency synthesis unit 100 without VCO and the frequency synthesis unit 200 with an internal integrated VCO matrix, respectively, to realize information transmission between the control unit and the first frequency synthesis unit and the second frequency synthesis unit.

[0062] The first switch circuit 800 adopts a single-pole double-throw switch; the input end of the first switch circuit 800 is used to connect the reference input, one output end is coupled to the input end of the first R divider 101, and the other output end is coupled to the input end of the second R divider 201, and is used for switching control between the reference input and the first frequency synthesis unit and the second frequency synthesis unit.

[0063] The second switch circuit 900 adopts a single-pole double-throw switch; the output end of the second switch circuit 900 is coupled to the VCTRL end of the VCO matrix unit 206, and its two input ends are coupled to the output ends of the first loop filter 105 and the second loop filter 205 respectively, and is used for switching control between the voltage control end VCTRL of the VCO matrix unit and the first loop filter and the second loop filter.

[0064] The output terminal RF_out of the VCO matrix unit 206 is coupled to the input terminal of the directional coupler 400, the coupling terminal of the directional coupler 400 is coupled to the input terminal of the amplifier 500, the output terminal of the amplifier 500 is coupled to the input terminal of the high-pass filter 600, and the output terminal of the high-pass filter 600 is coupled to the input terminal RF_in of the first N divider 102, forming a feedback path of the phase-locked loop in the local oscillator circuit.

[0065] In this embodiment, the frequency synthesizer with an internally integrated VCO matrix further includes a VCO calibration unit 207 and a Σ-Δ modulator 208 .

[0066] Combine the following Figure 1 and 2 A method for generating a local oscillator signal based on the broadband local oscillator circuit is described, which specifically includes the following steps:

[0067] S1, switch the single-pole double-throw switch SW1 to terminal 2, so that the reference input is connected to the second R divider, and the reference signal enters the second frequency synthesis unit through the REF_in2 port;

[0068] S2, switch the single-pole double-throw switch SW2 to terminal 2, so that the second loop filter is connected to the VCTRL terminal of the VCO matrix unit, and a phase-locked loop is formed inside the second frequency synthesis unit;

[0069] S3, configuring the second frequency synthesis unit to a calibration mode, configuring the values ​​of each register of the second frequency synthesis unit to lock its output frequency;

[0070] S4, using the self-compiled calibration program to read the parameters of the full frequency coverage and certain frequency step of the VCO matrix unit in the self-locking mode of the second frequency synthesis unit, saving it as an Excel file, and storing it in the FLASH unit for subsequent calling;

[0071] S5, switch the single-pole double-throw switch SW1 to terminal 1, so that the reference input is connected to the first R divider, and the reference signal enters the first frequency synthesis unit through the REF_in1 port;

[0072] S6, switching the single-pole double-throw switch SW2 to terminal 1, connecting the first loop filter to the VCTRL terminal of the second frequency synthesis unit, connecting the first loop filter to the VCO matrix unit, and forming a phase-locked loop with the first frequency synthesis unit, the VCO matrix unit, the directional coupler, the amplifier, and the high-pass filter;

[0073] S7, configure the values ​​of each register in the first frequency synthesis unit, configure the second frequency synthesis unit to manual mode, and only use the VCO matrix unit of the second frequency synthesis unit; call the VCO matrix unit parameters stored in the FLASH unit in step S4 according to the output frequency, so that the phase-locked loop output frequency in step S6 is locked.

[0074] The present invention is further described below in conjunction with specific embodiments and test data. The broadband local oscillator circuit and local oscillator signal generation method of the present invention are used to achieve local oscillator outputs covering two different frequency bands, as follows:

[0075] Example 1

[0076] Frequency coverage range: 8~16GHz local oscillator frequency output, signal amplitude: +6dBm±3dB, reference frequency input is 100MHz, phase detection frequency is 50MHz, phase noise ≤-100dBc / Hz@10kHz (RF input is 1GHz), the reference leakage, phase detection leakage, and phase noise measured data are as follows Figure 3a )、 Figure 3b )、 Figure 3c ) as shown.

[0077] according to Figure 3c ), and its phase noise index can be calculated to be PN=-81.176-10*lg100=-101.176dBc / Hz (RF input is 1GHz).

[0078] Example 2

[0079] Frequency coverage range: LO frequency output of 3.4~11.4GHz, signal amplitude: -7dBm±3dB, reference frequency input is 102.4MHz, phase detection frequency is 102.4MHz, phase noise ≤-108dBc / Hz@10kHz (RF input is 1GHz).

[0080] 1) The local oscillator output frequency is 4.368 GHz, and the RF input is 1 GHz. The measured data of reference leakage, phase detection leakage, and phase noise are as follows: Figure 4a )、 Figure 4b )、 Figure 4c ). Figure 4c ), and its phase noise index can be calculated to be PN=-89.042-10*lg100=-109.042dBc / Hz (RF input is 1GHz).

[0081] 2) The local oscillator output frequency is 5.3808 GHz, and the measured data of reference leakage, phase detection leakage, and phase noise are as follows: Figure 5a )、 Figure 5b )、 Figure 5c ). Figure 5c ), and its phase noise index can be calculated to be PN=-86.005-10*lg100=-106.005dBc / Hz.

[0082] 3) When the local oscillator output frequency is 11.369 GHz, the measured data of reference leakage, phase detection leakage and phase noise are as follows: Figure 6a )、 Figure 6b )、 Figure 6c ). Figure 6c ), and the phase noise index can be calculated to be PN=-81.534.005-10*lg100=-101.534dBc / Hz.

[0083] The specification and drawings of the present invention are considered to be illustrative rather than restrictive. On the basis of the present invention, those skilled in the art can make some substitutions and modifications to some of the technical features according to the disclosed technical content without creative labor, all of which are within the protection scope of the present invention.

Claims

1. A broadband local oscillator circuit, characterized in that: It includes a first frequency synthesis unit, a second frequency synthesis unit, a control unit, a directional coupler, an amplifier, a high-pass filter, a first switch circuit and a second switch circuit; The first frequency synthesis unit includes a first R frequency divider, a first N frequency divider, a first phase detector, a first charge pump and a first loop filter, the first R frequency divider and the first N frequency divider are respectively coupled to the input end of the first phase detector, and the first phase detector, the first charge pump and the first loop filter are coupled in sequence; The second frequency synthesis unit comprises a second R frequency divider, a second N frequency divider, a second phase detector, a second charge pump, a second loop filter and a VCO matrix unit, the second R frequency divider and the second N frequency divider are respectively coupled to the input end of the second phase detector, the second phase detector, the second charge pump and the second loop filter are coupled in sequence, and the output end of the VCO matrix unit is coupled to the input end of the second N frequency divider; The control unit is coupled to the first frequency synthesis unit and the second frequency synthesis unit respectively through a communication interface to achieve information transmission; The input end of the first switch circuit is used to connect the reference input, one output end is coupled to the input end of the first R frequency divider, and the other output end is coupled to the input end of the second R frequency divider, and is used for switching control between the reference input and the first frequency synthesis unit and the second frequency synthesis unit; The output end of the second switch circuit is coupled to the input end of the VCO matrix unit, and the two input ends thereof are respectively coupled to the output ends of the first loop filter and the second loop filter, and are used for switching control between the VCO matrix unit and the first loop filter and the second loop filter; The output end of the VCO matrix unit is coupled to the input end of the directional coupler, and the coupling end of the directional coupler is coupled to the first N frequency divider through an amplifier and a high-pass filter in sequence.

2. The broadband local oscillator circuit according to claim 1, characterized in that: The first frequency synthesis unit adopts a frequency synthesizer without VCO, and the second frequency synthesis unit adopts a frequency synthesizer with an internal integrated VCO matrix.

3. The broadband local oscillator circuit according to claim 2, characterized in that: The second frequency synthesis unit also includes a VCO calibration unit and a Σ-Δ modulator.

4. The broadband local oscillator circuit according to claim 1, characterized in that: The first switch circuit and the second switch circuit are single-pole double-throw switches.

5. The broadband local oscillator circuit according to claim 1, characterized in that: The control unit includes an FPGA chip and a FLASH unit mounted thereon.

6. A method for generating a local oscillator signal based on the broadband local oscillator circuit according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, switching the first switch circuit so that the reference input is connected to the second R divider; S2, switching the second switch circuit to connect the second loop filter to the VCO matrix unit, so that a phase-locked loop is formed inside the second frequency synthesis unit; S3, configuring the second frequency synthesis unit to a calibration mode, and configuring register parameters of the second frequency synthesis unit to lock its output frequency; S4, reading the parameters of the full frequency coverage and a certain frequency step of the VCO matrix unit in the self-locking mode of the second frequency synthesis unit, and storing them in the FLASH unit for subsequent use; S5, switching the first switch circuit so that the reference input is connected to the first R divider; S6, switching the second switch circuit to connect the first loop filter to the VCO matrix unit, so that the first frequency synthesis unit, the VCO matrix unit, the directional coupler, the amplifier, and the high-pass filter form a phase-locked loop; S7, configuring register parameters of the first frequency synthesis unit, configuring the second frequency synthesis unit to be in manual mode, calling the VCO matrix unit parameters in step S4 according to the output frequency, and locking the output frequency of the phase-locked loop in step S6.

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