CN-121994857-A - Microwave control method and microwave controller for electronic paramagnetic spectrometer

CN121994857ACN 121994857 ACN121994857 ACN 121994857ACN-121994857-A

Abstract

The invention provides a microwave control method and a microwave controller for an electronic paramagnetic spectrometer, wherein the microwave control method for the electronic paramagnetic spectrometer comprises the steps of controlling a microwave source to generate a microwave signal for paramagnetic resonance detection; the method comprises the steps of distributing a first power division signal and a second power division signal, inputting the first power division signal into a resonant cavity, detecting a reflected signal of the resonant cavity after resonance absorption of a sample to be detected, obtaining a first detection signal, shifting the phase of the second power division signal, obtaining a quadrature local oscillation signal, mixing the first detection signal and the local oscillation signal, obtaining an I down-conversion signal and a Q down-conversion signal, performing data processing to obtain detection result information, performing error analysis, and correcting a microwave source to enable the frequency of an output microwave signal to keep a first working frequency. According to the invention, the feedback control of the microwave signal is realized by establishing a feedback loop between the output and the microwave signal input of the microwave source, so that the high-precision control of the microwave in the electronic paramagnetic spectrometer is realized.

Inventors

ZHU JINFU
DING HONGLI
YANG JIAYUE
ZHANG WEIQING

Assignees

深圳先进光源研究院

Dates

Publication Date: 20260508
Application Date: 20251230

Claims (10)

1. A microwave control method for an electron paramagnetic spectrometer, comprising the steps of: controlling a microwave source to generate a microwave signal for paramagnetic resonance detection, wherein the frequency of the microwave signal is a first working frequency; The method comprises the steps of carrying out power distribution on a microwave signal to obtain a first power division signal and a second power division signal, inputting the first power division signal into a resonant cavity, and detecting a microwave reflected signal of a sample to be detected after resonance absorption occurs in the resonant cavity to obtain a first detection signal; Acquiring the first detection signal and the local oscillation signal, and mixing the first detection signal and the local oscillation signal to obtain an I down-conversion signal and a Q down-conversion signal; Sampling and data processing are carried out on the I down-conversion signal and the Q down-conversion signal to obtain an original baseband signal, and the original baseband signal is restored to obtain detection result information; Judging whether the frequency of the microwave signal is offset according to the original baseband signal, and correcting the microwave source according to the offset so as to enable the frequency of the output microwave signal to keep the first working frequency.
2. The method for controlling microwaves for an electronic paramagnetic spectrometer according to claim 1, wherein the steps of sampling and data processing the I down-converted signal and the Q down-converted signal to obtain an original baseband signal, and recovering to obtain detection result information include: Performing low-pass filtering on the I down-conversion signal and the Q down-conversion signal to obtain an I signal baseband component and a Q signal baseband component; And sampling and data processing are carried out on the I signal baseband component and the Q signal baseband component to obtain an original baseband signal, and the original baseband signal is used for restoring to obtain detection result information.
3. The method of claim 1, further comprising, after the step of controlling the microwave source to generate a microwave signal for paramagnetic resonance detection, the microwave signal being at the first operating frequency: performing attenuation control on the signal intensity of the microwave signal; And carrying out low-noise amplification on the microwave signal after the attenuation control is finished, wherein the signal power of the amplified microwave signal is positioned in a signal power target interval and is used for improving the signal-to-noise ratio.
4. The method for controlling microwave of electronic paramagnetic spectrometer according to claim 1, wherein the step of performing power distribution on the microwave signal to obtain a first power division signal and a second power division signal, wherein the first power division signal is input into a resonant cavity and a microwave reflected signal of a sample to be detected after resonance absorption occurs in the resonant cavity is detected to obtain a first detection signal, and the second power division signal is used for performing phase shift and obtaining a local oscillation signal orthogonal to the first power division signal comprises the steps of: the microwave signal is distributed into a first power division signal on a first power division path and a second power division signal on a second power division path through a power divider; On a first power division path, a sample to be detected is arranged in a resonant cavity, and the sample to be detected is detected by combining a first power division signal; detecting a reflected signal of a resonant cavity after resonance absorption of a sample to be detected to obtain a first detection signal; And on a second power division path, shifting the phase of the second power division signal to obtain a local oscillation signal with the phase difference of 90 degrees with the first detection signal, wherein the local oscillation signal is used for carrying out quadrature modulation on the first detection signal.
5. The method of claim 1, wherein the first operating frequency is an X-band frequency.
6. The method according to claim 1, wherein the step of determining whether the frequency of the microwave signal is shifted according to the original baseband signal and correcting the microwave source for the shift so that the frequency of the output microwave signal maintains the first operating frequency comprises: Collecting the original baseband signal; judging whether the frequency of the microwave signal is equal to the resonant frequency of the cavity according to the original baseband signal waveform; If the frequency of the microwave signal is not equal to the resonant frequency of the cavity, adjusting and outputting a microwave source control signal of the first working frequency according to the error, and correcting and outputting the frequency of the microwave signal.
7. The method for controlling microwaves for an electronic paramagnetic spectrometer according to claim 2, wherein the step of sampling and data processing the I signal baseband component and the Q signal baseband component to obtain a raw baseband signal, and the step of recovering the raw baseband signal to obtain detection result information includes: analog-to-digital sampling is carried out on the I signal baseband component and the Q signal baseband component to obtain the I signal digital component and the Q signal digital component; the I signal digital component is used for representing a signal real part, the Q signal digital component is used for representing a signal imaginary part, and the amplitude and the phase of the original baseband signal are obtained according to the signal real part and the signal imaginary part; and obtaining the original baseband signal according to the amplitude and the phase of the original baseband signal.
8. A microwave controller is characterized in that the microwave controller is used for realizing the microwave control method for the electronic paramagnetic spectrometer according to any one of claims 1-7, and comprises a microwave source, a power divider, a phase shifter, a circulator, a resonant cavity, an I/Q mixer and a measurement and control board card, The output end of the microwave source is connected with the input end of the power divider and is used for outputting a microwave signal with a first working frequency to the power divider; The first branch end of the power divider is connected with the phase shifter, the second branch end of the power divider is connected with the input end of the circulator and is used for dividing the microwave signal into a first power division signal and a second power division signal with the same power, outputting the first power division signal to the circulator and outputting the second power division signal to the phase shifter; The phase shifter is connected with a local oscillator signal end of the I/Q mixer and is used for shifting the phase of the second power division signal to obtain a local oscillator signal orthogonal to the first power division signal and outputting the local oscillator signal to the I/Q mixer; The detection end of the to-be-detected sample of the circulator is connected with the resonant cavity, and the signal output end of the circulator is connected with the radio frequency signal end of the I/Q mixer and is used for outputting the first power division signal to the resonant cavity; the resonant cavity is used for setting a sample to be detected and collecting and outputting the first detection signal to the circulator; the circulator outputs the first detection signal to the I/Q mixer; The baseband signal end of the I/Q mixer is connected with the signal acquisition end of the measurement and control board card and is used for mixing the first detection signal and the local oscillation signal and outputting an I down-conversion signal and a Q down-conversion signal to the measurement and control board card; And the signal output end of the measurement and control board is connected with the control end of the microwave source and is used for carrying out data processing on the I down-conversion signal and the Q down-conversion signal to obtain detection result information, judging whether the frequency of the microwave signal is offset or not according to the original baseband signal and correcting the microwave source aiming at the offset.
9. The microwave controller of claim 8, further comprising an attenuator and a low noise amplifier, wherein the attenuator and the low noise amplifier are positioned between the microwave source and the power divider, wherein an input of the attenuator is connected to an output of the microwave source, wherein an output of the attenuator is connected to an input of the low noise amplifier for reducing a signal strength of the microwave signal, and wherein an output of the low noise amplifier is connected to an input of the power divider for amplifying the microwave signal for improving a signal-to-noise ratio of the microwave signal.
10. The microwave controller of claim 8, wherein the measurement and control board card comprises an FMC functional daughter card, an FPGA daughter card, and a carrier plate, wherein, The FMC function sub-card and the FPGA sub-card are respectively inserted on the carrier board, a signal acquisition module, an automatic frequency control module and a waveform generation module are arranged on the FMC function sub-card, and the signal acquisition module is used for acquiring an I down-conversion signal and a Q down-conversion signal in the I/Q mixer through the carrier board, and outputting an I signal digital component and a Q signal digital component to the FPGA sub-card after analog-to-digital conversion; The input end of the automatic frequency control module is connected with the I/Q mixer, the output end of the automatic frequency control module is connected with the waveform generation module and is used for collecting the original baseband signal and judging whether the frequency of the microwave signal is equal to the resonant frequency of the cavity according to the waveform of the original baseband signal; The waveform generation module is connected with the control end of the microwave source through the carrier plate and is used for outputting a microwave source control signal of a first working frequency to the microwave source according to the error signal; The FPGA daughter card is provided with a signal processing module which is used for carrying out data processing and I/Q demodulation on the I down-conversion signal and the Q down-conversion signal to obtain detection result information; The carrier board is connected with the baseband signal end of the I/Q mixer, and is configured to access the I down-conversion signal and the Q down-conversion signal in the I/Q mixer, output the I down-conversion signal and the Q down-conversion signal to the FMC functional daughter card 93, and be used to communicate with an external host computer in real time to transmit the detection result information.

Description

Microwave control method and microwave controller for electronic paramagnetic spectrometer Technical Field The invention relates to the technical field of electron paramagnetic resonance, in particular to a microwave control method and a microwave controller for an electron paramagnetic spectrometer. Background Electron paramagnetic resonance (electron paramagnetic resonance, EPR) is a spectroscopic technique for studying substances with unpaired electrons and is also the only technique that can specifically recognize the structure of free radicals. Electron paramagnetic resonance technology has been developed for the study of samples with a paramagnetic moment, in particular samples with unpaired electrons. In order to realize good identification of free radicals, a plurality of high-precision systems are required to work together, and a microwave controller is required to generate high-precision and low-phase-noise radio frequency signals and realize high-resolution acquisition of the obtained signals. The currently proposed electron paramagnetic resonance technology microwave control generally adopts open-loop control, the frequency and the power of a microwave source are easy to drift due to external interference, and key parameters such as resonant frequency, phase and the like in a resonant cavity are affected, so that higher resolution and precision cannot be achieved, and the requirement of high-precision detection of free radicals cannot be met. Accordingly, the prior art is still in need of improvement and development. Disclosure of Invention In view of the shortcomings of the prior art, the invention aims to provide a microwave control method and a microwave controller for an electronic paramagnetic particle spectrometer, which are used for solving the problems that the existing microwave control method for the electronic paramagnetic particle spectrometer is low in microwave output precision and resolution and cannot be used for realizing high-precision detection of free radicals. The technical scheme of the invention is as follows: in a first aspect, the present invention provides a microwave control method for an electronic paramagnetic spectrometer comprising the steps of: controlling a microwave source to generate a microwave signal for paramagnetic resonance detection, wherein the frequency of the microwave signal is a first working frequency; The method comprises the steps of carrying out power distribution on a microwave signal to obtain a first power division signal and a second power division signal, inputting the first power division signal into a resonant cavity, and detecting a microwave reflected signal of a sample to be detected after resonance absorption occurs in the resonant cavity to obtain a first detection signal; Acquiring the first detection signal and the local oscillation signal, and mixing the first detection signal and the local oscillation signal to obtain an I down-conversion signal and a Q down-conversion signal; Sampling and data processing are carried out on the I down-conversion signal and the Q down-conversion signal to obtain an original baseband signal, and the original baseband signal is restored to obtain detection result information; Judging whether the frequency of the microwave signal is offset according to the original baseband signal, and correcting the microwave source according to the offset so as to enable the frequency of the output microwave signal to keep the first working frequency. The invention further provides that the steps of sampling and data processing the I down-conversion signal and the Q down-conversion signal to obtain an original baseband signal and restoring to obtain detection result information comprise the following steps: Performing low-pass filtering on the I down-conversion signal and the Q down-conversion signal to obtain an I signal baseband component and a Q signal baseband component; And sampling and data processing are carried out on the I signal baseband component and the Q signal baseband component to obtain an original baseband signal, and the original baseband signal is used for restoring to obtain detection result information. The invention further provides that after the step of controlling the microwave source to generate a microwave signal for paramagnetic resonance detection, the microwave signal is at the first operating frequency, the method further comprises: performing attenuation control on the signal intensity of the microwave signal; And carrying out low-noise amplification on the microwave signal after the attenuation control is finished, wherein the signal power of the amplified microwave signal is positioned in a signal power target interval and is used for improving the signal-to-noise ratio. The invention further provides a method for distributing power of the microwave signal to obtain a first power division signal and a second power division signal, wherein the first power division signal is input int