A differential microwave detection system and method

Abstract

The present invention discloses a differential microwave detection system and method, belonging to the technical field of microwave sensor detection. The present invention designs a microwave sensor device with a differential structure, and a system composed of circuit modules such as a phase-locked loop circuit, a band-pass filter, a frequency-domain real-time detection circuit, a digital signal processing circuit and a control circuit is used for performing fast frequency sweeping operation on the differential microwave sensor and extracting real-time frequency-domain microwave parameters, solving the problem that the traditional microwave detection method is easily affected by electromagnetic interference in the working environment and other common-mode factors in the environment, and improving the accuracy of microwave detection.

Description

Technical Field

[0001] The present invention relates to a differential microwave detection system and method, belonging to the technical field of microwave sensor detection. Background Art

[0002] Microwave detection technology, with its high detection accuracy, excellent real-time performance, and good reliability, is widely used in a variety of harsh detection scenarios. The principle of microwave detection is that when the parameter to be measured (Device Under Test, DUT) in the environment changes, the microwave parameters of the microwave device will also change accordingly. Therefore, the change in the microwave parameter can be measured to characterize the change in the quantity to be measured.

[0003] Traditional microwave detection units based on resonator structures need to be exposed to a complex electromagnetic environment and are extremely vulnerable to electromagnetic interference in the working environment and other common-mode factors in the environment. With the continuous development of modern detection technology, the trend of miniaturization and integration of microwave sensors also poses higher requirements for the anti-interference ability of devices.

[0004] Using a differential structure microwave sensor can effectively solve the above problems. By designing a symmetric resonator unit, differential microwave detection can be realized to improve the ability to resist common-mode interference. However, compared with the microwave detection technology based on resonators, the differential microwave detection circuit needs to extract not a single microwave parameter, but the difference signal of a group of microwave parameters, that is, differential-mode microwave parameters. However, there is no suitable detection circuit and detection algorithm in the prior art for extracting differential-mode microwave parameters.

[0005] The difficulties in extracting differential-mode microwave parameters are mainly reflected in the following aspects: First, when a differential microwave sensor is used to detect differential-mode signals, its reference resonance mode will split into two independent resonance modes, which causes the conventional microwave parameters such as insertion loss and return loss used in the existing microwave detection technology to change frequently and are no longer suitable as characterization parameters. Second, compared with traditional microwave detection methods, differential microwave detection requires obtaining more microwave parameters, and these parameters all appear in groups. Therefore, the detection circuit needs to have the ability of fast data matching and data processing; finally, since extracting differential-mode microwave parameters requires subtraction operations with reference resonance mode data, this also poses a challenge to the real-time performance of the detection circuit and system.

[0006] To address the above problems, a new circuit system architecture for differential microwave detection needs to be invented. Summary of the Invention

[0007] In order to improve the ability of microwave detection to resist common-mode interference, the present application proposes a differential microwave detection method. In view of the problems faced by differential microwave detection, such as the difficulty in extracting differential-mode microwave parameters and the frequent changes in conventional microwave parameters such as insertion loss and return loss, which are no longer suitable as characterization parameters, the present invention designs a differential microwave detection circuit and system.

[0008] A differential microwave detection system, the system comprising:

[0009] A phase-locked loop circuit, a bandpass filter, a differential microwave sensor, a frequency domain real-time detection circuit, a digital signal processing circuit and a control circuit; wherein the phase-locked loop circuit, the bandpass filter, the differential microwave sensor, and the frequency domain real-time detection circuit are sequentially connected, and the phase-locked loop circuit, the frequency domain real-time detection circuit and the digital signal processing circuit are respectively connected to the control circuit via a data bus;

[0010] The phase-locked loop circuit is used to realize the frequency sweep output within the working frequency range of the differential microwave sensor; the bandpass filter is used to filter out the noise interference outside the working frequency band of the sensor;

[0011] The frequency domain real-time detection circuit includes a radio frequency detection circuit, a high-speed analog-to-digital converter, a first-in first-out buffer and a preprocessing circuit, which are used to realize the real-time extraction of differential mode microwave parameters and the preprocessing operation of data;

[0012] The digital signal processing circuit and the control circuit are used to obtain corresponding differential mode microwave parameter data and control the operation logic of the differential microwave detection system;

[0013] The differential microwave sensor comprises two resonant detection units with completely identical electrical characteristic dimensions, which are symmetrically distributed on both sides of a feeder line; the feeder line is used for input and output of radio frequency signals.

[0014] Optionally, when there are objects to be detected in both resonant units on both sides of the differential microwave sensor, the differential microwave detection system enters a differential mode detection mode; when there is an object to be detected in only one resonant unit on one side of the differential microwave sensor, the differential microwave detection system enters a common mode detection mode.

[0015] Optionally, when the differential microwave detection system is in the differential mode detection mode, the reference resonant mode is split into two sub-resonant modes moving in opposite directions, and the differential mode microwave parameters include a 3dB bandwidth BW dif1 and BW dif2 , the frequency shift of the sub-resonant mode is f0-f dif_L and f dif_R -f0; When the differential microwave detection system is in the common mode detection mode, the reference resonant mode is split into two sub-resonant modes moving in the same direction, and the differential mode microwave parameters include a 3dB bandwidth BW com1and BW com2 , the frequency offset f of the sub-resonant mode com1 -f0 and f com2 -f0; the microwave parameters of the reference resonant mode include the 3dB bandwidth BW0 and the reference resonant frequency f0.

[0016] Optionally, the frequency-domain real-time detection circuit is connected to the digital signal processing circuit through a 32-bit data bus; the control circuit is connected to the frequency-domain real-time detection circuit through a 32-bit data bus and a 16-bit data bus respectively; the control circuit is connected to the phase-locked loop circuit and the digital signal processing circuit through the control bus respectively.

[0017] Optionally, the phase-locked loop circuit adopts a fourth-order type-II wideband fractional-N phase-locked loop, and a Sigma Delta modulator is arranged in the loop to suppress fractional spurs; the fourth-order type-II fractional-N phase-locked loop includes a frequency discriminator, a charge pump, a loop filter, and a voltage-controlled oscillator; among them, the loop filter LF1 is composed of capacitors C1, C2, C3, resistors R1 and R2 to form a third-order passive low-pass filter; the operating frequency of the voltage-controlled oscillator matches the operating frequency of the differential microwave sensor.

[0018] Optionally, the frequency-domain real-time detection circuit includes a radio frequency detection circuit, a high-speed analog-to-digital converter, a first-in first-out buffer, and a preprocessing circuit; among them, the radio frequency detection circuit is used to convert the high-frequency microwave signal output by the microwave sensor into a direct current analog signal, the high-speed analog-to-digital converter adopts a 12Bit high-speed analog-to-digital converter to convert the analog signal into a digital signal, the first-in first-out buffer is used to quickly match the frequency data with the corresponding amplitude data, and the preprocessing circuit draws the spectrum of the signal output by the microwave sensor through fast data calculation, and obtains the frequency offset of the split resonant mode compared with the reference resonant mode and their respective 3dB bandwidths.

[0019] The present application also provides a differential microwave detection method, which is characterized in that the method is implemented based on the above differential microwave detection system, and includes:

[0020] The control circuit configures the SDM module and the fractional-N divider module in the phase-locked loop circuit to ensure that the phase-locked loop circuit outputs a swept-frequency excitation with a frequency range of (fstart, fend), and loads it onto the microwave sensor through a low-noise amplifier; there is only a single resonant mode in the frequency domain of the microwave sensor, that is, the reference resonant mode, which is split into two sub-resonant modes that move in the same direction or in opposite directions according to the load conditions of the two resonant detection units;

[0021] The control circuit enables the frequency-domain real-time detection circuit, converts the high-frequency microwave signal output by the microwave sensor into a DC analog signal and then into a digital signal, and transmits the amplitude data output by the sensor to the first-in-first-out buffer FIFO through the data bus; meanwhile, the control circuit converts the configuration parameters of the fractional divider into the output frequency of the current phase-locked loop circuit and synchronizes it to the first-in-first-out buffer FIFO through the data bus;

[0022] After the first-in-first-out buffer FIFO polls and waits for the frequency data and amplitude data of the microwave sensor to match, it is input into the preprocessing circuit through the data bus. The preprocessing circuit compares and analyzes the real-time output data of the microwave sensor from the FIFO with the reference resonance mode spectrum template data from the controller, and performs data preprocessing on the difference signals of microwave parameters such as resonance point frequency shift and 3dB bandwidth;

[0023] The control circuit reads the output data of the preprocessing circuit through the data bus and discriminates the working mode of the current circuit system. If the current working mode is the differential mode detection mode, the control circuit controls the digital signal processing circuit to calculate the differential mode microwave parameters. The obtained microwave parameters include 3dB bandwidth BW dif1 and BW dif2 , the frequency offset of the sub-resonance mode f0 - f dif_L and f dif_R - f0; if the current working mode is the common mode detection mode, the control circuit controls the digital signal processing circuit to calculate the common mode microwave parameters. The obtained microwave parameters include 3dB bandwidth BW com1 and BW com2 , the frequency offset of the sub-resonance mode f com1 - f0 and f com2 - f0;

[0024] The control circuit determines whether the pre-scan period has ended. If it has ended, the single-cycle detection ends; if the current cycle has not ended, the control circuit loops to perform the frequency sweep operation.

[0025] Optionally, when using the above differential microwave detection system to detect the object to be measured, place the object to be measured in the bilateral resonance units of the differential microwave sensor respectively so that the differential microwave detection system is in the differential detection mode, and characterize the measured index of the object to be measured according to the measured resonance point frequency shift and 3dB bandwidth of the resonance mode.

[0026] Optionally, when using the above differential microwave detection system to detect the object to be measured, place the object to be measured in the unilateral resonance unit of the differential microwave sensor respectively so that the differential microwave detection system is in the common mode detection mode, and characterize the measured index of the object to be measured according to the measured resonance point frequency shift and 3dB bandwidth of the resonance mode.

[0027] The present application also provides a differential microwave sensor, characterized in that the differential microwave sensor includes two resonant detection units with exactly the same electrical characteristic dimensions, symmetrically distributed on both sides of the feeder; the feeder is used for input and output of radio frequency signals.

[0028] The beneficial effects of the present invention are:

[0029] The present application provides a differential microwave detection method, its circuit and system. By designing a microwave sensor device with a differential structure; when the differential microwave sensor is used to detect differential mode signals, its reference resonant mode will split into two independent resonant modes, which causes the conventional microwave parameters such as insertion loss and return loss used in the existing microwave detection technology to change frequently and are no longer suitable as characterization parameters. The present application selects the resonant point frequency shift and the 3dB bandwidth of the resonant mode to characterize the DUT, and designs a complete detection circuit, that is, a circuit system composed of circuit modules such as a phase-locked loop circuit, a band-pass filter, a frequency-domain real-time detection circuit, a digital signal processing circuit and a control circuit is used to perform fast frequency sweeping operation on the differential microwave sensor and extract real-time frequency-domain microwave parameters, solving the problem that the traditional microwave detection method is vulnerable to electromagnetic interference in the working environment and other common-mode factors in the environment. The radio frequency mechanism adopts a broadband fractional-N phase-locked loop PLL containing a Sigma-Delta modulation (SDM) module. The SDM module realizes the suppression of fractional spurs, and selecting a wide loop bandwidth shortens the transient response time of the PLL and improves the real-time performance of microwave detection; the microwave parameter detection unit is composed of a frequency-domain real-time detection circuit including a radio frequency detection circuit, a high-speed analog-to-digital converter, a first-in-first-out buffer and a preprocessing circuit, realizing the fast extraction of differential mode microwave parameters. The differential microwave detection method, its circuit and system provided by the present application improve the anti-environmental noise interference ability of microwave detection, and at the same time improve the accuracy and sensitivity of microwave detection. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for description in the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0031] Figure 1 It is a basic schematic block diagram of a differential microwave detection circuit system provided by an embodiment of the present invention.

[0032] Figure 2 It is a schematic diagram of the microwave detection in the differential mode and the frequency-domain working principle in the common mode provided by an embodiment of the present invention.

[0033] Figure 3 It is a schematic diagram of the basic structure of a differential microwave sensor provided by an embodiment of the present invention.

[0034] Figure 4 It is a schematic diagram of the specific implementation manners of the modules of the detection circuit provided by an embodiment of the present invention.

[0035] Figure 5 It is a flowchart of the operation logic of the entire circuit system in the control circuit provided by an embodiment of the present invention. Specific implementation manners

[0036] To make the objectives, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0037] Embodiment 1:

[0038] This embodiment provides an implementation method of a differential microwave detection circuit. As Figure 1 shown, the circuit includes: a phase-locked loop circuit 101, a band-pass filter 102, a differential microwave sensor 103, a frequency-domain real-time detection circuit 104, a digital signal processing circuit 105, and a control circuit 106. Among them, the frequency-domain real-time detection circuit 104 is connected to the digital signal processing circuit 105 through a 32-bit data bus 109; the control circuit 106 is respectively connected to the frequency-domain real-time detection circuit 104 through a 32-bit data bus 108 and a 16-bit data bus 107; the control circuit 106 is respectively connected to the phase-locked loop circuit 101 and the digital signal processing circuit 105 through control buses 110 and 111.

[0039] Among them, the phase-locked loop circuit 101 uses a wideband fractional-N phase-locked loop (PLL) containing a Sigma-Delta modulation (SDM) module for fast frequency sweeping operations within the working range of the differential microwave sensor. The passband of the band-pass filter 102 is (fstart, fend) for filtering out noise interference outside the working frequency band of the sensor. The frequency-domain real-time detection circuit 104 includes a radio frequency detection circuit, a high-speed analog-to-digital converter, a first-in-first-out buffer, and a preprocessing circuit for realizing real-time extraction of differential microwave parameters and preprocessing of data. The digital signal processing circuit 105 and the control circuit 106 are used to calculate and obtain corresponding differential microwave parameter data and control the operation logic of the entire circuit system.

[0040] Among them, the control bus 110 is used for the control circuit 106 to configure the SDM module and the fractional divider (F_DIV) in the wideband fractional-N phase-locked loop (PLL) in the phase-locked loop circuit 101; the control bus 111 is used for the control circuit 106 to configure various control parameters in the digital signal processing circuit 105;

[0041] Among them, the 16-bit data bus 107 is used for the control circuit 106 to synchronize the output frequency data of the current phase-locked loop to the frequency-domain real-time detection circuit 104; the 32-bit data bus 108 is used for the control circuit 106 to transmit the reference resonance mode template data to the frequency-domain real-time detection circuit 104; the 32-bit data bus 109 is used for the frequency-domain real-time detection circuit 104 to transmit the frequency and amplitude data of the microwave sensor after data preprocessing to the digital signal processing circuit 105.

[0042] Compared with the traditional microwave detection circuit, the differential microwave detection circuit provided by the present application provides an implementation method of the differential microwave detection circuit, which solves the problems that the traditional microwave detection method is vulnerable to electromagnetic interference in the working environment and other common-mode factors in the environment.

[0043] Embodiment 2:

[0044] This embodiment provides a differential microwave detection method. Taking a microwave sensor with a symmetric 2-resonator unit (see Figure 3 ) as an example, it provides two working modes: a differential mode detection mode and a common mode detection mode. See Figure 2 . Figure 2 In 201, 202, 203 are the frequency-domain schematic diagrams of the differential mode working mode of the microwave sensor; Figure 2 In 201, 204, 205 are the frequency-domain schematic diagrams of the common mode working mode of the microwave sensor.

[0045] Among them, 201 is the reference resonance mode of the microwave sensor, that is, when the resonant units of the microwave sensor are symmetrically unloaded, the frequency-domain output of the microwave sensor. 201 provides two main microwave parameters: 3dB bandwidth BW0 and reference resonance frequency f0. 202, 203 are the sub-resonance modes in the differential mode detection mode of the microwave sensor, which are formed by splitting the reference resonance mode and moving in opposite directions. Their working frequency range is (fstart, fend) to improve the accuracy of microwave detection. The 202 and 203 resonance modes respectively provide two microwave parameters: 3dB bandwidth BW dif1 and BW dif2 , the frequency offset of the sub-resonance mode f0 - f dif_L and f dif_R - f0; 204, 205 are the sub-resonance modes in the common mode detection mode of the microwave sensor, which are formed by splitting the reference resonance mode and moving in the same direction to eliminate common mode interference and improve the anti-interference ability of the sensor; the 204 and 205 resonance modes respectively provide two microwave parameters: 3dB bandwidth BW com1 and BW com2 , the frequency offset of the sub-resonance mode f com1 - f0 and f com2 - f0;

[0046] Figure 3 is a schematic diagram of the basic structure of a differential microwave sensor, corresponding to Figure 2 the differential mode detection mode shown. Among them, 301 and 302 are resonant detection units with exactly the same electrical characteristic dimensions, symmetrically distributed on both sides of the feeder 303. 303 serves as the feeder of the microwave sensor and is used for the input and output of radio frequency signals.

[0047] Figure 4 gives Figure 1 a specific implementation manner of the differential microwave detection circuit shown, where Figure 4 101 in corresponds to Figure 1 101 in, which serves as the sweep frequency excitation of the microwave detection system. A fourth-order type-II wideband fractional-N phase-locked loop 401 is adopted, and a Sigma Delta modulator (SDM) is set in the loop to suppress fractional spurs. The fourth-order type-II fractional-N phase-locked loop 401 includes a phase frequency detector (PFD), a charge pump (CP), a loop filter (LF1), and a voltage controlled oscillator (VCO). Among them, the loop filter LF1 consists of capacitors C1, C2, C3, resistors R1 and R2 to form a third-order passive low-pass filter. In practical applications, technicians can effectively suppress loop noise by reasonably configuring the zeros and poles of the loop. At the same time, LF1 selects a wide loop bandwidth to shorten the transient response time of the PLL and improve the real-time performance of microwave detection. Figure 4 the voltage controlled oscillator VCO in the phase-locked loop 401, whose operating frequency matches the operating frequency of the microwave sensor. Combining Figure 2 , its output frequency range is (fstart, fend).

[0048] The output signal of the VCO is input to the band-pass filter (BPF) 403 after passing through the low-noise amplifier (LNA) 402. The band-pass filter 403 is mainly used to filter the output radio frequency signal of the phase-locked loop 401. The band-pass filter 403 needs to introduce multiple transmission zeros in the transition band to improve the roll-off speed of the transition band and maintain a low insertion loss in its passband (fstart, fend) to reduce the attenuation of the band-pass filter to the radio frequency signal. The radio frequency output signal is loaded onto the microwave sensor (SENSOR) 404 after passing through the band-pass filter 403 to provide sweep frequency excitation for the operating frequency range of the differential structure microwave sensor.

[0049] Figure 4 104 in corresponds to Figure 1The frequency-domain real-time detection circuit 104 therein, and 104 includes a radio frequency detection circuit (RF_DET) 405, a high-speed analog-to-digital converter (ADC) 406, a first-in first-out buffer (FIFO) 408, and a preprocessing circuit (PRE_PRO) 412, which are used to realize the real-time extraction of differential-mode microwave parameters and the preprocessing operation of data, and provide a basis for judging the current working mode of the microwave sensor; the radio frequency detector RF_DET 405 in the frequency-domain real-time detection circuit 104 is used to convert the high-frequency microwave signal output by the microwave sensor into a direct-current analog signal, and the detection speed of the radio frequency detector RF_DET needs to match the frequency hopping and frequency scanning speeds of the radio frequency circuit; the high-speed analog-to-digital converter ADC 406 uses a 12-bit high-speed analog-to-digital converter to convert the analog signal into a digital signal; the first-in first-out buffer FIFO 408 is used to quickly match the frequency data (Freq[15:0]) with the corresponding amplitude data (Amp[15:0]).

[0050] The 16-bit data bus Amp[15:0] 407 connects the high-speed analog-to-digital converter (ADC) 406 and the first-in first-out buffer (FIFO) 408, and is used to synchronously transmit the amplitude data output by the microwave sensor; the 16-bit data bus Freq[15:0] 409 connects the control circuit (CONTROL) 415 and the first-in first-out buffer (FIFO) 408, and is used to synchronously transmit the frequency data output by the microwave sensor;

[0051] The 32-bit data bus Data_t[31:0] 410 connects the first-in first-out buffer (FIFO) 408 and the preprocessing circuit (PRE_PRO) 412, and is used to synchronously transmit the frequency and amplitude data after matching by the microwave sensor; the 32-bit data bus Data[31:0] 413 connects the preprocessing circuit (PRE_PRO) 412 and the digital signal processing circuit (DSP) 414, and is used to synchronously transmit the frequency and amplitude data of the preprocessed microwave sensor; the 32-bit data bus Temp[31:0] 411 connects the preprocessing circuit (PRE_PRO) 412 and the control circuit (CONTROL) 415, and is used to synchronously transmit the reference resonant mode spectrum template data.

[0052] The digital signal processing circuit (DSP) 414 draws the spectrum of the signal output by the microwave sensor through fast data calculation, and obtains the frequency offset of the split resonant mode compared with the reference resonant mode and their respective 3dB bandwidths.

[0053] The control circuit (CONTROL) 415 is used to control the operation logic of the entire circuit, and all control signals of this system are controlled and implemented by this module.

[0054] Among them, the control bus 416 is used to control the circuit 415 to configure the SDM module and the fractional divider (F_DIV) in the wideband fractional-N phase-locked loop (PLL) in the phase-locked loop circuit 401, so as to suppress fractional spurs and control the sweep step; the control bus 417 is used to control the circuit (CONTROL) 415 to configure various control parameters in the digital signal processing circuit (DSP) 414;

[0055] Figure 5 The basic control logic flow chart of the entire circuit system in the control circuit is shown. The process is as follows:

[0056] First of all, the controller 415 (corresponding to Figure 1 the control circuit 106 in) initializes each module of the entire differential microwave detection system, including enabling and initializing the phase-locked loop circuit 401, the radio frequency detection circuit 405, the high-speed analog-to-digital converter 406, the first-in first-out buffer 408, the preprocessing circuit 412, and the digital signal processing circuit 414 in sequence.

[0057] After the circuit system is initialized, the control circuit configures the wide SDM module and the fractional divider (F_DIV) module in the phase-locked loop circuit 401 through the control bus 416 to ensure that the phase-locked loop circuit outputs a sweep excitation with a frequency range of (fstart, fend), and loads it onto the microwave sensor through the LNA402.

[0058] After the control circuit enables the frequency-domain real-time detection circuit 104, it starts devices such as RF_DET405, ADC406, and FIFO408 in sequence, converts the high-frequency microwave signal output by the microwave sensor into a DC analog signal and then into a digital signal. The amplitude data output by the sensor is transmitted to the FIFO through the Amp[15:0] data bus 407; at the same time, the control circuit converts the configuration parameters of the F_DIV into the output frequency of the current PLL and synchronizes it to the FIFO through the Freq[15:0] data bus 409;

[0059] After the FIFO polls and waits for the frequency data and amplitude data of the microwave sensor to match, it stores the amplitude data in the high 16 bits and the frequency data in the low 16 bits, and inputs them into the preprocessing circuit (PRE_PRO) 412 through the Data_t[31:0] data bus 410;

[0060] The PRE_PRO compares and analyzes the real-time output data of the microwave sensor from the FIFO with the reference resonant mode spectrum template data Temp[31:0] 411 from the controller, and performs data preprocessing on the difference signals of microwave parameters such as resonant point frequency shift and 3dB bandwidth;

[0061] The control circuit reads the output data of PRE_PRO through the data bus Data[31:0]413 and determines the working mode of the current circuit system. If the current working mode is the differential mode detection mode, the control circuit controls the digital signal processing circuit (DSP) 414 to calculate the differential mode microwave parameters. The main microwave parameters obtained include the 3dB bandwidth BW dif1 and BW dif2 , the frequency shift of the sub-resonant mode is f0-f dif_L and f dif_R -f0; if the current working mode is the common mode detection mode, the control circuit controls the digital signal processing circuit (DSP) 414 to calculate the common mode microwave parameters, and the main microwave parameters obtained include the 3dB bandwidth BW com1 and BW com2 , the frequency shift f of the sub-resonant mode com1 -f0 and f com2 -f0.

[0062] When the resonant mode working frequency interval sweep is completed, the controller will determine whether the previous sweep cycle has ended. If it has ended, it proves that all sub-resonant mode working frequency intervals have been swept and the single cycle detection is completed. If the current cycle has not ended, the controller will perform the sweep operation cyclically.

[0063] Embodiment three:

[0064] The present embodiment provides a differential microwave detection method, which is implemented by the above-mentioned differential microwave detection system. In the method, when the symmetrical resonant units of the differential microwave sensor are all unloaded, there is and only a single resonant mode in the frequency domain, namely, the reference resonant mode 201. When there are objects to be detected in both resonant units on both sides, the system enters the differential mode detection mode, and the reference resonant mode is split into two sub-resonant modes moving in opposite directions, namely, sub-resonant modes 202 and 203 in the common mode mode. When there is an object to be detected in the resonant unit on one side, the system enters the common mode detection mode, which is used to eliminate common mode interference, and the reference resonant mode is split into two sub-resonant modes moving in the same direction, namely, sub-resonant modes 204 and 205 in the common mode mode.

[0065] The control circuit reads the output data of PRE_PRO and determines that the current differential microwave detection system is working in the differential mode detection mode. The frequency domain real-time detection circuit obtains the differential mode microwave parameters, including the 3dB bandwidth BW. dif1 and BW dif2 , the frequency shift of the sub-resonant mode is f0-f dif_L and f dif_R -f0. In the differential mode detection mode, the degree of change to be measured can be characterized by measuring the frequency shift of the resonance point, the 3dB bandwidth of the resonance mode, etc., and the following differential mode detection model is established:

[0066] Fdif (DUT) = a1F1(|BW0 - BW dif1 |) + a2F2(|BW0 - BW dif2 |) + a3F3(|f0 - f dif_L |) + a4F4(|f dif_R - f0|)

[0067] Wherein, a1, a2, a3, and a4 are the fitting coefficients of the corresponding terms of the multiple linear regression equation respectively. F1, F2, F3, and F4 are the model functions of the corresponding differential mode parameters respectively.

[0068] When the control circuit reads the output data of PRE_PRO and determines that the current differential microwave detection system is operating in the common mode detection mode, the frequency domain real-time detection circuit acquires the common mode microwave parameters, including the 3dB bandwidth BW dif1 and BW dif2 , the 3dB bandwidth BW com1 and BW com2 , the frequency offset f com1 - f0 and f com2 - f0. In the common mode detection mode, the degree of change of the quantity to be measured can be characterized by measuring the frequency shift of the resonance point, the 3dB bandwidth of the resonance mode, etc., and the following common mode detection model is established:

[0069] G com (DUT) = b1G1(|BW0 - BW com1 |) + b2G2(|BW0 - BW com2 |) + b3G3(|f0 - f com_L |) + b4G4(|f com_R - f0|)

[0070] Wherein, b1, b2, b3, and b4 are the fitting coefficients of the corresponding terms of the multiple linear regression equation respectively. G1, G2, G3, and G4 are the model functions of the corresponding common mode parameters respectively.

[0071] In the corresponding detection mode, the degree of change of the quantity to be measured can be characterized by measuring the frequency shift of the resonance point, the 3dB bandwidth of the resonance mode, etc., and the present application does not limit this part of the calculation.

[0072] Some steps in the embodiments of the present invention can be implemented by software, and the corresponding software program can be stored in a readable storage medium, such as an optical disc or a hard disk, etc.

[0073] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A differential microwave detection system, characterized in that, The system comprises: A phase-locked loop circuit, a bandpass filter, a differential microwave sensor, a frequency domain real-time detection circuit, a digital signal processing circuit and a control circuit; wherein the phase-locked loop circuit, the bandpass filter, the differential microwave sensor, and the frequency domain real-time detection circuit are sequentially connected, and the phase-locked loop circuit, the frequency domain real-time detection circuit and the digital signal processing circuit are respectively connected to the control circuit via a data bus; The phase-locked loop circuit is used to realize the frequency sweep output within the working frequency range of the differential microwave sensor; the bandpass filter is used to filter out the noise interference outside the working frequency band of the sensor; The frequency domain real-time detection circuit includes a radio frequency detection circuit, a high-speed analog-to-digital converter, a first-in first-out buffer and a preprocessing circuit, which are used to realize the real-time extraction of differential mode microwave parameters and the preprocessing operation of data; The digital signal processing circuit and the control circuit are used to obtain corresponding differential mode microwave parameter data and control the operation logic of the differential microwave detection system; The differential microwave sensor comprises two resonant detection units with completely identical electrical characteristic dimensions, which are symmetrically distributed on both sides of a feeder; the feeder is used for input and output of radio frequency signals; When there are objects to be detected in both resonant detection units on both sides of the differential microwave sensor, the differential microwave detection system enters a differential mode detection mode; when there is an object to be detected in a resonant detection unit on one side of the differential microwave sensor, the differential microwave detection system enters a common mode detection mode; When the differential microwave detection system is in the differential mode detection mode, the reference resonance mode splits into two sub-resonance modes moving in opposite directions, and the differential mode microwave parameters include the 3dB bandwidth BW dif1 and BW dif2 , the frequency offsets of the sub-resonance modes f0 - f dif_L and f dif_R - f0; when the differential microwave detection system is in the common mode detection mode, the reference resonance mode splits into two sub-resonance modes moving in the same direction, and the differential mode microwave parameters include the 3dB bandwidth BW com1 and BW com2 , the frequency offsets of the sub-resonance modes f com1 - f0 and f com2 - f0; the reference resonance mode microwave parameters include the 3dB bandwidth BW0 and the reference resonance frequency f0.

2. The system according to claim 1, wherein The frequency domain real-time detection circuit is connected to the digital signal processing circuit via a 32-bit data bus; the control circuit is connected to the frequency domain real-time detection circuit via a 32-bit data bus and a 16-bit data bus respectively; the control circuit is connected to the phase-locked loop circuit and the digital signal processing circuit via the control bus respectively.

3. The system according to claim 2, characterized in that, The phase-locked loop circuit adopts a fourth-order type II broadband fractional-frequency phase-locked loop, and a Sigma Delta modulator is arranged in the loop to suppress fractional spurious; the fourth-order type II fractional-frequency phase-locked loop includes a frequency detector, a charge pump, a loop filter and a voltage-controlled oscillator; wherein the loop filter LF1 is a third-order passive low-pass filter composed of capacitors C1, C2, C3, resistors R1 and R2; the operating frequency of the voltage-controlled oscillator matches the operating frequency of the differential microwave sensor.

4. The system according to claim 3, characterized in that, The frequency domain real-time detection circuit includes a radio frequency detection circuit, a high-speed analog-to-digital converter, a first-in-first-out buffer and a preprocessing circuit; wherein the radio frequency detection circuit is used to convert the high-frequency microwave signal output by the microwave sensor into a DC analog signal, the high-speed analog-to-digital converter uses a 12-bit high-speed analog-to-digital converter to convert the analog signal into a digital signal, the first-in-first-out buffer is used to quickly match the frequency data with the corresponding amplitude data, and the preprocessing circuit draws the spectrum of the microwave sensor output signal through fast data calculation, and obtains the frequency offset of the split resonance mode compared with the reference resonance mode and the respective 3dB bandwidth.

5. A differential microwave detection method, characterized in that, The method is implemented based on the differential microwave detection system according to claim 4, comprising: The control circuit configures the SDM module and the fractional divider module in the phase-locked loop circuit to ensure a swept-frequency excitation with the output frequency range of (fstart, fend) of the phase-locked loop circuit, and loads it onto the microwave sensor through a low-noise amplifier; there is only a single resonant mode in the frequency domain of the microwave sensor, that is, the reference resonant mode, which is split into two sub-resonant modes moving in the same direction or in opposite directions according to the load conditions of the two resonant detection units. The control circuit enables the frequency-domain real-time detection circuit to convert the high-frequency microwave signal output by the microwave sensor into a DC analog signal and then into a digital signal, and the amplitude data output by the sensor is transmitted to the first-in first-out buffer FIFO through the data bus; at the same time, the control circuit converts the configuration parameters of the fractional divider into the output frequency of the current phase-locked loop circuit and synchronizes it to the first-in first-out buffer FIFO through the data bus. After the first-in first-out buffer FIFO polls and waits for the frequency data and amplitude data of the microwave sensor to match, it is input into the preprocessing circuit through the data bus. The preprocessing circuit compares and analyzes the real-time output data of the microwave sensor from the FIFO with the reference resonant mode spectrum template data from the controller, and performs data preprocessing on the difference signals of microwave parameters such as resonant point frequency shift and 3dB bandwidth. The control circuit reads the output data of the preprocessing circuit through the data bus and determines the working mode of the current circuit system. If the current working mode is the differential mode detection mode, the control circuit controls the digital signal processing circuit to calculate the differential mode microwave parameters. The obtained microwave parameters include the 3dB bandwidth BW dif1 and BW dif2 , the frequency offset f0 - f of the sub-resonant mode dif_L and f dif_R - f0; if the current working mode is the common mode detection mode, the control circuit controls the digital signal processing circuit to calculate the common mode microwave parameters. The obtained microwave parameters include the 3dB bandwidth BW com1 and BW com2 , the frequency offset f com1 - f0 and f com2 - f0; The control circuit determines whether the pre-scan period has ended. If it has ended, the single-cycle detection ends; if the current cycle has not ended, the control circuit loops to perform the frequency-sweeping operation.

6. The method according to claim 5, wherein When using the differential microwave detection system to detect the object to be measured, the object to be measured is placed in the bilateral resonant detection units of the differential microwave sensor respectively to make the differential microwave detection system in the differential detection mode, and the measured resonant point frequency shift and 3dB bandwidth of the resonant mode are used to characterize the measured indexes of the object to be measured.

7. The method according to claim 6, characterized in that, When using the differential microwave detection system to detect the object to be measured, the object to be measured is placed in the unilateral resonant detection unit of the differential microwave sensor respectively to make the differential microwave detection system in the common-mode detection mode, and the measured resonant point frequency shift and 3dB bandwidth of the resonant mode are used to characterize the measured indexes of the object to be measured.

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