Tdr and fmcw co-probe adaptive matching liquid level measurement system and method

Abstract

The present application belongs to the technical field of radar liquid level measurement, and aims at the problems that the existing liquid level measurement system is difficult to realize common probe operation, impedance matching requirements are different, and double-mode signal crosstalk is serious, and provides a kind of TDR and FMCW common probe adaptive matching liquid level measurement system and method, the control processing module configures the matching network of different working modes according to the matching parameters output by the double-mode adaptive impedance matching module, the double-mode signals share the same probe for cooperative measurement, the double-mode adaptive matching module is used for real-time double-mode impedance matching and dynamic adjustment of liquid level measurement, cooperative work under the same probe, real-time adjustment of probe impedance state, and realization of signal dynamic matching.The present application has the advantages of low reflection loss, small measurement blind area, large dynamic range, strong anti-interference ability and good adaptability to complex working conditions, and is suitable for long-term operation and detection in complex environment.

Description

Technical Field

[0001] This invention belongs to the field of radar liquid level measurement technology, specifically relating to a TDR and FMCW co-probe adaptive matching liquid level measurement system and method. Background Technology

[0002] Radar level measurement technology is widely used in oil storage tanks, chemical containers, food processing, rail transportation, energy equipment, and industrial automation control due to its advantages such as non-contact operation, high precision, and strong resistance to environmental interference. Among them, guided wave radar level gauges based on the Time Domain Reflectometry (TDR) principle and radar level gauges based on the Frequency Modulated Continuous Wave (FMCW) principle are currently the two most widely used technologies in industrial level measurement. Existing TDR level measurement systems utilize the propagation time of high-speed narrow pulse signals in waveguides to acquire level information. They offer advantages such as small blind zones at close range, high real-time performance, and high resolution. However, their dynamic range is limited, and their detection performance is poor in long-distance and weak echo scenarios. In contrast, FMCW level measurement systems obtain beat frequencies by mixing continuously frequency-modulated signals with echo signals to achieve target distance measurement. They feature high sensitivity, strong long-distance detection capability, and good noise resistance. However, they are susceptible to transmission leakage, strong echoes at close range, multipath reflections, and complex operating conditions, and are prone to measurement blind zones in close-range areas.

[0003] To combine the advantages of both measurement methods, some measurement systems employ a combined TDR and FMCW measurement approach. However, current technologies typically use independent probe structures to achieve separate operation of the two modes, or simple mode switching to achieve dual-mode measurement, failing to enable collaborative dual-mode operation for liquid level measurement using a single probe. Since TDR signals are broadband pulse signals while FMCW signals are narrowband continuous frequency modulated signals, the two signals differ significantly in frequency characteristics, impedance requirements, and transmission methods. Therefore, under shared probe conditions, problems such as impedance mismatch, signal crosstalk, and echo distortion are prone to occur. Existing measurement systems lack an adaptive impedance adjustment mechanism for dual-mode shared probe operation. When the liquid level changes, the dielectric constant of the medium changes, the probe becomes contaminated, or the ambient temperature changes, the probe impedance changes, leading to increased reflection loss, enhanced standing waves, and decreased measurement accuracy. This easily results in increased liquid level detection errors, decreased measurement stability, and insufficient adaptability to complex operating conditions, severely impacting system measurement performance and industrial application effectiveness. Summary of the Invention

[0004] In view of the problems existing in the prior art, this invention provides a TDR and FMCW co-probe adaptive matching liquid level measurement system and method, which can be used simultaneously for TDR and FMCW dual-mode liquid level measurement, performing real-time dual-mode impedance matching and dynamic adjustment of liquid level measurement. By enabling the two-mode signals to work collaboratively under the same probe and adjusting the probe impedance state in real time, dynamic signal matching is achieved. This invention effectively solves the problems of impedance mismatch, signal crosstalk, and echo distortion, improves liquid level measurement accuracy, reduces measurement blind zone, and enhances measurement stability under complex working conditions, which is of great significance for improving the reliability of industrial field measurements.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A TDR and FMCW co-probe adaptive matching liquid level measurement system is disclosed. The system is housed within a co-probe liquid level gauge and includes a dual-mode signal generation module, a dual-mode adaptive impedance matching module, a co-probe measurement module, an echo signal processing module, and a control processing module. The dual-mode signal generation module acts as a signal generator, producing a TDR pulse excitation signal and an FMCW linear continuous frequency modulated signal for liquid level detection. The dual-mode adaptive impedance matching module includes a TDR broadband matching branch and an FMCW narrowband matching branch. The TDR broadband matching branch dynamically adjusts... The multi-stage LC network parameters achieve wideband impedance matching, and the FMCW narrowband matching branch achieves precise matching of the target frequency band by adjusting the microstrip stub length and equivalent capacitance, realizing real-time adaptive adjustment of TDR mode broadband impedance matching and FMCW mode narrowband impedance matching; the common probe measurement module realizes liquid level measurement in both TDR and FMCW modes through the same probe structure; the echo signal processing module receives the liquid level echo signal detected by the common probe liquid level gauge and performs beat frequency extraction and time delay calculation respectively; the control processing module performs mode switching selection and dynamic adjustment of impedance parameters, as well as dual-mode liquid level fusion calculation.

[0006] Furthermore, the common probe level gauge also includes a housing, an RF connector, an impedance matching transition structure, and a probe. The impedance matching transition structure is placed between the housing and the RF connector. The side of the RF connector away from the housing is connected to a flange for fixing the common probe level gauge. The flange is fixedly connected to the opening of the container being measured. The probe that transmits measurement signals and receives liquid level reflection echo signals and the threaded interface for connecting to the mounting base are placed on the other side of the flange. The probe signal is transmitted to the echo signal processing module through the RF connector. Various circuit functional modules are fixedly installed inside the housing, and the outer shell is provided with electrical interfaces and wiring terminals.

[0007] Furthermore, the impedance matching transition structure adopts a gradual impedance transition method, which enables the TDR broadband pulse signal and the FMCW continuous frequency modulation signal to form a smooth impedance change when entering the probe, reducing the reflection and standing wave effects of high-frequency signals at the connection position.

[0008] A dual-mode adaptive matching method for TDR and FMCW dual-mode liquid level measurement is implemented using the aforementioned TDR and FMCW shared-probe adaptive matching liquid level measurement system. This method utilizes the shared probe for collaborative measurement of both modes' signals, and dynamically adjusts the probe impedance in real time to achieve signal matching. Specifically, the method includes the following steps: Step i. The circuit system of the control processing module completes initialization. During the initialization process, the control processing module detects the current impedance state of the probe and establishes an initial matching parameter table to provide reference data for subsequent dynamic impedance adjustment. Step ii. TDR mode impedance detection and broadband adaptive matching: The TDR signal generation module in the dual-mode adaptive impedance matching module generates a high-speed narrow pulse signal, which is transmitted to the probe through the dual-mode adaptive impedance matching module and then emitted to the surface of the medium inside the container under test to form an electromagnetic reflection signal. The control processing module calculates the standing wave ratio based on the reflection signal, calculates the current impedance deviation based on the standing wave ratio value, and dynamically switches the access combination of the variable capacitor array and the switching inductor network according to the impedance deviation. Step iii. FMCW Mode Impedance Detection and Narrowband Adaptive Matching: The control processing module switches to FMCW working mode. The FMCW signal generation module in the dual-mode adaptive impedance matching module outputs a linear continuous frequency modulated signal. After the linear continuous frequency modulated signal is transmitted by the probe, the dual-mode adaptive impedance matching module detects the reflection parameters of the probe port in real time and obtains the impedance deviation information within the FMCW working frequency band. The control processing module starts the microstrip Stub matching network. Based on the obtained impedance deviation information, the control processing module adjusts the effective access length of the Stub through the RF switch and adjusts the bias voltage of the varactor diode to change the equivalent capacitance value, thereby achieving accurate dynamic impedance compensation within the preset narrowband target frequency band. Step iv. When the total equivalent input impedance of the dual-mode adaptive impedance matching module When the characteristic impedance is equal to that of the standard, the TDR and FMCW co-probe adaptive matching level measurement system enters the dual-mode collaborative working state.

[0009] Furthermore, in step ii, the reflection coefficient of the electromagnetic reflection signal... Represented as: in, The probe input impedance; Given the standard characteristic impedance; calculate the voltage standing wave ratio (VSWR): The control and processing module detects the reflection coefficient and standing wave ratio parameters in real time, while the dual-mode adaptive impedance matching module judges the current impedance change status of the probe in real time and performs dynamic compensation based on the impedance change status.

[0010] Furthermore, the control processing module activates the broadband LC matching network adjustment circuit. When the voltage standing wave ratio (VSWR) exceeds a set threshold, it dynamically switches the connection combination of the variable capacitor array and the switching inductor network via the PIN switch array; the equivalent input impedance of the broadband LC matching network... Represented as: in, Indicates the equivalent resistance. Indicates an adjustable inductor. This refers to an adjustable capacitor, which is adjusted in real time by an adjustable inductor. and adjustable capacitor Gradually optimize the matching status to make Matching to the standard characteristic impedance achieves wideband impedance matching in TDR mode.

[0011] Furthermore, in step iii, the instantaneous frequency expression of the linear continuous frequency modulated signal is: in, Indicates the starting frequency. Indicates the frequency modulation slope. Represents time; equivalent input impedance of the stub matching network. Represented as: in, Represents the propagation constant. Indicates the effective length of the stub.

[0012] Furthermore, the total equivalent input impedance of the dual-mode adaptive impedance matching module Parallel combination of branches of a broadband LC matching network and branches of a stub matching network: in, The equivalent input impedance for a broadband LC matching network. The equivalent input impedance of the Stub matching network.

[0013] A liquid level measurement method based on dual-mode adaptive matching of TDR and FMCW, specifically including the following steps: Step 1. The control processing module configures the broadband LC matching network of the TDR working mode according to the matching parameters output by the dual-mode adaptive impedance matching module, and establishes the pulse transmission timing and echo sampling window; then the TDR working mode is started, and the TDR signal generation module is controlled to transmit high-speed narrow pulse signals to the medium under test through the probe; Step 2. The echo signal processing module receives the reflected echo of the liquid level in the measured container and calculates the TDR liquid level value based on the pulse round-trip time: in, The speed at which electromagnetic waves propagate in the waveguide medium. The round-trip time of the pulse signal; Step 3. The control processing module automatically adjusts the parameters of the broadband LC matching network according to the impedance deviation obtained in TDR mode, so that the impedance deviation in TDR mode meets the requirement that the standing wave ratio is lower than the set threshold. Step 4. The control processing module switches to FMCW working mode, and the probe emits a linear continuous frequency modulated signal; Step 5. The echo signal processing module performs frequency mixing processing on the echo signal and the local oscillator signal to obtain the beat signal and beat frequency. Represented as: Calculate the FMCW level value from the beat frequency: in, At the speed of light, For frequency modulation slope, τ Echo delay time; Step 6. The control processing module dynamically adjusts the microstrip Stub matching network parameters based on the impedance deviation obtained in FMCW mode, so that the impedance deviation in FMCW mode meets the requirement that the standing wave ratio is lower than the set threshold. Step 7. The control processing module uses a weighted fusion method to perform a weighted joint calculation on the dual-mode measurement results and outputs the liquid level height value: in, Weighting coefficient , Dynamic allocation is performed based on the corresponding channel signal-to-noise ratio and measurement confidence level; the allocation is increased when high near-field measurement accuracy is required. When high sensitivity is required for far-field measurements, increase This enables optimal liquid level estimation across the entire measurement range.

[0014] In summary, compared with the prior art, the invention has the following beneficial effects: (1) The present invention adopts a dual-mode common probe structure of TDR and FMCW to realize the collaborative work of two different measurement modes on the same probe. Compared with the traditional dual-probe independent measurement method, it can effectively reduce the structural complexity, installation space occupation and hardware cost of the dual-mode liquid level measurement system, while avoiding the measurement reference deviation problem caused by the installation of multiple probes, and improving the integration and liquid level measurement consistency of the dual-mode adaptive matching liquid level measurement system.

[0015] (2) By setting up a TDR broadband matching branch and an FMCW narrowband matching branch, and combining a varactor diode array, a PIN switch array and a real-time reflection parameter detection mechanism, the present invention achieves adaptive impedance dynamic matching under dual-mode conditions. The dual-mode adaptive impedance matching system can adjust the matching parameters in real time according to the change of probe impedance, effectively reducing reflection loss, standing wave effect and echo distortion, and improving the echo signal transmission efficiency and liquid level measurement accuracy.

[0016] (3) This invention establishes a joint error function for TDR and FMCW dual modes, and performs collaborative iterative optimization on the parameters of the broadband LC matching network and the microstrip Stub matching parameters, so that the TDR mode meets the requirements of broadband low reflection transmission, and the FMCW mode meets the requirements of high-precision narrowband matching in the target frequency band. This solves the problem that broadband and narrowband matching are difficult to balance under the dual-mode common probe condition in the prior art, and improves the dynamic range and dual-mode compatibility.

[0017] (4) The present invention utilizes the reflection detection unit to collect the probe reflection parameters in real time, and combines the control module to dynamically adjust the matching network. Under complex working conditions such as liquid level change, medium dielectric constant change, probe contaminant, high temperature, high pressure, and strong electromagnetic interference, the impedance deviation is compensated in real time, reducing inter-mode crosstalk and signal attenuation problems, and improving the long-term operational stability and adaptability of the liquid level measurement system to complex environments.

[0018] (5) This invention uses TDR mode and FMCW mode for joint measurement and liquid level fusion calculation. In the near range, the TDR mode is used to make accurate measurements with small blind zone and high resolution. In the far range and weak echo range, the FMCW mode is used to make detection with high sensitivity and strong anti-noise performance. The fusion weight is dynamically allocated according to the signal-to-noise ratio and reliability of the dual-mode measurement results, so as to realize high-precision liquid level measurement in the whole range, effectively reduce the measurement blind zone and improve the detection capability of weak echo at long distance. Attached Figure Description

[0019] Figure 1 This is an overall flowchart of the TDR and FMCW dual-mode liquid level measurement method of the present invention; Figure 2 This is a block diagram of the dual-mode adaptive impedance matching module of the dual-mode radar level gauge of the present invention; Figure 3 This is a schematic diagram of the common probe installation and measurement principle of the dual-mode radar level gauge of the present invention; Figure 4 This is a block diagram of echo signal processing and liquid level fusion calculation for the dual-mode radar level gauge of the present invention; Figure 5 This is a schematic diagram of the common probe level gauge of the present invention.

[0020] In the diagram: 1-Housing; 2-Electrical interface; 3-Terminal; 4-Flange; 5-RF connector; 6-Impedance matching transition; 7-Probe; 8-Threaded interface. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings.

[0022] like Figures 1-5 As shown, this invention discloses a TDR and FMCW co-probe adaptive matching liquid level measurement system, which is placed inside the TDR and FMCW co-probe liquid level gauge. It utilizes impedance self-matching technology to achieve synchronous dynamic adaptation of dual-mode impedance under the condition of TDR and FMCW co-probe, reducing the error caused by inconsistent device positions. The system includes a dual-mode signal generation module, a dual-mode adaptive impedance matching module, a co-probe measurement module, an echo signal processing module, and a control processing module.

[0023] The dual-mode signal generation module generates a TDR pulse excitation signal and an FMCW linear continuous frequency modulated signal for liquid level detection. A dual-mode adaptive impedance matching module is installed between the dual-mode signal generation module and the common-probe measurement module. This module includes a TDR broadband matching branch and an FMCW narrowband matching branch, enabling real-time adaptive adjustment of the TDR broadband impedance matching and the FMCW narrowband impedance matching. The TDR broadband matching branch achieves wideband impedance matching by dynamically adjusting multi-level LC network parameters, while the FMCW narrowband matching branch achieves precise matching of the target frequency band by adjusting the microstrip stub length and equivalent capacitance. The control processing module performs collaborative closed-loop optimization of the two branches based on real-time acquired probe reflection parameters. The echo signal processing module receives the liquid level echo signal and performs beat frequency extraction and time delay calculation. The control processing module performs mode switching selection, dynamic impedance parameter adjustment, and dual-mode liquid level fusion calculation, while also achieving unified and coordinated mode switching timing. Real-time transmission of control and feedback signals is achieved between the modules via SPI or UART bus.

[0024] This invention employs a shared-probe structure to allow both TDR and FMCW modes to use the same probe for liquid level measurement. Compared to traditional dual-probe independent measurement methods, this reduces the number of probes required and the overall structural volume, lowering the installation complexity and manufacturing cost of the dual-probe liquid level measurement system. Furthermore, since both modes share the same measurement reference, liquid level measurement errors caused by misalignment of multiple probe installation positions can be avoided, improving measurement consistency.

[0025] like Figure 5 As shown, the structure of the common-probe level gauge includes: a housing 1, an electrical interface 2, a terminal block 3, a flange 4, an RF connector 5, an impedance matching transition structure 6, a probe 7, and a threaded interface 8. The housing 1 houses and secures the internal circuit modules; the housing 1 is equipped with the electrical interface 2 and the terminal block 3, the positions of which can be adjusted according to actual usage requirements. The electrical interface 2 provides power to the measurement system and external communication connections; the terminal block 3 enables signal connections and outputs between the various functional circuits; the flange 4 securely mounts the level gauge to the opening of the container being measured; the RF connector 5, located away from the housing, connects to the flange 4 for securing the common-probe level gauge, enabling high-frequency signal transmission between the main circuit and the probe; the flange 4 is fixedly connected to the opening of the container being measured, transmitting measurement signals and... The probe 7, which receives the reflected echo signal of the liquid level, and the threaded interface 8, which is used to connect to the mounting base, are located on the other side of the flange 4. The probe 7 is located at the end of the impedance matching transition structure 6 and is mechanically fixed with a nut. The signal of the probe 7 is transmitted to the echo signal processing module through the RF connector 5. The impedance matching transition structure 6 is located between the housing 1 and the RF connector 5 to reduce impedance changes at the circuit connection, reduce reflection loss, and facilitate dual-mode matching. The probe 7 is used to transmit measurement signals to the measured medium and receive the reflected echo signal of the liquid level. The threaded interface 8 is used to realize the mechanical fixed connection between the common probe liquid level gauge and the mounting base.

[0026] Among them, the impedance matching transition structure 6 adopts a gradual impedance transition method, so that the TDR broadband pulse signal and the FMCW continuous frequency modulation signal form a smooth impedance change when entering the probe, reducing the reflection and standing wave effect of high frequency signals at the connection position, improving the stability of dual-mode signal transmission, and reducing signal crosstalk between modes.

[0027] This invention also discloses a dual-mode adaptive matching method in the TDR and FMCW dual-mode liquid level measurement process. It utilizes a TDR and FMCW shared-probe adaptive matching liquid level measurement system to achieve real-time dynamic adjustment of the probe impedance. The dual-mode signals of the TDR and FMCW shared-probe adaptive matching liquid level measurement system share the same probe for collaborative measurement, and the probe impedance state is adjusted in real time to achieve dynamic signal matching. Specifically, it includes the following steps: Step i: Initialize the circuit system of the control processing module. After powering on, the control processing module completes the parameter configuration of each functional module, loads the default impedance parameters of the probe, and simultaneously starts the reflection parameter detection module, entering the ready-to-work state. During the initialization process, the control processing module detects the current impedance state of probe 7 and establishes an initial matching parameter table. Since impedance matching is achieved by adjusting the multi-stage LC network and microstrip line length of the connected circuit using control switches, an impedance reference table (the impedance displayed by the circuit when some switches are on) is first provided as the initial matching parameter table through a combination of calculation and testing. This provides reference data for subsequent dynamic impedance adjustment, improving the matching stability and measurement accuracy during the startup phase.

[0028] Step ii: TDR Mode Impedance Detection and Broadband Adaptive Matching: The TDR signal generation module in the dual-mode adaptive impedance matching module generates a high-speed narrow pulse signal, which is transmitted to probe 7 via the dual-mode adaptive impedance matching module and then emitted to the surface of the measured medium to form an electromagnetic reflection signal. Due to the difference in dielectric constant between probe 7 and the measured medium, an electromagnetic reflection signal is formed at the liquid level position. Reflection coefficient Represented as: in, The reflection coefficient; The probe input impedance; The standard characteristic impedance is 50Ω in this embodiment, but it can be adjusted according to actual usage requirements. Further calculation of the voltage standing wave ratio (VSWR) is performed. The control processing module calculates the current impedance deviation based on the standing wave ratio (SWR). A SWR of 1 indicates a perfect match, while a higher SWR indicates a more severe mismatch. Since impedance deviation cannot be directly measured, it is calculated based on the SWR to provide a basis for subsequent matching adjustments. By real-time monitoring of the reflection coefficient and SWR parameters, the dual-mode adaptive impedance matching module can determine the current impedance change of the probe. When impedance drift occurs due to changes in the dielectric constant of the measured medium, contaminants adhering to the probe surface, or changes in ambient temperature, timely dynamic compensation can be performed, thereby improving the stability of level measurement under complex operating conditions.

[0029] The control processing module activates the broadband LC matching network adjustment circuit. Based on the impedance deviation, when the voltage standing wave ratio (VSWR) exceeds a set threshold, it dynamically switches the connection combination of the variable capacitor array and the switching inductor network via a PIN switch array. This cyclic detection and adjustment continues until the VSWR falls below the set threshold. In industrial applications, a VSWR between 1 and 1.5 is considered a match. However, due to the high impedance matching accuracy requirements of high-frequency electromagnetic waves, even minor manufacturing errors can lead to impedance mismatch when the VSWR is between 1.3 and 1.5. Therefore, in this embodiment, the set threshold is set to 1.3. The equivalent input impedance of the broadband LC matching network is... Represented as: in, Indicates the equivalent resistance. Indicates an adjustable inductor. This indicates an adjustable capacitor. The system adjusts the adjustable inductor in real time. and adjustable capacitor Parameters are used to gradually optimize the matching state, so that... Matching to the standard characteristic impedance achieves wideband impedance matching in TDR mode, reducing reflection loss and improving the transmission efficiency of TDR pulse signals.

[0030] Since TDR signals are broadband high-speed pulse signals, they have high requirements for impedance continuity. This invention uses a broadband LC matching network to dynamically adjust the equivalent inductance and equivalent capacitance, so that the standing wave ratio is kept below the set threshold over a wide frequency range, thereby improving the resolution of near-field liquid level detection and reducing the near-field measurement blind zone.

[0031] Step iii: FMCW Mode Impedance Detection and Narrowband Adaptive Matching: The control processing module switches to FMCW operating mode, driving the FMCW signal generation module to output a linear continuous frequency modulated (LFM) signal. The instantaneous frequency expression of the LFM signal is: in, Indicates the starting frequency. Indicates the frequency modulation slope. Indicates time. After the linear continuous frequency modulated signal is transmitted through probe 7, the dual-mode adaptive impedance matching module detects the reflection parameters of the probe port in real time to obtain impedance deviation information within the FMCW operating frequency band. The method of obtaining the impedance deviation information is the same as that of obtaining the TDR impedance deviation information described above.

[0032] The control processing module activates the microstrip stub matching network. Based on the acquired impedance deviation information, the control processing module adjusts the effective access length of the stub via an RF switch, and simultaneously adjusts the varactor diode bias voltage to change the equivalent capacitance value, achieving dynamic impedance compensation within the preset narrowband target frequency band. This can be cyclically detected and adjusted until the standing wave ratio (VSWR) falls below a set threshold. In this embodiment, the preset narrowband target frequency band is 24-26 GHz, and impedance matching is performed within this range. The stub's equivalent input impedance... Represented as: in, Represents the propagation constant. Indicates the effective length of the stub. Total equivalent input impedance of the dual-mode adaptive impedance matching module. Parallel combination of branches of a broadband LC matching network and branches of a stub matching network: Step iv. When the condition is met When the impedance is equal to the standard characteristic impedance, the narrowband impedance matching of the FMCW mode is completed, and the TDR and FMCW co-probe adaptive matching liquid level measurement system enters the steady-state dual-mode collaborative working state.

[0033] Since the FMCW mode requires an error of less than 0.5% in the frequency modulation slope within the target frequency band and a phase difference of less than 5° between the transmitting and receiving channels, this invention achieves precise impedance compensation within the narrow band by using a microstrip stub structure and a varactor diode in combination. This reduces spectral distortion during continuous frequency modulation signal transmission and improves long-distance weak echo detection capability and anti-interference performance.

[0034] like Figure 1 As shown, this invention also discloses a liquid level measurement method based on dual-mode adaptive matching of TDR and FMCW. The process flow of each step based on the aforementioned dual-mode adaptive matching method is as follows: Figure 3 As shown, the specific steps include: Step 1. The control processing module configures the broadband LC matching network of the TDR working mode according to the matching parameters output by the dual-mode adaptive impedance matching module, and establishes the pulse transmission timing and echo sampling window; then the TDR working mode is started, and the TDR signal generation module is controlled to transmit high-speed narrow pulse signals to the medium under test through probe 7.

[0035] Step 2. The echo signal processing module receives the reflected liquid level echo and calculates the TDR liquid level value based on the pulse round-trip time: in, The speed at which electromagnetic waves propagate in the waveguide medium. The time to and from the pulse signal is the round-trip propagation time. Because the TDR mode has high time resolution and small blind zone, it can improve the accuracy of close-range liquid level detection, and is especially suitable for small-range detection scenarios where the liquid surface is close to the probe area.

[0036] Step 3. The control processing module automatically adjusts the parameters of the broadband LC matching network according to the TDR mode impedance detection and TDR broadband adaptive matching reflection parameter detection and adjustment process, so that the impedance deviation in TDR mode meets the requirement that the standing wave ratio is lower than the set threshold.

[0037] Step 4. The control processing module switches to FMCW working mode and drives probe 7 to emit a linear continuous frequency modulation signal.

[0038] Step 5. The echo signal processing module performs frequency mixing processing on the echo signal and the local oscillator signal to obtain the beat signal and beat frequency. Represented as: Calculate the FMCW level value from the beat frequency: in, At the speed of light, For beat frequency, For frequency modulation slope, τ The echo delay time is used because the FMCW mode has high spectral resolution and strong noise resistance, which can improve the sensitivity of long-distance liquid level measurement and enhance the detection capability of weak echo signals.

[0039] Step 6. The control processing module dynamically adjusts the microstrip Stub matching network parameters according to the FMCW mode impedance detection and FMCW narrowband adaptive matching detection and adjustment process, so that the impedance deviation in FMCW mode meets the requirement that the standing wave ratio is lower than the set threshold.

[0040] Step 7. The control processing module uses a weighted fusion algorithm to jointly calculate the dual-mode measurement results and outputs the final liquid level height value: in, Weighting coefficient , The weights and weighting coefficients for TDR level and FMCW level are respectively. , The signal-to-noise ratio of each channel and the measurement confidence level are dynamically allocated, and the allocation is increased when the near-field measurement accuracy requirement is high. When high sensitivity is required for far-field measurements, increase To achieve optimal liquid level estimation across the entire measurement range.

[0041] By employing a dual-mode fusion computing mechanism, this invention can comprehensively utilize the advantages of TDR mode's high precision at close range and FMCW mode's high sensitivity at long range, thereby reducing the measurement blind zone and improving the accuracy of liquid level measurement across the entire range and adaptability to complex working conditions.

[0042] Since TDR mode has the advantages of high resolution and small blind zone at close range, while FMCW mode has the advantages of high sensitivity and strong anti-interference at long range, this invention effectively reduces the near-field measurement blind zone and improves the accuracy and stability of liquid level measurement under complex working conditions (including high temperature, high pressure, strong corrosion, multiple foams and changes in dielectric constant of the medium).

[0043] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A TDR and FMCW co-probe adaptive matching liquid level measurement system, characterized in that, The TDR and FMCW co-probe adaptive matching level measurement system is placed inside the co-probe level gauge and includes a dual-mode signal generation module, a dual-mode adaptive impedance matching module, a co-probe measurement module, an echo signal processing module, and a control processing module, wherein: The dual-mode signal generation module acts as a signal generator, producing a TDR pulse excitation signal and an FMCW linear continuous frequency modulation signal for detecting liquid level. The dual-mode adaptive impedance matching module includes a TDR broadband matching branch and an FMCW narrowband matching branch. The TDR broadband matching branch achieves broadband impedance matching by dynamically adjusting the parameters of a multi-level LC network, while the FMCW narrowband matching branch achieves precise matching of the target frequency band by adjusting the length of the microstrip stub and the equivalent capacitance, thus realizing real-time adaptive adjustment of TDR mode broadband impedance matching and FMCW mode narrowband impedance matching. The common probe measurement module realizes liquid level measurement in both TDR and FMCW modes through the same probe structure; the echo signal processing module receives the liquid level echo signal detected by the common probe liquid level gauge and performs beat frequency extraction and time delay calculation respectively. The control processing module performs mode switching selection, dynamic adjustment of impedance parameters, and dual-mode liquid level fusion calculation.

2. The TDR and FMCW co-probe adaptive matching liquid level measurement system according to claim 1, characterized in that, The common probe level gauge also includes a housing (1), an RF connector (5), an impedance matching transition structure (6), and a probe (7). The impedance matching transition structure (6) is placed between the housing (1) and the RF connector (5). The RF connector (5) is connected to a flange (4) for fixing the common probe level gauge on the side away from the housing. The flange (4) is fixedly connected to the opening of the container being measured. The probe (7) that transmits measurement signals and receives liquid level reflection echo signals and the threaded interface (8) for connecting the mounting base are placed on the other side of the flange (4). The signal of the probe (7) is transmitted to the echo signal processing module through the RF connector (5). Each circuit function module is fixedly installed inside the housing (1). The outer shell (1) is provided with an electrical interface (2) and a wiring terminal (3).

3. The TDR and FMCW co-probe adaptive matching liquid level measurement system according to claim 2, characterized in that, The impedance matching transition structure (6) adopts a gradual impedance transition method, so that the TDR broadband pulse signal and the FMCW continuous frequency modulation signal form a smooth impedance change when entering the probe, reducing the reflection and standing wave effect of high frequency signals at the connection position.

4. A dual-mode adaptive matching method for TDR and FMCW dual-mode liquid level measurement, implemented using the TDR and FMCW co-probe adaptive matching liquid level measurement system as described in any one of claims 1 to 3, characterized in that, The dual-mode signals of a TDR and FMCW level measurement system are used to share the same probe for collaborative measurement. Dynamic signal matching is achieved by adjusting the probe impedance in real time. The specific steps include: Step i. The circuit system of the control processing module is initialized. During the initialization process, the control processing module detects the current impedance state of the probe (7) and establishes an initial matching parameter table to provide reference data for subsequent dynamic impedance adjustment. Step ii. TDR mode impedance detection and broadband adaptive matching: The TDR signal generation module in the dual-mode adaptive impedance matching module generates a high-speed narrow pulse signal, which is transmitted to the probe (7) through the dual-mode adaptive impedance matching module and then emitted to the surface of the medium in the container under test to form an electromagnetic reflection signal. The control processing module calculates the standing wave ratio based on the reflection signal, calculates the current impedance deviation based on the standing wave ratio value, and dynamically switches the access combination of the variable capacitor array and the switching inductor network based on the impedance deviation. Step iii. FMCW mode impedance detection and narrowband adaptive matching: The control processing module switches to FMCW working mode, and the FMCW signal generation module in the dual-mode adaptive impedance matching module outputs a linear continuous frequency modulated signal. After the linear continuous frequency modulated signal is transmitted through the probe (7), the dual-mode adaptive impedance matching module detects the reflection parameters of the probe port in real time, obtains the impedance deviation information in the FMCW working frequency band, and the control processing module starts the microstrip Stub matching network. According to the obtained impedance deviation information, the control processing module adjusts the effective access length of the Stub through the RF switch, and at the same time adjusts the bias voltage of the varactor diode to change the equivalent capacitance value, so as to achieve accurate impedance dynamic compensation in the preset narrowband target frequency band. Step iv. When the total equivalent input impedance of the dual-mode adaptive impedance matching module When the characteristic impedance is equal to that of the standard, the TDR and FMCW co-probe adaptive matching level measurement system enters the dual-mode collaborative working state.

5. The dual-mode adaptive matching method according to claim 4, characterized in that, In step ii, the reflection coefficient of the electromagnetic reflection signal Represented as: in, The probe input impedance; Given the standard characteristic impedance; calculate the voltage standing wave ratio (VSWR): The control and processing module detects the reflection coefficient and standing wave ratio parameters in real time, while the dual-mode adaptive impedance matching module judges the current impedance change status of the probe in real time and performs dynamic compensation based on the impedance change status.

6. The dual-mode adaptive matching method according to claim 5, characterized in that, The control processing module activates the broadband LC matching network adjustment circuit. When the voltage standing wave ratio (VSWR) exceeds a set threshold, it dynamically switches the connection combination of the variable capacitor array and the switching inductor network via a PIN switch array. The equivalent input impedance of the broadband LC matching network... Represented as: in, Indicates the equivalent resistance. Indicates an adjustable inductor. This refers to an adjustable capacitor, which is adjusted in real time by an adjustable inductor. and adjustable capacitor Gradually optimize the matching status to make Matching to the standard characteristic impedance achieves wideband impedance matching in TDR mode.

7. The dual-mode adaptive matching method according to claim 4, characterized in that, In step iii, the instantaneous frequency expression of the linear continuous frequency modulated signal is: in, Indicates the starting frequency. Indicates the frequency modulation slope. Represents time; equivalent input impedance of the stub matching network. Represented as: in, Represents the propagation constant. Indicates the effective length of the stub.

8. The dual-mode adaptive matching method according to claim 4, characterized in that, The total equivalent input impedance of the dual-mode adaptive impedance matching module Parallel combination of branches of a broadband LC matching network and branches of a stub matching network: in, The equivalent input impedance of the broadband LC matching network. The equivalent input impedance of the Stub matching network.

9. A liquid level measurement method using dual-mode adaptive matching of TDR and FMCW, based on the dual-mode adaptive matching method of claim 4, characterized in that, Specifically, the following steps are included: Step 1. The control processing module configures the broadband LC matching network of the TDR working mode according to the matching parameters output by the dual-mode adaptive impedance matching module, and establishes the pulse transmission timing and echo sampling window; then the TDR working mode is started, and the TDR signal generation module is controlled to transmit a high-speed narrow pulse signal to the medium under test through the probe (7); Step 2. The echo signal processing module receives the reflected echo of the liquid level in the measured container and calculates the TDR liquid level value based on the pulse round-trip time: in, The speed at which electromagnetic waves propagate in the waveguide medium. The round-trip time of the pulse signal; Step 3. The control processing module automatically adjusts the parameters of the broadband LC matching network according to the impedance deviation obtained in TDR mode, so that the impedance deviation in TDR mode meets the requirement that the standing wave ratio is lower than the set threshold. Step 4. The control processing module switches to FMCW working mode, and the probe (7) emits a linear continuous frequency modulated signal; Step 5. The echo signal processing module performs frequency mixing processing on the echo signal and the local oscillator signal to obtain the beat signal and beat frequency. Represented as: Calculate the FMCW level value from the beat frequency: in, At the speed of light, For frequency modulation slope, τ Echo delay time; Step 6. The control processing module dynamically adjusts the microstrip Stub matching network parameters based on the impedance deviation obtained in FMCW mode, so that the impedance deviation in FMCW mode meets the requirement that the standing wave ratio is lower than the set threshold. Step 7. The control processing module uses a weighted fusion method to perform a weighted joint calculation on the dual-mode measurement results and outputs the liquid level height value: in, Weighting coefficient , Dynamic allocation is performed based on the corresponding channel signal-to-noise ratio and measurement confidence level; the allocation is increased when high near-field measurement accuracy is required. When high sensitivity is required for far-field measurements, increase This enables optimal liquid level estimation across the entire measurement range.

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