A dual-frequency antenna-based ice layer thickness sensor and measurement method

Abstract

The application discloses a kind of ice layer thickness sensor and measurement method based on dual-frequency antenna, belong to radio frequency sensing technical field, to solve the problem of small range, transition zone misjudgment and poor anti-environmental interference ability of single-frequency microwave phase detection method.The sensor includes metal shell, radio frequency board, core control board, dual-frequency microstrip patch antenna, dual-frequency signal generator, power division circuit, amplitude-phase detector and algorithm processing module;Dual-frequency microstrip patch antenna adopts transceiver integrated structure, separates reference signal and incident signal by power division circuit, amplitude-phase detector extracts two-way phase difference, and algorithm processing module is based on bilinear interpolation algorithm, combined with thickness-phase difference two-dimensional characteristic plane to solve ice layer thickness.The application realizes relatively large range, high precision, high robustness ice layer thickness non-contact detection by dual-frequency signal physical synergy and algorithm fusion, and is suitable for real-time monitoring of road ice layer and other scenes.

Description

Technical Field

[0001] This invention belongs to the field of radio frequency sensing technology, and particularly relates to an ice thickness sensor and measurement method based on a dual-frequency antenna. Background Technology

[0002] Ice on the road surface is one of the main risk factors causing traffic accidents in icy and snowy weather conditions. Among the various existing technologies, microwave phase detection method has the advantages of being non-contact, high-precision, and easy to implement. It emits microwaves and detects the phase difference between the echo and the reference signal, and inverts the ice thickness based on the relationship between the phase difference and the ice thickness.

[0003] The current mainstream approach is based on microwave phase detection at a frequency of 2.4 GHz. However, this method has three inherent drawbacks: limited measurement range, misjudgment in the transition zone, and insufficient resistance to environmental interference. The 2.4 GHz microwave signal cannot simultaneously possess the strong penetration required for detecting thick ice and the high resolution required for detecting thin ice, resulting in a small effective measurement range for single-frequency systems that cannot simultaneously cover the detection requirements of both thin and thick ice. In the transition zone between thin and thick ice, the phase response of the single-frequency signal undergoes nonlinear distortion or enters a fuzzy region due to the inherent contradiction between penetration and resolution, leading to unreliable thickness inversion results and a high risk of misjudgment. The equivalent dielectric constant of the ice layer is easily affected by temperature, density, and impurity content, causing drift. Single-frequency phase difference information simultaneously couples thickness changes with changes in medium properties, lacking sufficient information dimensions to decouple the two. Therefore, when environmental conditions change or the ice layer is non-uniform, the system measurement error increases significantly, resulting in poor system robustness. Therefore, improving the accuracy of ice layer measurement has become an urgent problem to be solved in this field. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide an ice thickness sensor and measurement method based on a dual-frequency antenna. Through the physical coordination mechanism of dual-frequency signals, the low-frequency signal penetrates thick ice, while the high-frequency signal distinguishes thin ice, achieving a large range coverage of 0-50mm. The two sets of phase difference information returned by the ice layer are the basis for distinguishing thickness, identifying medium changes, and analyzing complex structures. Furthermore, the robustness and measurement accuracy of the system can be improved through algorithm fusion.

[0005] Technical Solution: The present invention provides an ice thickness sensor based on a dual-frequency antenna, comprising a metal casing, an RF board, a core control board, a dual-frequency microstrip patch antenna, a dual-frequency signal generator, a power divider circuit, an amplitude and phase detector, and an algorithm processing module; the RF board and the core control board are fixed in parallel on the internal support platform of the metal casing, the dual-frequency microstrip patch antenna is fixed to the antenna mounting position of the RF board, the dual-frequency signal generator, the power divider circuit, and the amplitude and phase detector are integrated in the RF module area of ​​the RF board, and the algorithm processing module is mounted on the core control board; the dual-frequency signal generator, the power divider circuit, the dual-frequency microstrip patch antenna, the amplitude and phase detector, and the algorithm processing module are sequentially connected by signals.

[0006] Furthermore, the metal casing is provided with mounting screw holes, a wave-transparent window, a cable hole, and an internal support platform; the mounting screw holes are four M4 through holes located at the four bottom corners of the metal casing; the wave-transparent window is a rectangular opening facing the radiating surface of the dual-frequency microstrip patch antenna, and a polytetrafluoroethylene cover plate is pasted below the opening; the inner wall of the cable hole is wrapped with a rubber sealing ring; the internal support platform consists of two platforms of the same height, with M3 screw holes on the upper surface.

[0007] Furthermore, the RF board is provided with board mounting holes, an RF module area, an antenna mounting position, and wiring terminals; the board mounting holes are four M3 through holes, aligned with the screw holes of the internal support platform; the RF module area is divided into a dual-frequency signal generator area and a power divider circuit and amplitude and phase detector area; the wiring terminals are three-pin headers, which are plugged and plugged into the wiring terminals of the core control board.

[0008] Furthermore, the dual-band microstrip patch antenna includes a ground layer, a dielectric substrate, a 2.4GHz radiating patch, a 5GHz radiating patch, and a microstrip feed line; the ground layer is made of copper foil and is attached to the lower surface of the dielectric substrate; the dielectric substrate is made of FR4_epoxy material with a thickness of 1mm, a relative permittivity εr=4.4, and a loss tangent TanD=0.02; the 2.4GHz radiating patch is a rectangular copper structure covering the upper surface of the dielectric substrate; the 5GHz radiating patch is a narrow rectangular copper structure extending from the edge of the main radiating patch; the microstrip feed line is impedance matched with 50Ω and connected to the power divider circuit through an SMA connector.

[0009] Furthermore, the dual-frequency signal generator includes a 2.4GHz low-frequency signal generation unit, a 5GHz high-frequency signal generation unit, a 50Ω impedance matching output port, a synchronization control module, a core drive circuit, and a signal amplification unit. The synchronization control module synchronously drives the two signal generation units to generate a dual-frequency composite signal, which is amplified by the signal amplification unit and then input to the power divider circuit through the 50Ω impedance matching output port.

[0010] Furthermore, the power divider circuit is a four-port structure, including a four-port impedance matching unit, a high-frequency filtering unit, and an isolation coupling unit; the four-port impedance matching unit includes four 50Ω impedance matching ports Term1, Term2, Term3, and Term4 and a 50Ω impedance matching microstrip line, the linewidth and length of which are optimized by ADS simulation; the high-frequency filtering unit includes multilayer inductors L1-L4 and high-frequency capacitors C1-C4; the isolation coupling unit includes isolation resistors R1 and R2 and high-frequency coupling capacitors C5 and C6.

[0011] Furthermore, the core of the amplitude and phase detector is the ADL5380 chip, which includes an amplitude and phase detection ADL5380 chip unit, an input signal matching unit, a power supply filtering unit, and an output signal conditioning unit. The input signal matching unit is equipped with 1nF CFOG dielectric capacitors C1 and C2, which are connected in series between the INPA terminal, the INPB terminal, and the chip pins, respectively. The power supply filtering unit consists of 1μF electrolytic capacitors C3 and C5 and 1nF ceramic capacitors C6, C7, and C8. The output signal conditioning unit is equipped with 510Ω metal foil resistors R1 and R2 and 1nF ceramic capacitors C9 and C10, and the output terminals are LPDO and HPDO terminals, which are connected to the algorithm processing module.

[0012] Furthermore, the algorithm processing module includes a voltage conversion circuit and a microcontroller and its surrounding circuits; the voltage conversion circuit converts 5V DC voltage to 3.3V DC voltage; the microcontroller and its surrounding circuits are used to construct a thickness-phase difference two-dimensional feature plane and solve for the ice layer thickness using a bilinear interpolation algorithm.

[0013] The present invention also discloses a method for measuring ice thickness based on the aforementioned sensor, comprising the following steps:

[0014] S1. Install and secure the metal casing, RF board, and core control board, ensuring that the wave-transmitting window faces the ice layer under test and that the dual-frequency microstrip patch antenna is unobstructed.

[0015] S2. Connects to 5V DC voltage via an external cable to power the dual-frequency signal generator and amplitude / phase detector; outputs 3.3V DC voltage via a voltage conversion circuit to power the microcontroller and its surrounding circuits and other circuits.

[0016] S3. The dual-frequency signal generator outputs a dual-frequency composite signal, which is then transmitted through a four-port power divider circuit. The reference signal is output to the INPA terminal of the amplitude and phase detector via a 50Ω impedance-matched microstrip line, and the incident signal is output to the feed terminal of the dual-frequency microstrip patch antenna via a coaxial cable.

[0017] S4. The dual-frequency microstrip patch antenna radiates the incident signal to the ice layer under test and simultaneously receives the echo signal formed after reflection from the upper and lower surfaces of the ice layer, which is then transmitted to the INPB end of the amplitude and phase detector via the feeder.

[0018] S5. The amplitude and phase detector compares the reference signal with the dual-frequency echo signal and outputs two original phase difference signals. Taking a dry, ice-free plane as a reference, the microcontroller collects the dual-frequency phase difference in this state as the reference phase difference. The ice thickness corresponding to this state is specified as 0mm.

[0019] S6. Prepare high-precision standard ice layers of 0mm-50mm, set data points with a step size of 0.5mm, calibrate the actual thickness with a laser thickness gauge, and measure and record the dual-frequency phase difference corresponding to each ice layer; construct a two-dimensional feature plane of thickness-phase difference in the microcontroller based on the measured data.

[0020] S7. For any measured dual-frequency phase difference, match the four nearest reference points in the two-dimensional feature plane, and use the bilinear interpolation algorithm to solve the coordination coefficient of each phase difference interval to obtain the interpolation function of thickness with respect to dual-frequency phase difference.

[0021] S8. Substitute the measured dual-frequency phase difference into the interpolation function to solve for the ice thickness value, thus completing one ice thickness measurement.

[0022] Furthermore, the polynomial form of the bilinear interpolation algorithm in step S7 is:

[0023] ;

[0024] in, , , , The coordination coefficients for bilinear interpolation. The measured phase difference is 2.4GHz. The measured phase difference is at 5GHz. This is the measured ice thickness value.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0026] 1. This invention utilizes a dual-frequency microwave signal coordination mechanism, combining the physical complementary characteristics of low-frequency and high-frequency signals, to achieve a large measurement range of ice thickness from 0 to 50 mm with a high resolution of 0.1 mm. The low-frequency signal has strong penetration and has a significant advantage in measuring thick ice; the high-frequency signal has high phase sensitivity, enabling high-precision measurement of thin ice, fundamentally expanding the measurement range and eliminating the transition zone.

[0027] 2. This invention, based on a bilinear interpolation algorithm, integrates information from dual-frequency phase difference signals, overcoming the limitations of one-dimensional mapping in traditional single-frequency microwave measurement systems. It calibrates a standard ice layer with a step size of 0.5 mm and extracts the original signal of the dual-frequency phase difference. By establishing a two-dimensional feature space for calibration between the dual-frequency phase difference and ice layer thickness, the ice layer thickness can be accurately calculated from the measured phase difference using interpolation methods. Compared to traditional single-frequency microwave measurement systems, this method significantly improves the identification and accuracy of the phase difference signal by utilizing the information redundancy of dual-frequency signals.

[0028] 3. This invention can decouple measurement errors caused by factors such as changes in ambient temperature, fluctuations in the relative permittivity of ice layers, and changes in surface condition during the interpolation process, thereby reducing their impact. Because the dual-frequency phase difference signal exhibits good discriminative power in the feature space, this invention can effectively reduce the influence of single parameter fluctuations on the measurement results, thus significantly improving the system's measurement robustness under complex environmental conditions.

[0029] 4. The ice thickness detection system proposed in this invention has simple hardware implementation, low cost, good real-time performance, and excellent anti-crosstalk capability in its physical structure and circuit design. The transceiver antenna and radio frequency circuit are connected via 50 Impedance matching and electromagnetic coupling design ensure that the S11 reflection coefficient amplitude is less than -10dB in both the 2.4GHz and 5GHz bands, guaranteeing low transmission loss of dual-frequency signals and high signal-to-noise ratio of front-end data acquisition. It can be stably applied to scenarios such as highway ice monitoring, airport runway and taxiway surface icing early warning, bridge deck icing risk monitoring, and meteorological environment monitoring, realizing real-time monitoring and early warning of road surface icing status, and has broad engineering application value. Attached Figure Description

[0030] Figure 1 This is a block diagram of the ice thickness sensor system of the present invention;

[0031] Figure 2 This is a three-dimensional structural schematic diagram of the ice thickness sensor of the present invention;

[0032] Figure 3 This is a schematic diagram of the PCB board structure and assembly of the ice thickness sensor of the present invention;

[0033] Figure 4 This is a three-dimensional structural schematic diagram of the dual-frequency microstrip patch antenna for the ice thickness sensor of the present invention;

[0034] Figure 5 This is a circuit diagram of the power distribution circuit for the ice thickness sensor of the present invention;

[0035] Figure 6 This is a circuit diagram of the amplitude and phase detector of the ice thickness sensor of the present invention;

[0036] Figure 7 This is a flowchart of the ice thickness sensor measurement method of the present invention;

[0037] Figure 8 This is a graph showing the S-parameters of the dual-frequency microstrip patch antenna for the ice thickness sensor of this invention.

[0038] The attached diagram is labeled as follows: 1. Metal casing; 1-1. Mounting screw hole; 1-2. Wave-transparent window; 1-3. Cable hole; 1-4. Internal support platform; 2. RF board; 2-1. Board mounting hole; 2-2. RF module area; 2-2-1. Dual-frequency signal generator area; 2-2-2. Power divider circuit and amplitude / phase detector area; 2-3. Antenna mounting position; 2-4. Wiring terminal; 3-1. Board mounting hole; 3-2. Algorithm processing module; 3-2-1. Voltage conversion circuit; 3-2-2. Microcontroller and its surrounding circuits; 3-3. Wiring terminal; 4. Dual-frequency microstrip patch antenna; 4-1. Grounding layer; 4-2. Dielectric substrate; 4-3. 2.4GHz radiating patch; 4-4. 5GHz radiating patch; 4-5. Microstrip feeder. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the application will be further described in detail below with reference to the accompanying drawings. The described embodiments are only a part of the embodiments involved in this invention. All non-innovative embodiments based on these embodiments by other researchers in the art are within the protection scope of this invention. Furthermore, the step numbers in the embodiments of this invention are only set for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0040] In one embodiment of the present invention, an ice thickness sensor based on a dual-frequency antenna, such as... Figure 2 As shown, it includes: a metal casing 1; mounting screw holes 1-1; a wave-transparent window 1-2; a cable hole 1-3; an internal support platform 1-4; an RF board 2; board mounting holes 2-1; an RF module area 2-2; a dual-frequency signal generator area 2-2-1; a power divider circuit and amplitude / phase detector area 2-2-2; an antenna mounting position 2-3; a terminal block 2-4; a core control board 3; board mounting holes 3-1; an algorithm processing module 3-2; a voltage conversion circuit 3-2-1; a microcontroller and its peripheral circuits 3-2-2; and a terminal block 3-3.

[0041] The metal housing 1 is used to protect the internal components of the sensor, realize embedded fixation under the road surface, and provide an installation reference for each component, including: mounting screw hole 1-1, wave-transparent window 1-2, cable hole 1-3, and internal support platform 1-4.

[0042] The metal casing 1, RF board 2, and core control board 3 are fixedly connected by screws. The dual-band microstrip patch antenna 4 is fixed to the antenna mounting position 2-3 by screws, which plays a fixed support role for signal radiation and reception.

[0043] like Figure 2 As shown, mounting screw holes 1-1 are four M4 through holes at the four corners of the bottom of the outer shell, used to fix the metal outer shell 1 to the road pre-embedded groove. The hole diameter is the same as the screw hole of the pre-embedded groove, and the thread type, pitch and direction of rotation are the same. The screw is passed through mounting screw holes 1-1 and screwed into the screw hole of the pre-embedded groove to complete the fixation.

[0044] The wave-transmitting windows 1-2 are rectangular openings, facing the radiating surface of the dual-frequency microstrip patch antenna. A polytetrafluoroethylene cover plate is pasted directly below the opening, so that the dual-frequency microwave signal radiated by the antenna can pass smoothly through the shell to reach the ice layer to be tested, and prevent rainwater and dust from entering.

[0045] Cable holes 1-3 are circular holes on the right side wall of the outer casing, with the inner wall wrapped with a rubber sealing ring, used to lead out and protect the coaxial cable;

[0046] The internal support platforms 1-4 are two platforms of the same height. The upper surface has M3 screw holes corresponding to the mounting holes of the circuit PCB board. The front platform is used to fix the RF board 2, and the rear platform is used to fix the core control board 3. The two boards are parallel and separate to avoid crosstalk between signals.

[0047] The radio frequency board 2, such as Figure 3 As shown, it includes: board mounting holes 2-1; RF module area 2-2; dual-frequency signal generator area 2-2-1; power divider circuit and amplitude and phase detector area 2-2-2; antenna mounting position 2-3; and wiring terminals 2-4.

[0048] The board mounting holes 2-1 are four through holes at the four corners of the RF board, used to fix the RF board 2 to the front inner support platform 1-4 of the metal shell 1. The fixing is achieved by passing M3 screws through the board mounting holes 2-1 and screwing them into the screw holes of the support platform.

[0049] The RF module area 2-2 is used to install the PCB board of the dual-frequency signal generator area 2-2-1, the power divider circuit and the amplitude and phase detector area 2-2-2, so as to realize the generation, transmission and phase difference detection of dual-frequency microwave signals;

[0050] Antenna mounting position 2-3 is the area on the upper surface of the RF board near the wave-transmitting window 1-2, and is provided with 4 positioning holes for fixing the dual-band microstrip patch antenna;

[0051] Terminal 2-4 is a 3-pin header that is plugged into and connected to terminal 3-3 of the core control board to output the phase difference voltage signal from the amplitude and phase detector.

[0052] Core control board 3, such as Figure 3 As shown, it includes: board mounting holes 3-1; algorithm processing module 3-2; voltage conversion circuit 3-2-1; microcontroller and its peripheral circuits 3-2-2; and terminal blocks 3-3.

[0053] The board mounting holes 3-1 are four through holes at the four corners of the core control board, used to fix the core control board 3 to the rear internal support platform 1-4 of the metal shell 1. The board is fixed by passing M3 screws through the board mounting holes 3-1 and screwing them into the screw holes of the support platform, and is placed separately and parallel to the radio frequency board 2.

[0054] The algorithm processing module 3-2 includes: a voltage conversion circuit 3-2-1; a microcontroller and its surrounding circuits 3-2-2, which realizes voltage conversion and processes phase difference information through algorithms;

[0055] Terminal 3-3 is a 3-pin female connector, and terminal 2-4 of RF board 2 is plugged in and plugged in to receive the phase difference voltage signal output by the amplitude and phase detector.

[0056] Dual-band microstrip patch antenna 4, such as Figure 4 As shown, the device is used to transmit dual-frequency microwave signals and receive echo signals, and includes: a ground layer 4-1, a dielectric substrate 4-2, a 2.4GHz radiating patch 4-3, a 5GHz radiating patch 4-4, and a microstrip feed line 4-5.

[0057] The grounding layer 4-1 is a rectangular plane made of copper foil, which is horizontally attached to the lower surface of the dielectric substrate 4-2 and fixed to the antenna mounting position 2-3 of the radio frequency board 2 by thermally conductive adhesive;

[0058] The dielectric substrate 4-2 is a rectangular thin plate made of FR4_epoxy material, with a thickness of 1mm and a relative permittivity of [missing information]. =4.4, loss tangent TanD=0.02, horizontally attached to the central area of ​​the rectangular grounding layer, and completely in close contact with the upper surface of the grounding layer;

[0059] 2.4GHz radiating patch 4-3: Made of copper, rectangular in structure, covering the upper surface of the dielectric substrate, corresponding to the 2.4GHz fundamental mode resonance, and is the core radiating and receiving carrier of low-frequency signals;

[0060] 5GHz radiating patch 4-4: Made of copper, it has a narrow rectangular structure that extends from the edge of the main radiating patch. It corresponds to the 5GHz high-order mode resonance and enhances the radiation efficiency of high-frequency signals through electromagnetic coupling.

[0061] Microstrip feed line 4-5: After 50Ω impedance matching, it has a branch structure and transmits signals through an SMA connector and a power divider circuit.

[0062] Furthermore, the S-parameters of the dual-band microstrip patch antenna are as follows: Figure 8As shown in the figure, the S11 curve reflects the good performance of the dual-band antenna. The S11 bandwidth of the 2.4GHz target frequency band and the 5GHz target frequency band is large, and the amplitude is less than -20dB. This indicates that the antenna has low signal reflection loss in the dual-frequency range, which can ensure high radiation and reception efficiency.

[0063] The power divider circuit is located in the power divider circuit and amplitude / phase detector area 2-2-2, such as... Figure 5 The diagram shows a four-port power distribution structure, which includes: a four-port impedance matching unit, a high-frequency filtering unit, and an isolation coupling unit.

[0064] Specifically, in the power divider circuit, the four-port impedance matching module includes four 50Ω impedance matching ports Term1, Term2, Term3, and Term4, and a 50Ω impedance matching microstrip line connecting each port.

[0065] The four-port impedance matching module has four 50Ω impedance matching ports: Term1, Term2, Term3, and Term4.

[0066] Term1 is the signal input terminal, which is connected to the output terminal of the dual-frequency signal generator via a microstrip line;

[0067] Term2 is the echo signal coupling output terminal, which outputs the incident signal to the ice layer to be measured. The reflected echo signal is output to the INPB terminal of the amplitude and phase detector through the isolation coupling via the Term4 port.

[0068] Term3 is the reference signal output terminal, which is connected to the INPA terminal of the amplitude and phase detector via a coaxial cable;

[0069] Term4 is the incident signal output terminal, which is connected to the microstrip feed line 4-5 of the dual-frequency microstrip patch antenna 4 via a coaxial cable;

[0070] The 50Ω impedance matching microstrip line width and length of the four-port impedance matching module are optimized through ADS simulation to match the port impedance, ensuring low-loss transmission of dual-frequency signals inside the circuit and avoiding amplitude and phase distortion caused by signal reflection.

[0071] The high-frequency filtering unit includes multilayer inductors L1-L4 and high-frequency capacitors C1-C4. Multilayer inductor L1 is connected in series between the Term1 port and the impedance matching microstrip line to suppress low-frequency interference signals from entering the circuit. High-frequency capacitors C1-C4 are connected in series between the four ports and ground to suppress power supply coupling high-frequency noise and useless harmonic interference generated by external electromagnetic interference.

[0072] The isolation coupling unit includes isolation resistors R1 and R2, and high-frequency coupling capacitors C5 and C6. Isolation resistor R1 is connected in series between the impedance matching microstrip lines of Term3 and Term4, utilizing the absorption function of the resistor to suppress crosstalk between the two signals, allowing the reference signal and the incident signal to be transmitted independently. Isolation resistor R2 is connected in series between Term1 and Term2 to prevent the input signal from directly entering the echo signal channel. High-frequency coupling capacitors C5 and C6 are connected in series between the Term2 port and the echo signal coupling path, and the Term4 port and the incident signal transmission path, utilizing the AC coupling function of the capacitors to separate and extract the echo signal from the incident signal while blocking the DC component, preventing the circuit's static operating point from shifting.

[0073] The amplitude and phase detector is located in the power divider circuit and amplitude and phase detector area 2-2-2. The core is the ADL5380 chip, including: power supply pins VCC1, VCC2, VCC3, signal input pins RFIP, RFIN, LOIP, LOIN, control pins ENBL, ADJ, signal output pins IHI, ILO, QHI, QLO, decoupling capacitors C1-C10, and current limiting resistors R1 and R2.

[0074] Specifically, in the amplitude and phase detector of this embodiment, such as Figure 6 As shown, a +5V DC voltage is connected to the VCC1, VCC2, and VCC3 pins respectively. A 1μF electrolytic capacitor C3 and a 1nF ceramic capacitor C6 are connected in parallel next to VCC1. A 1μF electrolytic capacitor C4 and a 1nF ceramic capacitor C7 are connected in parallel next to VCC2. A 1μF electrolytic capacitor C5 and a 1nF ceramic capacitor C8 are connected in parallel next to VCC3. The other end of each capacitor is connected to the GND1, GND2, and GND3 pins respectively and grounded.

[0075] The dual-frequency reference signal is connected to the LOIP pin via a 1nF coupling capacitor C2, and the dual-frequency echo signal is connected to the RFIP pin via a 1nF coupling capacitor C1. The RFIN and LOIN pins are directly grounded.

[0076] The ENBL pin is connected to a +5V DC voltage, the ADJ pin is directly grounded, and the NC pin is left floating.

[0077] The IHI pin is connected to a 1nF capacitor C9 via a 510Ω resistor R1. The other end of C9 is grounded. The connection point between R1 and C9 serves as the low-frequency phase difference output terminal LPDO, which is connected to the algorithm processing module 3-2 of the core control board 3.

[0078] The QHI pin is connected to a 1nF capacitor C10 via a 510Ω resistor R2. The other end of C10 is grounded. The connection point between R2 and C10 serves as the high-frequency phase difference output terminal HPDO, which is connected to the algorithm processing module 3-2 of the core control board 3.

[0079] Furthermore, the decoupling capacitors C1-C10 are used to smooth the DC voltage in the circuit and filter out low-frequency and high-frequency noise in the power supply, thereby reducing electromagnetic radiation interference and improving electromagnetic compatibility; the current limiting resistors R1 and R2 are used to condition the phase difference signal amplitude to the range of 0-3.3V to match the input voltage requirements of the microcontroller, and at the same time play an overcurrent protection role.

[0080] The ADL5380 chip is a broadband quadrature demodulation chip with an operating frequency covering 400MHz-6GHz. After receiving the dual-frequency reference signal from the INPA end and the dual-frequency echo signal from the INPB end, it separates the I-channel baseband signal (2.4GHz) and the Q-channel baseband signal (5GHz) through the internal quadrature mixer and extracts the phase difference information of the two channels simultaneously.

[0081] Ice thickness measurement based on the aforementioned ice thickness sensor is as follows: Figure 1 , Figure 2 and Figure 7 As shown, it includes the following steps;

[0082] Step 1: Install and secure all devices as required;

[0083] Step 2: Connect a 5V DC voltage via an external cable to power the dual-frequency signal generator and amplitude / phase detector; output a 3.3V DC voltage via a voltage conversion circuit to power the microcontroller and its surrounding circuits and other circuits.

[0084] Step 3: The dual-frequency signal generator emits a dual-frequency composite signal, which is then transmitted through a four-port power divider circuit. The reference signal is output to the INPA terminal of the amplitude and phase detector via a 50Ω impedance-matched microstrip line, and the incident signal is output to the feed terminal of the dual-frequency microstrip patch antenna via a coaxial cable.

[0085] Step four: The antenna radiates the incident signal to the ice layer under test and simultaneously receives the echo signal formed after reflection from the upper and lower surfaces of the ice layer, which is then transmitted to the INPB end of the amplitude and phase detector via the feeder.

[0086] Step 5: The amplitude-phase detector compares the reference signal with the dual-frequency echo signal and outputs two original phase difference signals. When the area under test is a dry, ice-free surface, the microcontroller acquires the dual-frequency phase difference under this condition as the reference phase difference, denoted as ( , ), and it is specified that the ice thickness corresponding to this state is 0mm;

[0087] Furthermore, setting an ice-free, dry plane as the reference is to eliminate the influence of the initial state of the road surface on the phase difference and ensure the accuracy of the zero point of ice thickness measurement;

[0088] Step six: Prepare high-precision standard ice layers ranging from 0mm to 50mm, setting 101 data points with a step size of 0.5mm, and calibrate the true thickness of each standard ice layer using a laser thickness gauge. (i=1,2,…,101), and then the dual-frequency phase difference corresponding to each ice layer was measured and recorded. , In the microcontroller, based on 101 sets of measured data, a system is constructed through software programming. For the X-axis, The thickness-phase difference two-dimensional feature plane along the Y-axis.

[0089] Furthermore, each coordinate point on the two-dimensional feature plane ( , (Corresponding to a unique ice thickness) That is, the thickness of the ice layer The function value at that coordinate point;

[0090] Step 7: In the microcontroller, for any measured phase difference ( , By matching the four nearest reference points in the two-dimensional feature plane, the coordinating coefficients of each phase difference interval are solved using the bilinear interpolation algorithm, and the interpolation function of the thickness of different phase difference intervals with respect to the dual-frequency phase difference is obtained.

[0091] Furthermore, let any measured phase difference be denoted as ( , The four nearest reference points in the two-dimensional feature plane are matched as follows: , , , ;

[0092] Furthermore, the bilinear interpolation algorithm is calculated as follows:

[0093] (1) Let the original mathematical model of the bilinear interpolation algorithm be:

[0094]

[0095] in, As a single-dimensional independent variable, , These are one-dimensional linear interpolation coefficients. This is the interpolation result;

[0096] (2) with For the X-axis, The measured ice thickness is shown on the Y-axis. To extend the function values ​​to a two-dimensional plane, the formula for bilinear interpolation is:

[0097]

[0098] in, This represents the measured phase difference at 2.4GHz collected by the microcontroller. This represents the measured phase difference at 5GHz acquired by the microcontroller. , These are the one-dimensional linear interpolation coefficients about the Y-axis. To obtain the measured ice thickness value after solving for the interpolation coefficients;

[0099] (3) Assume any measured phase difference ( , The four nearest reference points in the matched two-dimensional feature plane are

[0100]

[0101]

[0102]

[0103] in, , The phase difference between two adjacent reference points on the X-axis ( ), , The phase difference between two adjacent reference points on the Y-axis ( ), , , , These are the actual thickness values ​​obtained by laser calibration at four reference points;

[0104] (4) Perform one-dimensional linear interpolation in the X direction, with the Y-axis independent variable fixed as follows: When, the interpolation result in the X direction is

[0105]

[0106] When the Y-axis independent variable is fixed When the X-direction interpolation result is:

[0107]

[0108] (5) Substitute the interpolation result in the X direction into the linear interpolation in the Y direction, and the result is:

[0109]

[0110] (6) Expanding and rearranging into a polynomial form, and simplifying, we get:

[0111]

[0112] in, , , , The coordination coefficients for bilinear interpolation depend on the phase difference and thickness value of the four reference points;

[0113] (7) Substituting the four neighboring reference points into the polynomial form of the interpolation formula, since the bilinear interpolation passes through all reference points precisely, the error is 0, resulting in the following four equations:

[0114]

[0115]

[0116]

[0117]

[0118] (8) The following system of linear equations about the synergy coefficients is obtained by simplification:

[0119]

[0120]

[0121]

[0122]

[0123] (9) Transform the system of linear equations into matrix form:

[0124] =

[0125] (10) Solve the above matrix equations using microcontroller programming to obtain the coordination coefficients. , , , The value of the measured phase difference ( , By substituting the values ​​into the polynomial interpolation formula, the measured ice thickness can be obtained, thus completing the solution for the ice thickness in this phase difference interval.

[0126] Step 8: After completing the phase difference-thickness calibration of all reference points in the two-dimensional feature plane, the microcontroller can quickly solve for the ice layer thickness on any measured dual-frequency phase difference, thus completing a complete ice layer thickness calibration and measurement process.

[0127] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An ice thickness sensor based on a dual-frequency antenna, characterized in that, The system includes a metal casing (1), an RF board (2), a core control board (3), a dual-frequency microstrip patch antenna (4), a dual-frequency signal generator, a power divider circuit, an amplitude and phase detector, and an algorithm processing module (3-2). The RF board (2) and the core control board (3) are fixed in parallel on the internal support platform (1-4) of the metal casing (1). The dual-frequency microstrip patch antenna (4) is fixed to the antenna mounting position (2-3) of the RF board (2). The dual-frequency signal generator, the power divider circuit, and the amplitude and phase detector are integrated in the RF module area (2-2) of the RF board (2). The algorithm processing module (3-2) is mounted on the core control board (3). The dual-frequency signal generator, the power divider circuit, the dual-frequency microstrip patch antenna (4), the amplitude and phase detector, and the algorithm processing module (3-2) are connected in sequence. The metal casing (1) is provided with mounting screw holes (1-1), a wave-transparent window (1-2), a cable hole (1-3), and an internal support platform (1-4); the mounting screw holes (1-1) are four M4 through holes located at the four bottom corners of the metal casing (1); the wave-transparent window (1-2) is a rectangular opening facing the radiating surface of the dual-frequency microstrip patch antenna (4), and a polytetrafluoroethylene cover plate is pasted below the opening; the inner wall of the cable hole (1-3) is wrapped with a rubber sealing ring; the internal support platform (1-4) consists of two platforms of the same height, with M3 screw holes on the upper surface; The radio frequency board (2) is provided with board mounting holes (2-1), radio frequency module area (2-2), antenna mounting position (2-3) and wiring terminals (2-4); the board mounting holes (2-1) are 4 M3 through holes, which are aligned with the screw holes of the internal support platform (1-4); the radio frequency module area (2-2) is divided into a dual-frequency signal generator area (2-2-1) and a power divider circuit and amplitude and phase detector area (2-2-2); the wiring terminals (2-4) are 3-pin headers, which are plugged and plugged into the wiring terminals (3-3) of the core control board (3); The dual-band microstrip patch antenna (4) includes a ground layer (4-1), a dielectric substrate (4-2), a 2.4GHz radiating patch (4-3), a 5GHz radiating patch (4-4), and a microstrip feed line (4-5). The ground layer (4-1) is made of copper foil and is attached to the lower surface of the dielectric substrate (4-2). The dielectric substrate (4-2) is made of FR4_epoxy material with a thickness of 1mm, a relative permittivity εr=4.4, and a loss tangent TanD=0.

02. The 2.4GHz radiating patch (4-3) is a rectangular copper structure and covers the upper surface of the dielectric substrate (4-2). The 5GHz radiating patch (4-4) is a narrow rectangular copper structure. The microstrip feed line (4-5) is impedance matched with 50Ω and connected to the power divider circuit through an SMA connector. The dual-frequency signal generator includes a 2.4GHz low-frequency signal generation unit, a 5GHz high-frequency signal generation unit, a 50Ω impedance matching output port, a synchronization control module, a core drive circuit, and a signal amplification unit. The synchronization control module synchronously drives the two signal generation units to generate a dual-frequency composite signal, which is amplified by the signal amplification unit and then input to the power divider circuit through the 50Ω impedance matching output port. The power divider circuit is a four-port structure, including a four-port impedance matching unit, a high-frequency filtering unit, and an isolation coupling unit. The four-port impedance matching unit includes four 50Ω impedance matching ports Term1, Term2, Term3, and Term4, and a 50Ω impedance matching microstrip line. The linewidth and length of the impedance matching microstrip line are optimized by ADS simulation. The high-frequency filtering unit includes multilayer inductors L1-L4 and high-frequency capacitors C1-C4. The isolation coupling unit includes isolation resistors R1 and R2 and high-frequency coupling capacitors C5 and C6.

2. The ice thickness sensor based on a dual-frequency antenna according to claim 1, characterized in that, The core of the amplitude and phase detector is the ADL5380 chip, which includes an amplitude and phase detection ADL5380 chip unit, an input signal matching unit, a power supply filtering unit, and an output signal conditioning unit. The input signal matching unit is equipped with 1nF C0G dielectric capacitors C1 and C2, which are connected in series between the INPA terminal, the INPB terminal, and the chip pin, respectively. The power supply filtering unit consists of 1μF electrolytic capacitors C3 and C5 and 1nF ceramic capacitors C6, C7, and C8. The output signal conditioning unit is equipped with 510Ω metal foil resistors R1 and R2 and 1nF ceramic capacitors C9 and C10. The output terminals are LPDO and HPDO, which are connected to the algorithm processing module (3-2).

3. The ice thickness sensor based on a dual-frequency antenna according to claim 1, characterized in that, The algorithm processing module (3-2) includes a voltage conversion circuit (3-2-1) and a microcontroller and its surrounding circuits (3-2-2); the voltage conversion circuit (3-2-1) converts 5V DC voltage to 3.3V DC voltage; the microcontroller and its surrounding circuits (3-2-2) are used to construct a two-dimensional feature plane of thickness-phase difference and solve the ice layer thickness through a bilinear interpolation algorithm.

4. A method for measuring ice thickness based on the sensor described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Install and secure the metal casing, RF board, and core control board, ensuring that the wave-transmitting window faces the ice layer under test and that the dual-band microstrip patch antenna is unobstructed. S2. Connects to 5V DC voltage via an external cable to power the dual-frequency signal generator and amplitude / phase detector; outputs 3.3V DC voltage via a voltage conversion circuit to power the microcontroller and its surrounding circuits and other circuits. S3. The dual-frequency signal generator outputs a dual-frequency composite signal, which is then transmitted through a four-port power divider circuit. The reference signal is output to the INPA terminal of the amplitude and phase detector via a 50Ω impedance-matched microstrip line, and the incident signal is output to the feed terminal of the dual-frequency microstrip patch antenna via a coaxial cable. S4. The dual-frequency microstrip patch antenna radiates the incident signal to the ice layer under test and simultaneously receives the echo signal formed after reflection from the upper and lower surfaces of the ice layer, which is then transmitted to the INPB end of the amplitude and phase detector via the feeder. S5. The amplitude and phase detector compares the reference signal with the dual-frequency echo signal and outputs two original phase difference signals. Taking a dry, ice-free plane as a reference, the microcontroller collects the dual-frequency phase difference in this state as the reference phase difference. The ice thickness corresponding to this state is specified as 0mm. S6. Prepare high-precision standard ice layers of 0mm-50mm, set data points with a step size of 0.5mm, calibrate the actual thickness with a laser thickness gauge, and measure and record the dual-frequency phase difference corresponding to each ice layer; construct a two-dimensional feature plane of thickness-phase difference in the microcontroller based on the measured data. S7. For any measured dual-frequency phase difference, match the four nearest reference points in the two-dimensional feature plane, and use the bilinear interpolation algorithm to solve the coordination coefficient of each phase difference interval to obtain the interpolation function of thickness with respect to dual-frequency phase difference. S8. Substitute the measured dual-frequency phase difference into the interpolation function to solve for the ice thickness value, thus completing one ice thickness measurement.

5. The ice thickness measurement method according to claim 4, characterized in that, The polynomial form of the bilinear interpolation algorithm in step S7 is: ； in, , , , The coordination coefficients for bilinear interpolation. The measured phase difference is 2.4GHz. The measured phase difference is at 5GHz. This is the measured ice thickness value.

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