Miniaturized non-contact water flow velocity measurement radar system based on FMCW

Abstract

The invention discloses an FMCW-based miniaturized non-contact water flow velocity measurement radar system, and the system comprises a microstrip array antenna which radiates a linear frequency modulation continuous wave to a target area, and receives an echo signal; the radio frequency module generates a linear frequency modulation continuous wave, converts an echo signal of the microstrip array antenna into an electric signal, processes the electric signal to generate an intermediate frequency signal, and transmits the intermediate frequency signal to the control module; the control module coordinates the synchronism of signal emission and receiver data acquisition in the radio frequency module, processes the received intermediate frequency signal and calculates the flow rate; the power supply module provides required power for the radio frequency module and the control module. The system can be widely applied to dynamic monitoring of water areas such as rivers and the like by transmitting millimeter wave signals to the water surface and utilizing Doppler effect and scattering characteristics of echo signals to extract water velocity information, can be integrated on an unmanned aerial vehicle, can flexibly cover large-range water areas, supports rapid deployment of complex terrains and remote areas, and has a wide application prospect. And efficient data support is provided for flood prevention early warning, water resource management and environment monitoring.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrological monitoring, and in particular relates to a miniaturized non-contact water flow velocity measurement radar system based on FMCW. Background Art

[0002] Water velocity measurement technology is one of the core technologies in the field of hydrological monitoring and is widely used in water conservancy projects, flood prevention and disaster reduction, environmental monitoring, and water resources management. Traditional water velocity measurement methods mainly rely on contact equipment such as mechanical current meters, buoys, and acoustic Doppler current meters (ADCPs). These methods measure flow velocity through direct or indirect contact with the water body and have a certain degree of accuracy, but they have many limitations in practical applications. With global climate change and the frequent occurrence of extreme hydrological events, the demand for real-time and accurate monitoring of water flow parameters is increasing, which has promoted the continuous development of water velocity measurement technology.

[0003] In recent years, non-contact water velocity measurement technologies, including lidar, ultrasonic radar, and radar, have gradually gained attention. Lidar calculates flow velocity by emitting laser pulses and measuring the reflection time. It is highly accurate and non-contact, but is susceptible to interference from weather conditions such as rain and fog. Ultrasonic radar uses the Doppler effect of sound waves to measure flow velocity, but its accuracy decreases in water bodies with high sediment content. Radar technology, particularly frequency-modulated continuous wave (FMCW) radar, has become a research hotspot in the field of water velocity measurement due to its all-weather capability, high accuracy, and non-contact characteristics. FMCW radar transmits a continuously frequency-modulated signal and analyzes the Doppler frequency shift and Bragg scattering characteristics of the echo signal, enabling real-time and accurate water velocity measurement.

[0004] With technological advancements, water velocity measurement technology is evolving towards miniaturization, low power consumption, low cost, and high precision. Miniaturization facilitates deployment in resource-constrained scenarios, such as remote river channels or temporary monitoring sites. Low power consumption supports long-term operation and battery operation, adapting to remote monitoring needs. Low cost promotes widespread application and adoption of the technology. High-precision measurements meet the data quality requirements of modern hydrological monitoring.

[0005] However, existing technologies still face several challenges in practical application. Contact-based devices are susceptible to environmental influences and have high maintenance costs. Non-contact technologies such as lidar and ultrasonic radar are less adaptable in inclement weather or complex hydrological environments. While FMCW radar systems have advantages, their size, power consumption, and cost still need to be optimized. Furthermore, measurement accuracy and stability in high-speed or turbulent water conditions require further improvement.

[0006] In summary, the development of water velocity measurement technology reflects a trend from contact to non-contact, from small to large ranges, and from single-parameter to multi-parameter monitoring. As an emerging non-contact measurement method, FMCW radar technology holds broad application prospects, but it still requires continuous improvement in miniaturization, low power consumption, low cost, and high precision to meet the diverse needs of modern hydrological monitoring. Summary of the Invention

[0007] In view of the shortcomings of the above-mentioned traditional water flow velocity measurement technology and existing FMCW radar systems in hydrological monitoring applications, the present invention aims to design a miniaturized, low-power, low-cost and high-precision FMCW-based miniaturized non-contact water flow velocity measurement radar system to meet the diverse needs of modern hydrological monitoring.

[0008] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows: a miniaturized non-contact water flow velocity measurement radar system based on FMCW, integrated on a UAV platform, including a modularly designed microstrip array antenna, a radio frequency module, a control module and a power module;

[0009] The microstrip array antenna is used to radiate the linear frequency modulated continuous wave to the target area and receive its echo signal;

[0010] The radio frequency module is used to generate a linear frequency modulated continuous wave, and convert the echo signal of the microstrip array antenna into an electrical signal, and generate an intermediate frequency signal after processing the signal to transmit to the control module;

[0011] The control module is used to coordinate the synchronization of signal transmission in the radio frequency module and data acquisition in the receiver, as well as to process the received intermediate frequency signal and calculate the flow rate;

[0012] The power supply module provides required power to the radio frequency module and the control module.

[0013] Furthermore, the microstrip antenna array includes a plurality of microstrip patch antennas;

[0014] Each of the microstrip patch antennas comprises a ground layer, a dielectric substrate and a conductor patch arranged in sequence from bottom to top, and a microstrip feeder integrally formed with the conductor patch;

[0015] Rectangular slot structures are provided on the conductor patch on both sides of the microstrip feed line;

[0016] The method for determining the size of the rectangular slotted structure is as follows:

[0017] During the matching optimization process of the microstrip patch antenna, the slot depth of the rectangular slot structure is first adjusted to adjust its resonance point to near the target frequency, and then the slot width is adjusted to optimize the S11 parameter.

[0018] Furthermore, the width W and length L of each of the conductor patches are respectively:

[0019]

[0020] Where, represents the resonant frequency of the microstrip patch antenna, ε r represents the dielectric constant, ε0 represents the dielectric constant of vacuum, w represents the patch width, c represents the speed of light in vacuum, μ0 represents the magnetic permeability of vacuum, ΔL represents the stretched length of the microstrip transmission antenna, ε eff represents the effective dielectric constant, and h represents the dielectric height.

[0021] Furthermore, the microstrip antenna array connects the microstrip patch antennas via a series-parallel hybrid feeding network;

[0022] In the feeding network, the transmission signal is evenly distributed to each microstrip patch antenna through a T-type power divider, and a 1 / 4 wavelength impedance converter for impedance matching is connected between the main feed line and the input port of the microstrip feed line in each microstrip patch antenna.

[0023] Furthermore, the 1 / 4 wavelength impedance converter changes the impedance ratio of port 2 and port 3 by controlling the output power ratio of the two ports, thereby achieving impedance matching;

[0024] Among them, port 2 is the branch of the main line port 1 after the current is divided into two and does not flow to the 1 / 4 wavelength converter, and port 3 is the branch of the main line port 1 after the current is divided into two and passes through the 1 / 4 wavelength converter.

[0025] Furthermore, the input impedance and port matching performance of the feed network are optimized by adjusting the width of the 1 / 4 wavelength impedance transformer at the input port;

[0026] The port matching performance is determined according to the S parameters of the input port.

[0027] Furthermore, the radio frequency module is a dual-channel transceiver architecture, including a transmit link and a receive link;

[0028] The transmission chain includes a crystal oscillator, a phase-locked loop, a low-pass filter and a frequency synthesizer connected in sequence, and the output end of the frequency synthesizer is connected to the microstrip array antenna of the transmitting end;

[0029] The receiving link is a zero intermediate frequency architecture, including a four-channel receiving down-converter, whose input end is connected to the microstrip array antenna at the receiving end.

[0030] Furthermore, the microstrip array antenna at the transmitting end is an array antenna composed of 4×12 microstrip patch antennas;

[0031] The microstrip array antenna at the receiving end is an array antenna composed of dual-channel 2×12 microstrip patch antennas.

[0032] Furthermore, the loop filter includes a phase detector and a voltage-controlled oscillator;

[0033] The phase detector and the voltage controlled oscillator are connected via a stabilizing circuit;

[0034] The stabilization circuit includes a grounded capacitor C1, the non-grounded end of the grounded capacitor C1 is respectively connected to the output end of the phase detector, one end of the resistor R1 and one end of the resistor R2, the other end of the resistor R1 is grounded, and the other end of the resistor R2 is respectively connected to the grounded capacitor and the input end of the voltage-controlled oscillator.

[0035] Furthermore, the power supply module supplies power to the RF module and the power supply module through a step-by-step step-down DCDC power supply chip and a low voltage difference linear regulator.

[0036] The beneficial effects of the present invention are:

[0037] (1) The present invention designs a radar RF front-end system suitable for water flow velocity measurement, which adopts efficient signal generation and zero intermediate frequency receiving architecture to ensure the high stability and low noise characteristics of frequency modulated continuous wave signals. Compared with traditional complex RF systems, this design simplifies the circuit structure and reduces power consumption, which is suitable for the long-term operation requirements of UAV platforms. At the same time, it enhances the ability to capture weak echo signals, effectively improving the measurement accuracy in complex hydrological environments.

[0038] (2) The miniaturized single-transmitter, dual-receiver microstrip array antenna designed in the present invention achieves high gain and narrow beam characteristics, significantly improving the signal directivity and receiving sensitivity. Compared with traditional large antennas, the antenna is small in size and light in weight, making it easier to mount on drones. The optimized feeding network reduces mutual coupling interference, ensuring stable capture of surface reflection signals, and providing reliable support for non-contact water flow velocity measurement.

[0039] (3) The system of the present invention efficiently integrates the RF front-end, antenna array and control circuit through modular design, achieving the unity of miniaturization, low cost and high environmental adaptability; compared with traditional fixed equipment, the system can be flexibly deployed in remote or complex waters with the help of UAV platforms, and combined with optimized signal processing algorithms, it significantly improves the measurement coverage and data reliability, providing a convenient solution for flood prevention and warning and water resources management. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1This is a structural diagram of the miniaturized FMCW-based non-contact water flow velocity measurement system provided by the present invention.

[0041] Figure 2 This is a structural diagram of the microstrip patch antenna provided by the present invention.

[0042] Figure 3 This is a structural diagram of the microstrip array antenna provided by the present invention.

[0043] Figure 4 This is a structural diagram of the 1 / 4 wavelength impedance converter provided by the present invention.

[0044] Figure 5 Schematic diagram of the microstrip antenna array at the transmitting end and the receiving end provided by the present invention.

[0045] Figure 6 This is a circuit connection diagram of the miniaturized FMCW-based non-contact water flow velocity measurement system provided by the present invention.

[0046] Figure 7 This is a circuit diagram of the loop filter provided by the present invention. DETAILED DESCRIPTION

[0047] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0048] The embodiment of the present invention provides a miniaturized non-contact water flow velocity measurement radar system based on FMCW, which is integrated on a UAV platform. Figure 1 As shown, it includes a modularly designed microstrip array antenna, a radio frequency module, a control module and a power supply module;

[0049] The microstrip array antenna is used to radiate the linear frequency modulated continuous wave to the target area and receive its echo signal;

[0050] The RF module is used to generate linear frequency modulated continuous waves and convert the echo signal of the microstrip array antenna into an electrical signal, and then process it to generate an intermediate frequency signal and transmit it to the control module;

[0051] The control module is used to coordinate the synchronization of signal transmission in the RF module and data acquisition in the receiver, as well as to process the received intermediate frequency signal and calculate the flow rate;

[0052] The power module provides the required power for the RF module and the control module.

[0053] In the embodiment of the present invention, Figure 2 As shown, the microstrip antenna array includes several microstrip patch antennas;

[0054] Each microstrip patch antenna includes a ground layer, a dielectric substrate, and a conductor patch arranged in sequence from bottom to top, and a microstrip feed line integrally formed with the conductor patch;

[0055] Rectangular slot structures are provided on the conductor patch on both sides of the microstrip feed line;

[0056] The method for determining the size of the rectangular slotted structure is:

[0057] During the matching optimization process of the microstrip patch antenna, the slot depth of the rectangular slot structure is first adjusted to adjust its resonance point to near the target frequency, and then the slot width is adjusted to optimize the S11 parameter.

[0058] Compared to traditional microstrip patch antennas, the microstrip patch antenna provided in this embodiment has a rectangular slot structure design. By slotting the conductor patch, the impedance matching and radiation characteristics of the antenna are optimized. Specifically, the change in the depth of the rectangular slot structure not only has a significant impact on S11, but also has a great impact on the position of the antenna resonance point. The change in the slot width has a greater impact on S11, but has a relatively small impact on the resonance point of the patch antenna. Therefore, in the matching optimization process of the unit antenna, the resonance point of the antenna can be adjusted to near the target frequency by adjusting the slot depth, and then the slot width can be adjusted to optimize the S11 depth. The slot of the patch antenna can optimize the impedance matching of the antenna, optimize the antenna performance, and better meet the required indicators.

[0059] The rectangular slot structure in this embodiment changes the current distribution on the conductor patch, so that the antenna has better resonance characteristics at a frequency of 24 GHz, thereby improving the bandwidth gain. The broadened working bandwidth is compatible with the Doppler frequency shift caused by different water flow velocities (such as high-speed flow during flood season and slow flow during dry season), avoiding signal truncation and distortion caused by insufficient bandwidth of traditional antennas.

[0060] In this embodiment, the microstrip patch antenna generates electromagnetic radiation by utilizing transverse currents at the edge of the microstrip. When the patch size approaches the harmonic wavelength, the current forms a standing wave distribution at the edge of the patch, generating an electric field component perpendicular to the patch. The edge gap between the patch and the ground plane can be regarded as an equivalent magnetic current source, radiating electromagnetic waves outward through the gap. According to cavity mode theory, the microstrip antenna can be regarded as a resonant cavity formed by upper and lower metal plates. The electric field in the cavity undergoes a sudden change at the edge of the patch, forming a radiation field. Its radiation efficiency is closely related to the thickness and dielectric constant of the dielectric substrate and the shape of the patch. The patch size is usually adjusted to achieve resonance in a specific frequency band to meet the frequency requirements of the communication system.

[0061] Based on this, the width W and length L of each conductor patch in this embodiment are respectively:

[0062]

[0063] Where, represents the resonant frequency of the microstrip patch antenna, ε r represents the dielectric constant, ε0 represents the dielectric constant of vacuum, w represents the patch width, c represents the speed of light in vacuum, μ0 represents the magnetic permeability of vacuum, ΔL represents the stretched length of the microstrip transmission antenna, ε eff represents the effective dielectric constant, and h represents the dielectric height.

[0064] In this embodiment, the thickness and dielectric constant of the dielectric substrate in the microstrip patch antenna directly affect the efficiency and bandwidth of the microstrip antenna. Although a thicker substrate can enhance radiation, it is easy to excite surface waves, resulting in reduced efficiency. High dielectric constant materials can reduce the size of the antenna, but will reduce radiation efficiency and limit bandwidth. The size of the conductor patch determines the resonant frequency, and changes in its shape (such as rectangular, circular, and slot structures) can adjust the directivity and polarization characteristics. The feeding method (such as microstrip line feeding and coaxial line feeding) will affect the impedance matching and radiation pattern. In addition, changes in environmental parameters such as temperature and humidity will change the dielectric properties, resulting in a shift in the resonant frequency, so environmental adaptability must be considered in the design.

[0065] The manufacturing process of the microstrip patch antenna provided in this embodiment features convenient processing and significant cost-effectiveness, while also enabling multi-dimensional parameter optimization. By tuning geometric parameters and matching material properties, flexible control of resonant frequency, adaptive adjustment of polarization direction, radiation mode switching, and impedance matching optimization are achieved. This allows key performance indicators to be decoupled and adjusted based on physical parameters such as substrate thickness, patch size, and dielectric constant. Furthermore, its small size, light weight, and ease of integration facilitate the miniaturization requirements of this design.

[0066] In the embodiment of the present invention, Figure 3 As shown, the microstrip antenna array connects each microstrip patch antenna through a series-parallel hybrid feeding network;

[0067] In the feeding network, the transmitted signal is evenly distributed to each microstrip patch antenna through a T-type power divider, and a 1 / 4 wavelength impedance transformer is used to connect the main feed line and the input port of the microstrip feed line in each microstrip patch antenna to achieve impedance matching.

[0068] Specifically, hybrid feeding refers to the combination of series feeding and parallel feeding, which has advantages and disadvantages between series feeding and parallel feeding.

[0069] In this embodiment, the 1 / 4 wavelength impedance converter can be placed next to the output port or at a distance 1 / 2 from the output port. In this embodiment, the case of placing the converter next to the output port is taken as an example.

[0070] The quarter-wavelength impedance converter in this embodiment primarily provides impedance matching and is used when the load impedance does not match the characteristic impedance of the transmission line. Even if the main feeder is 50 ohms, the input impedance of each antenna element may not be 50 ohms, resulting in an impedance mismatch and, consequently, reflections. Therefore, a quarter-wavelength converter is required between each antenna element and the main feeder to convert the antenna element's impedance to 50 ohms, thereby reducing reflections.

[0071] In this embodiment, if Figure 4 As shown in the figure, the entire feed network can be regarded as a "one-to-two" basic power division structure, which is gradually nested from the two ends to the middle. Figure 4 In the figure, the main current is divided into two at the node, and the 1 / 4 wavelength impedance converter changes the impedance ratio of port2 and port3 by controlling the output power ratio of the two ports, thereby achieving impedance matching.

[0072] Among them, port 2 is the branch of the main line port 1 after the current is divided into two and does not flow to the 1 / 4 wavelength converter, and port 3 is the branch of the main line port 1 after the current is divided into two and passes through the 1 / 4 wavelength converter.

[0073] The working principle of this embodiment is to change the input impedance of the port3 branch by using 1 / 4 wavelength impedance transformation, thereby changing the impedance ratio of the two parallel branches port2 and port3, and correspondingly changing the current ratio of the two branches.

[0074] The function of the feed network in this embodiment is to adjust the output current of each output port to achieve amplitude weighting of the unit. This function is mainly achieved by examining the transmission coefficients of the input and output ports, that is, the amplitudes of the S parameters. The optimization approach is mainly to adjust the width of the 1 / 4 wavelength impedance transformer of the corresponding output port to optimize the amplitude ratio so that it is consistent with the expectation. As shown in the figure below, changing the width of the 1 / 4 wavelength impedance transformer between port 1 and port 2 will significantly change the transmission coefficient of the corresponding port 1, while having little effect on the transmission coefficients of other unrelated ports.

[0075] The working rules of the feeding network can be intuitively discovered through the current distribution on the feeding network: the surface current starts from the input port in the form of a wave, flows to each output port almost in phase after passing through the feeding network, and the current distribution of each output port also presents a tapered distribution of "large in the middle and small on both sides" under the adjustment of each impedance transformer.

[0076] In this embodiment, to achieve decoupling of the microstrip antenna array, for an M×N rectangular array antenna, the minimum spacing requirement between each microstrip patch antenna is as follows: To avoid strong electromagnetic coupling between adjacent array elements (resulting in signal loss or radiation pattern distortion), the spacing between rows and columns of the microstrip patch antennas must meet the following requirements:

[0077]

[0078] Where λ is the operating wavelength and θ is the beam pointing angle. To suppress sidelobes or optimize beam pointing, the spacing can be increased appropriately. However, do not increase it too much, as excessive spacing may result in multiple main lobes (grating lobes) in the radiation pattern, leading to energy dispersion.

[0079] After completing the design of the antenna unit and the feed network, the last step is to combine the two and design a microstrip array antenna that meets the index requirements, such as Figure 5 The figure shows the schematic diagram of the array antenna structure simulated by HFSS. Among them, the microstrip array antenna at the transmitting end is an array antenna composed of 4×12 microstrip patch antennas; the microstrip array antenna at the receiving end is an array antenna composed of dual-channel 2×12 microstrip patch antennas.

[0080] In this embodiment, in order to avoid mismatching of the combined microstrip array antenna, its input and output ports need to be optimized. The optimization method is to optimize the input impedance and port matching performance of the feeding network by adjusting the width of the 1 / 4 wavelength impedance transformer at the input port.

[0081] The port matching performance is determined according to the S parameters of the input port.

[0082] Furthermore, simulations show that the S11 parameter curve in a rectangular coordinate system shows that within the 20 GHz to 30 GHz frequency range, the resonance center is located at 24 GHz, indicating good matching. The Smith chart of the S11 parameter shows that the curve circles around the center with a small radius, and the real part of the normalized input impedance at the center frequency of 24 GHz is 0.9363, and the imaginary part is 0.0052, that is, the real part is close to 1 and the imaginary part is close to 0, which also shows that the feed network has good matching characteristics over a wide frequency band.

[0083] In this embodiment, the microstrip array antenna adopts a layout structure of one transmitting channel and two receiving channel antennas. In order to avoid the influence of this layout on the coupling characteristics of the transmitting antenna, combined with the isolation requirements between the transmitting and receiving channels given by the chip, the isolation of the two receiving antennas relative to the transmitting antenna is required to be no less than 30dB.

[0084] Furthermore, based on the miniaturization requirements of the present invention, the entire board layout should be kept as small and compact as possible. To facilitate subsequent testing, the three antennas all use coaxial bottom feeding. The entire dielectric substrate still uses Rogers4350 material with a thickness of 0.254mm. The entire board size is 92mm×87mm. The circuit board actually used in the system can be slightly shortened in length due to the use of microstrip feeding.

[0085] In the embodiment of the present invention, Figure 6 As shown, the RF module has a dual-channel transceiver architecture, including a transmit link and a receive link.

[0086] The transmission chain in this embodiment includes a crystal oscillator, a phase-locked loop, a low-pass filter, and a frequency synthesizer connected in sequence. The output end of the frequency synthesizer is connected to the microstrip array antenna at the transmitting end. Among them, the phase-locked loop is used to generate a linear frequency modulation wave of the transmission signal, and the frequency synthesizer is used to transmit the generated linear frequency modulation wave. The function of the loop filter is to convert the current form of the charge pump output into a voltage form and filter out high-frequency spurious, voltage ripple, and out-of-band noise.

[0087] In a specific example of this embodiment, the model of the phase-locked loop is ADF4159, which includes a low-noise digital phase detector, a precision programmable charge pump, and a programmable frequency divider. It can be used for FSK frequency shift keying modulation and PSK phase shift keying modulation. In addition, it can also generate wide-band swept frequency signal outputs, such as triangle wave and sawtooth linear swept frequency waveforms.

[0088] In a specific example of this embodiment, the frequency synthesizer is the ADF5901, a 24 GHz Tx monolithic microwave integrated circuit (MMIC) with an integrated 24 GHz VCO and dual Tx channels covering the 250 MHz ISM band (24 GHz to 24.25 GHz) for radar systems. The VCO generates a 24 GHz signal for both Tx channels and the LO output. Each Tx channel includes power control circuitry and a temperature sensor. All on-chip registers are controlled via a simple 4-wire interface. The VCO is connected to two transmitter PAs, providing 8 dBm output power, driving the LO outputs of the ADF5904 receiver, and providing differential auxiliary outputs for closed-loop control via the ADF4159 ramp generation PLL. The chipset combines these components to form a complete 24 GHz radar system RF signal chain.

[0089] In this embodiment, the loop filter includes a phase detector and a voltage controlled oscillator;

[0090] The phase detector and the voltage controlled oscillator are connected through a stabilizing circuit;

[0091] like Figure 7 As shown, the stabilization circuit includes a grounded capacitor C1, the non-grounded end of the grounded capacitor C1 is respectively connected to the output end of the phase detector, one end of the resistor R1 and one end of the resistor R2, the other end of the resistor R1 is grounded, and the other end of the resistor R2 is respectively connected to the grounded capacitor and the input end of the voltage-controlled oscillator.

[0092] In this embodiment, the loop filter is essentially a low-pass filter (LPF) constructed by R, C, or OPA. When the loop filter is in an open-loop state, its transfer function has a second-order pole when S is 0. Because its phase-frequency characteristic is a constant, the loop is in an unstable state.

[0093] In this embodiment, if Figure 7 As shown, in order to solve the unstable state of the loop, a stabilization circuit is designed in this embodiment. A branch structure of a resistor and a capacitor in series is adopted in the stabilization circuit, and a capacitor is introduced at the control voltage end. The addition of the resistor and capacitor series branch increases the transmission zero point in the transfer function. The introduction of the transmission zero point can improve the filtering ability of the filter and improve the stability of the loop filtering.

[0094] The receiving chain in this embodiment is a zero intermediate frequency architecture, including a four-channel receiving down-converter, whose input end is connected to the microstrip array antenna at the receiving end.

[0095] In a specific example of this embodiment, the receiver downconverter is the ADF5904, which uses a local oscillator input signal or an LO source generated by the ADF5901 to downconvert the receiver signal. All RF inputs on the ADF5904 are simple single-ended inputs that are internally connected to an integrated balun, which converts the receiver signal to a differential signal for higher amplification performance and downconversion. When designing the connection between the IC's RF port and the printed circuit board (PCB) antenna, the single-ended RF interface connection greatly simplifies the PCB design task; only 50 PCB traces are required, eliminating the need for external matching passive components, saving a significant amount of board space and achieving the design's miniaturization requirements.

[0096] In this embodiment of the present invention, the control module's main functions include: 1. RF front-end signal control: configuring the ADF4159 to generate FMCW modulation signals and controlling the operating parameters of the ADF5901 and ADF5904. 2. Data acquisition management: driving the ADC chip (AD9226) to sample the intermediate frequency signal and transmit the data to the FPGA. 3. Signal processing: implementing algorithms such as FFT, filtering, and flow velocity calculation. 4. Timing synchronization: ensuring the coordinated operation of all system modules.

[0097] In a specific example of this embodiment, the control module is based on the Alinx AC7020 development board and uses the Zynq7000's XC7Z020-1CLG400C chip. The core board has a streamlined size of 75mmx64mm, and the PCB adopts an 8-layer board design. The chip integrates an ARM Cortex-A9 dual-core processor and a programmable logic unit (PL). The memory has 4GB DDR3 SDRAM, which supports high-speed data processing; it has 256MB Quad SPI Flash for storing system startup images and configuration data. It has both software algorithm operation and hardware parallel processing capabilities, and is suitable for application scenarios of miniaturized water flow velocity radar systems that require the combination of software algorithms and hardware parallel processing.

[0098] In an embodiment of the present invention, the power module supplies power to the RF module and the power supply module through a step-by-step step-down DCDC power chip and a low voltage drop linear regulator.

[0099] In this embodiment, a low-dropout linear regulator (LDO) is a simple, low-cost solution, but is limited by efficiency and voltage drop and is suitable for low-current, low-noise scenarios. A DC-DC converter sacrifices some noise and complexity to achieve high efficiency and wide voltage adaptability, making it the core of high-current, high-performance systems. This system uses both to balance efficiency, noise, and cost.

[0100] In a specific example of this embodiment, the model of the DCDC chip is SCT2430, and the model of the LDO is LM1117. Specifically, the SCT2430 chip is used to first reduce the 12V voltage to 5V, and then the LM1117 chip can convert the 5V voltage to 3.3V or 1.8V to meet our power supply requirements, and the LM1117 chip is used to reduce the 5V voltage to 3.3V and 1.8V.

[0101] Based on the above-mentioned system structure, the present invention transmits millimeter-wave signals to illuminate the water surface and uses the Doppler effect and scattering characteristics of the echo signal to extract water flow velocity information. It can be widely used in the dynamic monitoring of water bodies such as rivers, reservoirs and channels. The system is integrated into an unmanned aerial vehicle platform, which can flexibly cover a large area of ​​water and support rapid deployment in complex terrain and remote areas, providing efficient data support for flood prevention and warning, water resources management and environmental monitoring.

[0102] Specific embodiments are used in the present invention to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas. At the same time, for those skilled in the art, according to the ideas of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

[0103] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and it should be understood that the scope of protection of the present invention is not limited to such specific descriptions and embodiments. Those skilled in the art can make various other specific variations and combinations based on the technical teachings disclosed in the present invention without departing from the essence of the present invention, and such variations and combinations are still within the scope of protection of the present invention.

Claims

1. A miniaturized non-contact water velocity measurement radar system based on FMCW, integrated on an unmanned aerial vehicle platform, characterized by: Includes modularly designed microstrip array antenna, RF module, control module and power module; The microstrip array antenna is used to radiate the linear frequency modulated continuous wave to the target area and receive its echo signal; The radio frequency module is used to generate a linear frequency modulated continuous wave, and convert the echo signal of the microstrip array antenna into an electrical signal, and generate an intermediate frequency signal after processing the signal to transmit to the control module; The control module is used to coordinate the synchronization of signal transmission in the radio frequency module and data acquisition in the receiver, as well as to process the received intermediate frequency signal and calculate the flow rate; The power supply module provides required power to the radio frequency module and the control module.

2. The miniaturized non-contact water flow velocity measurement radar system based on FMCW according to claim 1 is characterized in that: The microstrip antenna array includes a plurality of microstrip patch antennas; Each of the microstrip patch antennas comprises a ground layer, a dielectric substrate and a conductor patch arranged in sequence from bottom to top, and a microstrip feeder integrally formed with the conductor patch; Rectangular slot structures are provided on the conductor patch on both sides of the microstrip feed line; The method for determining the size of the rectangular slotted structure is as follows: During the matching optimization process of the microstrip patch antenna, the slot depth of the rectangular slot structure is first adjusted to adjust its resonance point to near the target frequency, and then the slot width is adjusted to optimize the S11 parameter.

3. The miniaturized non-contact water flow velocity measurement radar system based on FMCW according to claim 2 is characterized in that: The width W and length L of each conductor patch are respectively: Where, represents the resonant frequency of the microstrip patch antenna, ε r represents the dielectric constant, ε0 represents the dielectric constant of vacuum, w represents the patch width, c represents the speed of light in vacuum, μ0 represents the magnetic permeability of vacuum, ΔL represents the stretched length of the microstrip transmission antenna, ε eff represents the effective dielectric constant, and h represents the dielectric height.

4. The miniaturized non-contact water flow velocity measurement radar system based on FMCW according to claim 2 is characterized in that: The microstrip antenna array connects the microstrip patch antennas via a series-parallel hybrid feeding network; In the feeding network, the transmission signal is evenly distributed to each microstrip patch antenna through a T-type power divider, and a 1 / 4 wavelength impedance converter for impedance matching is connected between the main feed line and the input port of the microstrip feed line in each microstrip patch antenna.

5. The miniaturized non-contact water flow velocity measurement radar system based on FMCW according to claim 4 is characterized in that: The 1 / 4 wavelength impedance converter changes the impedance ratio of port 2 and port 3 by controlling the output power ratio of the two ports, thereby achieving impedance matching; Among them, port 2 is the branch of the main line port 1 after the current is divided into two and does not flow to the 1 / 4 wavelength converter, and port 3 is the branch of the main line port 1 after the current is divided into two and passes through the 1 / 4 wavelength converter.

6. The miniaturized non-contact water flow velocity measurement radar system based on FMCW according to claim 4 is characterized in that: By adjusting the width of the 1 / 4 wavelength impedance transformer at the input port, the input impedance and port matching performance of the feed network are optimized; The port matching performance is determined according to the S parameters of the input port.

7. The miniaturized non-contact water flow velocity measurement radar system based on FMCW according to claim 2 is characterized in that: The RF module has a dual-channel transceiver architecture, including a transmit link and a receive link; The transmission chain includes a crystal oscillator, a phase-locked loop, a low-pass filter and a frequency synthesizer connected in sequence, and the output end of the frequency synthesizer is connected to the microstrip array antenna of the transmitting end; The receiving link is a zero intermediate frequency architecture, including a four-channel receiving down-converter, whose input end is connected to the microstrip array antenna at the receiving end.

8. The miniaturized non-contact water flow velocity measurement radar system based on FMCW according to claim 7 is characterized in that: The microstrip array antenna at the transmitting end is an array antenna composed of 4×12 microstrip patch antennas; The microstrip array antenna at the receiving end is an array antenna composed of dual-channel 2×12 microstrip patch antennas.

9. The miniaturized non-contact water flow velocity measurement radar system based on FMCW according to claim 7, characterized in that: The loop filter includes a phase detector and a voltage controlled oscillator; The phase detector and the voltage controlled oscillator are connected via a stabilizing circuit; The stabilization circuit includes a grounded capacitor C1, the non-grounded end of the grounded capacitor C1 is respectively connected to the output end of the phase detector, one end of the resistor R1 and one end of the resistor R2, the other end of the resistor R1 is grounded, and the other end of the resistor R2 is respectively connected to the grounded capacitor and the input end of the voltage-controlled oscillator.

10. The miniaturized non-contact water flow velocity measurement radar system based on FMCW according to claim 1 is characterized in that: The power supply module supplies power to the RF module and the power supply module through a step-by-step step-down DCDC power supply chip and a low voltage difference linear regulator.

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