Side-mounted ultra-long-distance river flow velocity monitoring radar system and river flow velocity monitoring method

Abstract

The invention discloses a side-mounted ultra-long-distance river flow velocity monitoring radar system and a river flow velocity monitoring method. The side-mounted river flow velocity monitoring radar system comprises a wide-beam antenna array arranged on the side surface of a river bank; the waveform control module is configured to transmit linear frequency modulation continuous waves or linear frequency modulation interruption continuous wave signals with different parameters in a segmented manner according to a preset distance so as to realize segmented switching measurement in a distance measurement range exceeding 1100 meters; the radio frequency receiving and processing module is used for receiving echo radio frequency signals; a distance-Doppler spectrum is generated according to the received echo radio frequency signal; and the flow velocity estimation module analyzes the generated distance-Doppler spectrum broadening, estimates the flow velocity of the water body at different distance positions, and forms a one-dimensional flow velocity profile in the river channel direction. And in combination with a spectrum broadening analysis method, the distance-Doppler spectrum is processed, the water flow velocity of each distance section is estimated, and non-contact one-dimensional flow field monitoring is realized. The system has the characteristics of simple structure, strong distance measurement capability and good adaptability.

Description

Technical Field

[0001] The present invention belongs to the field of radar measurement technology, and specifically relates to an ultra-long-range non-contact flow velocity monitoring radar system suitable for deployment on river banks, and is suitable for one-dimensional flow velocity profile measurement in scenarios such as wide river channels. Background Art

[0002] Radar is an electronic system that uses the reflection or scattering properties of electromagnetic waves from a target to achieve detection and measurement. It can determine the target's distance by the time difference between the echo and the transmitted signal, and obtain the target's radial velocity through the Doppler frequency shift. Water velocity radar is a typical application of radar technology in hydrological monitoring. It uses the Bragg scattering effect of electromagnetic waves on perturbations on the water surface to achieve non-contact measurement of surface velocity.

[0003] Compared to traditional contact hydrological sensors, non-contact radar velocity measurement systems offer advantages such as flexible deployment, strong corrosion resistance, and ease of long-term operation. They are particularly suitable for monitoring flow velocity in areas with complex terrain or dangerous river channels. Existing products generally use linear frequency modulated continuous wave (LFM-CW) or linear frequency modulated interrupted continuous wave (LFM-ICW) systems, combined with range-Doppler spectrum processing, to extract target flow velocity information.

[0004] Some high-end current radars use phased array or fully digital array architectures, achieving steerable and high-resolution measurements through digital beamforming (DBF). However, these systems are typically complex, costly, and power-hungry, making them unnecessary for river surface velocity measurement. This is especially true for small and medium-sized rivers with simple, fixed flow patterns, where a fixed beam configuration can suffice.

[0005] In addition, the effective ranging of commercially available radar products is generally limited to around 300 meters, making it difficult to adapt to typical measurement scenarios such as wide rivers and large-span bridges, becoming the main technical bottleneck in the promotion of non-contact hydrological monitoring systems.

[0006] Therefore, there is an urgent need for a new water flow velocity measurement radar system with ultra-long-range ranging capability, simple structure, controllable cost, and the ability to stably extract one-dimensional velocity profiles to meet the flow velocity monitoring needs in actual river environments. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a side-mounted river flow velocity monitoring radar system, which realizes the ultra-long-range water velocity measurement function under the conditions of structural simplification and cost control by adopting a fixed wide-beam antenna array and a segmented switching transmission waveform strategy.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0009] A side-mounted river flow velocity monitoring radar system, comprising:

[0010] A wide-beam antenna array installed on the side of the riverbank is used to transmit and receive radar signals in a direction perpendicular to the river channel to cover the entire width of the river;

[0011] A waveform control module configured to transmit linear frequency modulation continuous wave (LFMCCW) or linear frequency modulation interrupted continuous wave (LFMICW) signals with different parameters according to preset distance segments, thereby achieving segmented switching measurement for a ranging range exceeding 1100 meters; wherein the preset distance segments are at least five distance segments that divide the ranging range, and each distance segment matches a set set of waveform parameters;

[0012] The radio frequency receiving and processing module receives the echo radio frequency signal and generates a range-Doppler spectrum based on the received echo radio frequency signal;

[0013] The velocity estimation module analyzes the generated range-Doppler spectrum broadening, estimates the water velocity at different distance positions, and forms a one-dimensional velocity profile in the river direction.

[0014] The waveform control module switches to transmit frequency-modulated waveforms with corresponding parameters according to the distance segment where the target is located. The parameters include waveform form, pulse interval, pulse width, and pulse accumulation number to ensure signal isolation between different distance segments and realize ultra-long-distance segmented measurement, thereby completing sequential detection and continuous coverage of multiple distance segments.

[0015] The total ranging range is divided into five distance segments: ultra-short range, short range, medium range, long range, and ultra-long range. The distances of ultra-short range, short range, medium range, long range, and ultra-long range are 0-30 meters, 30-300 meters, 270-570 meters, 540-840 meters, and 810-1110 meters, respectively. Adjacent distance segments overlap to ensure measurement continuity and coverage redundancy during switching. In the ultra-short range, the waveform control module transmits a continuous wave system for ranging; in the short range, medium range, long range, and ultra-long range, the waveform control module transmits a linear frequency-modulated interrupted continuous wave for ranging. The waveform control module uses preset waveform call logic to automatically switch to the corresponding waveform in the order of the distance segments within each complete measurement cycle. After each waveform completes a complete data acquisition and reception processing (including echo storage and spectrogram generation), the control module issues a switching command, driving the system to the next ranging segment, thereby achieving sequential detection and continuous coverage of each distance segment.

[0016] The pulse interval of the linear frequency modulation interrupted continuous wave transmitted by the short-range waveform control module is greater than or equal to 2μs, with a typical value of 4.4μs, the pulse width is less than or equal to 0.2μs, with a typical value of 0.07μs, and the number of pulse accumulation is greater than or equal to 8096, with a typical value of 8096; the pulse interval of the linear frequency modulation interrupted continuous wave transmitted by the medium-range waveform control module is greater than or equal to 3.8μs, with a typical value of 4.4μs, the pulse width is less than or equal to 1.8μs, with a typical value of 0.2μs, and the number of pulse accumulation is greater than or equal to 8096, with a typical value of 8096; The pulse interval of the linear frequency modulation interrupt continuous wave transmitted in the remote waveform control module is greater than or equal to 5.6μs, with a typical value of 7μs, the pulse width is less than or equal to 3.6μs, with a typical value of 0.4μs, and the pulse accumulation number is greater than or equal to 8096, with a typical value of 8096; the pulse interval of the linear frequency modulation interrupt continuous wave transmitted in the ultra-long-range waveform control module is greater than or equal to 7.4μs, with a typical value of 9μs, the pulse width is less than or equal to 5.4μs, with a typical value of 0.4μs, and the pulse accumulation number is greater than or equal to 8096, with a typical value of 16192.

[0017] The step of the radio frequency receiving and processing module generating a range-Doppler spectrum according to the received echo radio frequency signal includes:

[0018] The received echo RF signal first passes through a bandpass filter to suppress out-of-band noise and interference, then is sampled and digitally down-converted to baseband;

[0019] Coherently mix the baseband signal with the transmit reference signal to achieve de-skew;

[0020] By performing FFT operations within N scanning cycles, a two-dimensional range-velocity power spectrum is obtained.

[0021] The echo RF signal received by the RF receiving and processing module is:

[0022]

[0023] Among them, A r (θ, w1, p1) is the echo amplitude, f0 is the carrier frequency, k is the frequency modulation slope, T is the scanning period, θ is the azimuth angle, θ e is the effective beam width, N w (θ) is the number of wave trains at azimuth angle θ within the beam coverage range, N p (θ, w1) is the number of individual waves in the w1th wave train at azimuth θ, N w and N p is the unknown parameter of the statistical distribution, R(θ,w1,p1) is the distance from the radar to the scattering point of the p1th wave in the w1th wave train at azimuth angle θ, v s is the water velocity, v pis the phase velocity of gravity waves on the water surface, c is the propagation speed of electromagnetic waves;

[0024] The signal after de-skewing is expressed as:

[0025]

[0026] Where i is the sampling sequence, T s is the sampling interval.

[0027] By performing FFT operations within N scanning cycles, a two-dimensional range-velocity power spectrum is obtained:

[0028]

[0029] Among them, i R and i v represent the range unit and Doppler unit respectively; f s represents the sampling frequency;

[0030] From the obtained two-dimensional range-velocity power spectrum, extract the Doppler spectrum at different range units;

[0031] For each i R Doppler spectrum on the range unit, normalizing the spectrum lines to a uniform scale to eliminate absolute power differences:

[0032]

[0033] The Gaussian kernel function is used to smooth the power spectrum curve to suppress local fluctuations and noise peaks; the mathematical expression is:

[0034] power smooth [i R ,i v ]=power dB [i R ,i v ]·G(i v ), (for different i R )

[0035] Among them, the Gaussian kernel function G(i v ) is defined as:

[0036]

[0037] Among them, i0 is the center frequency unit index and σ is the kernel function width.

[0038] The method for the flow velocity estimation module to estimate the water flow velocity at different distance positions is:

[0039] Set the detection threshold, calculate the frequency spacing corresponding to the intersection points on both sides of the Doppler spectrum, and obtain the spectrum width △f;

[0040] According to the spectrum width △f, the corresponding water flow velocity is obtained;

[0041]

[0042] Where θ is the azimuth angle, f Bragg is the Bragg frequency and λ is the radar wavelength.

[0043] The detection threshold is set to a certain ratio between the peak value and the noise ground line.

[0044] The antenna array is a single wide-beam Yagi antenna array, which is fixedly installed on the side of the river bank, and the beam is pointed perpendicular to the direction of the river.

[0045] The present invention has the following beneficial effects:

[0046] 1. By adopting a fixed-point wide-beam antenna, the system avoids the complexity and cost burden of multi-channel beam control and is suitable for deployment in small and medium-sized rivers with stable flow directions.

[0047] 2. The waveform control module supports switching transmission parameters in sequence according to distance segments. By switching waveform parameters in segments and measuring them in sequence, it matches the detection requirements of different ranging segments, avoiding transmission and reception aliasing caused by excessive pulse width in close-range segments, while improving the echo energy and measurement accuracy in long-range segments, balancing efficiency and performance to achieve effective coverage of more than 1,100 meters.

[0048] 3. Use spectrum broadening analysis method to estimate flow velocity, which meets the needs of flow velocity extraction under wide beam conditions;

[0049] 4. The system has a compact overall structure, low power consumption, and low cost, making it easy to deploy on a large scale. It is particularly suitable for non-contact hydrological monitoring applications in wide river channels, cross-river structures, and other high-span applications.

[0050] Description of the accompanying tables and figures

[0051] Figure 1 1 is a block diagram of the overall structure of the radar system of the present invention;

[0052] Figure 2 A conceptual side view of the layout of the side-mounted radar of the present invention when installed on a river bank;

[0053] Figure 3 This is a top-down conceptual diagram of the layout of the side-mounted radar of the present invention when installed on a river bank;

[0054] Figure 4 This is a simulation example of the antenna array pattern in the present invention, where a is the E-plane pattern and b is the H-plane pattern;

[0055] Figure 5is the echo signal processing flow chart;

[0056] Figure 6 Schematic diagram of range-Doppler spectrum in the present invention;

[0057] Figure 7 This is a flow chart of the flow velocity estimation algorithm based on spectrum broadening of the present invention.

[0058] Table 1 is an example of the segmented ranging waveform parameter configuration of the present invention. DETAILED DESCRIPTION

[0059] like Figure 1 As shown, the present invention provides a side-mounted radar system for river flow velocity monitoring, which includes: a wide-beam antenna array installed on the side of the river bank, a waveform control module, a radio frequency receiving and processing module, and a flow velocity estimation module.

[0060] like Figure 2 and Figure 3 As shown, the antenna array is composed of multiple Yagi antennas to form a wide beam coverage structure, which is fixedly installed on a river bank platform or bracket. Figure 2 This is a side view conceptual diagram showing the geometric relationship of the antenna beam emitting perpendicular to the river channel; Figure 3 This is a bird's-eye view conceptual diagram, illustrating the coverage position and ranging direction of the radar deployment points relative to the overall river surface.

[0061] like Figure 1 , Figure 2 and Figure 3 As shown, this system is deployed on the bankside, with a beam coverage covering the entire width of the river. The system's fixed angle eliminates the need for directional control, enabling stable detection at varying distances from the river channel. It is suitable for one-dimensional natural river environments with clear flow directions and stable flow fields. Its simple installation structure supports single-point deployment and long-term operation.

[0062] like Figure 4 As shown in the figure, simulation results of the Yagi antenna array's directivity pattern show that in azimuth (perpendicular to the antenna array's orientation), its main beam's -3dB coverage angle is approximately 20.35°; in elevation (perpendicular to the ground), the main beam width is approximately 46.26°. At a typical installation altitude, this directivity ensures stable, non-contact coverage over a river width exceeding 1100 meters. Excellent sidelobe control effectively suppresses clutter interference from non-target directions.

[0063] As shown in Table 1, to effectively cover river widths from 0 to over 1100 meters, the present invention divides the total ranging range into five overlapping range segments: ultra-short range (0-30 meters), short range (30-300 meters), medium range (270-570 meters), long range (540-840 meters), and ultra-long range (810-1110 meters). The waveform control module dynamically configures the corresponding radar transmission parameters based on the propagation characteristics and system objectives of each range segment. In the ultra-short range (0-30 meters), the system uses a linear frequency modulated interrupted continuous wave (LFMCW) scheme for ranging. Due to the extremely short echo return time, using long pulses or a large pulse repetition period would cause overlap between the transmitted and received signals, reducing the signal-to-noise ratio. Therefore, a shorter sweep period is selected to avoid transmission interruptions, which is suitable for high time resolution and anti-overlap requirements. From the short range segment (30-300 meters), the system begins to use a linear frequency modulated interrupted continuous wave (LFMICW) scheme, which expands the receiving window and reduces near-field interference by controlling pulse interruptions. In this range, shorter pulse widths (e.g., 0.07 μs) and faster pulse repetition periods (e.g., 4.4 μs) are used to achieve rapid echo acquisition. Entering the medium- to long-range range (270-840 meters), due to the increased propagation path and weakened target scattering energy, to ensure sufficient echo energy and signal-to-noise ratio, the system gradually extends the transmit pulse width (e.g., 0.2-0.4 μs) to increase single-pulse energy, while appropriately increasing the pulse repetition interval (e.g., 7-9 μs) to avoid echo overlap. Simultaneously, the system increases the coherent integration period to enhance the noise immunity of the range and Doppler spectra. Particularly in the ultra-long-range range (810-1110 meters), the system increases the number of sweep cycles to 16,192 to enhance the spectral energy accumulation of weak echoes at long distances and improve velocity measurement stability.

[0064] Table 1

[0065]

[0066] The waveform control module contains multiple sets of preset waveform parameter configuration tables, each corresponding to the measurement requirements of a different ranging segment. These parameters include waveform type (such as LFMCW or LFMICW), frequency modulation slope, pulse width, pulse interval, number of sweep cycles, and coherent accumulation. Controlled by an embedded controller (such as an FPGA), this module uses an internal state machine to call and load the corresponding waveform parameters one by one, sequentially according to the range segment, during each complete measurement cycle, driving the radar signal generator to complete signal modulation, transmission, and measurement.

[0067] Specifically, the system first reads the corresponding waveform settings from the parameter table based on the current range configuration and loads them into the radar's digital waveform synthesis module (such as a DDS or digitally controlled oscillator). The generated FM signal is then converted to an analog intermediate frequency signal through a high-speed digital-to-analog converter (DAC), up-converted, and finally shaped by a power amplifier and filter before being output to the transmitting antenna to complete signal radiation. The main process is as follows:

[0068] 1. Initialize the control instructions and load the current distance segment parameters;

[0069] 2. Generate and transmit the waveform (CW or LFMICW);

[0070] 3. Receive the echo signal and process it (down conversion, DDC, FFT, etc.);

[0071] 4. Store the Doppler spectrum data of this segment;

[0072] 5. Automatically switch to the next distance segment and repeat steps 1 to 4;

[0073] 6. After the five sections of measurement are completed, they are combined to generate complete river surface velocity profile data.

[0074] 7. Repeat steps 1 to 6 according to the set cycle to achieve continuous monitoring and dynamic updating of river surface flow velocity.

[0075] The above-mentioned multi-segment waveform strategy dynamically adjusts the signal structure and detection strategy on the basis of taking into account both near-field high-speed detection and long-distance high-energy reception, effectively solving the near-field and long-distance compatibility and system resource optimization problems that are common in large-span velocity profile measurements.

[0076] like Figure 5 As shown in the figure, after the system receives the water surface echo signal, it first enters the RF front end and digital receiving link for processing, which mainly includes down conversion, difference frequency, accumulation and spectrum analysis.

[0077] 1. Echo signal acquisition and I / Q demodulation: The echo signal at the receiving end is input into the receiving module through intermediate frequency sampling. The system separates it into two signals, I (in-phase) and Q (quadrature) through local oscillator synchronous demodulation, completing the basic down-conversion process and facilitating subsequent difference frequency calculation and coherent processing.

[0078] 2. Low-pass filtering and beat frequency calculation: The I and Q signals are each passed through a bandwidth-adaptive low-pass filter to remove high-frequency components. Afterwards, a beat frequency calculation is performed with the reference transmit signal. This beat frequency process extracts frequency components related to target range and velocity, preserving the Doppler component within the range gate.

[0079] 3. Multi-range gate signal accumulation: The difference frequency results are gated and divided into pre-set range segments. The signals within each range gate are coherently accumulated over multiple pulse cycles, improving the signal-to-noise ratio of distant targets and forming an echo energy sequence with spatial location dimensions.

[0080] 4. Data caching and processing synchronization: The coherently accumulated data is cached through the BRAM (on-chip block RAM) module inside the FPGA, and the data structure is managed through control logic to ensure stable operation of the processing pipeline.

[0081] 5. Two-Dimensional Fast Fourier Transform (2D-FFT): The accumulated data matrix is ​​fed into the 2D-FFT module. The first-dimensional FFT extracts the range information, while the second-dimensional FFT extracts the Doppler frequency. This results in a range-Doppler spectrum, with the range gate number on the horizontal axis and the velocity spectrum distribution on the vertical axis.

[0082] like Figure 6 As shown, the velocity estimation module of the present invention uses a two-dimensional range-Doppler power spectrum as input, processes the spectrum at each range gate, and ultimately generates a one-dimensional velocity profile along the river surface. This method, based on the principle of spectrum broadening, differs from traditional point target velocity measurement methods and is particularly suitable for non-contact measurement of water velocity using wide-beam radar systems.

[0083] 1. Review of the principle of traditional narrow beam velocity measurement: In phased array or narrow beam radar, the water surface echo mainly comes from Bragg scattering. Bragg frequency f Bragg The phase velocity v of the water surface gravity wave p (The phase velocity direction can be far away or close). If the water body has an actual flow velocity v s , whose radial component to the radar is v s sin(θ), then the observation frequency f obs is the sum of the two:

[0084]

[0085] Among them, f flow It is the Doppler frequency shift caused by the actual flow velocity of the water, and λ is the signal wavelength.

[0086] On the Doppler spectrum, this manifests as a bimodal, symmetrical distribution. The shift in the peak represents the velocity contribution due to water flow. In traditional narrow-beam radar, the beamwidth is very small, and the θ value can be approximately assumed to be the same for all scattering points. Therefore, the observed spectral energy is concentrated in a single point or narrow band, and the shift in the main peak reflects the flow velocity.

[0087] 2. Such as Figure 6As shown in Figure 1, the wide beam antenna simultaneously illuminates multiple water surface areas with different incident angles θ. Therefore, the echo signals received within the same range gate come from multiple water scattering points in different directions, each with a different radial velocity component. Therefore, the echo of the Bragg wave train can be written as:

[0088]

[0089] Among them, A r (θ, w1, p1) is the echo amplitude, f0 is the carrier frequency, k is the frequency modulation slope, T is the scanning period, θ is the azimuth angle, θ e is the effective beam width, N w (θ) is the number of wave trains at azimuth angle θ within the beam coverage range, N p (θ, w1) is the number of individual waves in the w1th wave train at azimuth θ, N w and N p is an undetermined parameter of the statistical distribution, and R(θ,w1,p1) is the distance from the radar to the scattering point of the p1th wave in the w1th wave train at azimuth angle θ.

[0090] The signal bandwidth B satisfies B=kT.

[0091] In inland rivers, we can assume that the flow direction is consistent with the river banks, especially when the river banks are approximately straight. Therefore, v s sin(θ) is the radial component of the velocity relative to the radar. Unlike the point frequency shift observation mode of a single target in a traditional narrow beam radar, in the same range gate, the system receives not the echo of a single speed target, but the "superposition state" of multiple scatterer echoes with different incident angles and radial velocities. This is equivalent to the synthesis of the simultaneous observation results of multiple targets at the same range gate by a traditional radar. This difference in spatial velocity distribution is manifested as significant energy broadening in the spectrum. In the spectrum: the maximum frequency point corresponds to the velocity v s sin(θ)+v p , the minimum frequency point corresponds to -v s sin(θ)-v p In the absence of water flow, the spectrum broadening is caused only by the Bragg wave, and the corresponding velocity is 2v p Once the water flow exists, the spectrum line is further broadened, and the speed corresponding to the total spectrum width becomes 2(v s sin(θ)+v p ), therefore, by measuring the broadening range of the entire Doppler spectrum and deducting the known fixed part caused by the Bragg wave, the spectrum broadening contributed by the water flow can be calculated, thereby estimating the actual water flow velocity.

[0092] like Figure 7As shown, in order to accurately estimate the spectrum width, the system adopts the following processing flow:

[0093] 1. Spectrum Extraction: The received echo is first bandpass filtered to suppress out-of-band noise and interference, then sampled and digitally down-converted (DDC) to baseband. De-skewing is then achieved by coherently mixing the baseband signal with the transmitted reference signal. The de-skewing signal is represented as:

[0094]

[0095] Where i is the sampling sequence, T s is the sampling interval.

[0096] In equation (3), two terms play a crucial role. The first is the velocity-related component: 2πf0v p iT s / cv s [R(θ,w1,p1)]sinθ i T s / c, can be extracted by slow-time FFT. The second term: 2πk2R(θ,w1,p1) / c, is related to the distance and can be obtained by fast-time FFT.

[0097] By performing FFT operations within N scanning cycles, a two-dimensional range-velocity power spectrum can be obtained:

[0098]

[0099] Among them, i R and i v Represents the distance and Doppler unit respectively, one distance unit corresponds to the distance cf s / k / 2 / T / T s , one Doppler unit corresponds to the velocity c / f0NT. From the obtained two-dimensional range-velocity power spectrum, the Doppler spectra at different range units can be extracted.

[0100] 2. Normalization: for different i R Doppler spectrum on the range unit, normalizing the spectrum lines to a uniform scale to eliminate absolute power differences:

[0101]

[0102] 3. Gaussian smoothing: Use the Gaussian kernel function to smooth the power spectrum curve and suppress local fluctuations and noise peaks; the mathematical expression is:

[0103] power smooth [i R ,i v ]=power dB [iR ,i v ]·G(i v ), (for different i R ) (6)

[0104] The Gaussian kernel function G is defined as:

[0105]

[0106] Among them, i0 is the center frequency unit index and σ is the kernel function width.

[0107] 4. Threshold-based spectrum width detection: Figure 7 As shown in the example on the right, the detection threshold is set to a certain ratio between the peak value and the noise ground line (such as -6dB or an equivalent amplitude difference). The frequency spacing corresponding to the intersection points on both sides of the spectrum is calculated to obtain the spectrum width △f.

[0108] 5. Spectral width is converted to velocity: Based on the known azimuth angle θ and Bragg frequency f Bragg and radar wavelength λ, the corresponding water velocity is converted to:

[0109]

[0110] 6. One-dimensional flow field calculation: For each distance unit i R By repeating steps 2 to 5, a one-dimensional water velocity profile of the entire river surface in the radar direction can be obtained, forming a flow velocity distribution map in the direction away from the shore.

[0111] The system operates in the P-band, with a center frequency of 403MHz and a bandwidth of ≤50MHz. It can be flexibly configured based on site requirements and antenna configuration. The system features a simple structure, low power consumption, easy installation, and strong detection capabilities, making it particularly suitable for wide river channels.

[0112] It should be noted that the above implementation modes are only preferred embodiments of the present invention, and any equivalent modifications, replacements or combinations within the spirit of the present invention and the scope of the claims should also be regarded as the protection scope of the present invention.

Claims

1. A side-mounted river velocity monitoring radar system, characterized in that: include: A wide-beam antenna array installed on the side of the riverbank is used to transmit and receive radar signals in a direction perpendicular to the river channel to cover the entire width of the river; A waveform control module configured to transmit linear frequency modulation continuous wave (LFMCCW) or linear frequency modulation interrupted continuous wave (LFMICW) signals with different parameters according to preset distance segments, thereby achieving segmented switching measurement for a ranging range exceeding 1100 meters; wherein the preset distance segments are at least five distance segments that divide the ranging range, and each distance segment matches a set set of waveform parameters; The radio frequency receiving and processing module receives the echo radio frequency signal and generates a range-Doppler spectrum based on the received echo radio frequency signal; The velocity estimation module analyzes the generated range-Doppler spectrum broadening, estimates the water velocity at different distance positions, and forms a one-dimensional velocity profile in the river direction.

2. The river flow velocity monitoring radar system according to claim 1, characterized in that: The waveform control module switches to transmit frequency-modulated waveforms with corresponding parameters according to the distance segment where the target is located. The parameters include waveform form, pulse interval, pulse width, and pulse accumulation number to ensure signal isolation between different distance segments and realize ultra-long-distance segmented measurement, thereby completing sequential detection and continuous coverage of multiple distance segments.

3. The river flow velocity monitoring radar system according to claim 2, characterized in that: The total ranging range is divided into five distance segments, namely ultra-short range, short range, medium range, long range and ultra-long range. The distances of ultra-short range, short range, medium range, long range and ultra-long range are 0-30 meters, 30-300 meters, 270-570 meters, 540-840 meters and 810-1110 meters respectively; in the ultra-short range segment, the waveform control module transmits a continuous wave system for ranging; in the short range, medium range, long range and ultra-long range, the waveform control module transmits a linear frequency modulation interrupted continuous wave for ranging.

4. The river flow velocity monitoring radar system according to claim 3, characterized in that: The pulse interval of the linear frequency modulation interrupted continuous wave transmitted by the short-range waveform control module is greater than or equal to 2μs, with a typical value of 4.4μs, the pulse width is less than or equal to 0.2μs, with a typical value of 0.07μs, and the number of pulse accumulation is greater than or equal to 8096, with a typical value of 8096; the pulse interval of the linear frequency modulation interrupted continuous wave transmitted by the medium-range waveform control module is greater than or equal to 3.8μs, with a typical value of 4.4μs, the pulse width is less than or equal to 1.8μs, with a typical value of 0.2μs, and the number of pulse accumulation is greater than or equal to 8096, with a typical value of 8096; The pulse interval of the linear frequency modulation interrupt continuous wave transmitted in the remote waveform control module is greater than or equal to 5.6μs, with a typical value of 7μs, the pulse width is less than or equal to 3.6μs, with a typical value of 0.4μs, and the pulse accumulation number is greater than or equal to 8096, with a typical value of 8096; the pulse interval of the linear frequency modulation interrupt continuous wave transmitted in the ultra-long-range waveform control module is greater than or equal to 7.4μs, with a typical value of 9μs, the pulse width is less than or equal to 5.4μs, with a typical value of 0.4μs, and the pulse accumulation number is greater than or equal to 8096, with a typical value of 16192.

5. The river flow velocity monitoring radar system according to any one of claims 1 to 4, characterized in that: The step of the radio frequency receiving and processing module generating a range-Doppler spectrum according to the received echo radio frequency signal includes: The received echo RF signal first passes through a bandpass filter to suppress out-of-band noise and interference, then is sampled and digitally down-converted to baseband; Coherently mix the baseband signal with the transmit reference signal to achieve de-skew; By performing FFT operations within N scanning cycles, a two-dimensional range-velocity power spectrum is obtained.

6. The river flow velocity monitoring radar system according to claim 5, characterized in that: The echo RF signal received by the RF receiving and processing module is: Among them, A r (θ, w1, p1) is the echo amplitude, f0 is the carrier frequency, k is the frequency modulation slope, T is the scanning period, θ is the azimuth angle, θ e is the effective beam width, N w (θ) is the number of wave trains at azimuth angle θ within the beam coverage range, N p (θ, w1) is the number of individual waves in the w1th wave train at azimuth θ, N w and N p is the unknown parameter of the statistical distribution, R(θ,w1,p1) is the distance from the radar to the scattering point of the p1th wave in the w1th wave train at azimuth angle θ, v s is the water velocity, v p is the phase velocity of gravity waves on the water surface, c is the propagation speed of electromagnetic waves; The signal after de-skewing is expressed as: Where i is the sampling sequence, T s is the sampling interval; By performing FFT operations within N scanning cycles, a two-dimensional range-velocity power spectrum is obtained: Among them, i R and i v represent the range unit and Doppler unit respectively; f s represents the sampling frequency; From the obtained two-dimensional range-velocity power spectrum, extract the Doppler spectrum at different range units; For each i R Doppler spectrum on the range unit, normalizing the spectrum lines to a uniform scale to eliminate absolute power differences: The Gaussian kernel function is used to smooth the power spectrum curve to suppress local fluctuations and noise peaks; the mathematical expression is: power smooth [i R ,i v = power dB [i R ,i v ·G(i v ), (for different i R ). Among them, the Gaussian kernel function G(i v ) is defined as: Among them, i0 is the center frequency unit index and σ is the kernel function width.

7. The river flow velocity monitoring radar system according to claim 6, characterized in that: The method for the flow velocity estimation module to estimate the water flow velocity at different distance positions is: Set the detection threshold, calculate the frequency spacing corresponding to the intersection points on both sides of the Doppler spectrum, and obtain the spectrum width △f; According to the spectrum width △f, the corresponding water flow velocity is obtained; Where θ is the azimuth angle, f Bragg is the Bragg frequency and λ is the radar wavelength.

8. The river flow velocity monitoring radar system according to claim 7, characterized in that: The detection threshold is set to a certain ratio between the peak value and the noise ground line.

9. The river flow velocity monitoring radar system according to any one of claims 1 to 4, characterized in that: The antenna array is a single wide-beam Yagi antenna array, which is fixedly installed on the side of the river bank, and the beam is pointed perpendicular to the direction of the river.

10. A river flow velocity monitoring method based on the river flow velocity monitoring radar system according to any one of claims 1 to 9, characterized in that: include: According to the preset distance segment, it transmits linear frequency modulation continuous wave or linear frequency modulation interrupted continuous wave signals with different parameters to achieve segmented switching measurement of the ranging range exceeding 1100 meters; The radio frequency receiving and processing module receives the echo radio frequency signal and generates a range-Doppler spectrum based on the received echo radio frequency signal; According to the velocity estimation module, the generated range-Doppler spectrum broadening is analyzed to estimate the water velocity at different distance positions and form a one-dimensional velocity profile in the river direction.

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