Rainfall monitoring method and system based on low-frequency microwaves

Abstract

The invention relates to the technical field of rainfall monitoring, in particular to a rainfall monitoring method and system based on low-frequency microwaves. The method comprises the following steps: firstly, a microwave emission module generates a continuous microwave signal of which the frequency is a preset frequency, and directionally radiates the continuous microwave signal to an airspace of a to-be-detected area, and then an antenna assembly receives a scattered signal generated in the airspace of the to-be-detected area, and gains and filters the scattered signal to obtain a corresponding perfect signal; the signal processing module demodulates the perfect signal to extract the signal amplitude attenuation of the perfect signal, and calculates the real-time rainfall intensity of the to-be-measured area based on the signal amplitude attenuation; according to the scheme, microwave signals are directionally transmitted, a small to-be-monitored area of 1-10 km can be accurately covered, planar accurate monitoring is achieved, and the limitation of a traditional rainfall monitoring scheme is solved; the signal attenuation-rainfall intensity calibration model constructed based on the Mie scattering theory can ensure the accuracy of rainfall monitoring and meet the accuracy requirement of small-area fine monitoring.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rainfall monitoring, in particular to a rainfall monitoring method and system based on low-frequency microwave. BACKGROUND

[0002] Rainfall is an important influencing factor for natural disasters, and most geological disasters are directly or indirectly related to rainfall, such as landslides, mudslides, and group geological disasters caused by typhoons. Therefore, rainfall monitoring is an important means of disaster prevention and mitigation of geological disasters. At present, rainfall monitoring is usually achieved by traditional precipitation monitoring technologies such as weather radar and weather satellite. These means are widely used, but they are usually used for overall rainfall monitoring in a large area and cannot achieve accurate rainfall monitoring in a small area. Even if small-range monitoring equipment such as rain gauges is used, due to factors such as site layout, high price, and post-maintenance, it is difficult to promote its use on a large scale, at low cost, and with zero maintenance. SUMMARY

[0003] The main purpose of the present application is to provide a rainfall monitoring method and system based on low-frequency microwave, which aims to solve the problems that traditional rain gauge sites are subject to construction cost, terrain condition and maintenance difficulty, there are still a lot of space blanks between mountainous areas, hilly areas and densely populated urban areas, and it is difficult to continuously reflect the spatial distribution characteristics of rainfall and surface response; and the traditional rain gauge is difficult to capture sudden heavy rainfall process in time, resulting in lag and lack of representative of monitoring information, affecting the early judgment and accurate early warning of disaster risk.

[0004] The technical scheme provided by the present application is as follows: A rainfall monitoring method based on low-frequency microwave is applied to a rainfall monitoring system based on low-frequency microwave; the system comprises a microwave transmitting module, a microwave receiving module, a signal processing module and an antenna assembly; the microwave transmitting module and the microwave receiving module are electrically connected to the antenna assembly; the microwave receiving module is in communication connection with the signal processing module; the method comprises: After starting, the microwave transmitting module is preheated for a first preset time; The microwave transmitting module generates continuous microwave signals with a preset frequency, and radiates the continuous microwave signals to the airspace of the to-be-measured area with a preset beam angle through the antenna assembly; The antenna assembly receives the scattering signals generated by the continuous microwave signals in the airspace of the to-be-measured area and transmits them to the microwave receiving module; The microwave receiving module performs gain and filtering processing on the scattering signals to obtain corresponding perfect signals, and sends the perfect signals to the signal processing module; The signal processing module demodulates the perfect signal to extract signal amplitude attenuation of the perfect signal, and calculates real-time rainfall intensity of the to-be-measured area based on the signal amplitude attenuation.

[0005] Preferably, the system further comprises a power supply module and a storage and transmission module; the storage and transmission module is in communication connection with the signal processing module; the power supply module is used for supplying power to the microwave transmitting module, the microwave receiving module, the signal processing module, and the storage and transmission module; the signal processing module demodulates the perfect signal to extract signal amplitude attenuation of the perfect signal, and calculates real-time rainfall intensity of the to-be-measured area based on the signal amplitude attenuation, and further comprises: The signal processing module sends the real-time rainfall intensity of the to-be-measured area to the storage and transmission module for local storage.

[0006] Preferably, the system further comprises a housing and a mounting bracket; the housing is a cuboid box, and the inside is divided into upper space and lower space by a partition plate; the microwave transmitting module is arranged on the left side of the upper space, and the microwave receiving module is arranged on the right side of the upper space; the signal processing module, the storage and transmission module, and the power supply module are sequentially arranged from left to right in the lower space; and the bottom of the housing is connected to the mounting bracket through a flange plate.

[0007] Preferably, the antenna assembly comprises a transmitting antenna and a receiving antenna; the transmitting antenna and the receiving antenna are both in a horn shape; the transmitting antenna and the receiving antenna are fixed to the outer top of the housing through bolts; the transmitting antenna is electrically connected to the microwave transmitting module through an SMA coaxial connecting cable; and the receiving antenna is electrically connected to the microwave receiving module through an SMA coaxial connecting cable.

[0008] Preferably, the signal processing module demodulates the perfect signal to extract signal amplitude attenuation of the perfect signal, and calculates real-time rainfall intensity of the to-be-measured area based on the signal amplitude attenuation, and comprises: The signal processing module adopts an algorithm combining quadrature demodulation and Fourier transform to demodulate the perfect signal to extract signal amplitude actual attenuation of the perfect signal; The signal processing module acquires historical experience data, wherein the historical experience data comprises a plurality of historical data groups, and each historical data group comprises historical amplitude attenuation and historical rainfall intensity corresponding to each other; The signal processing module obtains a signal amplitude attenuation-rainfall intensity fitting curve based on the historical experience data; The signal processing module substitutes the signal amplitude actual attenuation into the signal amplitude attenuation-rainfall intensity fitting curve to obtain real-time rainfall intensity of the to-be-measured area.

[0009] Preferably, the signal processing module substitutes the actual signal amplitude attenuation amount into the signal amplitude attenuation amount-rainfall intensity fitting curve to obtain the real-time rainfall intensity of the to-be-measured area, and then further comprises: The signal processing module integrates the real-time rainfall intensity with a second preset time length as an integration time step to obtain the cumulative rainfall of the to-be-measured area in a past third preset time length, wherein the third preset time length is an integer multiple of the second preset time length.

[0010] Preferably, the signal processing module substitutes the actual signal amplitude attenuation amount into the signal amplitude attenuation amount-rainfall intensity fitting curve to obtain the real-time rainfall intensity of the to-be-measured area, and then further comprises: The signal processing module calculates the polarization ratio of the perfect signal, wherein the polarization ratio is the ratio of the horizontal polarization signal intensity to the vertical polarization signal intensity of the perfect signal. When the polarization ratio is greater than or equal to a first preset value and less than a second preset value, the signal processing module determines that the rainfall type of the to-be-measured area is drizzle. When the polarization ratio is greater than or equal to the second preset value and less than a third preset value, the signal processing module determines that the rainfall type of the to-be-measured area is moderate rain. When the polarization ratio is greater than or equal to the third preset value and less than a fourth preset value, the signal processing module determines that the rainfall type of the to-be-measured area is heavy rain. When the polarization ratio is greater than or equal to the fourth preset value, the signal processing module determines that the rainfall type of the to-be-measured area is snow.

[0011] Preferably, the system further comprises a cloud server in wireless communication connection with the storage and transmission module, and an audible and visual alarm in communication connection with the signal processing module; the method further comprises: The signal processing module sends the real-time rainfall intensity, the cumulative rainfall, and the rainfall type of the to-be-measured area to the storage and transmission module. The storage and transmission module sends the real-time rainfall intensity, the cumulative rainfall, and the rainfall type of the to-be-measured area to the cloud server for backup storage. When the real-time rainfall intensity is greater than a preset threshold, the signal processing module controls the audible and visual alarm to start.

[0012] The application also provides a rainfall monitoring system based on low-frequency microwave, which applies the rainfall monitoring method based on low-frequency microwave; the system comprises a microwave transmitting module, a microwave receiving module, a signal processing module, and an antenna assembly; the microwave transmitting module and the microwave receiving module are electrically connected to the antenna assembly; the microwave receiving module is in communication connection with the signal processing module.

[0013] By the technical scheme, the following beneficial effects can be achieved: The rainfall monitoring method based on low-frequency microwave provided by the application can solve the problem of lacking technical scheme for accurately monitoring rainfall in a small area. Firstly, the microwave transmitting module generates continuous microwave signals with a preset frequency, and the continuous microwave signals are radiated to the airspace of the to-be-measured area at a preset beam angle through the antenna assembly. Then, the antenna assembly receives the scattering signals generated by the continuous microwave signals in the airspace of the to-be-measured area and transmits the scattering signals to the microwave receiving module. The microwave receiving module processes the scattering signals to obtain corresponding perfect signals. The signal processing module demodulates the perfect signals to extract the signal amplitude attenuation of the perfect signals, and calculates the real-time rainfall intensity of the to-be-measured area based on the signal amplitude attenuation. The scheme can accurately cover a small to-be-measured area of 1-10 km and realize planar accurate monitoring, solving the limitations of the traditional rainfall monitoring scheme. The signal attenuation-rainfall intensity calibration model constructed based on the Mie scattering theory can ensure the accuracy of rainfall monitoring and meet the accuracy requirements of fine monitoring in a small area. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical schemes in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor based on the drawings shown.

[0015] Figure 1 The flow step diagram of the first embodiment of the rainfall monitoring method based on low-frequency microwave provided by the application is shown in the figure. Figure 2 The structure diagram of the mounting bracket provided in the third embodiment of the rainfall monitoring method based on low-frequency microwave provided by the application is shown in the figure.

[0016] Explanation of reference signs: 110, base; 120, connecting frame; 130, support rod; 140, sliding rail; 150, sliding seat; 160, first connecting arm; 170, second connecting arm; 180, sleeve; 190, rotating rod; 210, threaded rod; 220, support plate; 230, first gear; 240, second gear; 250, speed reducer; 260, motor. DETAILED DESCRIPTION

[0017] It should be understood that the specific embodiments described herein are only used to explain the application and not to limit the application.

[0018] The application provides a rainfall monitoring method and system based on low-frequency microwave.

[0019] As shown in the accompanying drawings Figure 1 In a first embodiment of the low-frequency microwave-based rainfall monitoring method proposed in the present application, the low-frequency microwave-based rainfall monitoring method is applied to a low-frequency microwave-based rainfall monitoring system; the system comprises a microwave transmitting module, a microwave receiving module, a signal processing module and an antenna assembly; the microwave transmitting module and the microwave receiving module are both electrically connected to the antenna assembly; the microwave receiving module is in communication connection with the signal processing module; the embodiment comprises the following steps: Step S110: After starting, the microwave transmitting module is preheated for a first preset time length.

[0020] Specifically, the first preset time length is preferably 30s, and by preheating, the microwave transmitting module enters the working mode after the frequency is stabilized. Step S120: The microwave transmitting module generates a continuous microwave signal with a preset frequency, and directs the continuous microwave signal to the airspace of the to-be-measured region with a preset beam angle through the antenna assembly.

[0021] Specifically, in this step, the microwave transmitting module generates a continuous microwave signal with a preset frequency (1.8GHz), which is transmitted to the antenna assembly through an SMA coaxial cable, and the antenna assembly directs the continuous microwave signal to the airspace of the to-be-measured region (for example, 10km ahead) with a preset beam angle (15°).

[0022] Specifically, the beam angle is taken as the axis with the extension line of the sensor as the axis, and then it is extended outward to the place where the energy intensity is reduced by half, which is called the beam angle, also known as the half-power beam width, which is related to the working frequency and the size of the antenna. This parameter affects the energy concentration degree and detection accuracy in the fields of ultrasonic waves, radars, sonars, etc.

[0023] In this embodiment, the beam angle directly determines the precision of the microwave monitoring of rainfall intensity and the size of the monitoring area, and the core relationship can be summarized as follows: the smaller the beam angle, the higher the spatial resolution of the rainfall intensity inversion, and the higher the precision of the rainfall monitoring, but the smaller the monitoring area; the larger the beam angle, the wider the observation coverage, but the inversion precision is easily affected by the mixing effect and decreases, and the precision of the rainfall monitoring is lower, but the monitoring area is larger.

[0024] Step S130: The antenna assembly receives the scattering signal generated by the continuous microwave signal in the airspace of the to-be-measured region and transmits it to the microwave receiving module.

[0025] Specifically, in the airspace of the to-be-measured region, the precipitation particles (raindrops, snowflakes, etc.) will scatter the continuous microwave signal, thereby generating a scattering signal, and the scattering signal will be captured by the antenna assembly and then transmitted to the microwave receiving module.

[0026] Step S140: the microwave receiving module performs gain and filtering processing on the scattering signal to obtain a corresponding perfect signal, and sends the perfect signal to the signal processing module.

[0027] Specifically, the microwave receiving module amplifies the received scattering signal (the gain is 35dB), and filters out the environmental noise (the filtering bandwidth is 100kHz) to obtain the processed perfect signal.

[0028] Step S150: the signal processing module demodulates the perfect signal to extract the signal amplitude attenuation of the perfect signal, and calculates the real-time rainfall intensity of the to-be-measured region based on the signal amplitude attenuation.

[0029] Specifically, the signal processing module in the embodiment is an FPGA (Field Programmable Gate Array) chip; the signal processing module demodulates the perfect signal to extract the signal amplitude attenuation, combines a preset signal attenuation-rainfall intensity calibration model, and calculates the real-time rainfall intensity (unit: mm / h) of the to-be-measured region; the rainfall amount (unit: mm) of the to-be-measured region can also be calculated according to time integration; at the same time, the rainfall type (such as drizzle, moderate rain, heavy rain, and snow) can also be distinguished through the polarization characteristics (polarization ratio) of the signal.

[0030] The rainfall amount monitoring method based on low-frequency microwave can solve the problem that there is currently no technical solution for accurately monitoring the rainfall amount in a small region; first, the microwave transmitting module generates continuous microwave signals with a preset frequency, and radiates the continuous microwave signals to the airspace of the to-be-measured region at a preset beam angle through the antenna assembly; then, the antenna assembly receives the scattering signals generated by the continuous microwave signals in the airspace of the to-be-measured region and transmits them to the microwave receiving module; the microwave receiving module performs gain and filtering processing on the scattering signals to obtain corresponding perfect signals; the signal processing module demodulates the perfect signals to extract the signal amplitude attenuation of the perfect signals, and calculates the real-time rainfall intensity of the to-be-measured region based on the signal amplitude attenuation; the present solution can accurately cover a small to-be-measured region of 1-10km through directional transmission of microwave signals, realize planar accurate monitoring, and solve the limitations of traditional rainfall monitoring solutions; the signal attenuation-rainfall intensity calibration model constructed based on the Mie scattering theory can ensure the accuracy of rainfall monitoring and meet the accuracy requirements of fine monitoring in a small region.

[0031] In addition, the present solution has fast response speed and strong real-time performance: the total delay of signal preprocessing and feature parameter extraction is less than or equal to 50ms, and the update frequency of rainfall intensity and rainfall amount can reach 1 minute / second, which is much faster than the response speed of a traditional rain gauge and can timely capture sudden rainfall processes such as short-time heavy rainfall; the present solution uses adaptive filtering technology to effectively suppress external interference.

[0032] In a second embodiment of the low-frequency microwave-based rainfall monitoring method proposed in the application, based on the first embodiment, the system further comprises a power supply module and a storage and transmission module; the storage and transmission module is in communication connection with the signal processing module; the power supply module is used to supply power to the microwave transmitting module, the microwave receiving module, the signal processing module, and the storage and transmission module; and step S150 further comprises the following steps: Step S210: The signal processing module sends the real-time rainfall intensity of the to-be-measured area to the storage and transmission module for local storage.

[0033] Specifically, after the power supply module is connected to the power supply, the signal processing module automatically completes self-checking of each module. The power supply module supports wide voltage input and backup power supply, and can stably work in a complex environment of -20℃-60℃ and humidity of 0-100% RH (no condensation), thereby improving the system operation reliability. The power supply module supports dual power supply mode of a solar panel (power generation power is 100W) and a lithium battery (capacity is 20Ah). The storage and transmission module is used to store historical monitoring data (i.e. real-time rainfall intensity, storage duration ≥30 days), and can also upload the monitoring data to a weather monitoring platform in real time.

[0034] In a third embodiment of the low-frequency microwave-based rainfall monitoring method proposed in the application, based on the second embodiment, the system further comprises a housing and a mounting bracket; the housing is a cuboid box (specific size: 30cm×20cm×15cm), is made of IP65-level waterproof aluminum alloy material, and is divided into upper space and lower space by a partition plate; the microwave transmitting module is arranged at the left side of the upper space, and the microwave receiving module is arranged at the right side of the upper space; the signal processing module, the storage and transmission module, and the power supply module are sequentially arranged from left to right in the lower space; and the bottom of the housing is connected to the mounting bracket through a flange plate.

[0035] Meanwhile, the mounting bracket can adjust the pitch angle (0-30°) and the height; and the mounting bracket is specifically a triangular bracket with adjustable pitch angle (the height range of the mounting bracket is 1.5-2.5m). By adjusting the pitch angle of the mounting bracket, the orientation pitch angle of the microwave transmitting module and the microwave receiving module is adjusted, thereby ensuring that the microwave transmitting module and the microwave receiving module can more accurately aim at the to-be-measured area.

[0036] As shown in FIG. 6, the microwave transmitting module and the microwave receiving module are arranged on the left side and the right side of the upper space of the housing respectively, and the signal processing module, the storage and transmission module, and the power supply module are sequentially arranged from left to right in the lower space of the housing. Figure 2As shown, in the embodiment, the specific structure of the mounting bracket comprises a base 110, a connecting frame 120, a support rod 130, a first connecting arm 160, a second connecting arm 170, a sleeve 180, a rotating rod 190, a threaded rod 210, a sliding rail 140, a sliding seat 150, a support plate 220, a motor 260 and a speed reducer 250; the base 110 is arranged below the connecting frame 120; the bottom of the support rod 130 is fixedly connected to the base 110; the top of the support rod 130 is hingedly connected to the bottom of the connecting frame 120; the sliding rail 140 is arranged at the bottom of the connecting frame 120, and the sliding seat 150 is slidingly arranged on the sliding rail 140; the top of the first connecting arm 160 and the top of the second connecting arm 170 are both fixedly connected to the sliding seat 150; one side of the outer wall of the rotating drum is hingedly connected to the bottom of the first connecting arm 160, and the other side of the outer wall of the rotating drum is hingedly connected to the bottom of the second connecting arm 170; the hinging shaft of the rotating drum is parallel to the hinging shaft of the support rod 130 relative to the connecting frame 120; the sliding direction of the sliding seat 150 is perpendicular to the hinging shaft of the rotating drum; the sleeve 180 is provided with internal threads capable of cooperating with the threaded rod 210; the support plate 220 is fixedly connected to the base 110, is above the base 110, and is below the sleeve 180; the rotating rod 190 penetrates through the support plate 220; the threaded rod 210 is coaxially fixedly connected to the top of the rotating rod 190; the threaded rod 210 is cooperatively screwed in the sleeve; the motor 260 and the speed reducer 250 are both arranged on the base 110; the bottom of the rotating rod 190 is coaxially connected with a first gear 230; the output shaft of the speed reducer 250 is coaxially connected with a second gear 240; the first gear 230 and the second gear 240 are engaged; the output shaft of the motor 260 is coaxially connected to the input shaft of the speed reducer 250.

[0037] In addition, the connecting frame 120 is further provided with a control module (for example, a single-chip microcomputer) and an angle sensor in communication connection with the control module; the control module can know the current pitch angle value of the connecting frame 120 in real time based on the angle sensor; the control module is further used for controlling the start-stop and rotating direction of the motor 260, so as to realize automatic adjustment of the pitch angle value of the connecting frame 120.

[0038] Through the above technical features, the specific structure of the mounting bracket is further improved; in use, the shell is arranged on the upper part of the connecting frame 120; when the pitch angle needs to be adjusted, the motor 260 only needs to be started to drive the rotating rod 190 to rotate, thereby driving the threaded rod 210 to rotate, so that the connecting frame 120 is driven to rotate around the hinging point of the support rod 130 under the cooperation of the sleeve 180, thereby adjusting the overall pitch angle of the connecting frame 120.

[0039] In a fourth embodiment of the low-frequency microwave-based rainfall monitoring method provided in the present application, based on the third embodiment, the antenna assembly comprises a transmitting antenna and a receiving antenna; both the transmitting antenna and the receiving antenna are horn-shaped; the transmitting antenna and the receiving antenna are fixed to the outer top of the shell by bolts; the transmitting antenna is electrically connected to the microwave transmitting module by an SMA coaxial connecting cable; and the receiving antenna is electrically connected to the microwave receiving module by an SMA coaxial connecting cable.

[0040] Specifically, the detailed parameters of the components in the system are as follows: The shell is made of aluminum alloy material (steel grade 6061), with a wall thickness of 2 mm and an anodized surface treatment; the specific model of the microwave transmitting module is AD9959, with an output power of 8 W, a normal working frequency of 1.8 GHz, a power supply voltage of 12 V DC, and a working temperature range of -40℃-60℃; the specific model of the microwave receiving module is AD8361, with a noise factor of 1.8 dB, a gain of 38 dB, an input impedance of 50Ω, and a power supply voltage of 12 V DC; the specific model of the FPGA chip in the signal processing module is Xilinx Artix-7 (model XC7A35T), which is matched with a 12-bit ADC (model AD7980) with a sampling rate of 1MSPS.

[0041] The storage and transmission module includes an SD memory card (with a capacity of 16 GB and a transmission speed level of Class 10) and a 4G module (specific model SIM7600) supporting TCP / IP protocol. The power supply module is a lithium battery with an output voltage of 12 V and a capacity of 20 Ah (type: lithium iron phosphate battery), and the charging method is solar charging, with a solar charging controller model of MPPT12V / 24V10A. Both the transmitting antenna and the receiving antenna are horn antennas with an aperture of 15 cm x 10 cm, a gain of 18 dBi, a beam angle of 15°, and a horizontal polarization mode; the material of the mounting bracket is Q235 steel, with a maximum load capacity of 20 kg, an adjustable angle range of 0-30°, and a folded height of 80 cm.

[0042] The assembly steps of the components in the system are as follows: Step 1: Assemble the shell, fix the internal partition plate in the shell with screws, ensure that the upper space accommodates the microwave transmitting module and the microwave receiving module, and the lower space accommodates the signal processing module, the storage and transmission module, and the power supply module. Step 2: Fix the microwave transmitting module and the microwave receiving module on the left and right sides of the upper space respectively through copper columns, and the distance between the microwave transmitting module and the microwave receiving module is 5 cm to avoid signal interference.

[0043] Step 3: sequentially fix the signal processing module, the storage and transmission module, and the power supply module in the lower space, connect the power supply module to the power supply interface of each module through the Dupont wire, and connect the signal processing module and the storage and transmission module through the SPI bus. Step 4: fix the transmitting antenna and the receiving antenna on the antenna mounting seat at the top of the shell through M5 bolts, the axis of the transmitting antenna and the receiving antenna need to be kept parallel to the side surface of the shell, and the distance between the transmitting antenna and the receiving antenna is 10 cm. Step 5: connect the transmitting antenna and the output interface of the microwave transmitting module through the SMA coaxial connecting cable, connect the receiving antenna and the input interface of the microwave receiving module through the SMA coaxial connecting cable, the length of the SMA coaxial connecting cable is 50 cm, and the joint is ensured to be tightened (the torque is 0.5 N m). Step 6: align the flange plate of the mounting bracket with the bottom mounting hole of the shell, fix through M8 bolts, adjust the height of the bracket to 2 m, and lock the adjusting knob.

[0044] In the fifth embodiment of the low-frequency microwave-based rainfall monitoring method provided in the application, based on the third embodiment, step S150 comprises the following steps: Step S510: the signal processing module adopts an algorithm combining quadrature demodulation and Fourier transform to demodulate the perfect signal, so as to extract the actual signal amplitude attenuation of the perfect signal.

[0045] Step S520: the signal processing module acquires historical experience data, wherein the historical experience data comprises a plurality of historical data groups, and each historical data group comprises historical amplitude attenuation and historical rainfall intensity corresponding to each other.

[0046] Step S530: the signal processing module obtains a signal amplitude attenuation-rainfall intensity fitting curve based on the historical experience data.

[0047] Specifically, when the microwave signal penetrates the space of the to-be-measured region, Mie scattering occurs between the microwave signal and the precipitation particles (raindrops, snowflakes, etc.) in the air, which causes the amplitude of the signal to attenuate, and the scattering effect is closely related to the size, concentration and shape of the precipitation particles. That is, the attenuation amplitude of the microwave signal and the rainfall intensity have a correlation relationship; based on the historical experience data (including a plurality of historical amplitude attenuation and historical rainfall intensity corresponding to each other), a signal amplitude attenuation-rainfall intensity fitting curve can be obtained, which can express the correlation relationship between the attenuation amplitude of the microwave signal and the rainfall intensity; based on this, the microwave signal is transmitted to the to-be-measured region, then the scattered signal returned by the to-be-measured region is received, and the amplitude attenuation of the scattered signal is extracted, so that the rainfall intensity of the to-be-measured region can be determined based on the amplitude attenuation.

[0048] Specifically, the abscissa of the fitting curve is the microwave signal amplitude attenuation, and the ordinate of the fitting curve is the rainfall intensity; for example, in the actual inversion process, it is measured that: when the signal amplitude attenuation is 2dB, the corresponding rainfall intensity is 10mm / h; when the signal amplitude attenuation is 5dB, the corresponding rainfall intensity is 30mm / h, so that the data can be used for inversion, and the signal amplitude attenuation of the received scattering signal is substituted into the signal attenuation-rainfall intensity calibration model after inversion, so that the corresponding real-time rainfall intensity can be calculated.

[0049] Step S540: The signal processing module substitutes the actual signal amplitude attenuation into the signal amplitude attenuation-rainfall intensity fitting curve to obtain the real-time rainfall intensity of the to-be-measured area.

[0050] In a sixth embodiment of the low-frequency microwave-based rainfall monitoring method provided in the application, based on the fifth embodiment, step S540 further includes the following steps: Step S610: The signal processing module integrates the real-time rainfall intensity with a second preset time length (1 minute) as an integration time step to obtain the cumulative rainfall of the to-be-measured area in a past third preset time length (for example, 1 hour), wherein the third preset time length is an integer multiple of the second preset time length.

[0051] Specifically, the embodiment provides a specific scheme for calculating the cumulative rainfall. The essence of integration with a time step is to discretize the integral operation of continuous time, that is, to divide the integral interval into a plurality of equidistant time steps (the second preset time length in the embodiment), and to approximately calculate the cumulative amount by using a numerical method, so as to obtain the cumulative rainfall of the to-be-measured area in a past time length (the third preset time length in the embodiment).

[0052] In a seventh embodiment of the low-frequency microwave-based rainfall monitoring method provided in the application, based on the fifth embodiment, step S540 further includes the following steps: Step S710: The signal processing module calculates the polarization ratio of the perfect signal, wherein the polarization ratio is the ratio of the horizontal polarization signal strength to the vertical polarization signal strength of the perfect signal.

[0053] Specifically, the polarization ratio (also known as the polarization ratio) of the microwave signal is a core parameter for characterizing the polarization characteristics of the microwave electromagnetic wave, and reflects the amplitude or power ratio relationship of different orthogonal polarization components in the microwave signal. The definition and calculation method thereof varies with the polarization state type.

[0054] Specifically, the polarization ratio of the microwave signal is the ratio of the "desired polarization component" to the "undesirable orthogonal polarization component"; in actual measurement or definition of the polarization ratio of a linearly polarized signal, first find the direction of the maximum electric field strength, which is the "main polarization direction" (i.e. the desired direction). Then, measure the component in the orthogonal direction which is 90 degrees to the main direction. The ratio of the two is the polarization ratio.

[0055] Therefore, the main direction can be horizontal, vertical, 45 degrees or any angle. If the main direction is vertical, the polarization ratio is the amplitude ratio of the vertical component / the amplitude ratio of the horizontal component; if it is 45 degrees, the polarization ratio is the amplitude ratio of the 45-degree component / the amplitude ratio of the 135-degree component.

[0056] In summary, if the desired polarization direction of the microwave signal is vertical, the polarization ratio of the microwave signal = the amplitude ratio of the vertical component / the amplitude ratio of the horizontal component; if the desired polarization direction of the microwave signal is horizontal, the polarization ratio = the amplitude ratio of the horizontal component / the amplitude ratio of the vertical component; if the desired direction of the microwave signal is inclined, the amplitude ratio of the component in the direction and its orthogonal direction is used for calculation.

[0057] Step S720: When the polarization ratio is greater than or equal to a first preset value (for example, 1) and less than a second preset value (for example, 1.2), the signal processing module determines that the rainfall type of the to-be-measured area is drizzle.

[0058] Step S730: When the polarization ratio is greater than or equal to the second preset value and less than a third preset value (for example, 1.8), the signal processing module determines that the rainfall type of the to-be-measured area is moderate rain.

[0059] Step S740: When the polarization ratio is greater than or equal to the third preset value and less than a fourth preset value (for example, 2.5), the signal processing module determines that the rainfall type of the to-be-measured area is heavy rain.

[0060] Step S750: When the polarization ratio is greater than or equal to the fourth preset value, the signal processing module determines that the rainfall type of the to-be-measured area is snow.

[0061] Specifically, the embodiment gives a specific scheme for determining the rainfall type. The particles of different precipitation types have significant differences in the ratio (polarization ratio) of the electric field strength of the horizontal polarization signal to the electric field strength of the vertical polarization signal, and the rainfall type can be distinguished by the polarization ratio.

[0062] The raindrop particles are small and uniform, so the polarization ratio is close to [1, 1.2); the moderate raindrop particles are moderate in size and relatively regular in shape, the polarization ratio is in the range of [1.2, 1.8); the heavy raindrop particles are large and irregular, the polarization ratio is in the range of [1.8, 2.5); the snowflake particles are fluffy in shape, and the polarization signal difference is significant in the scattering process, and the polarization ratio is greater than or equal to 2.5.

[0063] In an eighth embodiment of the low-frequency microwave-based rainfall monitoring method provided in the application, based on the seventh embodiment, the system further comprises a cloud server in wireless communication connection with the storage and transmission module, and an audible and visual alarm in communication connection with the signal processing module; the embodiment further comprises the following steps: Step S810: The signal processing module sends the real-time rainfall intensity, the cumulative rainfall, and the rainfall type of the to-be-measured area to the storage and transmission module.

[0064] Step S820: The storage and transmission module sends the real-time rainfall intensity, the cumulative rainfall, and the rainfall type of the to-be-measured area to the cloud server for backup storage.

[0065] Step S830: When the real-time rainfall intensity is greater than a preset threshold (50 mm / h), the signal processing module controls the audible and visual alarm to start.

[0066] In addition, when the system fails to work (for example, the emission power of the microwave emission module is less than 3W), the signal processing module also controls the audible and visual alarm to start.

[0067] The application further provides a low-frequency microwave-based rainfall monitoring system applying the low-frequency microwave-based rainfall monitoring method; the system comprises a microwave emission module, a microwave receiving module, a signal processing module, and an antenna assembly; the microwave emission module and the microwave receiving module are electrically connected to the antenna assembly; the microwave receiving module is in communication connection with the signal processing module.

[0068] The above-mentioned embodiment numbers of the application are only for description, and do not represent the advantages and disadvantages of the embodiments.

[0069] The embodiments of the application are described above in combination with the drawings, but the application is not limited to the above-mentioned specific embodiments, the above-mentioned specific embodiments are only illustrative, but not restrictive, and those skilled in the art can make many forms under the inspiration of the application without departing from the purpose of the application and the scope protected by the claims, which all belong to the protection of the application.

Claims

1. A low-frequency microwave-based rainfall monitoring method, characterized by, Be applied to low-frequency microwave-based rainfall monitoring system;The system includes microwave emission module, microwave receiving module, signal processing module and antenna assembly;The microwave emission module and the microwave receiving module are electrically connected to the antenna assembly; The microwave receiving module is in communication connection with the signal processing module;The method comprises: After starting, the microwave emission module preheats for a first preset time period; The microwave emission module generates continuous microwave signals with a preset frequency, and directs the continuous microwave signals to the airspace of the area to be measured with a preset beam angle through the antenna assembly; The antenna assembly receives the scattering signals generated by the continuous microwave signals in the airspace of the area to be measured and transmits them to the microwave receiving module; The microwave receiving module processes the scattering signals for gain and filtering to obtain corresponding perfect signals, and sends the perfect signals to the signal processing module; The signal processing module demodulates the perfect signals to extract the signal amplitude attenuation of the perfect signals, and calculates the real-time rainfall intensity of the area to be measured based on the signal amplitude attenuation.

2. The low-frequency microwave-based rainfall monitoring method of claim 1, wherein, The system further comprises a power supply module and a storage and transmission module;The storage and transmission module is in communication connection with the signal processing module;The power supply module is used to power the microwave emission module, the microwave receiving module, the signal processing module, and the storage and transmission module;The signal processing module demodulates the perfect signals to extract the signal amplitude attenuation of the perfect signals, and calculates the real-time rainfall intensity of the area to be measured based on the signal amplitude attenuation, and then comprises: The signal processing module sends the real-time rainfall intensity of the area to be measured to the storage and transmission module for local storage.

3. The low-frequency microwave-based rainfall monitoring method of claim 2, wherein, The system further comprises a housing and a mounting bracket;The housing is a rectangular box, and the inside is divided into upper space and lower space by a partition plate:The microwave emission module is arranged on the left side of the upper space, and the microwave receiving module is arranged on the right side of the upper space; The lower space is sequentially provided with the signal processing module, the storage and transmission module, and the power supply module from left to right;The bottom of the housing is connected to the mounting bracket through a flange.

4. The low-frequency microwave-based rainfall monitoring method of claim 3, wherein, The antenna assembly includes a transmitting antenna and a receiving antenna;The transmitting antenna and the receiving antenna are both horn-shaped;The transmitting antenna and the receiving antenna are fixed to the outer top of the housing by bolts;The transmitting antenna is electrically connected to the microwave emission module through an SMA coaxial connecting cable;The receiving antenna is electrically connected to the microwave receiving module through an SMA coaxial connecting cable.

5. The low-frequency microwave-based rainfall monitoring method of claim 3, wherein, The signal processing module demodulates the perfect signals to extract the signal amplitude attenuation of the perfect signals, and calculates the real-time rainfall intensity of the area to be measured based on the signal amplitude attenuation, comprising: The signal processing module demodulates the perfect signals using an algorithm combining quadrature demodulation and Fourier transform to extract the actual signal amplitude attenuation of the perfect signals; The signal processing module acquires historical experience data, wherein the historical experience data includes a plurality of historical data groups, and each historical data group includes corresponding historical amplitude attenuation and historical rainfall intensity; The signal processing module obtains a signal amplitude attenuation-rainfall intensity fitting curve based on historical experience data; The signal processing module substitutes the actual signal amplitude attenuation into the signal amplitude attenuation-rainfall intensity fitting curve to obtain the real-time rainfall intensity of the to-be-measured area.

6. The low-frequency microwave-based rainfall monitoring method of claim 5, wherein, The signal processing module substitutes the actual signal amplitude attenuation into the signal amplitude attenuation-rainfall intensity fitting curve to obtain the real-time rainfall intensity of the to-be-measured area, and then further comprises: The signal processing module takes the second preset time length as an integral time step, and integrates the real-time rainfall intensity to obtain the cumulative rainfall of the to-be-measured area in the past third preset time length, wherein the third preset time length is an integer multiple of the second preset time length.

7. The low-frequency microwave-based rainfall monitoring method of claim 5, wherein, The signal processing module substitutes the actual signal amplitude attenuation into the signal amplitude attenuation-rainfall intensity fitting curve to obtain the real-time rainfall intensity of the to-be-measured area, and then further comprises: The signal processing module calculates the polarization ratio of the refined signal, wherein the polarization ratio is the ratio of the horizontal polarization signal intensity to the vertical polarization signal intensity of the refined signal; When the polarization ratio is greater than or equal to the first preset value and less than the second preset value, the signal processing module determines that the rainfall type of the to-be-measured area is drizzle; When the polarization ratio is greater than or equal to the second preset value and less than the third preset value, the signal processing module determines that the rainfall type of the to-be-measured area is moderate rain; When the polarization ratio is greater than or equal to the third preset value and less than the fourth preset value, the signal processing module determines that the rainfall type of the to-be-measured area is heavy rain; When the polarization ratio is greater than or equal to the fourth preset value, the signal processing module determines that the rainfall type of the to-be-measured area is snow.

8. The low-frequency microwave-based rainfall monitoring method of claim 7, wherein, The system further comprises a cloud server in wireless communication connection with the storage and transmission module, and an audible and visual alarm in communication connection with the signal processing module; the method further comprises: The signal processing module sends the real-time rainfall intensity, the cumulative rainfall, and the rainfall type of the to-be-measured area to the storage and transmission module; The storage and transmission module sends the real-time rainfall intensity, the cumulative rainfall, and the rainfall type of the to-be-measured area to the cloud server for backup storage; When the real-time rainfall intensity is greater than a preset threshold, the signal processing module controls the audible and visual alarm to start.

9. A low-frequency microwave-based rainfall monitoring system, characterized by, The low-frequency microwave-based rainfall monitoring method of any one of claims 1-8 is applied; the system comprises a microwave transmitting module, a microwave receiving module, a signal processing module, and an antenna assembly; the microwave transmitting module and the microwave receiving module are both electrically connected to the antenna assembly; the microwave receiving module is in communication connection with the signal processing module.

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