Farmland environment rainfall monitoring system and method based on microwave link

Abstract

The invention relates to a farmland environment rainfall monitoring system and method based on a microwave link, and the system comprises a microwave transmitting module which is used for transmitting a microwave signal; the microwave receiving module is used for receiving microwave signals which are attenuated due to the influence of rainfall in a microwave link transmission process in a rainfall environment, and acquiring indication voltage of the strength of the received signals; the inversion module is used for inputting received signal strength indication voltage and outputting average rainfall intensity in a microwave link based on a rainfall inversion algorithm model established by the invention; wherein the rainfall inversion model is obtained by combining a microwave link average attenuation result caused by rainfall with a microwave rain attenuation model. According to the invention, accurate monitoring of regional rainfall dynamic states of different scales and different dimensions can be realized.

Description

Technical Field

[0001] The present invention relates to the field of microwave link monitoring technology, and in particular to a farmland environment rainfall monitoring system and method based on microwave links. Background Art

[0002] Rainfall is an important factor in inducing natural disasters. Most agricultural meteorological disasters are directly or indirectly related to rainfall, such as floods, waterlogging, and drought caused by long-term lack of rainfall. Therefore, rainfall monitoring is an important part of agricultural disaster prevention and mitigation. Although traditional precipitation monitoring technologies such as rain gauges, weather radars, and meteorological satellites have been widely used in various scientific research and practical applications, in modern precision agricultural production, there are often customized and refined production management needs based on subdivided fields. However, these traditional methods are still insufficient for dynamic, real-time, and accurate monitoring of precipitation in small-scale areas such as fields.

[0003] Agricultural precipitation mainly focuses on near-ground precipitation that affects crops, that is, rain, snow, hail, etc. that actually falls on the fields. Although rain gauges can accurately measure surface precipitation, as a fixed-point measurement method, their regional representativeness is poor. If you want to achieve accurate monitoring of local regional precipitation, the number of rain gauges required is often very large, and the construction and maintenance costs are high. The observations of meteorological radars and meteorological satellites are mostly aimed at atmospheric clouds, and it is difficult to monitor the dynamics of small-scale regional precipitation in the field and discover and track precipitation disasters. Secondly, meteorological satellites usually require a certain time interval to conduct multiple observations of the target area. There are limitations in time and spatial resolution, and it is difficult to achieve accurate monitoring of many small-scale precipitation, such as short-term local showers.

[0004] At present, most of the rainfall inversion research based on microwave links is still methodological exploration and simulation experiments, and there is still a lack of sufficient actual testing. At the same time, many rainfall inversion methods and model algorithms are relatively complex, difficult to operate in practice, and not easy to apply on a large scale. In particular, for many rain attenuation prediction models that have been proposed, these models are established using rain attenuation statistical data from rainfall environments in other regions. Due to their regional differences, these models cannot be directly used to study the impact of rainfall attenuation in my country's rainfall environment. Summary of the invention

[0005] In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide an equivalent and practical method to construct a microwave link rainfall inversion model, and to design and develop a rainfall sensor prototype based on the inversion model, to build a farmland environment rainfall monitoring system based on microwave links, and to further explore field-scale rainfall monitoring methods and applications.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A farmland environment rainfall monitoring system based on microwave links, comprising:

[0008] A microwave transmitting module, used for transmitting microwave signals;

[0009] A microwave receiving module is used to receive the receiving signal blocked by gas molecules and obtain an indication voltage of the receiving signal strength;

[0010] The inversion module is used to input the indicated voltage into a rainfall inversion model to obtain the average rainfall intensity in the microwave link; wherein the rainfall inversion model is obtained by combining the average attenuation result of the microwave link caused by rainfall with a microwave rain attenuation model.

[0011] Optionally, the inversion module comprises:

[0012] The model building submodule is used to obtain a rainfall inversion model by combining the average attenuation result of the microwave link caused by rainfall with the microwave rain attenuation model;

[0013] The A / D conversion submodule is used to integrate the rainfall inversion model, input the indication voltage into the rainfall inversion model, and obtain the average rainfall intensity in the microwave link.

[0014] Optionally, the model building submodule includes:

[0015] The microwave average attenuation result acquisition unit is used to obtain the microwave attenuation result based on the attenuation of microwave transmission during rainfall and the attenuation of microwave transmission in the adjacent time periods before and after rainfall, and in combination with the set fixed microwave transmission signal strength and frequency, and obtain the average attenuation result of the microwave link caused by rainfall through the microwave attenuation result combined with the linear correspondence between the received signal and the indication voltage.

[0016] Optionally, the method for obtaining the microwave attenuation result is:

[0017] A rain =(A SSL -A RSL )-(A SSL -A' RSL )=A' RSL -A RSL

[0018] Among them, A rain is the microwave rain attenuation, A RSL is the receiving signal strength of the microwave receiving end during rainfall; A' RSL A is the received signal strength of the microwave receiving end in the period before and after rainfall; SSL is the transmission signal strength of the transmitter.

[0019] Optionally, the method for obtaining the linear correspondence is:

[0020] A RSL =m·V RSSI +n

[0021] Among them, A RSL is the received signal strength at the microwave receiving end, V RSSI It is the received signal strength indication voltage at the receiving end of the microwave transmission equipment in a rainfall environment, and m and n are constants.

[0022] Optionally, the method for obtaining the average attenuation result of the microwave link caused by rainfall is:

[0023]

[0024] Where γ is the average attenuation of the microwave link caused by rainfall, D is the transmission distance between the microwave transmitter and the receiver, and V R ' SSI and V RSSI are the received signal strength indication voltages at the receiving end of the microwave transmission equipment in the time period before and after rainfall and in the rainfall environment, respectively. m and n are constants.

[0025] Optionally, the method for obtaining the microwave rain attenuation model is:

[0026] γ=kR α

[0027] Where R is the average rainfall intensity of the microwave path, γ is the average attenuation of the microwave link caused by rainfall, and k and α are coefficients.

[0028] Optionally, the method for obtaining the rainfall inversion model is:

[0029]

[0030] Where R is the average rainfall intensity along the microwave path, V R ' SSI and V RSSI are the received signal strength indication voltages at the receiving end of the microwave transmission equipment in the time period before and after rainfall and in the rainfall environment, respectively, and k and α are coefficients.

[0031] To achieve the above object, the present invention provides a method for monitoring rainfall in farmland environment based on microwave links, comprising:

[0032] Transmit microwave signals, receive signals blocked by gas molecules, and obtain a voltage indicating the strength of the received signal;

[0033] The indicated voltage is input into a rainfall inversion model to obtain an average rainfall intensity in the microwave link; wherein the rainfall inversion model is obtained by combining an average attenuation result of the microwave link caused by rainfall with a microwave rain attenuation model.

[0034] The beneficial effects of the present invention are:

[0035] Each group of microwave transmission equipment (transmitting end and receiving end) and A / D conversion module of the present invention together constitute a rainfall sensor prototype system, which directly outputs the average rainfall intensity value within the line-of-sight microwave link range to realize dynamic monitoring of rainfall between two points. If multiple groups of microwave transmission equipment are deployed and multiple intersecting microwave link networks are constructed, a near-ground two-dimensional rainfall field monitoring sensor network based on a microwave link network can be realized within a specified area. Therefore, the rainfall sensor prototype system can be easily operated and flexibly expanded into a rainfall monitoring sensor network for multiple regions; each monitoring site can be "single point to single point" (one-dimensional rainfall field dynamic monitoring of a single sensor), "multi-point to multi-point" (two-dimensional rainfall field dynamic monitoring of multiple sensors), or near-ground three-dimensional rainfall field dynamic monitoring can be performed to realize accurate monitoring of regional rainfall dynamics of different scales and dimensions. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0037] Figure 1 A schematic diagram of a prototype structure of a rainfall sensor of a farmland environment rainfall monitoring system based on a microwave link according to an embodiment of the present invention;

[0038] Figure 2 This is a flow chart of a method for monitoring rainfall in farmland environment based on microwave links according to an embodiment of the present invention;

[0039] Figure 3 V in the embodiment of the present invention RSSI With A RSL The corresponding expression intention;

[0040] Figure 4 This is a real-life picture of a field test system according to an embodiment of the present invention; wherein: Figure 4 a is the microwave receiving end equipment, Figure 4 b is the prototype of microwave link rainfall sensor;

[0041] Figure 5 The inversion rainfall intensity results of four rainfall events in different time periods according to the embodiment of the present invention; wherein, Figure 5 a is 17:00-21:00 on July 1, 2021, Figure 5 b is from 21:00 on July 5, 2021 to 2:00 the next day, Figure 5 c is 7:30-12:30 on July 12, 2021, Figure 5 d is 20:00-24:00 on July 12, 2021. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] like Figure 1 As shown, this embodiment discloses a farmland environment rainfall monitoring system based on a microwave link, including: a microwave transmitting module, used to transmit microwave signals; a microwave receiving module, used to receive received signals blocked by gas molecules, and obtain an indication voltage of the received signal strength; an inversion module, used to input the indication voltage into a rainfall inversion model, and obtain the average rainfall intensity in the microwave link; wherein the rainfall inversion model is obtained by combining the average attenuation result of the microwave link caused by rainfall with a microwave rain attenuation model.

[0045] Furthermore, the inversion module includes: a model building submodule, which is used to obtain a rainfall inversion model by combining the average attenuation result of the microwave link caused by rainfall with the microwave rain attenuation model; an A / D conversion submodule, which is used to integrate the rainfall inversion model, input the indication voltage into the rainfall inversion model, and obtain the average rainfall intensity in the microwave link.

[0046] Furthermore, the model building submodule includes: a microwave average attenuation result acquisition unit, which is used to obtain the microwave attenuation result based on the attenuation of microwave transmission during rainfall and the attenuation of microwave transmission in the adjacent time periods before and after rainfall, and combined with the set fixed microwave transmission signal strength and frequency, and obtain the average attenuation result of the microwave link caused by rainfall by combining the microwave attenuation result with the linear correspondence between the received signal and the indication voltage.

[0047] Specifically, the microwave link rainfall inversion model is constructed:

[0048] The ITU-R series rain attenuation models provided by the International Telecommunication Union have the characteristics of few input parameters, simple use, and wide application range. Among them, Recommendation ITU-R P.838-3 adopts the concept of equivalent path length to homogenize the non-uniformity of rainfall, so that the shortened path length multiplied by the unit path attenuation (attenuation rate) is the actual measured rainfall attenuation; and for microwave transmission in the frequency range of 1 to 1000 GHz and linear polarization (horizontal: H, vertical: V) horizontal path, the following microwave rain attenuation models and corresponding parameter reference values ​​are provided:

[0049] γ=kR α (1)

[0050] Where R is the average rainfall intensity of the microwave path (mm / h); γ is the average attenuation of the microwave link caused by rainfall (dB / km); the coefficients k and α can be calculated and determined by the frequency function obtained by fitting:

[0051]

[0052] Where, f is the microwave frequency (GHz); coefficient a j 、b j 、c j 、m k 、c k 、m a and c a The reference values ​​provided in Recommendation ITU-R P.838-3 are used respectively. (horizontal polarization is k H and α H , vertical polarization is k V and α V ).

[0053] During the rainfall process, except for raindrops, the changes of other environmental factors that cause microwave attenuation are relatively small. Therefore, the calculation of microwave rain attenuation in this embodiment uses the average attenuation value of microwave transmission under the environmental conditions in the time period before and after the rainfall as a reference, and the microwave rain attenuation value is obtained by the difference between the attenuation of microwave transmission during the rainfall process and the attenuation of microwave transmission in the time period before and after the rainfall. That is, the microwave rain attenuation A total It can be expressed as:

[0054] A rain =A total -A' total (4)

[0055] Among them, A total is the total attenuation of microwave transmission during rainfall (dB); A t ' otal is the microwave transmission attenuation in the immediate time period before and after rainfall (dB).

[0056] The total microwave transmission attenuation is calculated by the difference between the signal strength at the transmitting end (Send Signal Level, SSL) and the signal strength at the receiving end (Receive Signal Level, RSL) of the microwave transmission equipment. This embodiment sets the microwave transmission signal strength and frequency to fixed values. Therefore, the microwave rain attenuation A rain It can be further expressed as:

[0057] A rain =(A SSL -A RSL )-(A SSL -A' RSL )=A' RSL -A RSL (5)

[0058] Among them, A RSL is the received signal strength of the microwave receiving end during rainfall (dBm); A' RSL is the received signal strength (dBm) of the microwave receiving end in the period before and after rainfall; SSL is the transmission signal strength of the transmitter (dBm).

[0059] The received signal strength A at the microwave receiving end is known RSL The signal strength indicator voltage V RSSI (Received Signal Strength Indicator, RSSI)(RSSIPort Voltage) has a linear correspondence:

[0060] A RSL =m·V RSSI +n (6)

[0061] Therefore, the average attenuation of the microwave link caused by rainfall can be further expressed as:

[0062]

[0063] Where D is the transmission distance between the microwave transmitting end and the receiving end (km), V R ' SSI and V RSSI They are the received signal strength indicator voltage (V) at the receiving end of the microwave transmission equipment in the time period immediately before and after rainfall and in the rainfall environment.

[0064] Combining formula (7) with ITU-R P.838-3 rain attenuation calculation formula (1), we finally obtain the model algorithm of the average rainfall intensity of the microwave link based on the microwave received signal strength indicator voltage:

[0065]

[0066] The dependent variable R is the average rainfall intensity of the microwave path (mm / h); the independent variable V RSSI is the signal strength indicator voltage (V) of the microwave receiving end during rainfall; the coefficients k and α are obtained from the frequency functions (2) and (3).

[0067] Specifically, the microwave link rainfall sensor prototype design:

[0068] The sensor prototype design is as attached Figure 1 As shown, the receiving end of the microwave transmission equipment outputs a microwave receiving signal strength indication voltage V RSSI Signal to A / D conversion module, the A / D conversion module integrates the microwave received signal strength indication voltage V RSSI The rainfall inversion model outputs the average rainfall intensity within the distance from the transmitting end to the receiving end (microwave link) of the microwave device. Each pair of microwave transmission equipment and A / D conversion module together constitutes an average rainfall intensity sensor of a microwave link, realizing dynamic monitoring of rainfall between two points.

[0069] Specifically, the field test system is built:

[0070] In order to test the accuracy of the microwave link rainfall inversion model constructed in this embodiment and the application effect of the sensor prototype system, this embodiment built a field test system. Huawei OptiX RTN360 was used as the microwave transceiver experimental device.

[0071] The microwave transmission parameters are set to horizontal linear polarization (corresponding coefficient k H and α H ), horizontal channel and 60GHz output frequency. The corresponding relationship between the received signal strength indicator voltage and the received signal strength of the microwave transmission device is shown in the attached figure. Figure 3 As shown, we can then get V RSSI With A RSL The linear relationship (9) is shown in the above. In summary, the coefficients m = 15.91 and n = -91.59 in formula (8).

[0072] A RSL =15.91V RSSI -91.59 (9)

[0073] The experimental device was deployed in the standard experimental farmland area of ​​the experimental base of the Institute of Agricultural Environment and Sustainable Development of the Chinese Academy of Agricultural Sciences. Using a 10-meter standard meteorological pole, the transmitting and receiving ends of the microwave equipment were installed and fixed at a fixed height of 9 meters from the ground. Figure 4(a)-(b), ensure that there is no obstruction in the line of sight between the microwave equipment transmitting end and the receiving end, and avoid interference from obstacles such as crops and trees on the ground as much as possible. The distance between the microwave transmitting end and the receiving end (i.e., the length of the microwave link) D = 227m, and an automatic weather station is deployed in the middle of the link to collect rainfall data during the test.

[0074] Specifically, the model inversion accuracy verification:

[0075] like Figure 5 As shown in (a)-(d), the experiment selected four rainfall events from 17:00-21:00 on July 1, 2021, from 21:00 to 2:00 on July 5, from 8:00 to 12:30 on July 6, and from 20:50 to 23:59 on July 12, including light rain, moderate rain, heavy rain and rainstorm. In order to minimize the experimental errors caused by meteorological factors such as temperature, air pressure, and air humidity, the received signal strength indication voltage for a period of time before and after the rainfall event was selected as the basic voltage value for model inversion. Since the voltage signal acquisition frequency of this experimental system is 60s / time, it is necessary to perform sliding average processing on the instantaneous voltage value collected during the rainfall process to reduce the error caused by system voltage fluctuations. In this experiment, the instantaneous voltage value was processed with a sliding average of 5min, 10min and 15min, and the processed voltage values ​​were substituted into the inversion model to obtain the rainfall intensity inversion value. Then, the rainfall intensity values ​​at the time resolutions of 15min, 30min and 60min are calculated respectively by using the measured values ​​of the 1min rainfall data of the meteorological station. The model inversion values ​​are verified by comparing the accuracy with the measured values. The correlation and inversion error between the model inversion values ​​and the measured values ​​of rainfall intensity at different time resolutions are analyzed to verify the model inversion accuracy. This embodiment uses the correlation coefficient (r), absolute error (AE) and relative error (RE) to verify the model inversion accuracy.

[0076] like Figure 2 As shown, this embodiment also discloses a method for monitoring rainfall in a farmland environment based on a microwave link, including: transmitting a microwave signal, receiving a received signal blocked by gas molecules, and obtaining an indication voltage of the received signal strength; inputting the indication voltage into a rainfall inversion model to obtain the average rainfall intensity in the microwave link; wherein the rainfall inversion model is obtained by combining the average attenuation result of the microwave link caused by rainfall with a microwave rain attenuation model.

[0077] Specifically, the rainfall inversion model and the setting parameters of the field test system constructed based on the present invention are as follows: microwave link length D = 0.227 km; coefficient m = 15.91; the mean voltage V of the microwave receiving end receiving signal strength indicator before and after the rainfall event R ' SSI=2.08V; microwave frequency is f=60GHz; coefficients k=0.8606 and α=0.7656 are calculated from frequency function (3,4). Therefore, the rainfall intensity calculation formula based on the output voltage signal of the microwave device can be obtained, that is, the A / D conversion formula of the microwave link rainfall sensor of the field test system:

[0078]

[0079] According to the analysis of rainfall monitoring example data, the measured rainfall intensity values ​​with a time resolution of 15 minutes and 30 minutes have a better correlation with the model inversion value, and the correlation coefficient can reach up to 0.962. Compared with the voltage value after 10 minutes and 5 minutes of sliding average processing, the rainfall intensity inversion value has the best correlation with the measured value after 15 minutes of sliding average processing.

[0080] According to the experimental observation results of this experiment, the microwave link rainfall intensity inversion model constructed based on the ITU-R rain attenuation model has the ability to dynamically observe rainfall intensity at the field scale. Its inversion error comes from the record of the received signal indication voltage on the one hand, and also from other parameters such as water vapor and temperature. Since the construction of the ITU-R rain attenuation model is based on the LP spectrum distribution, and the model parameters do not include other parameters such as temperature, under different rainfall conditions, the model parameters need to be calibrated according to the measured rainfall intensity.

[0081] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A farmland environment rainfall monitoring system based on microwave link, characterized in that: include: A microwave transmitting module, used for transmitting microwave signals; A microwave receiving module is used in a rainy environment to receive microwave signals attenuated by rainfall during transmission through a microwave link, and obtain an indication voltage of the received signal strength; The inversion module is used to input the indicated voltage into a rainfall inversion model to obtain the average rainfall intensity in the microwave link; wherein the rainfall inversion model is obtained by combining the average attenuation result of the microwave link caused by rainfall with a microwave rain attenuation model.

2. The farmland environment rainfall monitoring system based on microwave link according to claim 1 is characterized in that: The inversion module comprises: The model building submodule is used to build a rainfall inversion model by combining the average attenuation results of microwave links caused by rainfall with the microwave rain attenuation model; The A / D conversion submodule is used to integrate the rainfall inversion model, input the indication voltage into the rainfall inversion model, and obtain the average rainfall intensity in the microwave link.

3. The farmland environment rainfall monitoring system based on microwave link according to claim 2 is characterized in that: The model building submodule includes: The microwave average attenuation result acquisition unit is used to obtain the microwave attenuation result based on the attenuation of microwave transmission during rainfall and the attenuation of microwave transmission in the adjacent time periods before and after rainfall, and in combination with the set fixed microwave transmission signal strength and frequency, and obtain the average attenuation result of the microwave link caused by rainfall through the microwave attenuation result combined with the linear correspondence between the received signal and the indication voltage.

4. The farmland environment rainfall monitoring system based on microwave link according to claim 3 is characterized in that: The method for obtaining the microwave attenuation result is: A rain =(A SSL -A RSL )-(A SSL -A' RSL )=A' RSL -A RSL Among them, A rain is the microwave rain attenuation, A RSL is the receiving signal strength of the microwave receiving end during rainfall; A' RSL A is the received signal strength of the microwave receiving end in the period before and after rainfall; SSL is the transmission signal strength of the transmitter.

5. The farmland environment rainfall monitoring system based on microwave link according to claim 3 is characterized in that: The method for obtaining the linear correspondence is: A RSL =m·V RSSI +n Among them, A RSL is the received signal strength at the microwave receiving end, V RSSI It is the received signal strength indication voltage at the receiving end of the microwave transmission equipment in a rainfall environment, and m and n are constants.

6. The farmland environment rainfall monitoring system based on microwave link according to claim 1 is characterized in that: The method for obtaining the average attenuation result of the microwave link caused by rainfall is: Where γ is the average attenuation of the microwave link caused by rainfall, D is the transmission distance between the microwave transmitter and the receiver, and V R ' SSI and V RSSI are the received signal strength indication voltages at the receiving end of the microwave transmission equipment in the time period before and after rainfall and in the rainfall environment, respectively. m and n are constants.

7. The farmland environment rainfall monitoring system based on microwave link according to claim 1 is characterized in that: The method for obtaining the microwave rain attenuation model is: γ=kR α Where R is the average rainfall intensity on the microwave path, γ is the average attenuation of the microwave link caused by rainfall, and k and α are coefficients.

8. The farmland environment rainfall monitoring system based on microwave link according to claim 1 is characterized in that: The method for obtaining the rainfall inversion model is: Where R is the average rainfall intensity along the microwave path, V R ' SSI and V RSSI are the received signal strength indication voltages at the receiving end of the microwave transmission equipment in the time period before and after rainfall and in the rainfall environment, respectively, and k and α are coefficients.

9. The monitoring method of the microwave link-based farmland environment rainfall monitoring system according to any one of claims 1 to 8, characterized in that: include: Transmit microwave signals, and receive microwave signals attenuated by rainfall during transmission through microwave links in a rainy environment, and obtain an indication voltage of the received signal strength; The indicated voltage is input into a rainfall inversion model to obtain an average rainfall intensity in the microwave link; wherein the rainfall inversion model is established by combining an average attenuation result of the microwave link caused by rainfall with a microwave rain attenuation model.

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