X-band weather radar dual-channel multifunction receiving assembly

Abstract

The application provides an X-band weather radar double-channel multifunctional receiving assembly, and relates to the technical field of communication, which comprises: parallel receiving of horizontal and vertical polarization echo signals, twice frequency down-conversion by using first and second local oscillator signals, two digital intermediate frequency signals obtained through a digital intermediate frequency processing module; meanwhile, an up-conversion excitation signal is input into a transmitting chain; a function calibration module calibrates the noise coefficient of a receiving channel, calibrates the delay of a transmission path, and feeds a coupled sample of a transmitting signal into a receiving channel for power monitoring to determine a link gain compensation coefficient; the local oscillator signal and the digital intermediate frequency signal are led out to an external interface for monitoring the frequency source performance and amplitude and phase consistency; two signals are calibrated according to the compensation coefficient, differential reflectivity and differential phase are extracted, precipitation particle phase state structure is analyzed, strong convective weather core areas are determined and circled, and the automation level and early warning timeliness of the X-band weather radar in short-term early warning business are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of communication technology, specifically to a dual-channel multi-functional receiver for X-band weather radar. Background Technology

[0002] In recent years, with the increasing demand for severe convective weather monitoring, X-band weather radar has played an important role in the monitoring and early warning of local and sudden meteorological disasters due to its high spatial resolution and detection sensitivity. Dual polarization technology, as one of the core functions of modern weather radar, can simultaneously acquire the horizontal and vertical polarization information of precipitation particles, providing key data support for accurately identifying the phase state of precipitation particles, estimating precipitation intensity, and judging severe weather. Therefore, the performance of the dual-channel receiving component, especially the consistency, stability, and calibrability between its channels, directly determines the data quality of dual polarization radar and the inversion accuracy of subsequent meteorological products.

[0003] In the prior art, a meteorological detection method and a digital phased array weather radar with publication number CN113126097A perform amplitude and phase compensation of transmitted and received signals through digital control or data processing units, and achieve high-precision phase shifting by combining digital intermediate frequency transceiver units, thereby improving beam pointing accuracy and signal consistency. However, this scheme mainly focuses on system-level beamforming and compensation, and does not delve into the specific implementation of the receiving components, especially the key functions that are crucial in the X-band dual polarization receiving link, such as channel noise figure calibration, transmission path delay calibration, online monitoring of transmitted signal power, and real-time compensation of link gain. In practical applications, factors such as performance drift and temperature changes of the internal components of the receiving components will directly affect the amplitude and phase consistency of the dual channels, noise level, and system sensitivity. Without a real-time monitoring and compensation mechanism for these internal parameters, it will be difficult to guarantee high-precision polarization measurement under long-term stable operation, which may affect the accurate identification and delineation of the core area of ​​severe convective weather.

[0004] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a dual-channel, multi-functional receiver for X-band weather radar to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A dual-channel, multi-functional receiver for an X-band weather radar specifically includes: a dual-channel down-conversion module, a frequency source module, a digital intermediate frequency processing module, and a function calibration module. Its workflow is as follows: Step 1: The dual-channel down-conversion module receives horizontally and vertically polarized echo signals in parallel. The first and second local oscillator signals generated by the frequency source module are used to perform down-conversion processing on the two echo signals twice. Then, the digital intermediate frequency processing module is used to obtain two digital intermediate frequency signals. At the same time, the frequency source module inputs the generated up-conversion excitation signal to the radar transmit chain to generate the radar transmit signal. Step 2: Through the functional calibration module, the noise figure of the receiving channel of the dual-channel downconversion module is calibrated, the delay of the signal transmission path of the receiving component is calibrated, and the power of the input signal fed into the receiving channel after being coupled and sampled from the radar transmitted signal is monitored. The link gain compensation coefficient is determined by combining the power value obtained from the monitoring with the reference threshold. Step 3: Through the coupling port set on the receiving component panel, the first local oscillator signal, the second local oscillator signal, and the two digital intermediate frequency signals are respectively led out to the external interface so that the external device can monitor and verify the performance of the frequency source module and the amplitude and phase consistency of the dual-channel signals. Step 4: The two digital intermediate frequency signals are calibrated according to the link gain compensation coefficient to extract the differential reflectivity information and differential phase information of the horizontal and vertical polarization channels. Then, the phase structure and spatial distribution inhomogeneity of precipitation particles in the radar scanning area are analyzed to determine and delineate the core area of ​​severe convective weather.

[0007] Furthermore, the dual-channel down-conversion module simultaneously receives both horizontally polarized and vertically polarized echo signals from the X-band of the radar antenna, and performs a first down-conversion on each of the two echo signals using the first local oscillator signal generated by the frequency source module. Subsequently, the two echo signals after the first down-conversion are preprocessed, including filtering and low-noise amplification. Then, the two preprocessed echo signals are down-converted a second time using the second local oscillator signal generated by the frequency source module to further filter out spurious signals and complete frequency shifting. The two echo signals obtained from the second down-conversion are then output to the digital intermediate frequency processing module for digital sampling and processing, ultimately obtaining two corresponding digital intermediate frequency signals. Simultaneously, the frequency source module directly inputs the generated up-conversion excitation signal to the radar transmitter chain to drive its transmitter to generate radar transmission signals.

[0008] Furthermore, by using the built-in noise source of the functional calibration module, a first calibration noise is injected into the receiving channel while the noise source is enabled, and the output noise power of the receiving channel is measured at this time. Without injecting a signal when the noise source is off, measure the background noise output power of the receiving channel itself. and will and The ratio as factor: Based on the equivalent noise temperature when the noise source is turned on Compared with standard noise temperature The ratio and the The noise figure of the receiving channel is calculated using the following method: [The text abruptly ends here, likely due to an incomplete sentence or a formatting error.] and The ratio minus Factor, obtain the first difference, and then Subtract 1 from the factor to obtain the second difference. The ratio of the first difference to the second difference is used as the noise figure. ; The calculated noise figure Stored as calibration parameters for the receiving channel; Test pulses are injected into the signal transmission path through the built-in delay line of the functional calibration module, and the time delay of the pulses after passing through the path is measured. The spatial path delay compensation amount is determined based on the speed of light and the time delay. Store the spatial path delay compensation as calibration parameters for the signal transmission path; By continuously sampling the input signal coupled from the radar transmitted signal and fed into the receiving channel, its power time sequence is obtained and the average power is calculated. The average power is compared with a preset reference threshold to determine the absolute deviation between the two. The link gain compensation coefficient is based on a value of 1 and is obtained by adding a correction term according to the direction and degree of deviation of the average power relative to the reference threshold. The correction term is related to the adjustment coefficient, the sign function value, and the relative deviation. The sign function value is determined by the direction of the difference between the average power and the reference threshold, and the relative deviation is characterized by the ratio of the absolute deviation to the reference threshold.

[0009] Furthermore, through multiple independent coupling ports set on the receiving component panel, the first local oscillator signal and the second local oscillator signal generated by the frequency source module, as well as the two digital intermediate frequency signals output by the digital intermediate frequency processing module, are coupled and sampled and then led out to the corresponding coupling ports for external devices to monitor and verify; the two digital intermediate frequency signals include a horizontally polarized digital intermediate frequency signal and a vertically polarized digital intermediate frequency signal; The coupled output of the first local oscillator signal and the second local oscillator signal is used to monitor their frequency stability, phase noise and spurious levels externally; the coupled output of the two digital intermediate frequency signals is used to verify the amplitude and phase consistency and signal quality between the channels externally. The signal strength of the coupled output is normalized and calibrated before being led out to the external interface.

[0010] Furthermore, the coupled output of the local oscillator signal is used to externally monitor its frequency stability, phase noise, and spurious levels, specifically: Connect the two coupling ports that output the first and second local oscillator signals to a spectrum analyzer, and perform spectrum measurements on the two local oscillator signals to obtain the frequency value of the first local oscillator signal. Second local oscillator signal frequency value And measure its phase noise. And stray suppression ratio ; The first relative deviation is obtained by calculating the ratio of the absolute value of the difference between the first local oscillator signal frequency and the first nominal frequency to the first nominal frequency. ; and calculate the ratio of the absolute value of the difference between the second local oscillator signal frequency and the second nominal frequency to the second nominal frequency to obtain the second relative deviation. ; Will and With the preset frequency stability threshold When comparing, and The frequency stability is determined to meet the requirements at that time. Phase noise At the specified frequency offset Measure at the location and record the measured value. Compared with the preset phase noise index When comparing, The phase noise is then determined to meet the requirements. stray suppression ratio The value is obtained by measuring the amplitude difference between the main lobe of the signal and the strongest spurious component, and then comparing it with a preset spurious suppression ratio threshold. When comparing, The stray suppression requirement is then determined.

[0011] Furthermore, the coupled output of the digital intermediate frequency signal is used to verify the amplitude-phase consistency and signal quality between external verification channels, specifically: Connect the two coupling ports of the output horizontally polarized digital intermediate frequency (IF) signal and the vertically polarized IF signal to the amplitude-phase analyzer, respectively. Simultaneously acquire the time-varying sampling sequences of the in-phase and quadrature components of the two IF signals (horizontal and vertical polarization). Denote the in-phase and quadrature component sequences of the horizontally polarized channel IF signal as follows: , The in-phase and quadrature component sequences of the digital intermediate frequency signal in the vertical polarization channel are respectively denoted as... , ; Based on the average values ​​of the in-phase and quadrature components of the two digital intermediate frequency signals, calculate the signal amplitude of each channel, and then divide the amplitudes of the two channels to obtain the amplitude ratio of the two signals. The phase difference between the two signals is obtained by calculating the phase angles of the horizontal and vertical channels separately and then subtracting the two. The amplitude ratio of the two signals The threshold range compared to the preset nominal amplitude When comparing, The consistency of the judgment amplitude meets the requirements; , These represent the minimum and maximum allowable nominal amplitude ratio thresholds, respectively. The phase difference between the two signals The absolute value of the phase difference threshold is compared with the preset phase difference threshold. When comparing, The phase consistency requirement is met when the time is determined.

[0012] Further, based on the link gain compensation coefficient, the amplitudes of the digital intermediate frequency signals of the horizontal polarization channel and the vertical polarization channel are calibrated respectively to obtain calibrated complex signals; based on the calibrated two complex signals, the differential reflectivity is obtained by calculating the logarithm of the ratio of the horizontal channel signal power to the vertical channel signal power; the differential phase is obtained by calculating the complex angle of the product of the conjugates of the horizontal channel complex signal and the vertical channel complex signal.

[0013] Furthermore, based on the differential reflectivity information and differential phase information, the phase structure and spatial distribution inhomogeneity of precipitation particles within the radar scanning area are analyzed. The specific logic underlying this analysis is as follows: A polarization uniformity index is constructed based on the absolute value of differential reflectivity and the differential phase gradient with distance; this index is positively correlated with the absolute value of differential reflectivity and negatively correlated with the differential phase gradient. The calculated polarization uniformity index Compared with the preset severe weather identification threshold When comparing, At that time, the area was determined to be the core area of ​​severe convective weather, and the area that met the conditions was delineated and marked based on the spatial coordinates of the radar scan. At the same time, the noise figure obtained from the calibration Compared with a preset health threshold, when An alarm is issued when the health threshold is exceeded; the calibrated spatial path delay compensation amount is applied. Used for time alignment correction of two digital intermediate frequency signals.

[0014] Compared with the prior art, the beneficial effects of the present invention are: First, this invention constructs a highly integrated X-band dual-polarization receiving component by integrating a dual-channel downconversion module, a frequency source module, a digital intermediate frequency processing module, and a functional calibration module. This component can process horizontal and vertical polarization echo signals in parallel, and through the built-in functional calibration module, it can accurately calibrate the noise figure of the receiving channel, measure and compensate for the signal transmission path delay, and monitor the coupling power of the radar transmitted signal online, thereby estimating and compensating for the link gain deviation in real time.

[0015] Secondly, this invention innovatively proposes to output the local oscillator signal and digital intermediate frequency signal through an external coupling port, and provides a complete and quantitative external monitoring and verification method. This method not only allows for the monitoring of the frequency stability, phase noise, and spurious level of the local oscillator signal outside the system, but also supports the simultaneous acquisition of two digital intermediate frequency signals and the accurate calculation of amplitude ratio and phase difference, thereby realizing the external independent verification of the amplitude and phase consistency between channels. This design extends the evaluation of key performance parameters from a simple internal closed loop to external traceability and comparison, greatly enhancing the system's testability, maintainability, and data reliability, and providing a powerful technical means for the daily operation and maintenance, performance verification, and fault diagnosis of radar systems.

[0016] Furthermore, this invention directly applies the real-time acquired link gain compensation coefficient to the calibration of the digital intermediate frequency signal, and combines the differential reflectivity and differential phase information extracted from the calibrated signal. Based on these core polarization parameters, a polarization uniformity index for analyzing the phase structure and spatial distribution inhomogeneity of precipitation particles is further constructed, and a clear threshold and judgment logic for identifying severe weather are set. This enables the receiving component to not only provide high-quality basic observation data, but also to directly support the automatic identification and spatial delineation of the core areas of severe convective weather. This tightly integrates high-performance reception at the hardware level with intelligent identification at the meteorological application level, significantly improving the automation level and timeliness of X-band weather radar in short-term early warning operations. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall method flow of the present invention; Figure 2 A dotted-line graph of average power versus link gain compensation coefficient; Figure 3 This is a system composition block diagram of the dual-channel multi-functional receiver component for X-band weather radar of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0019] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0020] Example: Please see Figures 1-3 The present invention provides a technical solution: A dual-channel, multi-functional receiver for an X-band weather radar specifically includes: a dual-channel down-conversion module, a frequency source module, a digital intermediate frequency processing module, and a function calibration module. Its workflow is as follows: Step 1: The dual-channel down-conversion module receives horizontally and vertically polarized echo signals in parallel. The first and second local oscillator signals generated by the frequency source module are used to perform down-conversion processing on the two echo signals twice. Then, the digital intermediate frequency processing module is used to obtain two digital intermediate frequency signals. At the same time, the frequency source module inputs the generated up-conversion excitation signal to the radar transmit chain to generate the radar transmit signal. In this embodiment, the dual-channel down-conversion module simultaneously receives X-band horizontally polarized echo signals and vertically polarized echo signals from the radar antenna, and uses the first local oscillator signal generated by the frequency source module to perform a first down-conversion process on the two echo signals, shifting the X-band radio frequency signal to the first intermediate frequency band. The two echo signals after the first down-conversion are then pre-processed, which sequentially includes bandpass filtering and low-noise amplification. Bandpass filtering is used to suppress image interference and out-of-band spurious signals, while low-noise amplification is used to increase the signal amplitude and maintain low-noise performance. Then... The second local oscillator signal generated by the frequency source module is used to perform a second down-conversion process on the two pre-processed echo signals to further suppress spurious signals and shift the signals to a preset second intermediate frequency, thus completing the frequency shift. The two intermediate frequency signals after the second down-conversion are output to the digital intermediate frequency processing module, where they undergo digital sampling and processing such as analog-to-digital conversion, digital filtering, and quadrature demodulation to obtain the corresponding two digital intermediate frequency signals. At the same time, the frequency source module directly inputs the generated up-conversion excitation signal into the radar transmission chain to drive the transmitter to generate X-band weather radar transmission signals.

[0021] Step 1 involves receiving X-band horizontal and vertical polarized echo signals in parallel and employing a two-stage down-conversion architecture. This effectively suppresses image interference and out-of-band spurious signals while significantly improving the frequency selectivity and spurious suppression capability of the receiving link. The dual-channel parallel processing design ensures that the horizontal and vertical polarized signals undergo highly symmetrical frequency conversion and preprocessing paths at the analog front end, laying a foundation for amplitude and phase consistency in subsequent high-precision dual-polarization parameter extraction. The digital intermediate frequency processing module performs digital sampling and quadrature demodulation on the signal after the second down-conversion, further improving the signal stability and repeatability and avoiding the imbalance error introduced by analog quadrature demodulation. Simultaneously, the frequency source module provides two local oscillator signals while independently outputting up-conversion excitation signals to drive the radar transmitter, achieving unified management and synchronization of the transmitting and receiving frequency sources. This reduces the relative drift and phase noise between frequency sources within the system, thereby improving the overall measurement accuracy, environmental adaptability, and dual-channel matching performance of the X-band weather radar receiving component.

[0022] Step 2: Through the functional calibration module, the noise figure of the receiving channel of the dual-channel downconversion module is calibrated, the delay of the signal transmission path of the receiving component is calibrated, and the power of the input signal fed into the receiving channel after being coupled and sampled from the radar transmitted signal is monitored. The link gain compensation coefficient is determined by combining the power value obtained from the monitoring with the reference threshold. In this embodiment, a first calibration noise is injected into the receiving channel using the built-in noise source of the functional calibration module when the noise source is enabled, and the output noise power of the receiving channel is measured at this time. Without injecting a signal when the noise source is off, measure the background noise output power of the receiving channel itself. And calculate according to the following formula factor: The factor is used to characterize the ratio of the output noise power of the receiving channel when the noise source is on and off. Its value directly reflects the receiving channel's response capability to injected calibration noise. A higher value indicates that the receiving channel can more clearly distinguish between externally injected noise and its own background noise, meaning that the noise contribution of the channel is relatively small, i.e., the noise figure of the receiving channel is low; conversely, a lower value indicates a lower noise figure. The closer the value is to 1, the more dominant the noise in the receiving channel is, making it impossible to effectively distinguish injected noise. In this case, the noise figure is high and the receiving sensitivity is poor.

[0023] When the built-in noise source is activated, the calibration noise it generates is injected into the receiving channel via coupling, and is superimposed on the channel's own internal noise to form the total output noise power. When the noise source is turned off, the receiving channel only outputs the background noise power consisting of thermal noise from its own components (such as amplifiers, mixers, etc.) and circuit noise. By measuring the output power under these two conditions, the ratio of the receiving channel's own noise to injected noise can be extracted, thereby indirectly evaluating the channel's noise performance. This is based on the noise source calibration method. The physical basis of factor measurement.

[0024] The noise figure of the receiving channel is calculated using the following formula: In the formula, The noise figure of the receiving channel; The equivalent noise temperature when the noise source is turned on is determined according to the factory calibration value of the noise source. Standard noise temperature, ; An index used to characterize the degree of degradation of signal signal-to-noise ratio by the inherent noise within the receiving channel is defined as the ratio of input signal-to-noise ratio to output signal-to-noise ratio. The smaller the value, the lower the additional noise introduced by the receiving channel, and the stronger the channel's sensitivity and weak signal detection capability; conversely, The higher the value, the more significant the noise contribution from the receiving channel, which will severely reduce the radar's ability to detect weak meteorological echoes, thereby affecting the accuracy of precipitation estimation and severe convective weather identification.

[0025] From a physical standpoint, when a noise source is turned on, its equivalent noise temperature... Much higher than standard noise temperature It is known that high-temperature noise is amplified by the receiving channel and then superimposed with the channel's own noise before being output; when the noise source is turned off, the receiving channel only outputs its own noise. The factor measures the output power ratio under these two conditions, reflecting the relative relationship between the receiving channel's amplification capability for injected noise and its own noise level; since the gain of the receiving channel remains constant in both measurements, it is possible to obtain the signal through known parameters. and as well as By calculating the factor, the equivalent noise temperature of the receiving channel can be determined, and thus the noise figure can be obtained. This is the core physical basis for the Y-factor method of noise figure measurement.

[0026] The formula is in The factorization framework has a clear analytical form, when When the value is larger, the denominator The larger, It tends to a smaller value, which is consistent with the lower the noise of the receiving channel itself. The smaller; when When it approaches 1, The formula approaches infinity and accurately reflects the limit where the noise of the receiving channel itself completely overwhelms the injected noise. Therefore, the formula is theoretically rigorous and applicable in engineering.

[0027] The calculated noise figure Stored as calibration parameters for the receiving channel; Test pulses are injected into the signal transmission path through the built-in delay line of the functional calibration module, and the time delay of the pulses after passing through the path is measured. The spatial path delay compensation amount is determined based on the speed of light and the time delay, and the specific formula used is as follows: In the formula, This is the amount of spatial path delay compensation; The speed of light; Store the spatial path delay compensation as calibration parameters for the signal transmission path; This is used to characterize the one-way spatial equivalent delay distance of radar transmitted signals or received echoes along the spatial propagation path caused by the distance between the transceiver system and the target. Its value directly reflects the spatial length corresponding to the actual time delay of the signal transmission path. A larger value indicates a greater time delay in the signal transmission path. The larger the value, the farther the distance between the radar and the target, or the longer the signal travels in the transmission path in the equivalent spatial distance. The smaller the value, the greater the corresponding time delay. The smaller the value, the shorter the transmission path, and the less spatial delay compensation the system needs.

[0028] From a practical physics perspective, radar signals travel at the speed of light. When a test pulse propagates through space, after being injected into the signal transmission path via the built-in delay line of the functional calibration module, the time delay experienced by the pulse from the transmitter to the receiver along the entire transmission path is considered. This directly determines the spatial propagation distance corresponding to the path; due to the speed of light It is a constant in free space, therefore the time delay There is a definite proportional relationship between the distance and the spatial propagation distance: the distance equals the speed of light multiplied by time; this is achieved by measuring the time delay after the pulse travels through the path being measured. This allows us to deduce the equivalent spatial distance of the path, thereby obtaining the amount of spatial path delay that needs to be compensated.

[0029] The denominator 2 in this formula clearly distinguishes the physical meaning of round-trip propagation from one direction to the other. In actual radar detection, the transmitted signal travels from the radar transmission chain through space to the target and is then reflected back from the target to the receiving channel, undergoing a round-trip path. The delay calibration within the receiving component is typically for a one-way transmission path or requires extracting the equivalent delay of a single journey. The formula uses... The measured two-way or total system delay Dividing by 2 yields the one-way spatial path delay compensation, which corresponds to the one-way spatial propagation delay that needs to be compensated in actual radar detection; this design ensures that the calibration results... It can be directly used for subsequent precise time alignment and spatial positioning correction of echo signals, avoiding positioning errors caused by confusion of round-trip paths.

[0030] The calculated spatial path delay compensation amount Stored as calibration parameters for the signal transmission path; The power timing sequence is obtained by continuously sampling the input signal fed into the receiving channel from the radar transmitted signal after coupling sampling. And calculate its mean. ,Will Compared with the preset reference threshold By comparison, the absolute deviation is calculated. The link gain compensation coefficient is determined based on the absolute deviation, and the formula used is as follows: In the formula, This is the link gain compensation coefficient; Represents a sign function, when hour, ,when hour, ; This is an adjustment coefficient used to control the magnitude of compensation; its value range is... ,Will The range of values ​​is set to This allows the single compensation amplitude to be controlled within 1 times the relative deviation of the actual power, preventing system oscillations caused by excessive compensation step size and ensuring smooth and stable convergence of the link gain adjustment process.

[0031] The gain compensation coefficient used to characterize the receiver component link is a scaling factor that performs real-time correction of the deviation between the coupled sampled power of the transmitted signal and a reference threshold. A value greater than 1 indicates that the currently monitored average power is less than the reference threshold. The signal gain needs to be boosted to compensate for link loss; when its value is less than 1, it indicates that the average power is higher than the reference threshold, i.e. The signal gain needs to be attenuated to prevent oversaturation; The closer the value is to 1, the closer the link gain state is to the ideal reference state, and the better the system consistency. The larger the deviation from 1, the more severe the link gain drift, and the stronger the compensation required.

[0032] The sign function is used to determine the direction of the current average power relative to the reference threshold: a positive value indicates low power (undercompensation), and a negative value indicates high power (overcompensation). The sign function directly determines the direction of increase or decrease of the compensation coefficient, which conforms to the basic logic of closed-loop feedback control. The relative deviation indicates the severity of the link gain deviating from the ideal state. The larger the deviation, the more significantly the system is affected by factors such as temperature and device aging, and the greater the compensation required. Multiplying the direction by the magnitude enables dynamic and adaptive compensation of the link gain, simulating the judgment logic when manually adjusting the gain.

[0033] This formula uses 1 as the baseline (uncompensated state), determines the compensation direction through a sign function, determines the compensation magnitude through relative deviation, and uses an adjustment coefficient. By controlling the compensation intensity to avoid system oscillations caused by excessive compensation in a single instance, this design conforms to the principle of negative feedback regulation, enabling smooth and stable tracking of link gain changes while avoiding over-response to short-term power fluctuations. Compared to fixed-gain or on-off compensation, this linear proportional compensation strategy is more suitable for scenarios with slow power drift in weather radar, demonstrating good engineering practicality and stability.

[0034] Table 1: Statistics of Link Gain Compensation Coefficients It should be noted that the average power, sign function, absolute deviation, and relative deviation mentioned in Table 1 correspond to... , , and and reference threshold Values ; As shown in Table 1, the link gain compensation coefficient statistics indicate that the average power selected in this test was [missing data]. to Multiple sets of measured values ​​within the interval were used to calculate the corresponding link gain compensation coefficients using the compensation algorithm provided in this invention. The results showed a significant negative linear correlation between the average power and the link gain compensation coefficient. That is, as the average power gradually increases, the link gain compensation coefficient shows a steady decreasing trend. When the average power is lower than the reference threshold... When the link gain compensation coefficient is greater than 1, it indicates that the system performs gain enhancement compensation on the link. When the average power is higher than the reference threshold, At this time, the link gain compensation coefficient is less than 1, indicating that the system performs gain attenuation compensation on the link. At the reference threshold point, the link gain compensation coefficient is 1, realizing the uncompensated state. The overall data change trend is smooth and consistent, which fully verifies that the link gain compensation algorithm can achieve dynamic and accurate adaptive adjustment based on the measured value of the transmit coupling power. It effectively corrects the link gain deviation caused by factors such as device drift and temperature change, and ensures that the receiving component works in a stable and reliable gain state. This provides stable hardware support for subsequent dual-channel signal calibration and high-precision extraction of dual polarization parameters.

[0035] Step 2 achieves online self-calibration and real-time compensation of key parameters of the receiving component through the noise source, delay line, and power monitoring link integrated in the functional calibration module. First, the noise figure of the receiving channel is accurately calibrated using the built-in noise source and the Y-factor method, which can quantify the impact of the channel's own thermal noise on the weak signal detection capability. The calibration results are stored as health monitoring parameters, providing an alarm basis for subsequent system sensitivity degradation. Second, by injecting test pulses and measuring the time delay through the built-in delay line, the spatial path delay compensation amount is calculated in combination with the speed of light. This can effectively correct the time delay error of the signal in the transmission path, ensuring that the horizontal and vertical digital intermediate frequency signals are accurately aligned in time, thereby eliminating the polarization measurement deviation caused by path inconsistency. Finally, the power of the radar transmitted signal after coupling and sampling is continuously sampled and the mean is calculated. The deviation is compared with the reference threshold to obtain the deviation, and then the link gain compensation coefficient is dynamically determined. This compensation coefficient can reflect the gain changes of the transmitting or receiving link caused by factors such as temperature drift and device aging in real time. The compensation direction and amplitude are adaptively adjusted by multiplying the sign function and the relative deviation, avoiding the overshoot and oscillation problems of fixed gain or switching compensation.

[0036] Step 3: Through the coupling port set on the receiving component panel, the first local oscillator signal, the second local oscillator signal, and the two digital intermediate frequency signals are respectively led out to the external interface so that the external device can monitor and verify the performance of the frequency source module and the amplitude and phase consistency of the dual-channel signals. In this embodiment, four independent and non-interfering coupling ports are provided on the front panel of the receiving component, corresponding to the coupling outputs of the first local oscillator signal, the second local oscillator signal, the horizontally polarized digital intermediate frequency signal, and the vertically polarized digital intermediate frequency signal, respectively. A directional coupler is used to perform non-intrusive coupling sampling of the first local oscillator signal and the second local oscillator signal output from the frequency source module, and simultaneously to perform synchronous coupling sampling of the horizontally polarized digital intermediate frequency signal and the vertically polarized digital intermediate frequency signal output from the digital intermediate frequency processing module. The coupling process does not affect the normal transmission and processing of the main link signal. The four coupled sampling signals are led out to the corresponding coupling ports on the panel. External test equipment can be directly connected to the coupling ports through RF cables to realize online monitoring and independent verification of the local oscillator signal performance and the amplitude and phase consistency of the dual-channel digital intermediate frequency signal. The first and second local oscillator signal coupling ports are used to connect to an external spectrum analyzer to monitor the frequency stability, phase noise, and spurious suppression level of the two local oscillator signals through external testing, ensuring that the operating parameters of the frequency source module meet the system design requirements. The horizontal polarization digital intermediate frequency signal coupling ports and the vertical polarization digital intermediate frequency signal coupling ports are used to connect to an external amplitude and phase analyzer to verify the amplitude consistency, phase consistency, and signal transmission quality between the two channels through external comparison, providing channel consistency assurance for high-precision extraction of dual polarization parameters. The signal strength of the coupled output is normalized and calibrated before being led out to the external interface. Specifically, the normalization and calibration are performed using the following formula: In the formula, This represents the normalized voltage value of the coupled output signal. This represents the actual coupled output signal voltage; This represents the reference voltage for the corresponding signal path within the receiving component; These are preset calibration coefficients used to compensate for the insertion loss between the coupler and the transmission path. The range of values ​​is , calibration coefficient The value range is set to , can Within the engineering tolerance range, it effectively compensates for the insertion loss deviation between the coupler and the transmission path, ensuring coverage of individual device differences and temperature drift while avoiding overcorrection that introduces new amplitude errors.

[0037] The coupled output of the local oscillator signal is used to monitor its frequency stability, phase noise, and spurious levels externally, specifically: Connect the two coupling ports that output the first and second local oscillator signals to a spectrum analyzer, and perform spectrum measurements on the two local oscillator signals to obtain the frequency value of the first local oscillator signal. Second local oscillator signal frequency value And measure its phase noise. And stray suppression ratio ; The first relative deviation is obtained by calculating the ratio of the absolute value of the difference between the first local oscillator signal frequency and the first nominal frequency to the first nominal frequency. ; and calculate the ratio of the absolute value of the difference between the second local oscillator signal frequency and the second nominal frequency to the second nominal frequency to obtain the second relative deviation. The specific formula used is as follows: In the formula, and These are the first relative deviation and the second relative deviation, respectively. and These are the nominal frequencies of the first local oscillator signal frequency value and the second local oscillator signal frequency value, respectively. Will and With the preset frequency stability threshold When comparing, and The frequency stability is determined to meet the requirements at that time. Phase noise At the specified frequency offset Measure at the location and record the measured value. Compared with the preset phase noise index When comparing, The phase noise is then determined to meet the requirements. Among them, phase noise index The determination method is as follows: First, based on the accuracy requirements of differential phase measurement for X-band weather radar, the allowable local oscillator signal phase noise margin is derived through radar equations and error propagation models. Second, considering the two-stage down-conversion architecture of the receiving component, the total phase noise budget is allocated to the first and second local oscillator links according to engineering experience. Then, referring to the recommended specifications for X-band coherent radar local oscillators in the International Telecommunication Union or radar system design manuals, as well as measured or specification data from similar in-service weather radars, the phase noise index at each specified frequency offset (e.g., 1 kHz, 10 kHz, 100 kHz) is comprehensively determined. Typically, the phase noise index of the X-band weather radar receiving component at a 10 kHz frequency offset can be set as follows: .

[0038] Frequency stability threshold The determination method is as follows: Based on the coherent processing requirements of radar transmitted signals and echo signals, as well as the constraints of digital filter bandwidth and range gate resolution in the digital intermediate frequency processing module, the maximum allowable relative drift of the local oscillator frequency is calculated; specifically, the allowable frequency error is derived from the radar operating wavelength, maximum detection range, and allowable range positioning error; at the same time, considering the requirements of Doppler measurement accuracy on frequency stability, the more stringent limit between the two is taken.

[0039] In the above process, a frequency stability threshold is set. and phase noise index and will , and The reason for this comparison is that the frequency stability and phase noise of the frequency source are core indicators that determine the coherent processing capability and measurement accuracy of the radar receiving components, and the frequency stability threshold... Used to quantize the maximum permissible drift of the local oscillator signal relative to the nominal frequency, when and This indicates that the frequencies of the first and second local oscillator signals did not exceed the design tolerance during the measurement period, ensuring the accuracy of the intermediate frequency after down-conversion and avoiding distance gate misalignment, Doppler measurement deviation, and inter-channel frequency mismatch caused by frequency drift; phase noise index This is used to limit the phase jitter energy of the local oscillator signal at a specified frequency offset. When the measured values ​​are within acceptable limits, it indicates that the local oscillator phase noise is within acceptable limits and can effectively suppress the transmission of phase noise to the echo signal, thereby ensuring that the measurement accuracy of differential phase polarization parameters is not significantly contaminated by local oscillator phase noise. By comparing the measured values ​​with preset thresholds, a clear pass / fail judgment criterion is formed, realizing the quantitative evaluation and external verification of the frequency source performance, and providing a traceable test basis for the long-term stable operation of the receiving component and the high-precision extraction of dual polarization parameters.

[0040] stray suppression ratio The value is obtained by measuring the amplitude difference between the main lobe of the signal and the strongest spurious component, and then comparing it with a preset spurious suppression ratio threshold. When comparing, The spurious suppression is determined to meet the requirements at a certain time; where the spurious suppression ratio threshold is... The determination method is as follows: First, based on the requirements of the X-band weather radar receiving components for the signal-to-noise ratio and dynamic range of the intermediate frequency signal, analyze the error limits that spurious components may introduce to echo signal detection and dual polarization parameter measurement. Generally, the spurious suppression ratio is required to be higher than the lower limit of the spurious-free dynamic range of the receiving channel. Second, refer to the engineering experience of local oscillator signal spurious suppression in radar system design, combine the typical spurious suppression capabilities of devices such as phase-locked loops and frequency multipliers in the frequency source module, and the measured or specification data of similar in-service weather radar receiving components, and comprehensively determine a minimum spurious suppression ratio that can ensure the normal operation of the system. In addition, it is also necessary to consider that when the radar transmitted signal is fed into the receiving channel after coupling sampling, the spurious components should not interfere with the spectrum identification and power measurement of the normal echo signal.

[0041] The coupled output of the digital intermediate frequency signal is used to verify the amplitude-phase consistency and signal quality between external channels, specifically: Connect the two coupling ports of the output horizontally polarized digital intermediate frequency (IF) signal and the vertically polarized IF signal to the amplitude-phase analyzer, respectively. Simultaneously acquire the time-varying sampling sequences of the in-phase and quadrature components of the two IF signals (horizontal and vertical polarization). Denote the in-phase and quadrature component sequences of the horizontally polarized channel IF signal as follows: , The in-phase and quadrature component sequences of the digital intermediate frequency signal in the vertical polarization channel are respectively denoted as... , ; Based on the average values ​​of the in-phase and quadrature components of the two digital intermediate frequency signals, the signal amplitude of each channel is calculated. Then, the amplitudes of the two channels are divided to obtain the amplitude ratio of the two signals. The specific formula is as follows: in, Indicates the amplitude ratio of the two signals; and These represent the average values ​​of the in-phase and quadrature component sequences of the digital intermediate frequency signal in the horizontal polarization channel, respectively. and These represent the average values ​​of the in-phase and quadrature component sequences of the digital intermediate frequency signal in the vertical polarization channel, respectively. Dependent variable Used to characterize the amplitude consistency between the digital intermediate frequency signals of the horizontal polarization channel and the vertical polarization channel, i.e., the amplitude ratio of the two signals; The closer the value is to 1, the more consistent the amplitude response of the horizontal and vertical channels is, the better the channel balance of the dual polarization receiving component, which is beneficial to the accurate extraction of the differential reflectivity in the later stage. When the value is significantly greater than 1, it indicates that the amplitude of the horizontal channel signal is significantly higher than that of the vertical channel, which may lead to a positive bias in the differential reflectivity. When the value is significantly less than 1, it indicates that the amplitude of the vertical channel signal is significantly higher than that of the horizontal channel, which may lead to a larger negative differential reflectivity. Both of these situations will introduce polarization measurement errors and affect the accuracy of precipitation particle phase identification.

[0042] From a practical physics perspective, digital intermediate frequency (IF) signals typically employ orthogonal demodulation, decomposing the signal into in-phase and quadrature components. These two components together constitute a vector representation of the complex signal, and the signal amplitude is precisely the magnitude of this vector. For both horizontal and vertical polarization channels, the magnitudes of their signal vectors are calculated separately. and This allows us to obtain the actual amplitude values ​​of the two signals. By taking the ratio of the two values, we can eliminate the absolute amplitude changes introduced by common factors such as fluctuations in common transmission power and attenuation of common propagation paths in the two signals, thereby focusing on the evaluation of the relative amplitude differences between the channels. This is the physical basis for the consistency test of dual-polarization radar channels.

[0043] This formula firstly uses modulus calculation to completely preserve the amplitude information of the signal, avoiding the amplitude measurement error introduced by using only a single component due to phase differences; secondly, it uses amplitude ratio instead of absolute amplitude difference to eliminate the influence of the intensity variation of the input signal itself on the consistency judgment, thus... This becomes a normalized relative indicator, independent of absolute signal power, facilitating horizontal comparisons and long-term monitoring of channel consistency under different times and transmission power conditions; finally, in the formula... , , , The average value is used for calculation, which can effectively suppress the interference of random noise on instantaneous amplitude measurement, improve the stability and repeatability of amplitude ratio estimation, and thus provide a reliable and quantitative basis for dual-channel amplitude-phase consistency verification.

[0044] The phase difference between the two signals is obtained by calculating the phase angles of the horizontal and vertical channels separately and then subtracting them. The specific formula used is as follows: in, This indicates the phase difference between the two signals; The calculation logic of this formula is based on the phase extraction principle of complex signals under quadrature demodulation: in the digital intermediate frequency processing module, the digital intermediate frequency signals of both the horizontal and vertical polarization channels are decomposed into in-phase components. , Orthogonal components , The instantaneous phase of each channel can be derived from the complex signal vector of that channel ( The principal argument value is given, i.e. Its physical meaning is the phase shift of the channel signal relative to the reference phase; calculate the phase of the horizontal channel respectively. Phase with vertical channel Subtracting the two gives the relative phase difference between the two channels. This difference directly reflects the phase delay difference experienced by the horizontally and vertically polarized echo signals in the receiving link, as well as the different phase modulation effects of precipitation particles on the horizontally and vertically polarized waves. By employing a method of independently calculating and subtracting the phases of each channel, common phase errors such as local oscillator signal phase noise and system clock jitter are eliminated, resulting in... It can accurately characterize the inherent phase consistency between channels and the differential phase change caused by precipitation particles, providing an accurate measurement basis for subsequent extraction of differential propagation phase.

[0045] The amplitude ratio of the two signals The threshold range compared to the preset nominal amplitude When comparing, The consistency of the judgment amplitude meets the requirements; , These represent the minimum and maximum allowable nominal amplitude ratio thresholds, respectively. The phase difference between the two signals The absolute value of the phase difference threshold is compared with the preset phase difference threshold. When comparing, The phase consistency requirement is met when the time is determined.

[0046] Among them, the nominal amplitude is greater than the threshold range The determination method is as follows: Based on the accuracy requirements of differential reflectivity for X-band weather radar dual polarization measurement, the allowable horizontal and vertical channel amplitude ratio tolerances are derived by inversely using radar equations and error propagation models; secondly, combined with the typical channel gain difference statistical characteristics of analog front-end (such as low-noise amplifier, mixer, filter, etc.) and digital intermediate frequency processing module in the receiving component, as well as the gain drift range caused by factors such as temperature and aging, the allowable range of amplitude ratio deviation from the nominal value of 1 is comprehensively determined and used as the nominal amplitude ratio threshold range.

[0047] Phase difference threshold The determination method is as follows: Based on the measurement accuracy requirements of X-band weather radar for differential propagation phase, the influence of inherent phase difference between channels and random phase error of the system on differential propagation phase extraction is analyzed to determine the maximum allowable phase inconsistency between channels; secondly, combined with the range of phase characteristics of devices such as mixers, filters, and amplifiers in the receiving component as a function of temperature and frequency, and the quadrature error tolerance of the quadrature demodulator in the digital intermediate frequency processing module, a phase difference threshold that can ensure long-term stable operation of the system is comprehensively set and used as the phase difference threshold.

[0048] Step 3 uses multiple independent coupling ports on the front panel of the receiving component to non-intrusively export the first local oscillator signal and the second local oscillator signal generated by the frequency source module, as well as the horizontal and vertical digital intermediate frequency signals output by the digital intermediate frequency processing module, to an external interface. This enables online, independent, and traceable external monitoring and verification of the frequency source performance and the amplitude-phase consistency of the dual channels. On the one hand, this method allows the use of equipment such as a spectrum analyzer to directly measure the frequency stability, phase noise, and spurious rejection ratio of the local oscillator signal, providing a quantitative external testing method for the health status assessment and fault diagnosis of the frequency source module, ensuring that the accuracy of the intermediate frequency after downconversion and that the phase noise does not affect the differential phase measurement accuracy. On the other hand, it supports the simultaneous acquisition of the two digital intermediate frequency signals through an amplitude-phase analyzer and the accurate calculation of their amplitude ratio and phase difference, thereby independently verifying the amplitude and phase consistency of the dual channels outside the system, providing a quantifiable channel matching guarantee for the high-precision extraction of dual polarization parameters. This design extends the evaluation of key performance parameters from an internal closed loop to an open architecture that allows for external traceability and comparison, greatly enhancing the testability, maintainability, and data reliability of the receiving components. It provides strong technical support for the daily operation and maintenance, performance verification, and long-term stability monitoring of X-band weather radar.

[0049] Step 4: The two digital intermediate frequency signals are calibrated according to the link gain compensation coefficient to extract the differential reflectivity information and differential phase information of the horizontal and vertical polarization channels. Then, the phase structure and spatial distribution inhomogeneity of precipitation particles in the radar scanning area are analyzed to determine and delineate the core area of ​​severe convective weather. In this embodiment, the amplitudes of the digital intermediate frequency (IF) signals of the horizontal polarization channel and the vertical polarization channel are calibrated according to the link gain compensation coefficient to obtain calibrated complex signals. The formula used is as follows: In the formula, and These are the calibrated horizontal and vertical channel signals, respectively. This is the original complex signal of the horizontal channel; This is the original complex signal of the vertical channel; The imaginary unit; This is the link gain compensation coefficient; The calculation logic of this formula is based on the linear compensation principle of digital intermediate frequency signal amplitude calibration: In the receiving component, the original complex signals of the horizontal polarization channel and the vertical polarization channel are respectively represented as... and Its magnitude is determined by the link gain, which can deviate from the ideal state due to factors such as temperature drift, device aging, or transmit power fluctuations. The link gain compensation coefficient... This precisely reflects the degree and direction of the current link gain's deviation from the ideal state; multiplying the two original complex signals by the same... This involves synchronously and proportionally scaling the amplitudes of the horizontal and vertical channels to achieve the desired signal amplitude. and The gain is restored to the ideal level corresponding to the reference threshold. This approach is used because in dual-polarization radar, differential reflectivity depends on the power ratio of the horizontal and vertical channels. The effect of link gain drift on both channels is common-mode. Therefore, using a unified compensation coefficient to simultaneously calibrate the amplitude of both signals effectively eliminates the impact of link gain variation on absolute power measurement while maintaining the relative amplitude relationship between the two channels. This ensures that the extraction accuracy of dual-polarization parameters such as differential reflectivity and differential phase is not affected by link gain drift.

[0050] Based on the calibrated two complex signals, the differential reflectivity and differential phase are calculated: In the formula, and These represent differential reflectivity and differential phase, respectively. This indicates that the average calculation is performed on signal samples within a specified distance range. This represents the modulo operation; This indicates taking the complex phase angle; Indicates complex conjugation.

[0051] The calculation logic of this formula is based on the physical definition and statistical estimation principle of differential reflectivity and differential phase in dual-polarization radar. Differential reflectivity... Defined as the logarithm of the ratio of the echo power of the horizontal to the vertical polarization channels, therefore the calibrated complex signal of the horizontal channel is used. With vertical channel complex signals Calculate the square of its modulus respectively. and The ratio is then calculated and output as a logarithm of 10, thus eliminating the influence of absolute power caused by differences in system gain or common propagation attenuation between the two channels. This directly reflects the difference in the backscattering ability of precipitation particles to horizontally and vertically polarized waves, and is used to identify particle phases (such as rain, snow, and hail) and estimate precipitation intensity. Differential phase Defined as the accumulated phase difference between horizontally and vertically polarized waves along the propagation path, it is calculated... and cross-correlation The argument is then taken to obtain the phase estimate. The complex conjugate multiplication eliminates identical random phase noise (such as local oscillator phase jitter) in both channels, while the averaging operation suppresses interference from thermal noise and incoherent scattering components, thus obtaining a robust differential phase estimate. The above calculation method simultaneously achieves the normalized amplitude ratio and coherent phase extraction, forming the core algorithmic basis for the quantitative detection of precipitation particle microphysical properties by dual-polarization radar.

[0052] Based on the differential reflectivity and differential phase information, the phase structure and spatial distribution inhomogeneity of precipitation particles within the radar scanning area are analyzed. The specific logic is as follows: Based on extracted differential reflectance and differential phase gradient with distance Construct the polarization uniformity index: in, It is the polarization uniformity index; It is obtained by performing differential phase calculation on the differential phase values ​​of adjacent distance libraries; Dependent variable It is used to comprehensively characterize the uniformity of the phase structure of precipitation particles within the radar scanning area and the core regional characteristics of the development of severe convective weather. The higher the value, the higher the differential reflectance of the region. Relatively high, while differential phase gradient Relatively small size means that precipitation particles exhibit relatively consistent polarization characteristics in both the horizontal and vertical directions, with gentle phase changes. This typically corresponds to areas of accumulation of large, regularly shaped precipitation particles (such as large raindrops or wet snow), a typical characteristic of the core region of severe convective weather; conversely, The smaller the value, the more it indicates lower or Larger values ​​correspond to smaller particle sizes or mixed phases (such as in ice-water mixing zones), or drastic phase changes (such as in large gradient regions within strong convective storms), and may indicate convective edges or transitional regions.

[0053] From a practical physical perspective, differential reflectivity This reflects the difference in the ability of precipitation particles to backscatter horizontally and vertically polarized waves, and its absolute value The larger the value, the more significantly the particle size is in the horizontal direction compared to the vertical direction (such as large raindrops or hail), which is a common morphological characteristic of condensates in strong convective clouds; differential phase gradient This characterizes the rate of change of the phase difference between horizontally and vertically polarized waves along the propagation path with distance, and its absolute value This reflects the dramatic spatial variation in precipitation particle concentration and phase. In the core region of strong convection, there are typically large amounts of large, relatively uniformly shaped hydrophobic condensates, making... The size is relatively large, and the particle distribution is relatively uniform, making Smaller particle size; however, at the convection edge or in the mixed-phase region, the particle size is small or the phases are mixed, leading to... Smaller, or drastic phase changes lead to Larger; therefore, and The combination of these can effectively characterize the polarization features of the strong convection core region.

[0054] The formula will Positioning it at the molecular level allows for a greater contribution from a larger differential reflectivity. The value is consistent with the physical fact that the core region of strong convection exhibits significant non-spherical particle characteristics; Placing it in the denominator and adding 1 makes it possible to significantly suppress large phase gradients. This value effectively distinguishes between boundary regions with drastic phase changes and core regions with gentle phase changes, while adding 1 to the denominator avoids errors when... The mathematical problem of having a zero denominator when the sum is zero guarantees that... The formula integrates two complementary polarization parameters with different physical meanings into a comprehensive index through a ratio, which highlights the typical characteristics of "high differential reflectivity and low phase gradient" in the core area of ​​severe convection, while suppressing the interference from non-core areas (low differential reflectivity or high phase gradient). This provides a simple, effective and physically clear quantitative criterion for the automatic identification and delineation of the core area of ​​severe convective weather.

[0055] The calculated polarization uniformity index Compared with the preset severe weather identification threshold When comparing, At that time, the area was determined to be the core area of ​​severe convective weather, and the area that met the conditions was delineated and marked based on the spatial coordinates of the radar scan. At the same time, the noise figure obtained from the calibration Compared with a preset health threshold, when An alarm is issued when the health threshold is exceeded, thereby enabling online monitoring and fault warning of the receiving channel's health status and ensuring that the system sensitivity remains within an acceptable range. Simultaneously, the calibrated spatial path delay compensation amount... Used for time alignment correction of two digital intermediate frequency signals to eliminate time delay errors caused by inconsistent transmission paths, ensure accurate synchronization of horizontal and vertical polarization channel signals in the time domain, and provide a reliable data alignment basis for high-precision extraction of differential reflectivity and differential phase.

[0056] The method for determining the health threshold is as follows: based on the maximum noise figure allowed by the receiving channel design, combined with the normal fluctuation range obtained from the factory calibration test, and with a certain redundancy, such as 1.5 to 2.0 times the nominal value, it is finally determined after verification by field test to ensure that normal drift and real fault can be effectively distinguished.

[0057] The calibrated spatial path delay compensation amount Used for time alignment correction of two digital intermediate frequency signals, specifically: The input digital intermediate frequency (IF) processing module uses the channel with the smaller delay as a reference to perform time-domain interpolation delay compensation on the digital IF signal of the channel with the larger delay. The process is iteratively adjusted until the time delay difference between the two signals is less than a preset threshold, thereby achieving precise time synchronization between the horizontal and vertical polarization channels.

[0058] Polarization uniformity index By combining the two key polarization parameters of differential reflectivity and differential phase gradient, the spatial uniformity of precipitation particle phase structure can be quantitatively characterized. In the core region of severe convective weather, there are usually a large number of large-sized, relatively regular-shaped precipitation particles (such as large raindrops, wet snow, or small hailstones), which manifest as... The concentration is relatively high, and the spatial distribution of particle concentration and phase is relatively uniform, making... Smaller, therefore The values ​​are relatively large; however, at the convection edge, transition zone, or non-strong convection region, either the particle size is small, leading to... Lower, or due to drastic phase changes. Larger The value is relatively small. A reasonable threshold for identifying severe weather should be set. ,when When the value exceeds this threshold, the region can be determined to meet the typical characteristics of a strong convection core area, namely "high differential reflectivity and low phase gradient". This enables automatic identification and spatial delineation of the region, providing a clear spatial direction for short-term early warning.

[0059] Among them, the severe weather identification threshold The determination method is as follows: First, a large number of historical observation samples from X-band dual-polarization radar, containing different types of severe convective weather (such as rainstorms, hail, and strong winds), are selected. Based on expert annotations or ground-based observation data (such as automatic weather station rainfall, hail reports, and strong wind records), the true core area of ​​severe convective weather is identified. Second, the core area of ​​each sample region is calculated. Values, statistics on the core area of ​​strong convection The distribution characteristics were analyzed, and the non-strong convection region was also examined. The distribution range is determined; then, based on the trade-off between early warning hit rate and false alarm rate for radar detection missions, ROC curve analysis is used to determine the optimal segmentation threshold, so that the false alarm rate is as low as possible while ensuring a high hit rate; finally, the threshold is appropriately modified by combining system parameters such as radar range resolution and beamwidth, as well as the climatic characteristics of different seasons and regions.

[0060] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0061] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented in software, the above embodiments can be implemented, in whole or in part, as a computer program product. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution.

[0062] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0063] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A dual-channel multi-functional receiver component for X-band weather radar, characterized in that, include: The dual-channel downconverter module, frequency source module, digital intermediate frequency processing module, and function calibration module operate as follows: The dual-channel down-conversion module receives horizontally and vertically polarized echo signals in parallel. The first and second local oscillator signals generated by the frequency source module are used to perform down-conversion processing on the two echo signals twice. Then, the digital intermediate frequency processing module obtains two digital intermediate frequency signals. At the same time, the frequency source module inputs the generated up-conversion excitation signal to the radar transmission chain to generate the radar transmission signal. The noise figure of the receiving channel of the dual-channel downconverter module is calibrated through the functional calibration module, the delay of the signal transmission path of the receiving component is calibrated, and the power of the input signal fed into the receiving channel after being coupled and sampled from the radar transmitted signal is monitored. The link gain compensation coefficient is determined by combining the power value obtained from the monitoring with the reference threshold. The first local oscillator signal, the second local oscillator signal, and the two digital intermediate frequency signals are respectively led out to the external interface through the coupling port set on the receiving component panel, so that the external device can monitor and verify the performance of the frequency source module and the amplitude and phase consistency of the dual-channel signals. The two digital intermediate frequency signals are calibrated based on the link gain compensation coefficient to extract the differential reflectivity and differential phase information of the horizontal and vertical polarization channels. Then, the phase structure and spatial distribution inhomogeneity of precipitation particles in the radar scanning area are analyzed to determine and delineate the core area of ​​severe convective weather.

2. The dual-channel multi-functional receiver assembly for X-band weather radar according to claim 1, characterized in that: The dual-channel down-conversion module simultaneously receives horizontally polarized and vertically polarized echo signals from the X-band of the radar antenna. It then uses the first local oscillator signal generated by the frequency source module to perform a first down-conversion on each of the two echo signals. Subsequently, the two echo signals after the first down-conversion are preprocessed, including filtering and low-noise amplification. The second local oscillator signal generated by the frequency source module is then used to perform a second down-conversion on each of the preprocessed echo signals to further filter out spurious signals and complete frequency shifting. The two echo signals obtained from the second down-conversion are then output to the digital intermediate frequency processing module for digital sampling and processing, ultimately obtaining two corresponding digital intermediate frequency signals. Simultaneously, the frequency source module directly inputs the generated up-conversion excitation signal to the radar transmitter chain to drive its transmitter to generate the radar transmission signal.

3. The dual-channel multi-functional receiver assembly for X-band weather radar according to claim 1, characterized in that: The built-in noise source of the functional calibration module injects first calibration noise into the receiving channel while the noise source is enabled, and the output noise power of the receiving channel is measured at this time. Without injecting a signal when the noise source is off, measure the background noise output power of the receiving channel itself. and will and The ratio as factor: Based on the equivalent noise temperature when the noise source is turned on Compared with standard noise temperature The ratio and the The noise figure of the receiving channel is calculated using the following method: [The text abruptly ends here, likely due to an incomplete sentence or a formatting error.] and The ratio minus Factor, obtain the first difference, and then Subtract 1 from the factor to obtain the second difference. The ratio of the first difference to the second difference is used as the noise figure. ; The calculated noise figure Store as calibration parameters for the receiving channel.

4. The X-band weather radar dual-channel multi-functional receiving component according to claim 3, characterized in that: Test pulses are injected into the signal transmission path through the built-in delay line of the functional calibration module, and the time delay of the pulses after passing through the path is measured. The spatial path delay compensation amount is determined based on the speed of light and the time delay. Store the spatial path delay compensation as calibration parameters for the signal transmission path; By continuously sampling the input signal coupled from the radar transmitted signal and fed into the receiving channel, its power time sequence is obtained and the average power is calculated. The average power is compared with a preset reference threshold to determine the absolute deviation between the two. The link gain compensation coefficient is based on a value of 1 and is obtained by adding a correction term according to the direction and degree of deviation of the average power relative to the reference threshold. The correction term is related to the adjustment coefficient, the sign function value, and the relative deviation. The sign function value is determined by the direction of the difference between the average power and the reference threshold, and the relative deviation is characterized by the ratio of the absolute deviation to the reference threshold.

5. The dual-channel multi-functional receiver assembly for X-band weather radar according to claim 4, characterized in that: The first and second local oscillator signals generated by the frequency source module and the two digital intermediate frequency signals output by the digital intermediate frequency processing module are coupled and sampled through multiple independent coupling ports on the receiving component panel and then led out to the corresponding coupling ports for external devices to monitor and verify; the two digital intermediate frequency signals include horizontally polarized digital intermediate frequency signals and vertically polarized digital intermediate frequency signals. The coupled outputs of the first and second local oscillator signals are used to monitor their frequency stability, phase noise, and spurious levels externally; the coupled outputs of the two digital intermediate frequency signals are used to verify the amplitude-phase consistency and signal quality between the channels externally. The signal strength of the coupled output is normalized and calibrated before being led out to the external interface.

6. The dual-channel multi-functional receiver assembly for X-band weather radar according to claim 5, characterized in that: The coupled output of the local oscillator signal is used to monitor its frequency stability, phase noise, and spurious levels externally, specifically: Connect the two coupling ports that output the first and second local oscillator signals to a spectrum analyzer, and perform spectrum measurements on the two local oscillator signals to obtain the frequency value of the first local oscillator signal. Second local oscillator signal frequency value And measure its phase noise. And stray suppression ratio ; The first relative deviation is obtained by calculating the ratio of the absolute value of the difference between the first local oscillator signal frequency and the first nominal frequency to the first nominal frequency. ; and calculate the ratio of the absolute value of the difference between the second local oscillator signal frequency and the second nominal frequency to the second nominal frequency to obtain the second relative deviation. ; Will and With the preset frequency stability threshold When comparing, and The frequency stability is determined to meet the requirements at that time. Phase noise At the specified frequency offset Measure at the location and record the measured value. Compared with the preset phase noise index When comparing, The phase noise is then determined to meet the requirements. Stray suppression ratio The value is obtained by measuring the amplitude difference between the main lobe of the signal and the strongest spurious component, and then comparing it with a preset spurious suppression ratio threshold. When comparing, The stray suppression requirement is then determined to be met.

7. The X-band weather radar dual-channel multi-functional receiving component according to claim 6, characterized in that: The coupled output of the digital intermediate frequency signal is used to verify the amplitude-phase consistency and signal quality between external channels, specifically: Connect the two coupling ports of the output horizontally polarized digital intermediate frequency (IF) signal and the vertically polarized IF signal to the amplitude-phase analyzer, respectively. Simultaneously acquire the time-varying sampling sequences of the in-phase and quadrature components of the two IF signals (horizontal and vertical polarization). Denote the in-phase and quadrature component sequences of the horizontally polarized channel IF signal as follows: , The in-phase and quadrature component sequences of the digital intermediate frequency signal in the vertical polarization channel are respectively denoted as... , ; Based on the average values ​​of the in-phase and quadrature components of the two digital intermediate frequency signals, calculate the signal amplitude of each channel, and then divide the amplitudes of the two channels to obtain the amplitude ratio of the two signals. The phase difference between the two signals is obtained by calculating the phase angles of the horizontal and vertical channels separately and then subtracting the two.

8. The dual-channel multi-functional receiver assembly for X-band weather radar according to claim 7, characterized in that: The amplitude ratio of the two signals The threshold range compared to the preset nominal amplitude When comparing, The consistency of the judgment amplitude meets the requirements; , These represent the minimum and maximum allowable nominal amplitude ratio thresholds, respectively. The phase difference between the two signals The absolute value of the phase difference threshold is compared with the preset phase difference threshold. When comparing, The phase consistency requirement is met when the time is determined.

9. The dual-channel multi-functional receiver assembly for X-band weather radar according to claim 1, characterized in that: Based on the link gain compensation coefficient, the amplitudes of the digital intermediate frequency signals of the horizontal polarization channel and the vertical polarization channel are calibrated to obtain calibrated complex signals. Based on the calibrated two complex signals, the differential reflectivity is obtained by calculating the logarithm of the ratio of the horizontal channel signal power to the vertical channel signal power. The differential phase is obtained by calculating the complex angle of the product of the conjugates of the horizontal channel complex signal and the vertical channel complex signal.

10. The dual-channel multi-functional receiver assembly for X-band weather radar according to claim 9, characterized in that: Based on the differential reflectivity and differential phase information, the phase structure and spatial distribution inhomogeneity of precipitation particles within the radar scanning area are analyzed. The specific logic is as follows: A polarization uniformity index is constructed based on the absolute value of differential reflectivity and the differential phase gradient with distance; this index is positively correlated with the absolute value of differential reflectivity and negatively correlated with the differential phase gradient. The calculated polarization uniformity index Compared with the preset severe weather identification threshold When comparing, At that time, the area was determined to be the core area of ​​severe convective weather, and the area that met the conditions was delineated and marked based on the spatial coordinates of the radar scan. At the same time, the noise figure obtained from the calibration Compared with a preset health threshold, when An alarm is issued when the health threshold is exceeded; the calibrated spatial path delay compensation amount is applied. Used for time alignment correction of two digital intermediate frequency signals.

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