阅读说明：本技术 一种基于空时频码波技术的同时多通道阵列处理方法 (Simultaneous multi-channel array processing method based on space-time-frequency code wave technology ) 是由 刘新安 李忱 洪伟 陆建兵 张兴海 王钱雨辰 于 2021-10-26 设计创作，主要内容包括：本发明公开了一种基于空时频码波技术的同时多通道阵列处理方法,步骤包括：雷达数据处理通过上行链路产生多个不同载频的带波形和频率相位调整的脉冲序列；送N个TR组件发射支路进行上变频和放大后经天线辐射出去,在空间合成覆盖设定空域的发射波束；所述发射波束在经过气象目标反射后,通过天线接收后进入N个TR组件接收支路,进行低噪声放大和模拟下变频处理,之后进入数字接收通道实现数字化处理；在数字接收通道中接收信号首先经AD转换成数字信号,然后通过不同的数字下变频实现频率分集,频率分集后的基带IQ信号送至信息处理系统,实现空域、时域、频域、解码和波形五个维度的联合处理,形成M路基数据后送数据处理进行存储和显示。(The invention discloses a simultaneous multi-channel array processing method based on a space-time-frequency code wave technology, which comprises the following steps: the radar data processing generates a plurality of pulse sequences with different carrier frequencies and with waveform and frequency phase adjustment through an uplink; sending the signals to N TR component transmitting branches for up-conversion and amplification, radiating the signals by an antenna, and spatially synthesizing a transmitting beam covering a set airspace; after being reflected by a meteorological target, the transmitted wave beam enters N TR component receiving branches after being received by an antenna, low-noise amplification and analog down-conversion processing are carried out, and then the transmitted wave beam enters a digital receiving channel to realize digital processing; a received signal in a digital receiving channel is firstly converted into a digital signal through AD, then frequency diversity is realized through different digital down-conversion, a baseband IQ signal after the frequency diversity is sent to an information processing system, the combined processing of five dimensions of a space domain, a time domain, a frequency domain, decoding and a waveform is realized, M roadbed data is formed, and then the M roadbed data is sent to data processing for storage and display.)

1. A simultaneous multi-channel array processing method based on space-time-frequency code wave technology is characterized by comprising the following steps:

1) the radar data processing is realized by controlling a frequency source to generate a plurality of pulse sequences with different carrier frequencies and adjusted frequency phases through an uplink by a radar control unit;

2) sending the signals to N TR component transmitting branches for up-conversion and amplification, radiating the signals by an antenna, and spatially synthesizing a transmitting beam covering a set airspace;

3) after being reflected by a meteorological target, the transmitted wave beam enters N TR component receiving branches after being received by an antenna, low-noise amplification and analog down-conversion processing are carried out, and then the transmitted wave beam enters a digital receiving channel to realize digital processing;

4) based on waveform information designed in an uplink, signals received in a digital receiving channel are firstly converted into digital signals through AD (analog-to-digital) and then frequency diversity is realized through different digital down-conversion, baseband IQ signals after frequency diversity are sent to an information processing system from a TR (transmitter-receiver) component through optical fibers, combined processing of five dimensions of spatial processing, time domain processing, frequency domain processing, decoding processing and waveform processing is realized in the information processing system, M roadbed data is formed and then the M roadbed data is sent to data processing for storage and display.

2. The simultaneous multi-channel array processing method based on space-time-frequency code wave technology according to claim 1, wherein the step 4) is specifically: in the information processing system, firstly, space domain processing is carried out to form a plurality of receiving wave beams covering different space domains, then waveform processing is carried out to extract required information, additional phase information is removed through decoding processing, then frequency domain processing is carried out to filter out non-meteorological signals such as clutter and the like, finally time domain correlation processing is carried out, meteorological parameters needing to be measured are calculated and processed, the meteorological parameters comprise reflectivity intensity, radial Doppler velocity and velocity spectrum width, and M roadbed data are formed and then sent to data processing to be stored and displayed.

3. The method according to claim 1 or 2, wherein the information processing system is provided with a spatial domain processing module, the spatial domain processing module is configured to implement multi-beam synthesis to form a plurality of received beams covering a set spatial domain, and a reconfigurable multi-channel array processing technique is adopted.

4. The simultaneous multi-channel array processing method based on space-time-frequency code wave technology according to claim 3, wherein the space domain processing module performs channel calibration and wavefront reconstruction, and the channel calibration method is as follows: inputting single carrier frequency at the front end of the receiver, calculating the amplitude and phase consistency of the channel, and adopting a channel calibration method of conjugate multiplication of a reference channel and channel data to be calibrated:

assume that the channel to be calibrated isThe reference channel isThen, the correction factor required for calculation is:

multiplying the calculated W by the correspondingThe channel realizes the accurate correction of the channel amplitude and phase, and the array plane reconstruction mainly means that the time sequence alignment of a plurality of frequency point detection beams and auxiliary beams is realized simultaneously when a plurality of detection beams are formed, so that the array plane reconstruction is completed through data exchange and weight reconstruction.

5. The method according to claim 1 or 2, wherein the information processing system is provided with a waveform processing module, and the waveform processing module designs a set of orthogonal phase encoded waveforms with good cross-correlation performance based on frequency diversity according to radar operation and weather detection requirements, and performs matched filtering according to respective waveforms during reception to obtain echoes matched with the signals.

6. The method of claim 5, wherein the waveform processing module comprises: designing a random multi-item code sequence, wherein the waveform sequence is as follows:and constant modulus condition is satisfied:(ii) a The autocorrelation function of the waveform sequence can be written as:

；

the integral side lobes and peak side lobes of the autocorrelation can be written as:

the goal of the waveform design is to minimize the integral or peak sidelobes of the autocorrelation

Then letting the integrated sidelobes or peak sidelobes of the autocorrelation be lowest can be described as:

considering the complex modulation situation in the pulse, the zero point gap exists in the waveform, and the zero point constraint can be increased:

for multiple sets of orthogonal waveforms, the cross-correlation constraint is added:

，

considering the problem of Doppler tolerance, the constraint that the side lobe does not lift and the main lobe does not fall when the Doppler change is increased:

，

and combining the intra-pulse composite modulation, the Doppler tolerance and the inter-pulse orthogonal index to design an ideal waveform.

7. The method as claimed in claim 1 or 2, wherein the information processing system is provided with a decoding processing module, and the decoding processing module performs random phase encoding on the transmitted pulse sequence, and then decodes the phase of the received signal to distinguish the phase information of the first and second echoes during reception, so as to eliminate the second and above received signals.

8. The method according to claim 1 or 2, wherein a frequency domain processing module is provided in the information processing system, and the frequency domain processing module is configured to implement frequency diversity and frequency domain clutter processing, wherein the frequency diversity is implemented in N TR components, and after the echo signal is subjected to AD sampling, the frequency diversity is implemented by performing down-conversion processing by using different digital local oscillator frequencies, and then filtering out other frequency separations to obtain a baseband IQ signal corresponding to a pulse carrier frequency; the frequency domain clutter processing is completed in the information processing system, the phase correlation between the reflected signals of the same carrier frequency pulse sequence is carried out, then the discrete Fourier transform processing is carried out to obtain the Doppler power spectrum of the signals, and the Doppler spectrum contains different frequency components.

9. The simultaneous multi-channel array processing method based on space-time-frequency code wave technology as claimed in claim 8, wherein the frequency domain processing module processing step includes: if the weather radar echo signal isT is the sampling time interval, K is the serial number of the sample,comprises the following steps:

after discrete fourier transform, the spectrum is:

whereinIs a discrete time-domain signal that is,is a corresponding discrete frequency domain signal, and the corresponding frequency spectrum is:

function of spectral density thereofCan be composed ofFind out

The average doppler frequency and spectral width are as follows:

whereinIn the above formulaIs the frequency of the signal or signals,are samples of a frequency of the signal being sampled,which represents the average doppler frequency of the doppler signals,indicating the spectral width.

10. The method as claimed in claim 1 or 2, wherein the information processing system is provided with a time domain processing module, the time domain processing module obtains weather target parameter information through time domain correlation processing, the weather target parameter information includes reflectivity intensity, radial velocity and velocity spectral width, and the calculation method of the weather target parameter information includes:

assuming that the sample volume contains a plurality of scattering particles moving relative to the radar, the field strength received by the radar from each scattering particle can be expressed asSince the amplitude of the echo intensity of each particle is not large, it can be written asIn the above formula, j is the corresponding physical quantity of the jth particle in the radar unit data sampling volume;

the contribution of all particles in the scattering volume to the echo amplitude is given by the following equation, which can be decomposed into real and imaginary parts:

from the above equation and the autocorrelation function of the complex amplitude, the following equation can be obtained:

when the number of pulses of the sampling signal meets the requirement of the accumulated number, calculating a base data product comprising a reflectivity factor, a radial speed and a speed spectrum width;

the power sum of the signals can be calculated by the formula:

when the reflectivity factor is calculated, factors such as a gain constant of a radar system, atmospheric attenuation, target distance attenuation and the like need to be considered, and a calculation formula of the reflectivity factor can be obtained according to a radar meteorological equation:

in the formula, echo (i) is the echo power of a target, RK is the distance between the target and a radar, ATMOS is an atmospheric attenuation factor, and SYSCAL is a radar system gain constant;

because of the fact thatThe combined formula can obtain a calculation formula of the radial velocity:

assuming that the radial velocity fluctuation of any particle satisfies normal distribution, the standard deviation of Doppler angular frequency is calculated, and a formula is obtained by combining the contribution formula of all particles in the scattering volume to the echo amplitude:

the above equation is normalized because the total echo power is equal to the sum of the echo powers of the individual particles when a large number of particles are alignedUnder the conditions ofThus, a calculation formula of the spectrum width is obtained:

in the above formulaIs the standard deviation of the doppler frequency, i.e. the width of the velocity spectrum:is the echo signal complex amplitude.

Technical Field

The invention relates to the field of all-digital phased array weather radars, in particular to a simultaneous multi-channel array processing method based on a space-time frequency code wave technology.

Background

Weather radars are the main equipment for observing meteorological phenomena at present, are successfully applied to meteorological guarantee and service of various industries such as urban disaster prevention and reduction, artificial influence weather, water conservancy, electric power, civil aviation, military and the like, and play an increasingly important role. With the continuous development of the phased array radar technology, the phased array technology is introduced into the weather radar, and CN202010072047.4 discloses a phased array weather radar polarization control method and a phased array weather radar system, wherein the phased array weather radar polarization control method includes: receiving a polarization mode selection; determining a first polarization parameter of each waveguide included in the phased array weather radar according to the polarization mode parameter; and sending the first polarization parameters to corresponding waveguides, so that the waveguides transmit/receive different polarization signals according to the first polarization parameters. By utilizing the outstanding advantages of free and flexible scheduling of phased array weather radar beams and adopting a proper method to improve the data processing quality of meteorological targets, the refined three-dimensional structure of strong disaster weather and the refining process of the strong disaster weather along with time evolution can be effectively obtained, the monitoring and early warning capability of the strong disaster weather is improved, and the method is bound to become the mainstream direction of the next generation of weather radar development.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a space-time frequency code wave technology-based simultaneous multi-channel array processing method which improves the monitoring capability of the full airspace weather phenomenon, improves the measurement precision, improves the anti-clutter processing capability and improves the monitoring and early warning capability of a phased array weather radar on strong disaster weather.

The purpose of the invention is realized by the following technical scheme.

A simultaneous multi-channel array processing method based on space-time-frequency code wave technology comprises the following steps:

1) the radar data processing is realized by controlling a frequency source to generate a plurality of pulse sequences with different carrier frequencies and adjusted frequency phases through an uplink by a radar control unit;

2) sending the signals to N TR component transmitting branches for up-conversion and amplification, radiating the signals by an antenna, and spatially synthesizing a transmitting beam covering a set airspace;

3) after being reflected by a meteorological target, the transmitted wave beam enters N TR component receiving branches after being received by an antenna, low-noise amplification and analog down-conversion processing are carried out, and then the transmitted wave beam enters a digital receiving channel to realize digital processing;

4) based on waveform information designed in an uplink, signals received in a digital receiving channel are firstly converted into digital signals through AD (analog-to-digital) and then frequency diversity is realized through different digital down-conversion, baseband IQ signals after frequency diversity are sent to an information processing system from a TR (transmitter-receiver) component through optical fibers, combined processing of five dimensions of spatial processing, time domain processing, frequency domain processing, decoding processing and waveform processing is realized in the information processing system, M roadbed data is formed and then the M roadbed data is sent to data processing for storage and display.

The step 4) is specifically as follows: in the information processing system, firstly, space domain processing is carried out to form a plurality of receiving wave beams covering different space domains, then waveform processing is carried out to extract required information, additional phase information is removed through decoding processing, then frequency domain processing is carried out to filter out non-meteorological signals such as clutter and the like, finally time domain correlation processing is carried out, meteorological parameters needing to be measured are calculated and processed, the meteorological parameters comprise reflectivity intensity, radial Doppler velocity and velocity spectrum width, and M roadbed data are formed and then sent to data processing to be stored and displayed.

The information processing system is provided with a spatial domain processing module, the spatial domain processing module is used for realizing multi-beam synthesis and forming a plurality of receiving beams covering a set spatial domain, and a reconfigurable multi-channel array processing technology is adopted.

The spatial domain processing module carries out channel calibration and array plane reconstruction, and the channel calibration method comprises the following steps: inputting single carrier frequency at the front end of the receiver, calculating the amplitude and phase consistency of the channel, and adopting a channel calibration method of conjugate multiplication of a reference channel and channel data to be calibrated:

assume that the channel to be calibrated isThe reference channel isThen, the correction factor required for calculation is:

multiplying the calculated W by the correspondingThe channel realizes the accurate correction of the channel amplitude and phase, and the array plane reconstruction mainly means that the time sequence alignment of a plurality of frequency point detection beams and auxiliary beams is realized simultaneously when a plurality of detection beams are formed, so that the array plane reconstruction is completed through data exchange and weight reconstruction.

The information processing system is internally provided with a waveform processing module, the waveform processing module designs a group of orthogonal phase coding waveforms with good cross-correlation performance on the basis of frequency diversity according to the radar working mode and the meteorological detection requirement, and performs matched filtering according to respective waveforms during receiving to obtain echoes matched with the signals.

The processing steps of the waveform processing module comprise: designing a random multi-item code sequence, wherein the waveform sequence is as follows:and constant modulus condition is satisfied:(ii) a Autocorrelation function of the waveform sequenceThe number can be written as:

；

the integral side lobes and peak side lobes of the autocorrelation can be written as:

the goal of the waveform design is to minimize the integral or peak sidelobes of the autocorrelation

Then letting the integrated sidelobes or peak sidelobes of the autocorrelation be lowest can be described as:

considering the complex modulation situation in the pulse, the zero point gap exists in the waveform, and the zero point constraint can be increased:

for multiple sets of orthogonal waveforms, the cross-correlation constraint is added:

，

considering the problem of Doppler tolerance, the constraint that the side lobe does not lift and the main lobe does not fall when the Doppler change is increased:

，

and combining the intra-pulse composite modulation, the Doppler tolerance and the inter-pulse orthogonal index to design an ideal waveform.

The information processing system is provided with a decoding processing module, and the decoding processing module carries out random phase coding on a transmitting pulse sequence and then distinguishes phase information of primary echoes and secondary echoes by decoding the phase of a received signal during receiving so as to eliminate secondary and above received signals.

The information processing system is internally provided with a frequency domain processing module which is used for realizing frequency diversity and frequency domain clutter processing, wherein the frequency diversity is realized in N TR components, after the echo signal is subjected to AD sampling, the down-conversion processing is carried out by adopting different digital local oscillator frequencies, then other frequency separation is filtered, a baseband IQ signal corresponding to a pulse carrier frequency is obtained, and the frequency diversity is realized; the frequency domain clutter processing is completed in the information processing system, the phase correlation between the reflected signals of the same carrier frequency pulse sequence is carried out, then the discrete Fourier transform processing is carried out to obtain the Doppler power spectrum of the signals, and the Doppler spectrum contains different frequency components.

The frequency domain processing module comprises the following processing steps: if the weather radar echo signal isT is the sampling time interval, K is the serial number of the sample,comprises the following steps:

after discrete fourier transform, the spectrum is:

whereinIs a discrete time-domain signal that is,is a corresponding discrete frequency domain signal, and the corresponding frequency spectrum is:

function of spectral density thereofCan be composed ofFind out

The average doppler frequency and spectral width are as follows:

whereinIn the above formulaIs the frequency of the signal or signals,are samples of a frequency of the signal being sampled,which represents the average doppler frequency of the doppler signals,indicating the spectral width.

The information processing system is provided with a time domain processing module, the time domain processing module acquires meteorological target parameter information through time domain correlation processing, the meteorological target parameter information comprises reflectivity intensity, radial speed and speed spectrum width, and the meteorological target parameter information is calculated in a mode comprising:

assuming that the sample volume contains a plurality of scattering particles moving relative to the radar, the field strength received by the radar from each scattering particle can be expressed asSince the amplitude of the echo intensity of each particle is not large, it can be written asIn the above formula, j is the corresponding physical quantity of the jth particle in the radar unit data sampling volume;

the contribution of all particles in the scattering volume to the echo amplitude is given by the following equation, which can be decomposed into real and imaginary parts:

from the above equation and the autocorrelation function of the complex amplitude, the following equation can be obtained:

when the number of pulses of the sampling signal meets the requirement of the accumulated number, calculating a base data product comprising a reflectivity factor, a radial speed and a speed spectrum width;

the power sum of the signals can be calculated by the formula:

when the reflectivity factor is calculated, factors such as a gain constant of a radar system, atmospheric attenuation, target distance attenuation and the like need to be considered, and a calculation formula of the reflectivity factor can be obtained according to a radar meteorological equation:

in the formula, echo (i) is the echo power of a target, RK is the distance between the target and a radar, ATMOS is an atmospheric attenuation factor, and SYSCAL is a radar system gain constant;

because of the fact thatThe combined formula can obtain a calculation formula of the radial velocity:

assuming that the radial velocity fluctuation of any particle satisfies normal distribution, the standard deviation of Doppler angular frequency is calculated, and a formula is obtained by combining the contribution formula of all particles in the scattering volume to the echo amplitude:

the above equation is normalized because the total echo power is equal to the sum of the echo powers of the individual particles when a large number of particles are alignedUnder the conditions ofThus, a calculation formula of the spectrum width is obtained:

in the above formulaIs the standard deviation of the doppler frequency, i.e. the width of the velocity spectrum:is the echo signal complex amplitude.

Compared with the prior art, the invention has the advantages that:

(1) the space-time frequency code wave technology is adopted, the core technology of phased array weather radar processing is broken through, and the data processing quality of meteorological targets is improved;

(2) based on the improvement of the quality of the detection data, the monitoring and early warning capability of the equipment on the medium and small-scale dangerous weather is further improved;

(3) through the space-time frequency code wave five-dimensional processing, detection data with high space-time resolution is provided for accurate aviation forecast early warning service, the air traffic control guarantee capability is improved, the flight safety of the passenger plane is guaranteed, and the method has very important significance for promoting the modernization process of civil aviation weather guarantee and service;

(4) the phased array weather radar is promoted to be further popularized and used, and the meteorological monitoring and early warning capability of China is further enhanced;

(5) the full airspace weather phenomenon monitoring capability is improved, and full airspace scanning and processing are ensured to be completed in one volume scanning period;

(6) the measurement precision is improved, and three-dimensional meteorological target information is provided for meteorological analysis personnel, so that more accurate forecast is facilitated;

(7) the clutter rejection processing capability is improved, and the data reliability and the weak signal detection capability are improved by the multi-processing method.

Drawings

FIG. 1 is a block diagram of a phased array weather radar system according to the present invention.

FIG. 2 is a flow chart of the present invention.

Fig. 3 is a flow chart of quadrature phase encoded waveform processing.

Fig. 4 is a comparison graph of the minimum elevation PPI observation of 07 lattice wind front radar at 18 days 6 months.

Fig. 5-13 are graphs comparing the observation process of phased array weather radar with the new generation weather radar.

Fig. 14 is a vertical cross-sectional view of a gust front.

Detailed Description

The invention is described in detail below with reference to the drawings and specific examples.

Examples

The hardware of a certain phased array weather radar (see figure 1) system is structurally divided into an outdoor part and an indoor part, the outdoor part mainly comprises an antenna pedestal, an antenna array surface (comprising N waveguide slot antennas, a comprehensive network, array surface monitoring, an N-channel digital TR component, 1 monitoring component, an array surface power supply and the like), light transmission and Digital Beam Forming (DBF), and the indoor part comprises signal processing, servo (antenna control), health management (comprising a database), data processing (comprising radar information display and meteorological information processing), a secondary product generation server, and auxiliary equipment such as cables, cabinets, networks and the like.

In order to realize the optimal detection and processing of meteorological targets, the simultaneous multi-channel array processing method based on the space-time frequency code wave technology is created based on the design of a phased array weather radar and is fused with the work of the whole radar system. The method is based on a multi-channel parallel processing software architecture, realizes multi-domain combined reinforcement system processing design from five dimensions of space domain, time domain, frequency domain, coding and waveform, and realizes multi-channel parallel stereo detection and processing of meteorological targets.

The simultaneous multi-channel array processing process based on the space-time-frequency code wave technology is integrated with the work of the whole radar system, and the specific processing flow is shown in figure 2.

Firstly, radar data processing is carried out, a frequency source is controlled by a radar control unit through an uplink to generate a plurality of pulse sequences with different carrier frequencies and with wave forms and frequency phase adjustment, then the pulse sequences are sent to N TR component transmitting branches to carry out up-conversion and amplification, then the pulse sequences are radiated out through an antenna, and transmitting beams covering a set airspace are synthesized in space. After being reflected by a meteorological target, the transmitting signals are received by an antenna and then enter N TR component receiving branches for low-noise amplification and analog down-conversion processing, and then enter a digital receiving channel to realize digital processing. Based on waveform information designed in an uplink, a received signal in a digital receiving channel is firstly converted into a digital signal through AD (analog-to-digital) and then frequency diversity is realized through different digital down-conversion, a baseband IQ signal after the frequency diversity is sent to an information processing system from a TR (transmitter-receiver) component through an optical fiber, and the combined processing of five dimensions of a space domain, a time domain, a frequency domain, a coding domain and a waveform is realized in the information processing system. In the information processing system, firstly, space domain processing is carried out to form a plurality of receiving wave beams covering different space domains, then waveform processing is carried out to extract required information, additional phase information is removed through decoding processing, then frequency domain processing is carried out to filter out non-meteorological signals such as clutter and the like, finally time domain correlation processing is carried out, meteorological parameters (reflectivity intensity, radial Doppler velocity, velocity spectrum width and the like) required to be measured are calculated and processed, and M roadbed data is formed and then sent to data processing for storage and display.

Based on the transmitted signal design in the uplink, the matching processing of the received signals is realized in the downlink through the combination of the space domain, the waveform, the decoding, the frequency domain and the time frequency five dimensions, and the requirement of simultaneous working of the phased array weather radar multi-beam is considered, so that the information processing system adopts a multi-channel parallel processing architecture in design, mainly comprises five processing modules, namely a space domain processing module, a waveform processing module, a decoding processing module, a frequency domain processing module and a time domain processing module.

1) The airspace processing module: the main function is to realize multi-beam synthesis, form a plurality of receiving beams covering a set airspace, adopt a reconfigurable multi-channel array processing technology, support more than 300 paths of digital channels for parallel processing, realize the switching of various array surface combinations in real time in a digital part, form beams in a full array or partial sub-arrays, generate 40 paths of receiving beams with the interval of 0.2 degree at most in real time by a system, and finish the rapid parallel processing of the 40 paths of receiving beams. Channel calibration and wavefront reconstruction are required to achieve optimal processing synthesis. The channel calibration mainly refers to calibrating the amplitude and the phase of a channel to ensure good digital beam side lobe performance, and the adopted main method comprises the following steps: the method comprises the steps of inputting single carrier frequency at the front end of a receiver, calculating the amplitude and phase consistency of a channel, and adopting a channel calibration method of conjugate multiplication of a reference channel and channel data to be calibrated.

Assume that the channel to be calibrated isThe reference channel isThen, the correction factor required for calculation is:

multiplying the calculated W by the correspondingThe channel realizes the accurate correction of the channel amplitude and phase, and the array plane reconstruction mainly means that the time sequence alignment of a plurality of frequency point detection beams and auxiliary beams is realized simultaneously when a plurality of detection beams are formed, so that the array plane reconstruction is completed through data exchange and weight reconstruction.

2) The waveform processing module: the main function is to design a group of orthogonal phase coding waveforms with good cross-correlation performance on the basis of frequency diversity according to the working mode of the radar and the meteorological detection requirement, and to perform matched filtering according to the respective waveforms during receiving, and only obtain the echo matched with the signal due to small response of other signals passing through the filter, thereby further improving the isolation between different pitching beams in the multi-beam mode. The process flow is shown in FIG. 3.

The processing steps of the waveform processing module comprise: designing a random multi-item code sequence, wherein the waveform sequence is as follows:and constant modulus condition is satisfied:(ii) a The autocorrelation function of the waveform sequence can be written as:

；

the integral side lobes and peak side lobes of the autocorrelation can be written as:

the goal of the waveform design is to minimize the integral or peak sidelobes of the autocorrelation

Then letting the integrated sidelobes or peak sidelobes of the autocorrelation be lowest can be described as:

considering the complex modulation situation in the pulse, the zero point gap exists in the waveform, and the zero point constraint can be increased:

for multiple sets of orthogonal waveforms, the cross-correlation constraint is added:

，

considering the problem of Doppler tolerance, the constraint that the side lobe does not lift and the main lobe does not fall when the Doppler change is increased:

，

and combining the intra-pulse composite modulation, the Doppler tolerance and the inter-pulse orthogonal index to design an ideal waveform.

3) The decoding processing module: when the repetition frequency of the radar working pulse is higher, a secondary echo signal appears to cause the distance measurement distortion of a meteorological target, random phase coding is needed to be carried out on a transmitting pulse sequence for solving the problem, and then the phase information of a primary echo and a secondary echo is distinguished by decoding the phase of a receiving signal during receiving, so that the secondary and above receiving signals are eliminated. The decoding processing module 3# is mainly used to implement the above functions.

The method of phase change can expand the unambiguous distance and eliminate the deviation of the spectral moment estimation caused by echo superposition. The estimation of velocity in Doppler weather radar Pulse Pair Processing (PPP) algorithmWhen the phase information of the echo is extractedWhen the primary echo and the secondary echo are included in the signalCan be expressed as the sum of the primary and secondary echoes:

by usingWhen the velocity of the primary and secondary echoes is calculated, an error of the velocity estimation value is inevitably caused, and the purpose of the phase encoding is to change the phase of the secondary echo so thatSo that the secondary echo no longer affects the estimation of the primary echo speed; otherwise, the phase of the primary echo is changed so thatSo that the primary echo does not affect the estimation of the secondary echo velocity. Sequence for transmitting pulsesPerforming modulation, i.e. phase subtraction of transmitted pulse sequencesIn this way, the primary echoes are synchronized and the secondary echoes are synchronizedThe modulation is carried out by the following steps,also, we can multiply the echo sampled signal bySo that the secondary echoes are synchronized and the primary echoes are synchronizedThe modulation is carried out by the following steps,. The random phase method meansIs a randomly varying value.

4) The frequency domain processing module: the method has the main functions of realizing frequency diversity and frequency domain clutter processing, wherein the frequency diversity is mainly realized in a TR component, after an echo signal is subjected to AD sampling, in order to obtain signals reflected by different carrier frequency pulses, at the moment, the down-conversion processing is carried out by adopting different digital local oscillator frequencies, then other frequency separation is filtered, a baseband IQ signal corresponding to a pulse carrier frequency is obtained, and the frequency diversity is realized; the frequency domain clutter processing is completed in the information processing, after the processing of the decoding processing module 3#, the phase correlation between the reflected signals of the same carrier frequency pulse sequence is realized, then the Discrete Fourier Transform (DFT) processing is carried out to obtain the Doppler power spectrum of the signals, and the Doppler spectrum contains different frequency components, which are echoes generated by the scattering of electromagnetic waves by some non-meteorological target bodies and false echoes caused by the radar performance. Birds, insects, airplanes, ground clutter and the like are interference clutter frequency components and are non-meteorological information needing to be filtered in a frequency domain.

If the weather radar echo signal isT is the sampling time interval, K is the serial number of the sample,comprises the following steps:

after discrete fourier transform, the spectrum is:

whereinIs a discrete time-domain signal that is,is a corresponding discrete frequency domain signal, and the corresponding frequency spectrum is:

function of spectral density thereofCan be composed ofFind out

The average doppler frequency and spectral width are as follows:

whereinIn the above formulaIs the frequency of the signal or signals,are samples of a frequency of the signal being sampled,which represents the average doppler frequency of the doppler signals,indicating the spectral width.

Since the radar return signal inevitably contains noise, the signal received by the radar always includes a weather signal and a noise signal. In order to obtain a pure meteorological spectrum, in actual operation, the complex time sequence of an IQ channel received by a Doppler radar receiver is firstly subjected to FFT (fast Fourier transform) processing to obtain a complex frequency spectrum sequence, and then the complex frequency spectrum sequence is subtracted by the complex frequency spectrum sequence. A new complex spectrum sequence is obtained and substituted into the formula to obtain the spectrum width and frequency values.

5) The time domain processing module 5 #: the main function of the method is to acquire meteorological target parameter information (including reflectivity intensity (Z), radial velocity (V), velocity spectrum width (W) and the like) through time domain correlation processing.

Assuming that the sample volume contains a plurality of scattering particles moving relative to the radar, the field strength received by the radar from each scattering particle can be expressed asSince the amplitude of the echo intensity of each particle is not large, it can be written asIn the above formula, j is the corresponding physical quantity of the jth particle in the radar unit data sampling volume;

the contribution of all particles in the scattering volume to the echo amplitude is given by the following equation, which can be decomposed into real and imaginary parts:

from the above equation and the autocorrelation function of the complex amplitude, the following equation can be obtained:

when the number of pulses of the sampling signal meets the requirement of the accumulated number, calculating a base data product comprising a reflectivity factor, a radial speed and a speed spectrum width;

the power sum of the signals can be calculated by the formula:

when the reflectivity factor is calculated, factors such as a gain constant of a radar system, atmospheric attenuation, target distance attenuation and the like need to be considered, and a calculation formula of the reflectivity factor can be obtained according to a radar meteorological equation:

in the formula, echo (i) is the echo power of a target, RK is the distance between the target and a radar, ATMOS is an atmospheric attenuation factor, and SYSCAL is a radar system gain constant;

because of the fact thatThe combined formula can obtain a calculation formula of the radial velocity:

assuming that the radial velocity fluctuation of any particle satisfies normal distribution, the standard deviation of Doppler angular frequency is calculated, and a formula is obtained by combining the contribution formula of all particles in the scattering volume to the echo amplitude:

the above equation is normalized because the total echo power is equal to the sum of the echo powers of the individual particles when a large number of particles are alignedUnder the conditions ofThus, a calculation formula of the spectrum width is obtained:

in the above formulaIs the standard deviation of the doppler frequency, i.e. the width of the velocity spectrum:is the echo signal complex amplitude.

The time domain processing module can process a plurality of beam baseband IQ signals in parallel in real time based on the processing algorithm to obtain output parameters required by the system: reflectivity intensity (Z), radial velocity (V), and velocity spectrum width (W).

The processing technology is successfully applied to the Beijing great-rise international airport phased array weather radar, the radar adopts a receiving and transmitting unit level full digitalization technology, a method for jointly processing weather echo signals in multiple domains such as space-time frequency code waves and the like is created, a self-adaptive software framework (a commercial platform) for signal and data processing is established, a rapid and fine detection strategy of the phased array radar suitable for civil aviation airport air traffic control weather guarantee is developed, and compared with the existing business weather radar, the radar can better provide more accurate and rapid weather detection data for civil aviation four-dimensional flight.

In the running time of more than one year, five-dimensional multi-domain combined processing is carried out on a plurality of typical weather processes such as downburst, gust and hail by adopting a space-time frequency code wave technology based on detection data, the processing result has the characteristics of high time resolution, high distance resolution and high angle resolution, more detail changes of the weather processes can be reflected, and particularly, the weather details which cannot be detected by the conventional weather radar are observed in a low-level airspace. A typical case for the radar gust observation is detailed below.

And 6, 18 days in 2020, a gust front process is found in west of great-minded airports in Beijing, and the process is subjected to refined five-dimensional multi-domain combined processing based on the radar detection data. The method comprises the steps of firstly carrying out space domain processing to form 40 receiving beams covering 0.2-20.2 degrees, then carrying out ultra-low side lobe pulse compression processing to extract required information, then removing additional phase information through digital domain decoding processing, then carrying out frequency domain processing to filter out ground clutter, non-meteorological signals of airplanes and the like, and finally carrying out time domain correlation and quality control processing, and calculating and processing meteorological parameters (reflectivity intensity, radial Doppler velocity, velocity spectrum width and the like) required to be measured, wherein the calculation result is shown in figure 4.

In fig. 4, at 07 o ' clock at 18 o ' clock at 6 month, there is a strong convection system that is continuously moving from northwest to beijing, creating a gust front process, (a) is a maxing phased array weather radar minimum elevation PPI observation map for the 07 o ' clock at 6 month 18 day of the gust front radar; (b) and (3) carrying out minimum elevation angle PPI observation images on the new generation weather radar with the 6-month and 18-day 07 dot wind front radar, and comparing (a) with (b), so that the wind front observed by the C-PAR radar is clearer. Therefore, the space-time frequency code wave technology is adopted, and the processing effect of the low-altitude gust wind front is better promoted.

As shown in fig. 5-13, the gust front process is continuously enhanced from 6 o' clock 30 at 18 th 6 th month, and as the strong convection moves, the gust front becomes clear and away from the strong convection body. Comparing the observed data within 12 minutes, it can be seen that 6 points 42 minutes result in fuzzy gust front process observed by the new generation weather radar, while the gust front observed by the 6 points 32 minutes phased array weather radar is relatively clear. Therefore, the phased array weather radar can discover and identify the gust front process earlier by adopting the space-time frequency code wave technology.

Fig. 14 shows a cross-sectional analysis of a gust that is processed based on space-time-frequency code wave technology: (a) PPI; (b) a strength vertical profile; (c) a classical model; (d) obtaining a vertical section of the echo intensity and the radial velocity by using the velocity vertical section, and clearly reflecting the detailed characteristics of the wind gust front process: at 6 hours of 6 months, 18 days and 46 minutes, the echo intensity of the gust front is about 10-20dBZ, and the distance from the radar is about 40 km. The maximum strength of the strong convection system behind the wind power generation system exceeds 40dBZ, and the distance between the maximum strength and the wind power generation system is about 20km from a gust wind front. And from the strong convection structure, the influence of high-rise northwest wind leads the high-rise movement to the low-rise, so that the convection system inclines downwards in the wind direction, and the low-rise gust front is positioned below the high-rise convection cloud anvil. The high-altitude convection precipitation is evaporated in the falling process, so that no precipitation exists on the ground, a low-altitude cooling pool is formed, and the forward propulsion of the cooling pool process is also an important reason for the formation of a gust front.