CN117081681A

CN117081681A - Space echo simulation system based on digital triplets and control method

Info

Publication number: CN117081681A
Application number: CN202310967756.2A
Authority: CN
Inventors: 孙亚光; 李挺; 任宏伟
Original assignee: Beijing Huaqing Ruida Technology Co ltd
Current assignee: Beijing Huaqing Ruida Technology Co ltd
Priority date: 2023-08-02
Filing date: 2023-08-02
Publication date: 2023-11-17

Abstract

A space echo simulation system and control method based on digital triplets belongs to the field of radio frequency simulation, and comprises a test unit, a signal receiving unit, a signal processing unit, a synthetic angle modulation unit, a signal radiation unit, a control center and an optical fiber switching matrix module; the channel selection is performed by the composite angle modulation unit, so that echo simulation of a large number of signals at different angles can be performed on the basis of the original antenna array. The scene of echo simulation is more vivid; in the case of a large increase in analog signal quantity, the cost does not rise and fall.

Description

Space echo simulation system based on digital triplets and control method

Technical Field

The invention belongs to the field of radio frequency simulation, and particularly relates to the field of radar echo semi-physical simulation of digital signal amplitude-phase modulation.

Background

At present, when an echo is simulated in a laboratory, an echo simulator is generally adopted to simulate the echo by combining a radio frequency switch matrix array feed system, and echo simulation data is obtained by adopting a statistical echo model or a terrain actual data calculation mode for different echo scenes. However, since the echoes are distributed over an extremely wide range, the echoes occupy a wide range in terms of distance and angle, and particularly in terms of angle, there are main lobe echoes, side lobe echoes, altitude line echoes, and the like. The echo simulator can only simulate the expansion characteristic in distance, but can not simulate the expansion in angle; the conventional radio frequency switch matrix array feed system can only simulate the echo characteristics of discrete points in a limited angle in consideration of the layout cost, and cannot show the actual angle characteristics in a space domain.

With the progress of simulation technology, the echo scattering point feature simulation requires a large-scale expansion in distance and angle to simulate the echo environment close to the real scene. At present, no more advanced simulation system and method have been found at home and abroad, and the echo characteristics of multiple scattering points can be simulated in a realistic manner in a space domain.

Before the missile is formally put into use, a large number of simulation tests are required, and the semi-physical simulation system has the characteristics of low cost, good confidentiality, vivid electromagnetic environment and the like, and is incomparable with the all-digital simulation system. The tested radar guide head is directly connected into the simulation test loop, the hardware generates the radar target echo signal in real time, the real electromagnetic environment is realistically reproduced, and the performance of the tested radar can be accurately evaluated. Therefore, the construction of a semi-physical radio frequency simulation laboratory becomes an important component of the development stage of the seeker.

The semi-physical radio frequency simulation system realistically reproduces the target of the radar seeker and the battlefield environmental signals in a laboratory, including the spatial attribute and the signal characteristics of the target, so as to test and evaluate various performance indexes of the seeker, and at present, an array feed simulation method is commonly adopted in countries around the world.

The traditional array feed simulation laboratory generates radio frequency signals required by simulation by a signal simulation system, amplitude and phase adjustment of ternary combination signals are carried out through an array feed network, and the ternary combination channels are gated and then radiated by an array antenna. The array feed network is composed of a large number of microwave devices such as amplifiers, attenuators, phase shifters, equalizers, switches and the like, and in the use process, various devices are controlled through electric signals, and power supply of active microwave devices such as the amplifiers and the like is considered.

Along with the increase of simulation requirements, simulation scenes are more and more complex, the number of target points to be simulated and modulated is more and more, when the number of the simulation target points is increased, microwave devices in an array feed network are multiplied, and on the basis of the increase of cost, a large amount of test calibration work and feed network control logic modification are also required.

Disclosure of Invention

The invention discloses a space echo simulation system and a control method based on a digital triplet, which are used for solving the technical problems of simulating a large number of echo signals, effectively reducing the scale and cost of hardware and improving the simulation fidelity of the echo in a radio frequency simulation dark room.

For a better understanding of the objects, structures and functions of the present invention, a compacting tool according to the present invention will be described in further detail with reference to the accompanying drawings.

The present invention will be further described in detail below with reference to specific embodiments and with reference to the accompanying drawings, in order to make the objects, technical solutions and advantages of the present invention more apparent.

It should be noted that, in the drawings or the text of the specification, implementations not shown or described are all forms known to those of ordinary skill in the art, and not described in detail. Furthermore, the above definitions of the elements and methods are not limited to the specific structures, shapes or modes mentioned in the embodiments, and may be simply modified or replaced by those of ordinary skill in the art.

Those skilled in the art will appreciate that the modules in the apparatus of the embodiments may be adaptively changed and disposed in one or more apparatuses different from the embodiments. The modules or units or components of the embodiments may be combined into one module or unit or component and, in addition, they may be divided into a plurality of sub-modules or sub-units or sub-components. Any combination of all features disclosed in this specification (including any accompanying claims, abstract and drawings), and all of the processes or units of any method or apparatus so disclosed, may be used in combination, except insofar as at least some of such features and/or processes or units are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Also, in the unit claims enumerating several means, several of these means may be embodied by one and the same item of hardware.

Similarly, it should be appreciated that in the foregoing description of exemplary embodiments of the disclosure, various features of the disclosure are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various disclosed aspects. However, the disclosed method should not be construed as reflecting the intention that: i.e., the claimed disclosure requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this disclosure.

In order to solve the technical problems, the specific technical scheme of the invention is as follows:

a space echo simulation system based on digital triplets comprises a test unit, a signal receiving unit, a signal processing unit, a synthetic angle modulation unit, a signal radiation unit, a control center and an optical fiber switching matrix module;

the testing unit comprises a tested radar or a guide head and a multi-degree-of-freedom turntable; the radar or the seeker is arranged on the multi-degree-of-freedom turntable during testing, and the multi-degree-of-freedom turntable can realize the posture adjustment of the tested radar;

The signal receiving unit is used for receiving radio frequency signals transmitted by the radar, down-converting the radio frequency signals to low intermediate frequency, converting the low intermediate frequency signals into digital signals through analog-to-digital conversion, and transmitting the digital signals through optical fibers;

a signal processing unit; receiving simulation scene information and a digital excitation signal output by a signal receiving unit through an optical fiber, calculating the characteristics of each scattering point of the space echo, generating space echo data under a corresponding scene, and outputting the space echo data through the optical fiber;

the angle modulation unit is synthesized, the angle control module completes the angle modulation and simultaneously selects the triplet of the signal radiation unit, outputs the intermediate frequency analog signal to the up-conversion module of the signal radiation unit,

the signal radiation unit is used for receiving the intermediate frequency analog signals output by the synthetic angle modulation unit, up-converting the intermediate frequency analog signals into radio frequency signals of corresponding frequency bands, adjusting signal power at the same time and finally radiating the signals by the antenna array;

the control center controls each unit of the space echo simulation system, integrally controls each unit and can send instructions to each unit;

the method comprises the steps of storing simulation scene library data, calling the simulation scene library data for calculation of a signal processing unit according to simulation scene parameter setting of a tester, applying variables to a test link according to a manual instruction in the middle of the test, and controlling actions and feedback of each unit by a control center according to feedback of the changes of the applied variables of each unit;

Fiber switching matrix module: the real-time transmission interaction of the multipath optical fiber signals is realized, the signal data are received and distributed to each signal processing module, and on the other hand, the space echo scattering point signals are sent to each angle modulation module through the optical fiber matrix.

Further, the signal receiving unit comprises a radio frequency down-conversion module, an ADC sampling module, a digital-to-analog conversion FPGA computing module and an optical fiber interface module;

the radio frequency down-conversion module is used for receiving radio frequency signals, the radio frequency signals emitted by the radar are down-converted into low intermediate frequency signals and automatically control signal gain, and the output intermediate frequency signals are kept at set power;

the ADC sampling module receives the intermediate frequency signal outputted by the radio frequency down-conversion and sequentially carries out sampling and quantization steps, and the analog signal is converted into a digital signal;

the digital-to-analog conversion FPGA calculation module performs preprocessing operation on the digital signals, including frequency mixing, filtering and extraction of the digital signals, so that high-speed and accurate processing of the digital signals can be realized;

and the optical fiber interface module: the digital signals are converted into optical signals, and the optical signals are output through optical fibers to receive control of a computing center.

Further, the signal processing unit comprises a high-performance FPGA calculation module and an optical switching component;

The high-performance FPGA calculation module is used for performing orthogonal transformation, extraction and filtering treatment on the digital excitation signal output by the receiving unit and converting the digital excitation signal into an IQ complex signal;

combining the characteristic information of each scattering point of the echo of the received simulation scene information, and carrying out target characteristic modulation on the signal; calculating the amplitude, phase, distance, azimuth, pitching and Doppler information of each echo scattering point at the current moment;

according to the number of hardware channels of the system, the resource scale of the digital signal processing module and the hardware resource scale of the digital triplet system, selecting scattering points to be output at the current moment through a scattering point selection strategy, and outputting information of each scattering point to a signal processing unit for echo characteristic modulation;

then, carrying out electro-optical conversion on the digital signals carrying the target characteristics, entering an optical switching network, and carrying out triad channel selection on each path of target signals according to the distribution condition of the synthesized target angles;

and the optical switching assembly is responsible for receiving and transmitting data of each connecting unit and converting digital signals and optical signals.

Further, the composite angle modulation unit comprises an FPGA component, a DAC component and an optical fiber component;

the FPGA component is used for receiving data of each space echo scattering point, modulating signal amplitude and phase according to an echo azimuth angle and pitch angle control information and a ternary combination angle gravity center formula, controlling the precise angle of each echo scattering point in space and modulating the RCS characteristics of a target; selecting the triads of the signal radiation units according to the selection basis while modulating, and transmitting the selection result to the signal radiation units through a network;

The DAC component is used for performing digital-to-analog conversion on the digital signal to obtain an intermediate frequency analog signal, and transmitting the intermediate frequency analog signal to an up-conversion module of the signal radiation unit;

the optical fiber interface component is responsible for receiving the digital signals sent by the signal processing unit;

the signal radiation unit comprises a radio frequency up-conversion module and a radiation antenna array;

up-conversion module: up-converting the intermediate frequency signal output by the composite angle modulation unit into a radio frequency signal, controlling the amplitude of the signal, and transmitting the signal to a horn radiation unit of an antenna array;

the horn radiating unit of the antenna array radiates out the radio frequency signals generated by the up-conversion module.

Further, the radio frequency down-conversion module is composed of a local oscillation module and a frequency conversion module, the local oscillation module provides local oscillation signals needed during frequency conversion, the frequency conversion module is composed of an attenuator, an amplifier, a filter and a mixer, the frequency conversion function from radio frequency signals to intermediate frequency signals is realized through combination, and meanwhile, the radio frequency down-conversion module has a signal automatic gain control function and can automatically adjust the input radio frequency signals with different powers to intermediate frequency signals with the same power.

Further, the radio frequency up-conversion module is composed of a local oscillation module and a frequency conversion module, the local oscillation module provides local oscillation signals required during frequency conversion, the frequency conversion module is composed of an attenuator, an amplifier, a filter and a mixer, the frequency conversion function from intermediate frequency signals to corresponding radio frequency bands is realized through combination, and meanwhile, the radio frequency up-conversion module has a signal power adjusting function and adjusts output radio frequency signal power according to simulation requirements.

Further, the signal processing unit performs characteristic modulation on the preprocessed digital signal, and modulates delay and Doppler information of the signal in real time according to the requirement on the simulation signal in the experimental process to obtain a digital signal carrying simulation target information; making a simulation echo for the target echo, the body echo, the surface echo and the environment interference; and multiplexing one digital signal into three paths of signals, entering a digital switching network, selecting the three paths of signals according to the angle information of the target, and outputting the three paths of signals in the form of optical signals in corresponding three paths of antenna channels.

Furthermore, a set of combined angle modulation units and a set of signal radiation units are carried behind each antenna on the array surface, after signals enter the combined angle modulation units in the form of optical signals, the amplitudes and phases of the three paths of signals are respectively modulated according to a triplet gravity center formula, and further digital-to-analog conversion is carried out, so that intermediate frequency analog signals are obtained; finally, the signals are converted to corresponding radio frequency bands by radio frequency up-conversion and radiated through the antenna.

The invention also provides a control method of the space echo simulation system based on the digital triplet, which comprises the following operation steps:

S1, determining an azimuth pitching range which can be simulated by an array plane according to the size of the antenna array plane triplet;

s2, planning an echo simulation scene and generating a corresponding elevation digital map;

s3, calculating trajectory data, determining the position of a target point, and calculating trajectory position and beam pointing information at corresponding moments according to the trajectory information at the current moment;

s4, dividing grid cells of scattering surfaces/bodies in the echo scene, wherein the number of divided grids on the flat ground is relatively small, and the number of the grids of the undulating units is relatively large;

s5, calculating the center of each grid cell according to the divided grid cells, and calculating the azimuth and pitch angle of each grid cell center under the radar/guidance head antenna pointing coordinate system;

s6, calculating the ground wiping angle of the grid unit in the simulation range of the array surface, and calculating the normalized scattering coefficient of the grid unit according to the ground scattering coefficient calculation model and the grid ground material characteristics;

s7, calculating a central Doppler value at a corresponding moment according to the position information of each scattering unit, and correcting the Doppler value of the grid unit according to the time domain correlation/frequency domain broadening characteristic of the sea-land echo;

s8, outputting a scattering characteristic coefficient sequence corresponding to each grid cell of the scattering land/sea echo at the current moment, wherein the sequence comprises an amplitude value, a phase position, a distance, an azimuth value, a pitching value and a Doppler value corresponding to RCS values corresponding to each grid cell;

S9, receiving radar/pilot signals, modulating radar transmission signals according to the amplitude, phase, distance and Doppler values of RCS of each scattering sequence, generating echo data under a corresponding airspace, and controlling corresponding digital triplet channels according to the azimuth angle and pitch angle of the array surface corresponding to the scattering point to radiate echo signals of corresponding angles to the space;

s10, repeating the above process for each current scattering sequence, so as to realize the modulation simulation of all echo scattering characteristic data at the current ballistic moment and realize the simulation process of multi-angle echoes of the space scene at the corresponding moment;

s11, repeating the processes of S3-S10 at different simulation moments, and realizing the simulation process of the space distributed equivalent echo in the whole targeting process.

The further improved control scheme can also be used for manual intervention, and the simulated model and scene can be manually intervened at any time at different moments, so that the system can be used for radar detection training or countermeasure training.

The method overcomes the limitation of the traditional radio frequency switch matrix feed system in the number of simulated echo scattering points, improves the cost performance of simulation, adopts a digital triplet feed system to simulate the echo, and can solve the problem of airspace angle expansion. During simulation, each digital triplet on the antenna array surface can simulate a certain number of scattering characteristics, the whole antenna array can simulate the space distribution of echoes in a larger angle range, then the echo characteristic computing equipment controls the distance expansion characteristics and the frequency domain broadening characteristics of the echoes, so that the airspace, the distance and the frequency domain characteristics of a large number of echo scattering points in a space test scene can be simulated equivalently, and echo data characteristics in a planning scene can be simulated equivalently in a laboratory.

Compared with the traditional semi-physical radio frequency simulation system, the method adjusts the amplitude and phase adjusting part of the ternary combination signal from the radio frequency domain to the digital domain, the advantages of flexibility, stability, reliability and the like of digital signal processing are fully reflected in the simulation system, and meanwhile, the limitation of a microwave switch matrix is avoided by skillfully utilizing a photoelectric conversion and optical switching network, so that the method is called as a digital ternary group. Not only is a number of microwave devices saved, including but not limited to amplifiers, phase shifters, attenuators, equalizers, but also the system is provided with higher flexibility and stability.

In summary, compared with the prior art, the invention has the following beneficial effects:

1. the invention overcomes the limitation of the traditional radio frequency switch matrix feed system in the number of simulated echo scattering points, can simulate the characteristics of a large amount of echo scattering points in a airspace, solves the problem of the expansion of the airspace echo angle, and effectively improves the simulation fidelity of the echo in a radio frequency simulation darkroom;

2. when the same target point number is simulated, the cost is lower than that of the traditional array feed network, a large number of microwave devices are saved, the flexibility is high, the FPGA resource can be reasonably planned on the current basis by increasing the target point number, hardware is not necessarily required to be increased, and the device and the cost required by the hardware are smaller than those of the traditional array feed network if the hardware is increased;

3. Compared with the traditional radio frequency switch matrix array feed system, the echo simulation system disclosed by the invention has the advantages that the signal transmission is carried out by adopting optical fiber media for digital signal transmission, so that the signal-to-noise ratio of the transmission signal can be greatly improved, and the interference of other electromagnetic signals in a laboratory is not easy to occur; the digital signal processing is higher and more stable than the radio frequency domain modulation precision;

4. the cost performance of echo airspace expansion simulation is greatly improved, the test workload is small, and a large number of test calibration works are reduced;

5. the photoelectric conversion and optical switching network is skillfully utilized, and the method is more reliable and flexible than a microwave switch matrix.

Drawings

FIG. 1 is a schematic diagram of the overall structure of the present invention;

FIG. 2 is a schematic diagram of a spatial echo calculation of a spatial echo simulation system;

FIG. 3 is a schematic diagram of Doppler modulation calculated range delay;

FIG. 4 is a graph of Doppler frequency versus velocity;

FIG. 5 is a schematic diagram of a coarse bit control algorithm triplet partitioning in accordance with the present invention;

FIG. 6 is a graph of test ballistic data for a radar of the present invention;

FIGS. 7-14 are diagrams of distributed echo front simulation implementations of different eye relief distances according to the present invention;

fig. 15 is a schematic diagram of the maximum output capability of the most common triplet antenna;

fig. 16 is a diagram of an arrangement and triplets of the entire antenna array plane.

Detailed Description

In order to better understand the purpose, structure and function of the present invention, the following describes in further detail a space echo simulation system and control method based on digital triplets with reference to the accompanying drawings.

In order to overcome the limitation of the traditional radio frequency switch matrix feed system on the number of simulated echo scattering points, the simulation cost performance is improved, and the problem of airspace angle expansion can be solved by adopting the digital triplet feed system to perform echo simulation. During simulation, each digital triplet on the antenna array surface can simulate a certain number of scattering characteristics, the whole antenna array can simulate the space distribution of echoes in a larger angle range, then the echo characteristic computing equipment controls the distance expansion characteristics and the frequency domain broadening characteristics of the echoes, so that the airspace, the distance and the frequency domain characteristics of a large number of echo scattering points in a space test scene can be simulated equivalently, and echo data characteristics in a planning scene can be simulated equivalently in a laboratory.

In order to achieve the above purpose, the present invention provides a space echo simulation system and a control method based on digital triplets.

A digital triplet-based spatial echo simulation system, comprising: the system comprises a testing unit, a signal receiving unit, a signal processing unit, a synthetic angle modulation unit, a signal radiation unit, a control center and an optical fiber switching matrix module.

The testing unit comprises a tested radar or a guide head and a multi-degree-of-freedom turntable. The radar or the seeker is arranged on the multi-degree-of-freedom turntable during testing, and the multi-degree-of-freedom turntable can realize the posture adjustment of the tested radar.

the device comprises a radio frequency down-conversion module, an ADC sampling module, a digital-to-analog conversion FPGA computing module and an optical fiber interface module.

The radio frequency down-conversion module is used for receiving radio frequency signals, down-converting the radio frequency signals transmitted by the radar into low intermediate frequency signals and automatically controlling signal gain so as to keep the output intermediate frequency signals at constant power;

the ADC sampling module receives the intermediate frequency signal outputted by the radio frequency down-conversion and sequentially carries out sampling and quantization steps to convert the analog signal into a digital signal;

the digital-to-analog conversion FPGA calculation module carries out the operations of mixing, filtering and digital signal preprocessing on the digital signals, so that the digital signals can be processed at high speed and accurately;

A signal processing unit; and receiving simulation scene information and a digital excitation signal output by a signal receiving unit through an optical fiber, calculating the characteristics of each scattering point of the space echo, generating space echo data under a corresponding scene, and outputting the space echo data through the optical fiber.

The system comprises a high-performance FPGA computing module and an optical switching assembly.

performing target feature modulation on the signal by combining the characteristic information (echo simulation scene information, trajectory information and the like) of each scattering point of the echo of the received simulation scene information; calculating the amplitude, phase, distance, azimuth, pitching and Doppler information of each echo scattering point at the current moment;

and then carrying out electro-optical conversion on the digital signals carrying the target characteristics, entering an optical switching network, and carrying out triplet channel selection on each path of target signals according to the distribution condition of the synthesized target angles.

And after the angle modulation unit is combined, the angle control module outputs an intermediate frequency analog signal to the up-conversion module, and the up-conversion module comprises an FPGA component, a DAC component and an optical fiber component.

and the DAC component is used for performing digital-to-analog conversion on the digital signal to obtain an intermediate frequency analog signal, and transmitting the intermediate frequency analog signal to an up-conversion module of the signal radiation unit.

And the optical fiber interface component is responsible for receiving the digital signals sent by the signal processing unit.

And the signal radiation unit is used for receiving the intermediate frequency analog signals output by the synthetic angle modulation unit, up-converting the intermediate frequency analog signals into radio frequency signals of corresponding frequency bands, adjusting signal power at the same time and finally radiating the signals by the antenna array.

The antenna comprises a radio frequency up-conversion module and a radiation antenna array.

Up-conversion module: the intermediate frequency signal output by the composite angle modulation unit is up-converted to a radio frequency signal, the amplitude of the signal is controlled, and then the signal is transmitted to a horn radiation unit of an antenna array.

For an antenna array, each antenna may radiate multiple scattering points, and each antenna (except for the edge antenna) on the array plane is also shared by six triplets. After the rectangle where the scattering point is located is determined, the number of the triples where the scattering point is located is only two, and then the scattering point is determined to be in any one of the two triples according to the parity of the sum of row and column numbers.

The total number of array antennas is not a multiple of 3, each antenna is shared by six triplets, the array edge is not complete, 96 scattering points can be output by each antenna, 2080 scattering points can be simultaneously output by the whole array, 96 scattering points can be simultaneously output by each triplet, and when a certain group of more than 96 scattering points need to appear in the same triplet, the importance of the scattering points needs to be ordered and selected and removed. The selection is carried out by the FPGA component, the selection basis is priority guarantee sequence, and the priority is target echo > plane echo > body echo > meteorological echo > birdbath echo.

The control center controls each unit of the space echo simulation system, integrally controls each unit and can send instructions to each unit.

And the simulation scene library data is used for storing the simulation scene library data, and is called for calculation of the signal processing unit according to the simulation scene parameter setting of the tester.

In the echo calculation model, the echo is classified into a surface echo, a body echo, a meteorological echo and a bird group echo;

the surface echo comprises a target echo and a terrain scene echo;

the volume echo comprises a topography factor echo, a building echo,

Weather echoes include echoes of various weather conditions, such as cloud cover, rain, micro water droplets in air, lightning, geomagnetism, and the like;

the shoal echoes include aircraft echoes of both flying animals and non-target classes.

And the control center can also apply variable to the test link according to the manual instruction in the middle of the test, and control the action and feedback of each unit according to the feedback of the variation of the applied variable of each unit.

Fiber switching matrix module: the real-time transmission interaction of the multipath optical fiber signals is realized, the signal data are received and distributed to each signal processing module, and on the other hand, the space echo scattering point signals are sent to each angle modulation module through an optical fiber matrix;

The radio frequency down-conversion module consists of a local oscillation module and a frequency conversion module, the local oscillation module provides local oscillation signals required during frequency conversion, the frequency conversion module consists of an attenuator, an amplifier, a filter and a mixer, the frequency conversion function from the radio frequency signals to the intermediate frequency signals is realized through combination, and meanwhile, the radio frequency down-conversion module has a signal automatic gain control function and can automatically adjust the input radio frequency signals with different powers to the intermediate frequency signals with the same power.

The frequency conversion module comprises an attenuator, an amplifier, a filter and a mixer, combines the intermediate frequency signals to the corresponding radio frequency band, has a signal power adjusting function, and adjusts the output radio frequency signal power according to simulation requirements.

The spatial echo calculation principle of the spatial echo simulation system based on the digital triplets in the invention is shown in figure 2.

The calculation models adopted by the invention are the models which are verified in the process of the invention, and are specifically set forth as follows:

1. radar ground object echo

The ground object echo experience model selects Gamma model with constant coefficient

σ ⁰ =γsin (ψ) (formula 1)

Wherein, psi is the angle of mopping.

The parameters of a typical backscatter coefficient Gamma model for different ground echoes are shown in the following table,

and calculating corresponding ground scattering coefficients according to dielectric constant characteristics of different echo ground surfaces.

The surface echo scattering coefficient can be written as the product of 3 factors

ρ＝ρ ₀ ρ _s ρ _v (equation 2)

Wherein ρ is ₀ Is the fresnel reflection coefficient; ρ _s Specular reflectance for rough surfaces; ρ _v Absorption coefficient of vegetation for covering a surface. The surface reflectance is closely related to the electrical characteristics of the ground, the roughness of the surface and the vegetation factor of the surface.

The media parameters for a typical surface are shown in the table below

Media type	Relative dielectric constant	Conductivity of surface material
			Moist soil	25	0.02
General soil	15	0.005
			Dried soil	3	0.001
Snow, ice	3	0.001
			Fresh water (X wave band)	65	15
Seawater (P band)	75	5
			Seawater (X wave band)	60	15

2. Temporal and spatial correlation of echoes

The time correlation and the space correlation can effectively describe the correlation characteristics of the echo, so that the echo signal has a certain widening on the frequency domain. The spatial correlation of echoes of different terrain is shown in the following table

Through the relevant scale, when the spatial distribution echo calculation is carried out, the spatial echo characteristics can be modulated, and more real two-dimensional distribution echo is formed.

The time dependence of the echo, which is an important feature of the echo in the echo MTI/MTD processing and which is important in the echo MTI/MTD processing, is represented by the frequency domain broadening, i.e. the spectral broadening, between the echo pulses, the correlation time being closely related to the echo spectral broadening.

Typical correlation times for echoes in different frequency bands are shown in the following table

The correlation time calculation formula is shown as follows

Where w is wind speed.

3. The power spectral distribution of the echo is mainly composed of a gaussian spectrum and a cubic spectrum.

The Gaussian power spectrum can be expressed as

Wherein: f (f) ₀ For spectral center frequency, f _3dB For a 3dB bandwidth, α is a constant

The exponential echo model is:

the power spectrum model of the n-th power spectrum model is as follows:

4. delay and Doppler modulation calculation

The radar works by transmitting a radio frequency pulse signal, receiving an echo, and obtaining target information by analyzing the echo, as shown.

Assume thatThe radar transmit pulse mathematical expression is shown below, wherein A _i For the transmission amplitude, τ is the signal pulse width, PRT is the pulse repetition period, f ₀ As a function of the carrier frequency,as a function of the intra-pulse modulation.

The transmitted pulse impinges on the target and the echo expression transmitted back is shown below, where Δt is the target delay.

Let the relative distance between the target and the radar be R, the propagation speed of the electromagnetic wave in the air be the speed of light C (30 km/s). Since the electromagnetic wave is to travel a double-pass distance, the delay between the echo and the transmitted pulse is Δt=2r/C, so the radar performs measurement of the target distance from the delay of the received echo and the transmitted signal.

The target moves along a certain track, and the relative distance between the radar and the target changes with time. Assuming that the initial relative distance between the target and the radar is R ₀ The radial movement speed of the target relative to the radar is v _r The amount of delay can be expressed as:

Δt＝2×(R ₀ -v _r t)/C (formula 11)

In the presence of relative velocity between the radar and the target, the echo signal will produce a doppler frequency relative to the transmitted signal as shown below, where λ=c/f ₀ Is the signal wavelength.

It is the radar that uses doppler to extract the radial velocity of a target to distinguish between stationary and moving targets. Order of the Chinese medicineF when the target moves towards the radar direction _d >0, the echo carrier frequency increases, and vice versa, as shown.

5. Ternary combination gravity center formula

When the three radiation sources in the triplet are equal in phase, the relationship between the position of the target synthetic signal and the amplitudes of the three radiation sources can control the position change of the target synthetic signal by changing the amplitude ratio of the three radiation sources, and the relationship between the amplitude and the synthetic angle is called a gravity center formula:

where ψ is the azimuth of the equivalent radiation center,is the high-low angle of the equivalent radiation center, ψ ₁ ,ψ ₂ ,ψ ₃ Azimuthal coordinates of three radiating antennas for triplet, < ->Pitch coordinates of three radiating antennas of triplet E ₁ ,E ₂ ,E ₃ Is the transmitted signal amplitude for three radiating antennas.

When the angle position of the synthesized target is determined, the angle position of each antenna of the triplet where the synthesized target is positioned can be determined, and then the signal amplitude values of three radiation antennas are further calculated:

the process of selecting and radiating the triplets of the echo simulation system based on the digital triplets comprises the following steps: coarse bit control algorithm and fine angle control algorithm.

Further, the coarse bit control algorithm is as follows:

the echo characteristic calculation device follows a coarse bit control algorithm when assigning the calculated echo scattering point data to the angle modulation unit.

Dividing an antenna array area into a rectangular frame and a triangular frame according to the positions of antenna units, firstly determining the rectangular frame where the antenna array area is located according to the angle information of echo scattering points, and then determining the triangular position of the scattering points in the rectangular frame.

Assuming that the azimuth angle of an echo scattering point angle is theta and the pitch angle is phi; the azimuth angle spacing of the fixed array antenna unit is theta ^* Pitch angle interval is phi ^* . The array control angle is normalized first using the horn array angle spacing.

θ/θ ^* ＝int(θ/θ ^* ) +fraction (θ/θ) ^* ) (equation 15)

Φ/Φ ^* ＝int(Φ/Φ ^* ) +fraction (phi/phi) ^* ) (equation 16)

In order to determine the rectangular frame number where the target is located using the information in the normalization process, the rounding principle in the above normalization process needs to be specified. The rounding principle here is to take an integer close to 0: i.e. for positive numbers, selecting the largest integer not greater than the normalized value; and taking the minimum integer which is not smaller than the normalized value for the negative number. The number of the rectangular box where the target is located can be obtained from the above integer.

After determining the rectangular frame in which the target is located, it is necessary to determine which triangle of the rectangular frame the control angle is within, as shown in fig. 5 below. At this time, the analysis is performed in two cases, namely, the case that the sum of the row and column numbers of the rectangular frame where the target is located is even and odd. If the sum of the row and column numbers of the rectangular frame where the target is located is an odd number, the slope of the oblique line distinguishing the two triangles is positive at this time, otherwise, is negative, as shown in fig. 5, the number with brackets is the row and column number selected by the triplet, and the number without the number is the antenna matrix number.

After the triangle to which the echo scattering point belongs is selected, three vertexes corresponding to the triplet in which the triangle belongs are the positions of the angle modulation units corresponding to the echo scattering point.

Further, the fine angle control algorithm is as follows:

the fine angle control of the echo scattering points in the array plane triplets is determined according to an angle scintillation equation.

The angular position of the triplet equivalent radiation center is defined by an azimuth/elevation coordinate system. The origin of the coordinate system is at the intersection of the axes of the three-axis turret frame.

The change or movement of the radiation signal equivalent radiation center can be described by an angular scintillation equation. In the angular scintillation equation, the angle of the equivalent radiation center relative to the reference direction is a function of:

(1) The angular position of the radiated signal;

(2) the relative amplitude and phase of each radiation signal at the origin of the coordinate system;

the phase of each radiation antenna radiation signal in the triplet is controlled by the program-controlled phase shifter, so that the phases of the radiation signals are equal on the origin of the target array spherical array coordinate system, the amplitude center of the radiation signals of the three radiation antennas of the triplet is the position (expressed by the angular position) of the equivalent radiation center, and the formed equivalent radiation center position is necessarily in the area of the triplet.

According to the actual use state, a small angle approximation can be made to the angle scintillation equation, and the following equation set for describing the position of the equivalent radiation center angle is obtained:

wherein phi is the azimuth angle of the equivalent radiation center, phi is the high and low angles of the equivalent radiation center, phi 1, phi 2, phi 3 are the azimuth coordinates of three radiation antennas of the triplet, phi 1, phi 2, phi 3 are the pitch coordinates of three radiation antennas of the triplet, and E1, E2, E3 are the transmitted signal amplitudes of the three radiation antennas.

As can be seen from the angle scintillation equation, controlling the amplitudes E1, E2, E3 of the three radiating antennas enables to control the position of the combined radiating center (i.e. the equivalent radiating center) of the three radiating antennas inside the triplet area, for accurate positioning and for ease of calculation and control of the position, the amplitudes E1, E2 and E3 of the three radiating antennas are chosen in the following way: i.e. the sum of the amplitudes of the three radiating antennas is constant, E1+ E2+ E3 = 1, so that the amplitude of the combined signal at the intersection of the axes of the three axes table frame depends on the power level of the external radio frequency signal supplied to the feed subsystem, independently of the angular position of the equivalent radiating centre.

The system has the operation processes that a radar to be tested is placed on a turntable, after a simulation experiment is started, a signal receiving unit receives radio frequency signals radiated by the radar, down-converts the signals to intermediate frequency signals, and carries out analog-to-digital conversion on the signals, and digital signal preprocessing operations such as frequency conversion, filtering, extraction and the like are carried out on the obtained digital signals;

the signal processing unit performs characteristic modulation on the preprocessed digital signal, and modulates delay and Doppler information of the signal in real time according to the requirement on the simulation signal in the experimental process to obtain a digital signal carrying simulation target information; the simulated echo can be made for the target echo, the body echo, the surface echo and the environment interference; multiplexing one digital signal into three paths of signals, entering a digital switching network, selecting three paths of signals according to the angle information of the target, and outputting the three paths of signals in the form of optical signals in corresponding three paths of antenna channels;

a set of combined angle modulation units and a set of signal radiation units are carried behind each antenna on the array surface, after signals enter the combined angle modulation units in the form of optical signals, the amplitudes and phases of the three signals are modulated respectively according to a triplet gravity center formula, and digital-to-analog conversion is further carried out, so that intermediate frequency analog signals are obtained; finally, the signals are converted to corresponding radio frequency bands by radio frequency up-conversion and radiated through the antenna.

And (3) simulating a single target, wherein the tested radar is placed on the turntable before a simulation experiment is started, and each unit is controlled by the simulation main control equipment in the simulation process. The number of array antennas is 80, the array azimuth range is-35 DEG, and the pitch range is-20 deg.

After the tested radar is started, the signal receiving unit receives radar radiation signals through an antenna or a cable, the radar radiation signals enter the radio frequency down-conversion module, the radio frequency down-conversion module carries out down-mixing and filtering on the signals according to the control of the simulation main control equipment to obtain intermediate frequency analog signals, automatic power control is carried out at the same time, the intermediate frequency signals with stable power are obtained, the intermediate frequency signals enter the analog-to-digital conversion chip, sampling and quantization steps are sequentially carried out on the signals to obtain digital signals, and in order to ensure the stability and accuracy of subsequent signal processing, the obtained digital signals need to be preprocessed, namely quadrature mixing, frequency measurement and filtering.

The preprocessed digital signals enter a signal processing unit, characteristic modulation is carried out on the simulated target signals according to control signals of the simulation main control equipment, the characteristic modulation comprises the distance of the target and the speed characteristic of the target (according to delay and Doppler modulation basis), for a single target, the single target can only appear in one triple antenna at the same time, three paths of digital signals carrying the characteristic of the target enter a digital switching network structure, channel selection is carried out on the three paths of signals according to target angle position information sent by the simulation main control equipment, and finally the three paths of signals are output in an optical signal form through a triple antenna channel where the angle is located.

The composite angle modulation units at the front ends of the corresponding triad channel antennas receive optical signals output by the digital switching network, the signals are modulated according to signal amplitudes calculated by a gravity center formula, the digital signals are further converted into analog signals, and finally the signals are radiated by the antennas after being converted into corresponding frequency bands by the radio frequency up-conversion module, so that the target signals are radiated at the designated angle positions.

When the target angle changes, the digital switching network modulates the signals to the corresponding triplet channels according to the changed angle, and the signals enter the compound angle modulation units and the signal radiation units corresponding to the changed triplet channels to finally radiate.

The modulation process for multiple targets is substantially identical to that of a single process, for example 10 targets, each with a different angular position.

And respectively modulating the information of the ten targets in the signal processing unit to obtain ten paths of digital signals respectively carrying the information of the ten targets, multiplexing the ten paths of digital signals into three paths of signals, entering a digital switching network, and respectively transmitting the three paths of signals of each target to corresponding triplet channels by the digital switching network according to the angle information of each target.

Multiple targets may also enter the same triplet channel.

When the target number increases, only the signal processing units need to be increased, and one signal processing unit can modulate dozens of target signals at the same time; for a traditional array feed system, a large number of microwave devices such as switches, attenuators, amplifiers and the like are needed to be added for adding a target signal.

Fig. 6 shows test ballistic data of the test radar, with the thick line area being the pilot start distance.

Fig. 7-14 are diagrams of analog signals of different eye relief distances during the radar test described above.

As shown in fig. 15, the large circles at the vertices and centers of the hexagons represent antennas, and the small circles in the middle of the triangle formed by the connection of the respective antennas represent signal scattering points. Taking the simplest seven antennas as an example, in the most ideal state, scattering points in six triplets are uniformly distributed. The antenna 0 in the center is shared by six triplets, at this time, each triplet outputs 16 scattering points with individually adjustable angles, and the seven antennas output 96 scattering points with individually adjustable angles. The "antenna No. 0" reaches the maximum output capability, and the remaining six antennas do not reach the maximum output capability.

As shown in fig. 16, when 80 antennas form an array plane, except for the antennas at the edge positions, each antenna can be regarded as a "number 0 antenna", on the premise that each antenna outputs 96 scattering points with individually adjustable angles, if n triplets are shared on the array plane, the array plane can output 16n scattering points with individually adjustable angles. The triplets are made up of three adjacent antennas, and the "big triplets" are not considered, and the edge antennas do not reach the maximum capacity, but are considered to have reached the maximum capacity of the array plane. At present, the 80 antennas form 130 triplets, and the number of scattering points with independently adjustable angles, which can be output by the array plane at the same time, is 2080.

In the conventional array feed system, the total number of generated scattering points depends on the signal generation system, but whether the angles of the scattering points can be independently modulated depends on the number of precisely controlled and roughly controlled channels, so that currently, the number of basic 6,8,16 channels is very small, namely, at most 32 scattering points with independent adjustable angles are rare, if a large number of scattering points appear on a matrix surface, a plurality of scattering points are output by one channel, and all the scattering points are output at the same angle on the matrix surface, but only the modulation information carried by signals is different. And the digital triplets can realize independent modulation angles of a large number of scattering points, which is more similar to the real environment.

However, in the conventional radio frequency switch matrix feed system, only 1 scattering point can be output by a single channel due to the limitation of hardware scale and a switch. From the above, it can be seen that the number of echo scattering points that can be output is expanded by a factor of hundreds relative to the rf switch matrix feed system.

The control method of the echo simulation system based on the digital triples comprises the following steps:

In further application, the system can be used as training equipment, emergency parameters can be introduced into a scene calculation model at any time in the running process, the emergency parameters are rapidly fed back to each unit of a calculation center instruction to carry out calculation and call, calculation data are transmitted to a signal modulation module, new modulation is carried out on analog echoes, and the analog echoes are output to an array unit. The test radar receives echoes, data are transmitted to a calculation center through a calculation unit and a data transmission unit of the radar, analog signals and detection signals are compared, difference values and variances are given, a tester is fed back, and the tester can debug the radar according to the feedback data. The time, manpower and material resource loss of the radar field working condition test are greatly saved.

Meanwhile, the countermeasure training can be performed.

The equipment debugging and calibration aspect is also faster and more accurate, because the control center can acquire the running state and the data of receiving and dispatching of each unit through the optical fiber switching matrix module, in the modulation calibration, only need with test radar change into calibration radar, compare through the record data of the analog echo signal data and analog signal that the analysis calibration radar received, can be fast through the calculation adjustment of each unit of control center instruction, when the deviation is less than the settlement threshold value, can reach the test requirement.

The invention discloses a space echo simulation system based on a digital triplet and a control method thereof; and in the radio frequency simulation darkroom, equivalent simulation of echo airspace, distance and frequency domain characteristics in a laboratory in a space test scene is realized. Compared with the traditional radio frequency switch matrix feed system, the simulation quantity of echo scattering points can be greatly improved, the hardware scale and the cost are effectively reduced, and the simulation fidelity of the echo in the radio frequency simulation darkroom is improved. The method overcomes the limitation of the traditional radio frequency switch matrix feed system in the number of simulated echo scattering points, improves the cost performance of simulation, adopts a digital triplet feed system to simulate the echo, and can solve the problem of airspace angle expansion. During simulation, each digital triplet on the antenna array surface can simulate a certain number of scattering characteristics, the whole antenna array can simulate the space distribution of echoes in a larger angle range, then the echo characteristic computing equipment controls the distance expansion characteristics and the frequency domain broadening characteristics of the echoes, so that the airspace, the distance and the frequency domain characteristics of a large number of echo scattering points in a space test scene can be simulated equivalently, and echo data characteristics in a planning scene can be simulated equivalently in a laboratory.

Compared with the traditional semi-physical radio frequency simulation system, the method has the advantages that the amplitude and phase adjusting part of the ternary combination signal is adjusted from the radio frequency domain to the digital domain, the digital signal processing flexibility, the stability, the reliability and the like are more fully reflected in the simulation system, meanwhile, the photoelectric conversion and the optical switching network are skillfully utilized, and the limitation of the microwave switch matrix is avoided, so that the method is called as a digital ternary group. A large number of microwave devices including but not limited to amplifiers, phase shifters, attenuators, and equalizers are saved, and the system has higher flexibility and stability.

3. Compared with the traditional radio frequency switch matrix array feed system, the echo simulation system disclosed by the application has the advantages that the signal transmission is carried out by adopting optical fiber media for digital signal transmission, so that the signal-to-noise ratio of the transmission signal can be greatly improved, and the interference of other electromagnetic signals in a laboratory is not easy to occur; the digital signal processing is higher and more stable than the radio frequency domain modulation precision;

It will be understood that the application has been described in terms of several embodiments, and that various changes and equivalents may be made to these features and embodiments by those skilled in the art without departing from the spirit and scope of the application. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the application without departing from the essential scope thereof. Therefore, it is intended that the application not be limited to the particular embodiment disclosed, but that the application will include all embodiments falling within the scope of the appended claims.

Claims

1. The space echo simulation system based on the digital triplets is characterized by comprising a test unit, a signal receiving unit, a signal processing unit, a synthetic angle modulation unit, a signal radiation unit, a control center and an optical fiber switching matrix module;

2. The digital triplet-based spatial echo simulation system according to claim 1, wherein the signal receiving unit,

the device comprises a radio frequency down-conversion module, an ADC sampling module, a digital-to-analog conversion FPGA computing module and an optical fiber interface module;

3. The digital triplet-based spatial echo simulation system according to claim 1, wherein the signal processing unit comprises a high performance FPGA computation module and an optical switching component;

4. The digital triplet-based spatial echo simulation system according to claim 1, wherein the synthetic angle modulation unit comprises an FPGA component, a DAC component, and an optical fiber component;

5. The digital triplet-based spatial echo simulation system according to claim 2, wherein,

6. The digital triplet-based spatial echo simulation system according to claim 4, wherein,

7. The space echo simulation system based on the digital triplets according to any one of claims 1-6, wherein the signal processing unit performs characteristic modulation on the preprocessed digital signal, and modulates delay and doppler information of the signal in real time according to the requirement on the simulation signal in the experimental process to obtain a digital signal carrying simulation target information; making a simulation echo for the target echo, the body echo, the surface echo and the environment interference; and multiplexing one digital signal into three paths of signals, entering a digital switching network, selecting the three paths of signals according to the angle information of the target, and outputting the three paths of signals in the form of optical signals in corresponding three paths of antenna channels.

8. The space echo simulation system based on the digital triplets according to any one of claims 1 to 6, wherein a set of combined angle modulation units and a set of signal radiation units are mounted behind each antenna on the array surface, after signals enter the combined angle modulation units in the form of optical signals, the amplitude and the phase of the three signals are modulated according to the gravity center formula of the triplets respectively, and digital-to-analog conversion is further carried out, so that intermediate frequency analog signals are obtained; finally, the signals are converted to corresponding radio frequency bands by radio frequency up-conversion and radiated through the antenna.

9. The method for controlling a digital triplet-based spatial echo simulation system according to any one of claims 1-6, wherein,

10. The method for controlling a digital triplet-based spatial echo simulation system according to claim 9, wherein the artificial model and scene can be manually interposed at any time at different moments.