RU189247U1 - SIMULATOR OF REFLECTED RADAR SIGNALS - Google Patents

Abstract

The utility model relates to radar, or, more precisely, to ranging or radio altimetry, namely, devices for simulating the time-frequency structure of a radar signal reflected from one or several targets and / or the underlying surface. real, complete testing of equipment and algorithms of radar operation in the whole range of simulated aircraft heights and distances. Technical result is achieved due to d Namic control of modulation parameters and digital signal processing with variable modulation parameters, when the reflected signal is generated based on the current radiated signal, with the possibility of continuous phase change and simulated delay, Doppler frequency and attenuation of the generated signal imitator. 1 il.

Description

 The utility model relates to radar, more precisely, to ranging or radio altimetry, namely, to devices to simulate the time-frequency structure of a radar signal reflected from one or more targets and / or underlying surface.

The common problem of creating simulators is the formation of equivalent reflected echo signals with the possibility of end-to-end testing and monitoring of the parameters of the microwave and low-frequency paths of radiation and signal processing in wide ranges of parameters of the emitted and received signals.

 When operating the simulator as part of a semi-natural modeling complex (ISM), it is necessary to take into account all the main parameters of the possible phono-target situation (FCF) for technical and functional verification of the correctness of the on-board radar in conditions close to real, critical and even beyond.

 Existing complexes PNM for radio altimeters (RV), radio range finders and radar systems (radar) are able to solve the problem of simulating radar signals reflected from one or more reflectors on the carrier frequency, but without controlling their characteristics in real time or without taking into account the possibility of variation and instability of parameters modulation (amplitude, frequency, phase) of the emitted signal, especially for complex-modulated signals, for example, with linear frequency modulation (LFM).

 Known is the implementation of ground testing of radar systems of onboard equipment based on a radio bezekhovoe camera, which implements the imitation of reflections from spatially distributed objects, taking into account the surface texture and interference protection. The common drawbacks of the known solutions are the active use of a radio bezhekhovoy chamber, the emphasis is shifted to the formation of the FTSO from point targets. Simulation requires the determination of the emitted signal or additional synchronization with the radar, which means that it is impossible to fully test the transceivers on the carrier frequency, especially with variable or unknown modulation parameters. The disadvantages of methods for generating textures of 3D objects include the laboriousness of forming an arbitrary boundary between thematic data when drawing up a texture map and the impossibility of generating a realistic terrain texture in real time (“Method for generating texture in real time and a device for its implementation”, Bodin O.N. and others. - Patent of the Russian Federation No. 2295772. September 26, 2005).

 Also known development GosNIIAS simulators with a focus on the use of modern principles of digital signal processing (DSP) with the possibility of the formation of multipoint targets. In the article "Features of the formation of phono-target situation on the complexes of semi-natural modeling of airborne radar systems of final guidance" (DV Khlebnikov, Yu.D. Kislitsyn, ES Konanykhin, DV Laznkov - STC Aviation Systems in the XXI century " A collection of reports. Moscow: State Research Institute of Aviation Systems, 2017. p. 70–80), with mention of simulators based on the SBIS 1879 VMZ, performed at UPPB Detal JSC (Kamensk-Uralsky Sverdlovsk Region), features the formation of FC in complexes PNM airborne radar. The principles are based on the use of radio frequency memory channels to simulate targets, for moving and distributed around the corner - several synchronized channels. General disadvantages of the proposed solutions - the relationship between the possibility of creating diverse and adequate reflections from the underlying surfaces with specific parameters of the radio frequency memory of echo signals as close as possible to real conditions is not clear.

 In the RF patent №2522502 for a simulated radar signal with synthesized aperture (S.Valov, A.I. Sirotin, S.V. Shcherbakov. Priority date: 10/12/2012) DSP is to use two ADC quadrature signal components, two filters with finite impulse response (FQIC), the coefficients for which are received via the I / O bus from the external processor with the update period of the impulse response of the scene T <1 / 2DFd, where DFd is the width of the Doppler signal spectrum. The circuit also contains a quadrature multiplier and a direct digital synthesis generator, which can be used to generate a group Doppler shift of the frequency of the generated signal - PROTOTIP.

 The disadvantage of the prototype is the impossibility of qualitative imitation of equivalent low altitudes of the aircraft when changing the parameters of the probing signal due to the presence of a delay in the analog and digital signal processing circuits. Most modern RV and RVS change the modulation parameters, for example, the chirp slope to improve accuracy. To increase the noise immunity, it is possible to apply the random (pseudo-random) law of parameters change, which does not allow to establish a unique dependence of the modulation parameters on the parameters of the simulated environment.

Therefore, in order to qualitatively simulate the equivalent small heights of an aircraft, in addition to the possibility of frequency shifting, it is necessary to determine in real time the magnitude of such a shift in accordance with the instantaneous parameters of the probing signal and the amount of self-delay in analog and digital signal processing circuits.

The technical task of the utility model is the construction of a practical simulator for as close as possible to real, thorough testing of equipment and algorithms for radar operation in the entire range of simulated aircraft heights and distances to the target.

The technical result is achieved by dynamically controlling the parameters of modulation and digital signal processing with variable modulation parameters, when the reflected signal is generated based on the current radiated signal, with the possibility of continuous phase change and simulated delays, Doppler frequency and attenuation of the generated signal, for chirp signals it is possible to simulate distances with a delay of less than the proper delay of the simulator.

To solve this problem, a simulated radar signal simulator is proposed, which is characterized by the fact that it contains a pre-filter, an adjustable amplifier, a quadrature mixer, a two-channel ADC, a RAM of signal samples, a first and second address generator, a digital shaping filter, a complex multiplier, a two-channel DAC, quadrature modulator, adjustable attenuator, calculator of imitation parameters, AM and FM detector unit, RAM of filter coefficients, low-frequency (LF) quadrature local oscillator, high hour total (HF) local oscillator, synthesizer of the 1st clock frequency, synthesizer of the 2nd clock frequency, master of the 2nd clock frequency, calculator of the current difference, delay comparison unit and scenario simulation block with the following connections: radio probe sound input A (t) through Pre-filter and adjustable amplifier are connected to the first RF input of the quadrature mixer, the second input of which is connected to the output of the RF local oscillator Fg, the output (Iin, Qin) of the quadrature mixer is connected to the analog input of the quadrature signal The left ADC, with the second clock input of which is connected to the output of the synthesizer of the 1st clock frequency Ft ₁ , the same output is also connected to the input of the first address shaper, the output of the two-channel ADC (I, Q) is connected to the 1st and The 2nd master inputs S (t) and f (t) of the simulation parameters calculator, the 3rd master input of which is connected to the output of the script simulation block, the output of the two-channel ADC (I, Q) is also connected to the RAM input of the signal samples, with clock inputs recording and reading and _{zap MF} and which are connected outputs of the first and second pho tors, addresses, and the output of the address through computer current difference are connected to the first input Δa delay comparator, the second input of which is connected to the output Δa _treb calculator simulation parameters, a RAM signal samples output connected to the signal input (Ir, Qr) digital shaping filter, the output of which (Io, Qo) is connected to the input (Iout, Qout) of a two-channel D / A converter via a complex multiplier, the output of the delay comparison unit is connected to the synthesizer input of the 2nd clock frequency through a second clock frequency master; od which Ft ₂ is connected to the input of the said second location and a second clock input of the two-channel DAC, whose output is connected to the analog input (Iw, Qw) of the quadrature modulator, the second input of which is connected to the output RF oscillator Fg, computer simulation parameters with their calculated values at the output U _k through the RAM of the filter coefficients is connected to the second input of the digital shaping filter, the outputs Df _i and Dϕ _i through the low-frequency quadrature local oscillator connected to the second input of the complex multiplier, the output V _{control is} connected to the control the master clock input of the 2nd clock frequency, the output (f _min , f _max ) is connected to the control input of the prefilter, output E _{0 is} connected to the control input of the adjustable amplifier, and output E _{i is} connected to the control input of the adjustable attenuator, the radio frequency input of which is connected to the output of the quadrature modulator, and the output of which X (t) is the generated final signal of the simulator.

Features of the proposed structure of building an electronic simulating complex:

• The simulated reflected signal is a continuous copy of the emitted signal, summed up taking into account the programmed delays and quadrature modulation parameters (amplitude, Doppler frequency shift).

• The arbitrary nature of the movement of the aircraft (JIA).

• Dynamic change of the main parameters of the simulation in accordance with the specified scenario.

The method of constructing simulated echoes of a relay type is based on performing continuous conversion of a probing microwave signal from a radar transmitter antenna into a simulated reflected signal fed further to a receiver antenna. At the same time, by changing the conversion parameters, it is possible to imitate the movement of the radar / LA along a predetermined trajectory over the simulated surface under conditions of a variable scene / FCT. Connection to the radar is possible using pairs of transmit-receive antennas (including in an anechoic chamber), as well as, to improve accuracy and exclude emissions, directly with microwave cables.

To be able to quickly and accurately control simulation parameters, you must use digital signal processing (DSP) methods. Then, when simulating the reflection from the target for the radar or the underlying surface for the RV, the equivalence of the reflected signal generated on the microwave signal can be achieved by performing the following basic transformations:

1) transferring the probing signal to the low-frequency region (to the Nyquist work area — the ADC analog-to-digital converter band) and digitizing it (with a sampling frequency of at least twice the signal's bandwidth);

2) variable delay to simulate a given variable range (altitude for RS);

3) variable attenuation of the signal to simulate attenuation in accordance with the propagation distance and characteristics of the reflecting surface (reflectors of the scene / FCT);

4) imitation of the effects of the Doppler frequency shift, as well as imitation of the ranges due to the frequency shift (with the chirp), with the possibility of variable frequency shift (and phase) of the generated signal;

5) formation of an extended portrait in range in accordance with the type of simulated reflection, the characteristics of the radar, the simulated trajectory and reflectors of the FTS;

6) digital-to-analog conversion (DAC) of the received signal and its transfer to the original microwave region;

The listed items 2-5 of the main signal transformations can be performed in an arbitrary order, and item 3 can be distributed and implemented using attenuators before performing the ADC, after performing the DAC, and also during digital multiplication.

The drawing shows a functional electrical circuit of a utility model of a relay-type simulator for generating a return signal for a radar, which shows:

 1 - prefilter;

 2 - adjustable amplifier;

 3 - quadrature mixer;

 4 - two-channel ADC;

 5 - RAM of signal samples;

 6 - FA1 - the first address generator;

 7 — FA2 — second address driver;

 8 - CFP - digital forming filter;

 9 - complex multiplier;

 10 - two-channel DAC;

 11 - quadrature modulator;

 12 - adjustable attenuator;

 13 - calculator of imitation parameters;

 14 is a block of AM and FM detectors;

 15 - RAM of filter coefficients;

 16 - low-frequency (LF) quadrature local oscillator;

 17 - high frequency (HF) local oscillator;

 18 - 1 clock synthesizer;

 19 - 2nd clock synthesizer;

 20 - unit of the 2nd clock frequency;

 21 - current difference calculator;

 22 is a unit for comparing delays;

 23 — script simulation block;

 A (t) is the probing radio signal from the output of the radar transmitter (or from the simulator receiving antenna);

 H, V, evolution, DNA, EPR - data of the simulated flight of the aircraft, i.e. altitude, velocity, angular evolution (roll and pitch) of the carrier / radar, antenna pattern, effective dispersion area of the PTsF reflectors;

 S (t) and f (t) are the output signals of the AM and FM detectors, respectively;

 X (t) is the generated signal corresponding to the reflected signal from the moving in distance (height) scene / FCT.

 The simulator works as follows.

The sounding radio signal A (t), coming from the output of the radar transmitter or the simulator receiving antenna, passes through a pre-filter. At the same time to eliminate noise and possible signals from other radars, the bandwidth of the pre-filter can be adjusted within specified limits, for example, from f _min to f _max , since most radars are tunable single-frequency. An adjustable amplifier is used to match the signal level. The magnitude of the gain (attenuation) E ₀ is determined from the condition of optimal use of the ADC discharge grid, i.e. The signal levels at the ADC input correspond to (do not exceed) the maximum level for the selected ADC circuits.

The frequency range (f _min , f _max ) of the prefilter and the coefficient E _{0 of the} adjustable amplifier can also change during the operation of the simulator. In particular, for some types of radars, it is possible to use a priori information about the dependence of the center frequency, frequency range and / or radar power level on the working conditions: altitude, flight speed, approach speed, etc. Since these conditions are reproduced, i.e. known along the entire simulated trajectory, it allows you to match the frequency range and signal level for the further formation of the reflected signal with greater accuracy. Also, for a specific radar sample, there is the possibility of continuous matching of the frequency range and signal level based on the results of the evaluation of modulation parameters (including the necessary averaging and other time-frequency processing performed in the simulation parameters calculator) using the S (t) and f (t) signals AM and FM World Detectors. In the simplest case, an adjustable amplifier can perform an automatic gain control function (AGC) to maintain the signal level at the proper level.

Next, the signal enters the quadrature mixer, which, using an RF local oscillator signal, performs frequency conversion and demodulation with the formation of quadrature signal components (Iin, Qin) at an intermediate (zero) frequency to simplify further digital processing and the formation of the reflected signal. Note that hereinafter, the auxiliary filtering blocks of the useful part of the spectrum of signals are part of the corresponding signal conversion blocks.

The received signal (in the form of two quadrature components Iin, Qin) is digitized in a two-channel ADC. The resulting component (I, Q) is fed to the inputs of the AM and FM detectors and stored in the RAM of the signal samples. In this case, digitization in the ADC, detection of AM / FM modulation and recording into RAM of signal samples (I, Q) are performed with a clock frequency of Ft ₁ (or multiply) of the 1st clock frequency generated by the synthesizer.

Reading from the RAM of signal samples (Ir, Qr), further DSP and DAC operation are performed with a clock frequency of Ft ₂ (or multiple) generated by the synthesizer of the 2nd clock frequency. To generate physical addresses and _spare recording and reading in _MF and / from RAM uses two signal samples shaper addresses: FA1 and FA2, respectively. They can be implemented as cyclic binary counters in the range from 0 to a _max , so that after reaching the maximum value of a _max on the next clock cycle, the counting would continue from 0.

In the current difference calculator, the value Yes is calculated:

Yes = mod ((a _max + and _zap - a _{MF), (a max +1))} ,

where a _max is the maximum word address in RAM for storing quadrature signal samples; mod (v1, v2) is the standard operation for finding the remainder of dividing the 1st operand by the 2nd. If a _max = (2 ⁿ - 1), where n is an integer, i.e. corresponds to the width of the address range of the RAM of the signal samples, it is possible to simplify the expression and use subtraction within n bits with ignoring the sign bit, which corresponds to the calculation of the bitwise operation "And", where the mask is the value of a _max :

Yes = (and _zap - a _mc ) & (2 ⁿ - 1) = (and _zap - a _mch ) & a _max .

In such an implementation, the RAM of the signal samples operates in the FIFO (First Input - First Output) mode, i.e. implements the function of the delay line. For example, in the case of the absence of Doppler shift simulation for the radar portrait being formed, the clock frequency values are: Ft ₁ = Ft ₂ , therefore, the delay implemented in the RAM of the signal samples is approximately equal to:

τ _Yes ≈ 2 Yes / (Ft ₁ + Ft ₂ ) = Yes / Ft ₁ .

The expression gives an approximate value of the true delay in RAM, and its accuracy is determined by the method of taking into account (averaging, smoothing or ignoring the deviation) of the effect of an asynchronous change in address values leading to jumps in Yes values by the value of the least significant bit of the address, i.e. jumps from 0 to 1. While ignoring jumps, the accuracy of the delay in the simulator Dτ ≈ 1 / Ft ₁ . Therefore, by increasing the clock frequency, a given accuracy of setting the delay in the simulator can be ensured, for example, less than the real resolution of the radar in range.

When implementing the averaging method (or integration within the sampling interval) of these jumps, the value of Yes will contain the fractional part of the current address difference, which will allow you to more accurately control the process of imitating “static” relative distance radar portraits.

In practice, most trajectories imply a continuous change in the relative distance to simulated radar portraits of targets. In the prior art (prototype, patents DE 3803993B3, US 4450447) it is known that if the clock read frequency from the FIFO differs from the write frequency, the frequency shift can be simulated, since the carrier / intermediate frequency of the reproduced oscillation changes. Therefore, in the proposed simulator to simulate a Doppler value Fd calculator simulation parameters generates a signal V _Ctrl equal with the value of the relative speed of approach points simulated scene / FTSO Radar V _r, and dial the second clock frequency for a given V _Ctrl generates the tuning signal synthesizer 2nd clock frequency to the value of Ft ₂ so that:

Ft ₂ = Ft ₁ + Fd,

where Fd = 2V _r / λ is the value of the Doppler shift for given values of the radiation wavelength λ and the relative velocity of approach with the radar V _r , i.e. when removing V _r <0 and Ft ₂ <Ft ₁ .

In this case: τ _Yes ≈ 2 Yes / (Ft ₁ + Ft ₂ ), and the accuracy of setting the delay in the simulator Dτ ≈ 2 / (Ft ₁ + Ft ₂ ). However, since the clock frequencies Ft ₁ and Ft _{2 are} not synchronized, in fact, the simulated delay Δτ will smoothly change: decrease with Ft ₁ > Ft ₂ , or increase with Ft ₁ <Ft ₂ . Consequently, the change of the phase of the simulated reflected signal will also be smooth, and the delay of the reflected signal recorded by the radar and the range will not be discrete.

Calculator simulation parameters for a given trajectory LA generates the required delay value Δa _required in accordance with the current minimum range R _min to the nearest reflector simulated scene FTSO:

τ = 2 R_min /with; Δа_require = max (Ft_one (2 R_min / s - τ_o), Δа_min),

where τ _o is the imitator's own delay, i.e. minimum realizable delay, which takes into account all the delays of the selected components and connections of the simulator blocks during analog and digital signal processing; c is the speed of light; max () - function taking the maximum value of the above, in this case intended to limit the minimum value, so that in any case Δa _treb ≥ Δa _min. The possible value for Δa _min depends on the type of RAM of the signal samples used, usually Δa _min = 0 ... 2.

Variable coordinates of the LA trajectory (H, V, evolution) and also all the constant and variable radar parameters (DN, frequency range and carrier frequency f ₀ , etc.) and FCT (characteristics of reflectors: position / relief, EPR, speed and the direction of movement of a number of scene reflectors / FCT, etc.) come from the script imitation block.

Comparing unit compares the delays (subtracts) the current value and the required delay Yes Δa _des. It is necessary to determine the sign of achieving a predetermined height Yes = Δa _requires to stop the change in the RAM simulated range signal samples to achieve a predetermined magnitude range. This task is performed by a clock frequency setting master 2, which, in case the value of V _con = 0, sets Ft ₂ = Ft ₁ . If a smooth change of the simulated range: Y ≠ Δa _treb and V _Ctrl = V _r ≠ 0, so that Ft = Ft _{2 1} + 2V _r / λ, i.e., Imitation control is performed at a given speed and without jumps over the simulated range.

The digital shaping filter of the FPC performs the formation of an extended portrait in range in accordance with the type of simulated reflection by performing a convolution of the signal (Ir, Qr) with the impulse response of the scene signal represented by a set of complex values of the coefficients of the FSC U _k . The FPC can be implemented on the basis of a fully complex PCF or, like the prototype, on the basis of a PCF pair for two quadrature signal components. It is also possible to implement in the frequency domain by multiplying the spectra ("Down range return simulator" patent US 6075480 from 07.13.2000). The current values of the coefficients of the FSC U _k come from the auxiliary RAM of the filter coefficients (dual port, i.e. with the possibility of simultaneous writing and reading). They are calculated in the simulator of simulation parameters and, like the prototype, can be updated with a specified period of the impulse response of the scene T <1 / 2DFd, where DFd is the width of the Doppler signal spectrum, as well as when a change in the structure / parameters of the probing signal is detected.

To account for the required group Doppler frequency shift of the generated signal, as well as to simulate the ranges due to the frequency shift, the digital complex multiplier shifts the signal in frequency (phase) by complexly multiplying the quadrature signal components (Io, Qo) by a quadrature harmonic signal with frequency Δf _i and phase Δϕ _i from the block of low-frequency (LF) quadrature local oscillator, made according to one of the typical schemes for direct digital synthesis (DDS).

Using the specified non-zero frequency shift Δf _i allows you to simulate the range due to the frequency shift for radar with long probing signals with chirp ("Device to simulate a false radar target when probing signals with linear frequency modulation." - Patent RU 2625567 from 07.07.2016). In the proposed device, the imitation of delays less than the intrinsic delay of the simulator τ _o is due to the frequency shift of the generated signal. In this case, the condition: Ft ₁ (2 R _min / s - τ _o ) <Δa _min . Therefore, the output of the calculator value Δa set simulation parameters _requires a = Δa _min and V _Ctrl = 0, a frequency offset using the LF block quadrature LO is performed on the value Δf _i, which depends on the modulation chirp parameter ( "Transforming a radar signal HIL multipath propagation modeling" , AS Bokov, et al. - “Reliability and quality of complex systems.” Penza: PSU, 2017. No. 3. P. 60-67), namely, from the sign and slope of the frequency change:

Δf _i = 2 (K _f (Ro - R) - V _r f) / c,

where K _f = df / dt is the steepness of the frequency change of the probing signal with chirp; Ro = τ _o с / 2 - the minimum range implemented by the simulator; R is the required simulated range; f is the instantaneous frequency of the probing signal, for broadband signals, you can use the FM detector signal, then f = | Fg ± f (t) |, where the sign “±” depends on the selected settings of the filters and the quadrature mixer of the simulator.

The value of the slope (signed) can be obtained by analyzing the change in the signal f (t) from the output of the FM detector of the proposed simulator, including in real time. A possible way to implement digital AM and FM detectors, with reduced analysis time, is also given in the description of a low-delay wideband signal repeater (“Wideband low latency repeater and methods”. WO2013 / 184232 A1. Priority date: 08.06.2012).

The use of a predetermined non-zero phase shift Δϕ _i allows to reduce the possible effects of phase instability of the reflected signal being generated (“Effect of DRFM”, Herselman, Nel, Cilliers. - CSIR, 2006). ) arising from the discrete nature of the range change. As it was said, in the proposed device, imitation of delays less than the imitator's own delay is due to the frequency shift Δf _i , which, when DSP has some discreteness, depends on the accuracy of the selected methods and components for the implementation of the low-frequency quadrature local oscillator radar signals ”, AS Bokov et al. - collection of works IREVR-2017, DOI: 10.1109 / RSEMW.2017.8103635). When imitating delays of a more intrinsic delay of the simulator, there is no discreteness of the range change, but the use of an additional phase shift Δϕ _i makes it possible to simulate more complex conditions / propagation instabilities in air and signal reflections from various types of surface without additional correction of the DFF coefficients U _k .

Thus, the signal (Iout, Qout) corresponds to the reflected signal from the target moving radio portrait of the target (the surface for the simulated height JIA). It is converted to analog form in a two-channel DAC. Then, in the quadrature modulator, it is transferred to the original radio frequency region, and is attenuated in the adjustable attenuator by the value of E _i to simulate the attenuation corresponding to the range and the average EPR of the simulated FC.

The generated output signal X (t) is then fed to the output of the simulator to re-emit the transmitting antenna of the simulator in the direction of the receiving antenna of the radar or fed directly into the input circuit of the receiver of the radar during laboratory testing.

The digital part of the simulator, from ADC to DAC inclusive, can be implemented using separate microcircuits, or using complex solutions - "systems on a chip", for example, with digital signal memory (DSM) technologies, radio frequency memory (DRFM) ), Radio-on-Chip or System-on-Chip (SoC). To implement the functions of DSP, including amplitude and frequency detection, FIFO, digital modulation and filtering can be used programmable logic integrated circuit (FPGA). For example, the XC7Z045 FPGA of the Zynq-7000 family contains specialized DSP blocks with high signal width, as well as an ARM CORTEX A9 1 GHz dual-core processor, whose software will be able to simulate a script, calculate simulation parameters, and effectively manage all DSP blocks in real time (prototype , “A semi-natural modeling complex for end-to-end testing, testing and testing of airborne radar systems and devices,” AS Bokov et al. - Proceedings of the International Symposium “Reliability and Quality.” Enza, 2018. V. 1. S. 40-45).

The quadrature mixers / modulators, heterodyne / synthesizers, amplifiers / attenuators and filters for matching the levels and range of working frequencies (for example, with the signals of the local oscillators) are known from the prior art for radio industry technology, therefore they can be chosen from well-known components from Analog Devices, Hittite, IDT, Maxim Integrated, Qorvo, Texas Instruments, etc., or designed in accordance with the recommendations for the construction of radio frequency paths of the radars used frequency range.

During stationary tests, it is convenient to directly connect cables to the radar system under investigation without using antennas. In the case of using a common receiving-transmitting antenna, you can use a circulator, an antenna switch with operation gating, for example, by a threshold estimate of the signal level S (t) at the AM output of the simulator detector.

Claims (1)

Reflected radar signal simulator, characterized in that it contains a prefilter, adjustable amplifier, quadrature mixer, two-channel ADC, RAM signal samples, first and second address drivers, digital shaping filter, complex multiplier, two-channel DAC, quadrature modulator, adjustable attenuator, calculator of parameters imitations, AM and FM detectors, RAM of filter coefficients, low frequency quadrature local oscillator, high frequency local oscillator, 1 clock frequency synthesizer, 2 clock frequency synthesizer stota, 2nd clock frequency adjuster, current difference calculator, delay comparing unit, scenario simulation block with the following connections: radio input signal A (t) through a pre-filter and adjustable amplifier connected to the first radio frequency input of the quadrature mixer, the second input of which is connected the output of the RF local oscillator Fg, the output (Iin, Qin) of the quadrature mixer is connected to the analog input of the quadrature signal of the two-channel ADC, the second clock input of which is connected to the second clock input of the synthesizer th frequency Ft _1, the same output is also connected to the input of the first driver address output two-channel ADC (I, Q) through the block AM and FM detectors connected to the 1st and the 2nd predetermined inputs S (t) and f (t) calculator simulation parameters, 3rd defining input coupled to an output simulation script unit, an output two-channel ADC (I, Q) is also connected to the input of RAM signal samples with the clock inputs of the recording and _zap and reading and _MF are connected outputs of the first and second shapers Addresses, as well as these outputs of the address formers through the calculator the gaps of the difference are connected to the first input Δa of the delay comparison unit, the second input of which is connected to the output Δa _of the simulation parameters calculator, the output of the RAM of the signal samples is connected to the signal input (Ir, Qr) of the digital shaping filter, the output of which (Io, Qo) is via the complex multiplier connected to the input (Iout, Qout) of a two-channel D / A converter, the output of the delay comparison unit is connected to the input of the second clock frequency synthesizer through the 2nd clock frequency generator, the output of which Ft _{2 is} connected to the input of the second address driver and the second clock in the two-channel D / A converter, whose output is connected to the analog input (Iw, Qw) of the quadrature modulator, with the second input of which is connected to the output of the RF heterodyne Fg, the calculator of simulation parameters with its calculated values of the output U _{k is} connected via the RAM of the filter coefficients to the second input of the digital shaping filter, outputs Δf _i and Δϕ _i through the low-frequency quadrature local oscillator is connected to the second input of the complex multiplier, output V _{control is} connected to the control input of the unit of the 2nd clock frequency, output (f _min , f _max ) is connected to the control The pre-filter input, output E _{0 is} connected to the control input of the adjustable amplifier, and output E _{i is} connected to the control input of the adjustable attenuator, the radio-frequency input of which is connected to the output of the quadrature modulator, and the output X (t) is the generated final signal of the simulator.

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