RU2463623C1 - Radar station for automatic range monitoring - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: radar station for automatic range monitoring has an antenna, an antenna switch, first and second mixers, first and second intermediate-frequency amplifiers, a synchroniser, a transmitter, a heterodyne, first, second, third and fourth circuits consisting of series-connected corresponding time selector, narrow-band filter and amplitude estimating unit, comparator unit, control unit, strobe generator, reference generator, first and second subtractor units, connected to each other in a certain manner.

EFFECT: high accuracy of monitoring range of small-size moving targets owing to bias error compensation for estimating range of small-size moving target, caused by passive jamming spatially superimposed with the target.

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Description

The invention relates to the field of radar and can be used in radar stations for measuring the coordinates of small moving targets.

The closest in technical essence to the proposed technical solution is a radar station (radar) for automatic tracking of the range of a ground small-sized moving target (see Turnetskiy L.S. Analysis of the work of a radar station for automatic tracking of a range of a ground target. // Radio Electronics of Intelligent Transport Systems: Scientific -technical collection, Issue 5. - SPB .: Publishing House of SZTU, 2011, pp. 44-49), selected as a prototype. The prototype contains a series-connected antenna, an antenna switch, a mixer, an intermediate frequency amplifier and a video detector, a synchronizer, a transmitter and a local oscillator connected in series, the output of which is connected to the second input of the mixer, and the second output of the transmitter is connected to the second input of the antenna switch, the first and second circuits, consisting of from a series-connected corresponding time selector, a narrow-band filter and an amplitude estimation unit, series-connected comparison unit, control and strobe generator, the second input of which is connected to the second output of the synchronizer, and the first and second output - to the first inputs of the first and second time gates.

The disadvantage of the prototype is the low accuracy of tracking the range of a small moving target due to the influence of spatial inhomogeneity of passive interference generated by reflections from elementary reflectors (for example, from the Earth's surface or clouds of dipole reflectors spatially aligned with the target) on the radar.

The technical result is to increase the accuracy of tracking the range of a small moving target by compensating for the bias error in estimating the range of a small moving target due to passive interference spatially combined with the target.

The invention consists in the following.

The proposed radar station (radar) for automatic range tracking contains, in the same way as the prototype, a series-connected antenna, an antenna switch, a first mixer and a first intermediate frequency amplifier (IFA), a synchronizer, a transmitter and a local oscillator in series, the output of which is connected to the second input the first mixer, and the second output of the transmitter is connected to the second input of the antenna switch, the first and second circuits, consisting of series-connected corresponding time about a selector, a narrow-band filter and an amplitude estimation unit, a comparison unit, a control unit, and a strobe generator, the second input of which is connected to the second output of the synchronizer, and the first and second outputs are connected to the first inputs of the first and second time selectors, respectively. In contrast to the prototype, the proposed radar contains a serially connected reference generator, a second mixer, the second input of which is connected to the output of the first UPCH, and the second UPCH, the third and fourth circuits, consisting of the corresponding third and fourth time selectors, the third and fourth narrow-band filters, connected in series the third and fourth amplitude estimation blocks, the first and second subtraction blocks, the first inputs of each of which are connected to the outputs of the first and second amplitude estimation blocks, respectively the second inputs of each of which are connected to the outputs of the third and fourth amplitude estimation blocks, respectively, and their outputs are connected respectively to the first and second inputs of the comparison block, while the first inputs of the third and fourth time selectors are connected to the output of the second amplifier, and the second inputs to the first inputs, respectively, of the first and second temporary selectors, the second inputs of which are connected to the output of the first amplifier.

The invention is illustrated by drawings, where

figure 1 presents a structural electrical diagram of the proposed radar automatic tracking range, where indicated:

1 - antenna;

2 - antenna switch;

3-1 - the first mixer;

3-2 - the second mixer;

4-1 - the first UPCH;

4-2 - the second UPCH;

5 - synchronizer;

6 - transmitter;

7 - local oscillator;

8-1 - temporary selector of the first chain;

8-2 - temporary selector of the second circuit;

8-3 - temporary selector of the third chain;

8-4 - temporary selector of the fourth chain;

9-1 - narrow-band filter of the first circuit;

9-2 - narrow-band filter of the second circuit;

9-3 - narrow-band filter of the third circuit;

9-4 - fourth-band narrow-band filter;

10-1 - unit for estimating the amplitude of the first circuit;

10-2 - unit for evaluating the amplitude of the second circuit;

10-3 - unit for evaluating the amplitude of the third circuit;

10-4 - unit for estimating the amplitude of the fourth circuit;

11 is a comparison unit;

12 - control unit;

13 - strobe generator;

14 - reference generator;

15-1 - the first block of subtraction;

15-2 - the second block of subtraction.

Figure 2 presents the spectral characteristics of the output signals of the respective blocks and the amplitude-frequency characteristics of the blocks, explaining the principle of operation of the proposed radar.

- дисперсия сигнала цели; ΔF_П - ширина спектра межпериодных флюктуаций пассивной помехи на входе РЛС.Figure 3 presents graphical dependences on the ratios of dispersions of passive interference, respectively, in the channels of the first and second strobes of the systematic error, normalized to the duration of the probe pulse τ _u , in the prototype with quadratic Δ _k and linear Δ _l detection in the video detector at the output of the first amplifier, where F _c , F _n - respectively, the upper and lower boundary frequencies of the passband of the narrow-band filter, σ ² _{П (1,2)} - dispersion of passive interference, respectively, in the channels of the first and second gates;

- dispersion of the target signal; ΔF _P is the width of the spectrum of inter-period fluctuations of passive interference at the radar input.

The proposed radar (figure 1) contains the same as the prototype, a series-connected antenna 1, an antenna switch 2, a first mixer 3-1 and a first amplifier 4-1, a series-connected synchronizer 5, a transmitter 6 and a local oscillator 7, the output of which is connected with the second input of the first mixer 3-1, and the second output of the transmitter 6 is connected to the second input of the antenna switch 2, the first and second circuits, consisting of a series-connected corresponding time selector 8, a narrow-band filter 9 and an amplitude estimation unit 10, in series connected by a comparison unit 11, a control unit 12 and a strobe generator 13, the second input of which is connected to the second output of the synchronizer 5, and the first and second outputs to the first inputs of the first 8-1 and second 8-2 time selectors, respectively.

In contrast to the prototype, the proposed radar introduced serially connected reference generator 14, a second mixer 3-2, the second input of which is connected to the output of the first UPCH 4-1, and the second UPCH 4-2, the third and fourth circuits, consisting of series-connected corresponding third 8-3 and fourth 8-4 time selector, third 9-3 and fourth 9-4 narrow-band filter, third 10-3 and fourth 10-4 amplitude estimation block, the first 15-1 and second 15-2 subtraction blocks, first inputs each of which is connected to the outputs, respectively, of the first 10-1 and the second 10-2 amplitude estimation blocks, the second inputs of each of which are connected to the outputs of the third 10-3 and fourth 10-4 amplitude estimation blocks, respectively, and their outputs are connected respectively to the first and second inputs of the comparison unit 11. In this case, the first inputs of the third 8-3 and the fourth 8-4 time selectors are connected to the output of the second converter 4-2, and the second inputs are connected to the first inputs of the first 8-1 and second 8-2 time selectors, respectively, the second inputs of which are connected to the output of the first converter 4-1 .

The work of the proposed radar is as follows.

The synchronization pulse from the first output of the synchronizer 5 is fed to the input of the transmitter 6. The transmitter 6 generates probing pulses, which through the antenna switch 2 enter the antenna 1, where they are then emitted into space. The pulses reflected from the target are received by the antenna in conjunction with a passive interference signal spatially aligned with the target. The received signal through the antenna switch 2 is fed to the first input of the first mixer 3-1, the second input of which receives oscillations from the local oscillator 7. The oscillation frequency of the local oscillator 7 is set so that the frequency difference between the radiated antenna signal and the local oscillator 7 is equal to the intermediate frequency f _pc , i.e. the center tuning frequency of the first OPC 4-1.

In the first mixer 3-1, the frequency of the received signal is reduced to an intermediate frequency f _pc . Next, the signal is fed to the input of the first amplifier 4-1, the bandwidth of which is consistent with the duration of the radio pulse, where it is amplified to the required level. The signal (direct) from the output of the first amplifier 4-1 is supplied simultaneously to the second input of the second mixer 3-2 and to the signal (second) inputs of the first 8-1 and second 8-2 time selectors of the first and second circuit, respectively.

In the second mixer 3-2, the input signal input to its second input is mixed with the voltage from the reference generator 14, which is supplied to the first input of the second mixer 3-2.

The reference oscillator 14 generates stable continuous harmonic oscillations with a frequency equal to twice the intermediate tuning frequency of the first 4-1 and second 4-2 IF (figure 2, g). At the output of the second mixer 3-2 there are two spectral components: total and difference. The signal from the output of the second mixer 3-2 is fed to the input of the second amplifier 4-2, which selects only the difference component of the spectrum, for which it has an amplitude-frequency characteristic the same as the first amplifier 4-1. At the output of the second IF signal spectrum 4-2 is mirror rotated with respect to the intermediate frequency f _IF spectrum signal obtained at the output of a first IF amplifier 4-1 (2, d), i.e. Spectral conversion of the direct signal from the output of the amplifier 4-1 is performed and a spectrally converted signal is obtained. From the output of the UPCH 4-2, the spectrally converted signal is supplied to the first (signal) inputs of the temporary selectors 8-3 and 8-4 of the third and fourth circuits.

The strobe generator 13 generates pulses of the first (leading) and second (lagging) pulses delayed by the duration relative to the beginning of the first strobe, for example, of a rectangular shape, the strobe duration being equal to the duration of the probe pulses, and their front should coincide with the energy center of gravity of the pulse from the target, which and is carried out continuously using the entire radar tracking system. The gate generator 13 is synchronized by pulses arriving at its second input from the second output of the synchronizer 5 for linking the moments of formation of the gates to the time delay of the signal reflected from the target relative to the moment of radiation of the probe pulse antenna.

Consider the processing of signals in the channel of the first (leading) gate.

Direct and spectrally converted signals (Fig.2, a and Fig.2, d) are respectively received at the second input of the temporary selector 8-1 and at the first input of the temporary selector 8-3. To the first input of the temporary selector 8-1 and to the second input of the temporary selector 8-3, selector pulses of the first strobe are fed from the first output of the strobe generator 13, the moments of generating the strobe in which are controlled by the signals from the output of the control unit 12, arriving at the first input of the strobe generator 13. The selector pulses of the first gate open the temporary selectors 8-1 and 8-3 for a time equal to the duration of the corresponding strobe.

From the outputs of the temporary selectors 8-1 and 8-3 during the operation of the first gate, the direct and spectrally transformed signals (Fig. 2, a and Fig. 2, e) are received respectively at the inputs of the corresponding narrow-band filters 9-1 and 9-3 of the circuits. The amplitude-frequency characteristics of the narrow-band filters 9-1 and 9-3 of the first and third circuits (Fig.2, b and Fig.2, e) are identical; they have bandwidths in the range of possible Doppler frequencies from F _gmin to F _{gmax of} the moving target signal at an intermediate frequency, from f _pc + F _fmin to f _pc + F _gmax .

In the future, for definiteness, we assume that the target moves toward the radar and the Doppler frequency offset is positive (Fig. 2, a).

The signal energy (dispersion) of the target, which passed to the output of the temporary selectors 8-1 and 8-3 of the first and third circuits, is directly proportional to the overlap area of the pulse reflected from the target and the pulse of the first strobe, and the energy (dispersion) of passive interference spatially combined with the target passed to the output of the temporary selectors 8-1 and 8-3 of the first and third circuits is proportional to the total reflective surface of the reflectors falling into the spatial resolution element, which coincides with the target forming the passive interference in this strobe.

The output of the first narrow-band filter 9-1 passes the spectral components of both the signal of a moving target and the spectral components of passive interference, spatially combined with the target, falling into its passband (Fig. 2, c).

The output of the third narrow-band filter 9-3, corresponding to the processing chain of the spectrally transformed signal, will pass the spectral components of only the passive interference, spatially aligned with the target, falling into its passband (Fig. 2, g), which due to the symmetry of the normal envelope of the passive spectrum the interference in this area has the same dispersion as the dispersion of passive interference residues that have passed the first narrow-band filter 9-1 of the first direct signal circuit.

From the output of the first narrow-band filter 9-1, an additive mixture of the target signal and the residual passive interference (Fig.2c), spatially aligned with the target, is fed to the input of the first amplitude estimation block 10-1, at the output of which the signal is proportional to the dispersion estimate of this mixture. The signal from the output of the amplitude estimation block 10-1 is fed to the first input of the subtraction block 15-1.

From the output of the third narrow-band filter 9-3 of the third circuit (Fig. 2, k), the components of the passive interference spectrum spatially aligned with the target are fed to the input of the third amplitude estimation block 10-3, the output of which is proportional to the dispersion estimate of the passive interference received at his entrance.

The signal from the output of the third block of the estimation of the amplitude of 10-3 goes to the second input of the first block of subtraction 15-1 of the channel of the first gate. In the subtraction unit 15-1 of the channel of the first strobe, the signal from the output of the first block for estimating the amplitude 10-1 of the signal is subtracted from the output of the third block for estimating the amplitude of 10-3.

Due to the fact that the signal from the components of the spectrum of passive interference at the output of the first block of amplitude estimation 10-1 is equal to the signal of passive interference spatially aligned with the target, at the output of the third block of amplitude estimation 10-3, the signal at the output of the first subtraction block 15-1 the channel of the first gate is proportional only to the target signal at the output of the first amplitude estimation block 10-1, which is proportional to the dispersion of the target signal at the output of the first narrow-band filter 9-1 and, accordingly, the overlap area of the target signal and the first gate and is not dependent from the dispersion of passive interference, spatially combined with the target, at the outputs of the first 8-1 and third 8-3 time channel selectors of the first strobe.

Signal processing in the channel of the second strobe is carried out similarly to the operation of the channel of the first strobe, taking into account the time delay of the second strobe.

The energy (dispersion) of the target signal transmitted to the output of the second 8-2 time channel selector of the second strobe is directly proportional to the overlap area of the pulse reflected from the target and the second strobe pulse, and the energy (dispersion) of passive interference spatially combined with the target passed to the output of the second 8-2 and fourth 8-4 temporary channel selectors of the second strobe is proportional to the effective reflective surface of the elements forming the passive interference spatially aligned with the target in the second strobe.

The signal from the output of the second amplitude estimation block 10-2 is supplied to the first input of the second subtraction block 15-2. The signal from the output of the fourth block of the estimation of amplitude 10-4 is supplied to the second input of the second block of subtraction 15-2 of the channel of the second gate. In the second block subtracting channel 15-2 of the second strobe, the signal from the output of the second block for estimating the amplitude of 10-2 is subtracted from the output of the fourth block for estimating the amplitude of 10-4.

The signal at the output of the second subtraction block 15-2 of the second strobe channel is proportional only to the target signal at the output of the second amplitude estimation block 10-2, which is proportional to the dispersion of the target signal at the output of the second narrow-band filter 9-2 and, accordingly, is proportional to the overlap area of the target signal and the second the gate and does not depend on the variance of passive interference spatially combined with the target at the outputs of the second 8-2 and fourth 8-4 time channel selectors of the second gate.

The signal from the output of the first subtraction block 15-1 enters the first input of the comparison unit 11, the second input of which receives the signal from the output of the second subtraction block 15-2. In the comparison block 11, the signal received at its second input is subtracted from the signal received at its first input. The signal from the output of the comparison unit 11 is an error signal of only a temporary mismatch between the energy center of the target pulse from the output of the first IFA 4-1 and the front of the selector pulses of the first and second gates generated by the strobe generator 13. In the case of equal signals at the first and second inputs of the comparison unit 11 the first strobe overlaps in area with half the target's pulse, and the second strobe overlaps with the second half of the target's pulse. In the case of inequality of the signals at the first and second inputs of the comparison unit 11, an error signal is generated at its output, which acts through the control unit 12 on the temporary position of the gates generated by the strobe generator 13, so as to reduce the mismatch to zero.

Due to the fact that the signals at the outputs of the subtraction blocks 15-1 and 15-2 of the channels of the first and second gates do not depend on the dispersion of passive interference within the corresponding gates, but depend only on the overlap areas of the corresponding gates with the target pulse, an error signal at the output of the block 11, does not depend on differences in the properties (powers) of passive interference spatially aligned with the target in the first and second gates, but depends only on the temporal mismatch between the energy center of the target pulse and the front of the strobe pulses.

In the proposed radar, tracking the range to a small moving target is carried out with high accuracy regardless of the nature of the spatial properties of the reflectors forming a passive interference spatially combined with the target.

In the prototype, the low accuracy of tracking the range of a small moving target is due to a measurement error, the normalized values of which are shown in Fig. 3, caused by spatial heterogeneity of the power of passive interference spatially aligned with the target in the channels of the first (leading) and second (delayed) gates. In most cases, passive noises falling into the first and second gates have different intensities in view of the differences in specific effective reflective surfaces that formulate passive noises in the corresponding gates. Therefore, the dispersion of the passive interference residues passing through the first narrow-band filter in the channel of the first gate differs from the dispersion of the passive interference residues passing through the second narrow-band filter in the channel of the second gate. As a result, at the output of the comparison unit, in addition to useful information about the temporal position of the pulse of a small moving target, there is a measurement error signal due to the difference in the variances of passive noise passing through the first and second narrow-band filters of the channels of the first and second gates. The presence of a measurement error signal leads to an error in the mismatch of the temporal position of the center of the received signal of the small moving target and the front of the selector strobes and, as a result, the accuracy of automatic tracking of the range of the small moving target is reduced.

The proposed automatic range tracking radar increases the accuracy of automatic tracking of the range of a small moving target by 20-70% of the duration of the probe pulse by compensating for measurement errors caused by the inequality of passive jamming powers spatially aligned with the target in the channels of the first (leading) and second (delayed) gates.

With the intensive development of modern technology of airborne radars, air traffic control radars, increasing the accuracy of automatic tracking of the range of a small moving target under the influence of spatially inhomogeneous passive interference spatially combined with the target is an urgent task and speaks of the promising application of the proposed technical solution.

Claims (1)

An automatic range tracking radar containing a series-connected antenna, an antenna switch, a first mixer and a first intermediate frequency amplifier (IFA), serially connected synchronizer, transmitter and local oscillator, the output of which is connected to the second input of the first mixer, and the second output of the transmitter is connected to the second the input of the antenna switch, the first and second circuits, consisting of a series-connected corresponding time selector, a narrow-band filter and amplitude estimation lock, connected in series to the comparator, generating an error signal for zeroing the time mismatch between the energy center of the target pulse and the front of the strobe pulses, a control unit for controlling the moment of generating the gates, and a strobe generator, the second input of which is connected to the second output of the synchronizer and the first and second outputs generating pulses of the first leading and second lagging, delayed by the pulse duration relative to the beginning of the first, gates - to the first inputs of the first and second time selectors, respectively, characterized in that a reference generator, a second mixer, a second input of which is connected to the output of the first amplifier, and a second amplifier, the third and fourth circuits, consisting of the corresponding the third and fourth time selector, the third and fourth narrow-band filter and the third and fourth amplitude estimation blocks, the first, second, third and fourth amplitude estimation blocks The first and second subtraction blocks, the first inputs of each of which are connected to the outputs of the first and second blocks of amplitude estimation, the second inputs of each of which are connected to the outputs of the third and fourth blocks of amplitude estimation, respectively, are calculated to estimate the dispersion of the mixture of the target signal and the passive interference residues, and their outputs are connected respectively to the first and second inputs of the comparison unit, while the first inputs of the third and fourth time selectors are connected to the output of the second amplifier, the second inputs to the first inputs respectively, the first and second time selectors, the second inputs of which are connected to the output of the first amplifier.

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