RU2532258C1 - Method of detecting broadband parametric scatterers - Google Patents

Method of detecting broadband parametric scatterers Download PDF

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RU2532258C1
RU2532258C1 RU2013135592/07A RU2013135592A RU2532258C1 RU 2532258 C1 RU2532258 C1 RU 2532258C1 RU 2013135592/07 A RU2013135592/07 A RU 2013135592/07A RU 2013135592 A RU2013135592 A RU 2013135592A RU 2532258 C1 RU2532258 C1 RU 2532258C1
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pulses
radio
radio pulses
signal
pulse
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Николай Юрьевич Бабанов
Сергей Викторович Ларцов
Валерий Павлович Самарин
Андрей Викторович Клюев
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Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Нижегородский государственный технический университет им. Р.Е. Алексеева", НГТУ
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Abstract

FIELD: radio engineering, communication.
SUBSTANCE: invention relates to methods of detecting broadband parametric scatterers which are secondary sources of electromagnetic radiation. A probing signal irradiates a broadband parametric scatterer, wherein, due to the parametric generation phenomenon, a series of packets is formed and re-emitted, said packets consisting of two series of radio pulses of a response signal, the instantaneous frequency of which is twice less than the instantaneous frequency of the pumping signal. The series of radio pulses of the response signal is coherent, is synchronised with one of one of doubled auxiliary radio pulses and behaves as a coherent series with a known law of variation of the phase of high-frequency filling from pulse to pulse. The series of doubled auxiliary radio pulses is encoded based on a different law. Furthermore, corresponding radio pulses of the first and second series of doubled auxiliary radio pulses are anti-phase, while radio pulses of the first and second series of radio pulses of the response signal are in-phase.
EFFECT: high sensitivity of the receiving device of a system for detecting broadband parametric scatterers and longer range of the search system.
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Description

The invention relates to methods for detecting passive responder markers, which are secondary sources of electromagnetic radiation.
Known by the [Radio complex search markers, patent RU 2108596, G01S 13/75, publ. 04/10/1998; Nonlinear passive marker - parametric diffuser, patent RU 2336538, C01S 13/74, publ. 01/20/2008] a method for detecting parametric scatterers. The method allows to solve the problem of detecting objects, in particular people, marked with passive nonlinear responder markers, which are used as parametric scatterers. The method consists in the fact that a parametric diffuser is previously placed on the search object; the region of space in which the search object can be located is irradiated with a probe signal, which is formed as a sequence of narrow-band radio pulses at a frequency f; a signal scattered by the marker is received at a subharmonic frequency equal to f / 2; in case of exceeding the detection threshold, a decision is made on the presence of a search object in the detection zone.
This method has a significant drawback, namely, insufficient sensitivity of the receiving device due to the fact that coherent reception of the scattered signal is not provided. When each pulse scattered by a signal marker at a subharmonic frequency is excited, two equally probable phase values are possible, differing by π [P. Gorbachev. Signal generation by a system of passive subharmonic scatterers // Radio Engineering and Electronics, 1995, v.40, N11, pp. 1606-1610], as a result, the signal scattered by the subharmonic is not coherent, even with a coherent sounding signal.
The specified disadvantage is overcome in the method for detecting parametric scatterers, known from [S. Lartsov A probe signal for detecting parametric scatterers // Radio Engineering, 2000, N5, pp. 8-12].
It is proposed to generate a probing signal in the form of a sequence of packets of narrow-band coherent radio pulses of a pump signal with a high-frequency filling frequency f and a sequence of packets of narrow-band coherent pairs of synchronizing radio pulses with a high-frequency filling frequency f / 2. In this case, both sequences have the same pulse durations τ, pulse repetition periods T and pulse repetition periods T 1 . In addition, the pulse width of the clock signal is significantly shorter than the pulse width of the pump signal, the trailing edge of the first clock radio pulse from the pair coincides with the leading edge of the second clock radio pulse from the pair. The high-frequency filling phase of the first synchronizing radio pulse corresponds to the symbol of the chosen phase coding law, the high-frequency filling phase of the second synchronizing radio pulse of a pair always differs by π from the high-frequency filling phase of the first synchronizing radio pulse of a pair, in addition, the trailing edge of the first synchronizing radio pulse coincides with the leading edge of the sounding pulse of the probe signal .
As a result, the excitation of a parametric scatterer occurs under conditions of the existence of an external action at the excitation frequency. Under these conditions, the phase of the excited oscillation at the subharmonic frequency ceases to be random and is determined by the phase of the external action, that is, the phase of the pulses of the synchronizing signal. However, pulses of such a synchronizing signal interfere with the reception of a useful signal, since they will be scattered from the objects surrounding the parametric diffuser and the underlying surface and will be received at the receiver input simultaneously with the useful signal. It is impossible to eliminate such an interference due to temporary selection; it can only be compensated. Therefore, after a synchronizing radio pulse, it was proposed to emit a compensating radio pulse with the opposite phase, while the synchronizing radio pulse sets the coding law of the phase of the scattered signal, and a compensating radio pulse is necessary for the mutual compensation of both pulses in the optimal receiver of the signal received at the subharmonic frequency.
The disadvantage of the method for detecting parametric scatterers, known from [Lartsov S.V. The probe signal for detecting parametric scatterers // Radio Engineering, 2000, N5, pp. 8-12], is that a narrow-band radio signal is used as a pump signal, while the capabilities of broadband parametric scatterers for generating broadband scattered signals, for example, radio pulses with linear frequency modulation, which may be subject to compression, as a result of which a pulse can be generated at the output of the receiving device, the duration of which is significantly shorter e radio pulse duration of the pump signal. In other words, the ambiguity in determining the distance to the parametric scatterer is determined by the duration of the radio pulse of the pump signal and cannot be improved.
In addition, with coherent accumulation of the burst of pulses, the useful signal and the dual auxiliary radio pulses, which are an obstacle, will grow equally, since the coding laws are the same for the useful signal and for the interference.
These disadvantages are eliminated in the known patent RU 2408896, G01S 13/79, publ. 01/10/2011, a method for detecting broadband parametric diffusers, selected as a prototype.
A prototype method for detecting broadband parametric scatterers, namely, that the broadband parametric scatterer is preliminarily placed on the search object, the area of the space in which the search object can be located is irradiated with a probing signal, which forms a response signal consisting of series in the process of parametric generation on the parametric scatterer packs of sequences of radio pulses of the response signal, with each pack consisting of two sequences of the same size The patterns encoded in accordance with the selected binary coding law, which is a binary sequence, the opposite characters of which correspond to the out-of-phase values of the phases of the high-frequency filling of the radio pulses of the response signal; signal, and the instantaneous frequency of the radio pulses of the pump signal is twice the instant the frequency of the response radio pulses, in addition, the probe signal includes an auxiliary signal consisting of a series of bursts of sequences of auxiliary radio pulses, each packet consisting of two synchronous sequences of dual auxiliary radio pulses with the same dimension as the sequences of the radio pulses of the response signal, the first and second of the dual auxiliary radio pulses have opposite phases of high-frequency filling, phases of high-frequency the fillings of the corresponding auxiliary radio pulses for the first and second of the sequences of dual auxiliary radio pulses in each packet also have opposite values, in addition, the phase of the high-frequency filling of each first of the dual auxiliary radio pulses changes from the current dual auxiliary radio pulse to the next dual auxiliary radio pulse in accordance with a binary alternative law encoding for which a minimum level of For synchronous accumulation according to an algorithm that ensures the maximum level of accumulation of the received signal in accordance with the selected binary coherent accumulation law, the opposite symbols of the alternative binary coding law correspond to the antiphase values of the high-frequency filling phase of the first of the dual auxiliary radio pulses, while the duration of each of the auxiliary radio pulses and the time the gap between the trailing edge of the first and the leading edge of the second of the double of the auxiliary radio pulses is substantially shorter than the duration of the radio pulse of the pump signal, the moments of the leading and trailing edges, the corresponding serial numbers of the auxiliary radio pulses in the packets are the same, one of the double auxiliary radio pulses is a synchronizing radio pulse, the initial phase of its high-frequency filling corresponds to the current symbol of the selected binary coding law, at this one of the time moments of the radiation of the synchronizing radio pulse coincides with the front the front of the radio pulse of the pump signal, at this moment in time, the instantaneous frequency of the high-frequency filling of the synchronizing radio pulse is two times less than the instantaneous frequency of the high-frequency filling of the radio pulses of the pump signal, if the current symbols of the selected and alternative coding laws coincide, then for the corresponding dual auxiliary radio pulses the first auxiliary radio pulse is synchronizing radio pulse, and if the current characters of the selected and alternative law coding does not match, then the synchronizing radio pulse is the second of the corresponding dual auxiliary radio pulses, while the instantaneous frequency of the radio pulses of the pump signal and dual auxiliary radio pulses is changed according to the corresponding linear laws, changing in the same direction, and the duration of the first and second of the dual auxiliary radio pulses selected so as to minimize their level at the output of the synchronous filter, consistent with the radio pulse of the response signal la, receive a response signal, while simultaneously compensating for a series of packets of sequences of dual auxiliary radio pulses and synchronously accumulating a series of packets of sequences of radio pulses of the response signal according to algorithms that provide the maximum level of accumulation of the received signal in accordance with the shape and internal modulation of each radio pulse of the response signal selected by the encoding law , as well as by adding temporary implementations of the first and second sequences of the radio sov response signal in each of the sequences of bursts of radio pulses signal, above the detection threshold deciding the presence in the zone of detection of the search object.
The advantage of the prototype method over analogs is that it provides scattering from a broadband parametric scatterer of broadband scattered signals, which can be compressed to significantly shorter in the receiving device, while there remains the possibility of coherent accumulation of the received scattered signal, and auxiliary radio pulses are not accumulated and compensated, Why are conditions provided when pairs of auxiliary radio pulses are encoded according to an alternative law? i. This law assumes the smallest level of coherent summation of the received signals in the receiver, which is already configured to receive the signal according to another - selected coding law.
The disadvantage of this technical solution is a certain violation of the synchronism of the generated response signals for the duration of the dual auxiliary radio pulses, however, this time is significantly less than the duration of the pump radio pulse. Technically, the ability to emit auxiliary radio pulses encoded in accordance with an alternative coding law, and at the same time generate radio pulses of the response signal in accordance with the selected coding law, is carried out due to the fact that the first or second of the dual auxiliary radio pulses, respectively, the instantaneous frequencies, are synchronized which synchronization occurs, are different for the first and second clock pulses, their duration can also be different.
In addition, auxiliary pulses are emitted by synchronous paired bursts. The corresponding pulses in the packets are the same in shape and type, but are out of phase. This makes it possible in the receiving device to realize their mutual compensation by simple addition of the received sequences. Pulses of the response signal are also formed by paired bursts, but they are in-phase, although they are not synchronized along the leading edge, and will be amplified when added.
The disadvantage of the prototype method is that each of the radio pulses of a sequence of pairs of connected packets of dual auxiliary radio pulses when passing through a synchronous filter, matched with the radio pulses of the response signal, accumulates in the same way as the radio pulse of the response signal. In this case, the time structure of auxiliary radio pulses changes: their envelope becomes close to the form sin (x) / x. In the region of the main maximum, there is an effective mutual compensation of auxiliary radio pulses, and in the region of the “sidewalls” such mutual compensation is absent, since the frequencies of the radio pulses are different. As a result, the fact that the instantaneous frequency of the radio pulses of the pump signal and the dual auxiliary radio pulses is changed according to the corresponding linear laws, changing in the same direction, leads to the fact that each of the dual auxiliary radio pulses, being a kind of “piece” of the implementation of the radio pulse of the response signal accumulate almost optimally in a synchronous filter tuned to the radio pulse of the response signal, while the mutual compensation of the dual auxiliary radio pulses will occur then ko stretches thereof. In the remaining time sections, even coherent addition of the dual auxiliary radio pulses can occur.
Thus, the provided measures to weaken the auxiliary radio pulses when receiving a response signal proposed in the prototype method are insufficient, which is a disadvantage of the prototype.
The problem of increasing the sensitivity of the receiving device and the range of the search system.
The technical result is the creation of conditions under which auxiliary radio pulses in a synchronous filter, consistent with the radio pulses of the response signal, were not subjected to coherent accumulation, but rather weakened.
The technical result is achieved due to the fact that a new technical solution is proposed, namely, a method for detecting broadband parametric scatterers, namely, that the broadband parametric scatterer is preliminarily placed on the search object, the area of the space in which the search object can be located is irradiated with a probe signal, forming in the process of parametric generation on a parametric diffuser, a response signal consisting of a series of packets of sequences of radio pulses about signal, in this case, each packet consists of two sequences of the same dimension, encoded in accordance with the selected binary coding law, which is a binary sequence, the opposite symbols of which correspond to the antiphase values of the phases of the high-frequency filling of the radio pulses of the response signal, for this the probe signal is emitted consisting of a series of packets sequences of radio pulses of the pump signal, in which each radio pulse is synchronized with the radio pulse of the actual signal, and the instantaneous frequency of the radio pulses of the pump signal is twice the instantaneous frequency of the radio pulses of the response signal, in addition, the probe signal includes an auxiliary signal consisting of a series of bursts of sequences of auxiliary radio pulses, each packet consisting of two synchronous sequences of dual auxiliary radio pulses with that the same dimension as that of the sequences of the radio pulses of the response signal, while the phases of the high-frequency filling correspond x auxiliary radio pulses for the first and second of the sequences of dual auxiliary radio pulses in each burst have opposite values, in addition, the phase of high-frequency filling of each first of the dual auxiliary radio pulses changes from the current dual auxiliary radio pulse to the next dual auxiliary radio pulse in accordance with the binary alternative coding law, for which the minimum level is ensured with synchronous accumulation by alg an rhythm that provides the maximum level of accumulation of the received signal in accordance with the selected binary law of coherent accumulation, while the opposite symbols of the alternative binary coding law correspond to antiphase values of the high-frequency filling phase of the first of the dual auxiliary radio pulses, while the duration of each of the auxiliary radio pulses and the time interval between the trailing edge first and leading edge of the second of the dual auxiliary radio there are much less times than the duration of the radio pulse of the pump signal, the moments of the leading and trailing edges, the corresponding serial numbers of the auxiliary radio pulses in the packets are the same, one of the double auxiliary radio pulses is a synchronizing radio pulse, the initial phase of its high-frequency filling corresponds to the current symbol of the selected binary coding law, with one of the time moments of the radiation of the synchronizing radio pulse, the signal coincides with the leading edge of the radio pulse pump, at this point in time, the instantaneous frequency of the high-frequency filling of the clock pulse is half the instantaneous frequency of the high-frequency filling of the pump pulse, and if the current characters of the selected and alternative coding laws are the same, then for the corresponding dual auxiliary radio pulses the first auxiliary radio pulse is the synchronizing radio pulse, and if the current characters of the selected and alternative coding laws do not match, then s the synchronizing radio pulse is the second of the corresponding dual auxiliary radio pulses, wherein the instantaneous frequency of the radio pulses of the pump signal and dual auxiliary radio pulses is changed linearly, and the durations of the first and second of the dual auxiliary radio pulses are selected so as to minimize their level at the output of the synchronous filter, matched with the radio pulse response signal, receive a response signal, while simultaneously compensating for series of packets of of dual auxiliary radio pulses and synchronous accumulation of a series of packets of sequences of radio pulses of the response signal according to algorithms that provide the maximum level of accumulation of the received signal in accordance with the shape and internal modulation of each radio pulse of the response signal, selected by the coding law, and also by adding temporary implementations of the first and second sequences of radio pulses of the response signal in each of the packs of sequences of radio pulses of the signal, with n raising the detection threshold, they decide on the presence of a search object in the detection zone, while the linear laws of change of the instantaneous frequency of the radio pulses of the pump signal and the change of the instantaneous frequency of the dual auxiliary radio pulses are opposite, and the dual auxiliary radio pulses are formed so that the phases of their high-frequency filling are such that they synchronize the radio pulses of the response signal were excited in antiphase.
The essence of the invention lies in the fact that a new mechanism for attenuation of auxiliary radio pulses when receiving a response signal is proposed. The proposed mechanism is as follows. In the prototype method, an auxiliary radio pulse with linear frequency modulation, propagating along an optimal filter agreed with it, is compressed by approximately the size of its base. If a radio pulse of the same duration propagates along the same filter, with a linear frequency modulation, but with the opposite law for changing the instantaneous frequency, it will, on the contrary, be stretched. Accordingly, the intensity of such a signal decreases and the noise introduced by auxiliary radio pulses decreases. And since it is the level of this interference that significantly affects the real sensitivity of the receiver of the search system, the sensitivity of this receiver increases.
The indicated effect is shown in Fig. 1, which shows the oscillograms of the results of a machine experiment for passing through a filter, matched with a rectangular linear-frequency-modulated radio pulse with a duration of 10 μs and a frequency change from 250 MHz to 300 MHz, short radio pulses having a duration of 1 μs: first the pulse corresponds to an input radio pulse without frequency modulation having a high-frequency filling frequency of 255 MHz, the second pulse corresponds to an input radio pulse with a change in the carrier frequency you linearly from 250 MHz to 255 MHz, the third pulse corresponds to the input radio pulses with carrier frequency linearly from 255 MHz to 250 MHz. It is clearly seen that a radio pulse with the inverse law of frequency change passes through the filter worst of all, matched with a rectangular linear-frequency-modulated radio pulse of 10 μs duration and a frequency change from 250 MHz to 300 MHz, while it does not accumulate in a matched filter, but vice versa , there is a blur.
In the new technical solution, the main purpose of the auxiliary radio pulses — to ensure synchronization of the radio pulses of the response signal — is fulfilled, since at the time of pumping the radio pulses the frequency of the auxiliary radio pulse is equal to the frequency of the radio pulse of the response signal, as a result of which the phase of this auxiliary radio pulse at this moment will determine the phase of the excited in the broadband parametric response pulse generator. After excitation, the auxiliary signals do not affect the process of parametric generation and, being an undesirable interference at the input of the receiver of the response signal, must be eliminated at the output of this receiver and, therefore, may have a different modulation than that of the response signal.
Since in the proposed technical solution, unlike the prototype, the synchronizing radio pulses are not part of the implementation of the radio pulse of the response signal, and the sections corresponding to the times at which the excitation and synchronization of the radio pulse of the response signal may not be synchronous, the requirement in the prototype of the antiphase of the first and second of auxiliary radio pulses is no longer relevant and may not be performed. It is essential that the response signals excited by the first and second auxiliary radio pulses must be antiphase.
The claimed technical solution can be implemented using a detector of broadband parametric scatterers, the structural diagram of which is presented in figure 2, where 1 is the shaper; 2 - generator of auxiliary radio pulses; 3 - pump signal generator; 4, 5 - high-frequency amplifiers; 6, 7 - antennas; 8 - broadband parametric diffuser; 9 - antenna; 10 - high-frequency amplifier; 11 - receiver; 12 - indicator.
The output I of the shaper 1 is connected to the control input of the auxiliary radio pulse generator 2, the output II of the shaper 1 is connected to the control input of the pump signal generator 3, the output III of the shaper 1 is connected to the clock input of the receiver 11.
The signal output of the generator 2 auxiliary radio pulses is connected to the input of the high-frequency amplifier 4. The output of the high-frequency amplifier 4 is connected to the input of the antenna 6.
The signal output of the pump signal generator 3 is connected to the input of the high-frequency amplifier 5. The output of the high-frequency amplifier 5 is connected to the input of the antenna 7.
In the irradiation zone of the antennas 6, 7 is a broadband parametric diffuser 8.
In the area of re-emission of the response signal from the broadband parametric diffuser 8, the antenna 9 is located.
The output of the antenna 9 is connected to the input of the high-frequency amplifier 10. The output of the high-frequency amplifier 10 is connected to the signal input 2 of the receiver 11, the output of the receiver 11 is connected to the input of the indicator 12.
The detector broadband parametric diffusers operates as follows.
A person who is potentially at risk of becoming distressed on the water is equipped with a life jacket with an attached marker - a broadband parametric diffuser.
The selected and alternative coding laws are determined. In particular, such laws can be binary sequences of 3 characters: for the selected coding law, the Barker sequence “1”, “1”, “-1”; for an alternative coding law - the sequence “1”, “1”, “1”.
A probe signal is emitted, consisting of a series of bursts of sequences of radio pulses of the pump signal and of a series of bursts of sequences of auxiliary pulses of radio pulses.
To do this, in the shaper 1, a synchronizing sequence of short video pulses is formed, which synchronizes the operation of the detector of broadband parametric scatterers (Fig. 3, conditional waveform A).
The sequence of short video pulses in the same driver 1 is converted into a series of packs of sequences of video pulses of the selected coding law, with each packet consisting of two sequences of video pulses of the same dimension encoded in accordance with the selected binary coding law, while the opposite symbols of the coding law correspond to bipolar video pulses. The duration of the video pulses is equal to the duration of the duty cycle when the radio pulses of the probe signal are emitted. Moreover, both the first and second sequences of video pulses of the selected coding law from one packet are encoded according to the same selected coding law, but based on opposite elements. That is, the selected coding law - the Barker sequence "1", "1", "-1" - is implemented in the first sequence from the packet as a sequence of video pulses with polarities "+", "+", "-", and in the second sequence of the same burst of video pulses have the polarity "-", "-", "+". The conditional waveform of one pack of sequences of video pulses of the selected coding law is presented in figure 3, curve B.
At the same time, the sequence of short video pulses in the same driver 1 is converted into a series of packets of sequences of video pulses of an alternative coding law, with each packet consisting of two sequences of the same dimension encoded in accordance with an alternative binary coding law, while the opposite symbols of the coding law correspond to bipolar video pulses. The duration of the video pulses is equal to the duration of the duty cycle when the radio pulses of the probe signal are emitted. Moreover, both the first and second sequences of video pulses of the selected coding law from one packet are encoded according to the same alternative coding law, but based on opposite elements. That is, an alternative coding law - the Barker sequence “1”, “1”, “1” - is implemented in the first sequence from the packet as a sequence of video pulses with polarities “+”, “+”, “+”, and in the second sequence of video pulses from the same burst of video pulses have the polarity "-", "-", "-". The conditional waveform of one packet of sequences of video pulses of the alternative coding law is shown in Fig. 3, curve B.
A series of packets of sequences of video pulses of the alternative coding law are converted in the former 1 into a series of packets of sequences of envelopes of the envelopes of the dual auxiliary radio pulses. The envelope of the dual auxiliary radio pulses consists of two short video pulses having different polarities, while the duration and time interval between these video pulses are the same and equal to about 5 ÷ 10% of the duty cycle when the radio pulses of the probe signal are emitted and equal to 1 μs. The leading edge of the first video pulse of the envelope of the dual auxiliary radio pulses coincides with the leading edge of the corresponding video pulse in a series of packets of sequences of video pulses of the alternative coding law. The polarity of the first video pulse of the envelope of the dual auxiliary radio pulses is the same as that of the corresponding video pulse in a series of packets of sequences of video pulses of the alternative coding law. A series of packs of sequences of envelopes of the dual auxiliary radio pulses through the output I of the shaper 1 are fed to the control input of the generator 2 of the auxiliary radio pulses. The conditional waveform of one pack of envelope sequences of the dual auxiliary radio pulses is shown in figure 3, curve G.
At the same time, through the output I of the shaper 1, a synchronizing sequence arrives at the control input of the generator 2 of auxiliary radio pulses.
At the same time, a series of packs of sequences of video pulses of the selected coding law are converted in the driver 1 into a series of packs of sequences of envelopes of radio pulses of the pump signal. The trailing edge of the video pulses of a series of bursts of sequences of envelopes of the radio pulses of the pump signal coincides with the trailing edge of the corresponding video pulses of the bursts of sequences of sequences of pulses of the selected coding law. The formation of the leading edge of the video pulses of a series of packets of sequences of envelopes of the radio pulses of the pump signal is performed according to the following rule: if the polarity of the corresponding video pulses in the series of packets of sequences of video pulses of the selected coding law and in the series of packets of sequences of video pulses of the alternative coding law coincide, then the leading edge of the envelope of the radio pulses of the pumping signal coincides corresponding synchronizing video pulse, and if not, then the front videopulses series of RF pulse sequences packs envelopes pump signal coincides with the corresponding edge of the second clock of a video envelope. The conditional waveform of one pack of sequences of envelopes of the radio pulses of the pump signal, is presented in figure 3, curve D
At the same time, a series of bursts of sequences of starting video pulses of the pump signal are formed in driver 1. The trailing edge of the video pulses of a series of bursts of sequences of starting video pulses of the pump signal coincides with the trailing edge of the corresponding video pulses of the bursts of sequences of video pulses of the selected coding law. The leading edge of the video pulses of a series of bursts of sequences of starting video pulses of the pump signal is at the end of the first corresponding synchronizing video pulse. Thus, all video pulses of a series of bursts of sequences of starting video pulses of a pump signal have the same duration, for example, 10 ms.
The conditional waveform of one pack of sequences of starting video pulses of the pump signal is shown in figure 3, curve E.
In the generator of 2 auxiliary radio pulses, a series of packets of sequences of envelopes of dual auxiliary radio pulses are converted into a series of packets of sequences of dual auxiliary radio pulses.
In the presence of a video pulse from a series of packets of envelopes of the envelopes of dual auxiliary radio pulses at the input of the generator 2 of auxiliary radio pulses, a radio pulse from a series of packets of sequences of envelopes of the envelopes of dual auxiliary radio pulses is generated at its output. The time parameters of radio pulses from a series of packets of envelope sequences of dual auxiliary radio pulses are the same: duration 1 μs, frequency varies from 255 MHz to 250 MHz. The initial phase of the high-frequency filling of the second of the dual auxiliary radio pulses is determined (previously calculated) as the opposite (different by π) phase of the high-frequency filling at a frequency of 255 MHz of a conventional linear-frequency-modulated radio pulse with a frequency change from 250 MHz to 300 MHz and a duration of 10 μs, then is at a time equal to 1 μs from the beginning. In this case, the phase of the high-frequency filling of this conditional linear-frequency-modulated radio pulse at the initial moment, that is, at a frequency of 255 MHz, should be equal to the phase of the high-frequency filling of the first of the dual auxiliary radio pulses in the region of its trailing edge. The conditional waveform of one burst from a series of bursts of sequences of dual auxiliary radio pulses is shown in Fig. 3, curve J.
(It should be noted that the images of the sinusoidal radio signals in Figs. 3, 4, 5, 6, 7 are made conditionally, that is, the number of oscillation periods on the curves does not correspond to the real one and is presented to indicate the direction of the physical process. The real number of periods is much larger and cannot be presented in a clear illustration within reasonable limits.)
A series of packs of sequences of dual auxiliary radio pulses from the output of the generator 2 of auxiliary radio pulses are fed to the input of a high-frequency amplifier 4, where they are amplified and radiated into space in the direction of the assumed location of the broadband parametric scatterer 8.
A series of packs of sequences of envelopes of the radio pulses of the pump signal, a series of packs of sequences of starting video pulses of the pump signal, a synchronizing sequence through the output II of the former 1 are supplied to the control input of the pump signal generator 3.
At the same time, the synchronizing sequence, a series of packets of sequences of envelopes of the radio pulses of the pump signal and a series of packets of sequences of envelopes of the dual auxiliary radio pulses through the output III of the former 1 are fed to the synchronizing input 1 of the receiver 11.
In the pump signal generator 3, the video pulses of a series of bursts of sequences of starting video pulses of the pump signal determine the beginning and end of the generated linear frequency-modulated radio pulse, in which the generated radio pulse changes its frequency from 500 MHz to 600 MHz in 10 μs. These video pulses are fed to the output of the pump signal generator 3, provided that at its input there is a video pulse of a series of packs of sequences of envelopes of the radio pulses of the pump signal. As a result, at the output of the pump signal generator 3, a series of bursts of sequences of radio pulses of the pump signal are generated, and some of the radio pulses of the pump signal are generated with the following parameters: duration 10 μs, linear frequency change from 500 MHz to 600 MHz; and the remaining radio pulses of the pump signal have parameters: a duration of 9 μs, a linear change in frequency from 510 MHz to 600 MHz. The conditional waveform of one pack of sequences of radio pulses of the pump signal is shown in figure 3, curve I.
A series of packs of sequences of radio pulses of the pump signal from the output of the pump signal generator 3 are supplied to the input of the high-frequency amplifier 5, where they are amplified and transmitted through the antenna 7 into space in the direction of the assumed location of the broadband parametric scatterer 8.
In broadband parametric scatterer 8 as a result of its irradiation with a series of packets of sequences of radio pulses of the pump signal and series of packets of sequences of dual auxiliary radio pulses, as a result of parametric generation, a response signal is re-emitted into space in the form of series of packets of sequences of radio pulses. The conditional waveform of one packet of sequences of radio pulses of the response signal is presented in figure 3, curve K.
The response signal is received by the antenna 9, amplified by a high-frequency amplifier 10 and fed to the signal input 2 of the receiver 11.
Antenna 9 also receives a series of packets of sequences of dual auxiliary radio pulses due to reflections from local objects and the underlying surface, then a series of packets of sequences of dual auxiliary radio pulses are amplified by high-frequency amplifier 10 and fed to signal input 2 of receiver 11.
The received sequences are processed in the receiver 11. The processing of the received sequences occurs at three time intervals: on the burst interval, on the sequence interval, on the radio pulse interval of the response signal.
When processing on the interval of each burst, the realizations of the first and second received sequences are added together.
The result of such processing for one packet of sequences of radio pulses of the response signal is presented in Fig. 4. Curve A corresponds to the conditional waveform of the first sequence of radio pulses of the response signal, curve B corresponds to the conditional waveform of the second sequence of radio pulses of the response signal, curve C corresponds to the result of their addition, the result of coherent addition of the radio pulses of the response signal is clearly visible.
The processing result for one pack from a series of packs of sequences of dual auxiliary radio pulses is presented in FIG. 5. Curve A corresponds to a conditional waveform of the first sequence of dual auxiliary radio pulses, curve B corresponds to a conditional waveform of the second sequence of dual auxiliary radio pulses.
The addition results for the sequence of dual auxiliary radio pulses in principle correspond to the complete mutual compensation of the auxiliary signals, since they are emitted in the first and second sequences synchronously and in antiphase. However, such complete mutual compensation does not occur due to the manifestation of random factors: noise, changes in the environment during the period of the series, etc. Therefore, it is important to ensure that during processing at time intervals equal to the sequence and duration of the radio pulse of the response signal, no jamming dual auxiliary radio pulses accumulate.
The results of processing the sequence of radio pulses of the response signal in accordance with the selected coding law are presented in Fig. 6, here curves A, B, C correspond to the steps of processing the input signal in accordance with the 3-element Barker code algorithm, and the resulting signal is shown on curve D. It is clearly seen that in the region of the main maximum, the signal amplitude increased three times.
The processing results in accordance with the selected coding law of the sequence of dual auxiliary radio pulses are presented in Fig. 7, here curves A, B, C correspond to the steps of processing the input signal in accordance with the 3-element Barker code algorithm, and the resulting signal is shown on curve D. It is clearly seen that accumulation does not occur.
Processing each radio pulse of the response signal in the filter, matched with a linear-frequency-modulated radio pulse with a linear frequency change from 250 MHz to 300 MHz, having a duration of 10 μs, will lead to the appearance of a maximum above the input signal level by the base value.
The result of a machine experiment passing through the same filter, consistent with a linear frequency-modulated radio pulse with a linear frequency change from 250 MHz to 300 MHz and having a duration of 10 μs, dual auxiliary radio pulses with a duration of 1 μs and with a linear frequency change from 255 MHz to 250 MHz is shown in FIG. On the left are the dual auxiliary radio pulses, on the right is the signal waveform at the output of the matched filter. It should be noted that the signals in the process of passing through the filter close, but do not overlap. In a short overlap region, it is essential that the initial pulses are out of phase, therefore, an increase in signal is not observed.
The output signal is observed on the screen of indicator 12.
When the output signal exceeds the detection threshold, a decision is made about the presence in the detection zone of an object marked with a broadband parametric diffuser 8.
Shaper 1 can be implemented according to [V.G. Gusev, Yu.M. Gusev. Electronics. M .: Higher School, 1991, 2nd edition revised and supplemented, pp. 489-585].
As a generator 2 of auxiliary radio pulses and a generator 3 of a pump signal, a standard generator G4-164 can be used.
As high-frequency amplifiers 4, 5, amplifiers from the standard generator G4-128 can be used. As antennas 6, 7, 9, antennas P6-33 can be used.
Broadband parametric diffuser 8 can be manufactured according to [N.Yu. Babanov, A.S. Korsakov, S.V. Lartsov. An experimental study of the amplitude-frequency properties of subharmonic scatterers // Design and Technology of Electronic Tools, 2008, No. 3, p.22-27].
As a high-frequency amplifier 10, a standard low-noise amplifier MAX 2640 can be used.
The receiver 11 can be formed from an analog-to-digital converter of the ADC ZET 230 and a signal processor TMS 320 C 2000. As an indicator 12, a Pentium 4 computer can be used.
Thus, the proposed technical solution allows to reduce the level of the interfering signal at the output of the receiver, caused by the reflections of the dual auxiliary radio pulses from the underlying surface and surrounding objects, which leads to an increase in the range of the search system.

Claims (1)

  1. A method for detecting broadband parametric scatterers, namely, that a broadband parametric scatterer is preliminarily placed on the search object, the area of the space in which the search object can be located is irradiated with a probe signal, which forms a response signal consisting of a series of sequences radio pulses of the response signal, with each pack consisting of two sequences of the same dimension, encoded in accordance with the selected binary coding law, which is a binary sequence whose opposite symbols correspond to the out-of-phase values of the phases of the high-frequency filling of the radio pulses of the response signal, for this purpose, the probing signal is emitted consisting of a series of packets of sequences of radio pulses of the pump signal in which each radio pulse is synchronized with the radio pulse of the response signal, and the instantaneous frequency of the radio pulses of the pump signal is twice the instantaneous h the frequency of the radio pulses of the response signal, in addition, the probing signal includes an auxiliary signal consisting of a series of bursts of sequences of auxiliary radio pulses, each packet consisting of two synchronous sequences of dual auxiliary radio pulses with the same dimension as the sequences of the radio pulses of the response signal, with the phases high-frequency filling of the corresponding auxiliary radio pulses for the first and second of the sequences of dual auxiliary radio pulses in each burst have opposite values, in addition, the phase of high-frequency filling of each first of the dual auxiliary radio pulses changes from the current dual auxiliary radio pulse to the next dual auxiliary radio pulse in accordance with the binary alternative coding law, for which the minimum level is ensured during synchronous accumulation according to the algorithm providing the maximum level of accumulation of the received signal in accordance with the selected binary coherent accumulation law, while the opposite symbols of the alternative binary coding law correspond to antiphase values of the high-frequency filling phase of the first of the dual auxiliary radio pulses, while the duration of each of the auxiliary radio pulses and the time interval between the trailing edge of the first and leading front of the second of the dual auxiliary radio pulses than the duration of the radio pulse of the pump signal, the moments of the front and rear the edges of the corresponding serial numbers of the auxiliary radio pulses in the packets coincide, one of the double auxiliary radio pulses is a synchronizing radio pulse, the initial phase of its high-frequency filling corresponds to the current symbol of the selected binary coding law, while one of the time moments of the radiation of the synchronizing radio pulse coincides with the leading edge of the pump pulse, at this moment in time, the instantaneous frequency of the high-frequency filling of the clock the diode pulse is half the instantaneous frequency of the high-frequency filling of the radio pulses of the pump signal, in this case, if the current characters of the selected and alternative coding laws coincide, then for the corresponding dual auxiliary radio pulses the first auxiliary radio pulse is a synchronizing radio pulse, and if the current characters of the selected and alternative coding laws do not match , then the synchronizing radio pulse is the second of the corresponding dual auxiliary radio pulses, while the instantaneous frequency of the radio pulses of the pump signal and the dual auxiliary radio pulses is changed linearly, and the durations of the first and second of the dual auxiliary radio pulses are selected so as to minimize their level at the output of the synchronous filter matched with the radio pulse of the response signal, a response signal is received, when this simultaneously compensates for series of packets of sequences of dual auxiliary radio pulses and synchronous accumulation of series of packets of the sequence of radio pulses of the response signal according to algorithms that provide the maximum level of accumulation of the received signal in accordance with the shape and internal modulation of each radio pulse of the response signal, selected by the coding law, and also by adding time implementations of the first and second sequences of radio pulses of the response signal in each of the packets of sequences of the radio pulses of the signal, when the detection threshold is exceeded, they decide on the presence of a search object in the detection zone, I distinguish iysya in that the laws of variation of the linear instantaneous frequency RF pulse RF pulse twin auxiliary pump signal and the instantaneous frequency changes are opposite, and dual ancillary RF pulses are formed so that the phase of the high-frequency are such that the RF pulses of the response signal synchronized excited in antiphase.
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