RU2159942C1 - Procedure detecting location of living objects and microwave locator for realization of procedure - Google Patents

Abstract

FIELD: search and rescue service. SUBSTANCE: procedure is intended for active probing of obstructions formed as result of emergencies and natural calamities for objective detection of presence of man with signs of life such as breathing, heart beat, stirring. Radio frequency signal with duration Tu is emitted in accordance with procedure. Reflected signal is received in fixed time interval Tn equal in duration to fixed duration Tu of emitted signal with delay τ₃ between finish of emission of signal and start of reception of reflected signal. If modulated component with frequency of pulse and/or breathing of man is detected its level is measured. Duration of reception of reflected signal is changed to decreased level of modulated component relative to its level of initial reflected radio frequency signal and to moment of finish of its arrival. Distance is found by duration of reception of reflected signal with modulated component. Microwave locator for realization of procedure incorporates modulator and transmitter composed of generator, power divider and transmitting antenna. Receiver includes receiving antenna, SHF receiver, preamplifier/demodulator, signal processing unit. Modulator with change of carrier frequency can change duration of controlling pulses and their recording. Locator is supplemented with first pulse modulator of transmitter and second pulse SHF of receiver. Modulator has controlling output coupled to controlling input of second pulse modulator to receive reflected signal by receiver with delay with regard to termination of emission of signal by transmitter and change of time of switch-on of SHF receiver. Signal processing unit can measure level of modulated component. EFFECT: enhanced quality of detection and noise immunity. 16 cl, 16 dwg

Description

 The invention relates to a search and rescue service and can be used for active sensing of debris formed as a result of accidents and natural disasters, for an objective determination of the presence of a person with signs of life: breathing, palpitations, movement.

 Various devices are known that use the principle of operation of a radio wave interferometer using a compensation channel to isolate the modulated component of the radio frequency signal corresponding to the pulse rate of a person or his breath.

 These devices are used for non-contact diagnostics, and can also be used to detect a living object in the rubble, for example, formed as a result of earthquakes, accidents or during avalanches. The main limitation of the use of such devices for the purpose of detecting living people in the rubble is the inability to select a range search range, high sensitivity to the presence of an operator working with the device.

 A known electronic system for detecting a living object, comprising a modulator and a transmitter consisting of a generator, a power divider, a transmitting antenna, a receiver consisting of a receiving antenna, a microwave receiver, a preamplifier / demodulator, a signal processing unit, the second signal output of the power divider is connected to the control the input of the microwave receiver, while one of the control outputs of the modulator is connected to the control input of the microwave receiver. (DE, A, 4241664).

 In this device, the DC component is compensated in the reflected signal at the input of the microwave receiver before amplification, which leads to additional noise introduced by the compensation means, and the modulator serves only to provide the possibility of amplification of the signal component modulated by a living object outside the 1 / f noise region. Thus, in the device at the input there is an additional source of amplitude and phase noise, which limits the minimum level of the received signal and reduces the sensitivity, and such a device cannot determine the distance to a living object.

 The closest is a method for detecting the location of a living object, which includes emitting a radio frequency signal, receiving a reflected radio frequency signal at the site of emission of the radio frequency signal, isolating a component of the received radio frequency signal, modulated in amplitude and phase, corresponding to the pulse rate and / or respiration of a living stationary object, judging by the selected component about the detection of a living object. (IEEE TRANSACTIONS ON BME, V. 33, 7, July, 1986, KUN-MU CHEN, D.MISRA, H.-R. CHUANG, "An X-band microwave Life-Detection system").

 The method provides for the compensation of the reflected microwave signal from the mass of stationary objects, the selection and analysis of the variable component of the reflected signal associated with the mentioned signs of human vital activity, based on a comparison of its amplitude and phase with their constant values of the emitted signal. The reason for using compensation is the specificity of the device implementing this method. In the presence of a reflected microwave signal from a lightproof barrier and other strongly reflecting stationary objects in the area of the radiation pattern of the device’s transceiver antenna, as well as due to the direct penetration of part of the signal from the transmitter path to the receiver path, the latter receives a high-level background signal with a constant amplitude and phase, able to go beyond the linearity range of the receiver gain. On the other hand, a radio frequency signal reflected from a living object is twice attenuated by an obstacle during the direct passage of the radiated signal and the return path of the reflected RF signal. The attenuation of signals also occurs due to the removal of a living object located behind the barrier, in proportion to the 4th power of the distance to it. In addition, the power level of the modulated component of the useful signal that carries information about the life of the object is 10 ... 1000 times less than the power of the total signal reflected from the object.

 These circumstances lead to the requirement to ensure that the transmission path of the very large dynamic energy range of the reflected RF signal reaches 100-150 dB. In this case, the dynamic energy range of the useful signal usually does not exceed 90 dB. Hence, the need arises, before the first amplifier of the receiver, to remove all useless information about stationary objects by removing the background signal. This is achieved by introducing a compensating microwave circuit, the output of which, by controlling its parameters, selects a signal approximately equal in amplitude to the background and opposite in phase. The compensating signal is summed with the received at the input of the receiver in the passive adder. The output of the adder receives power approximately equal to the difference in power of the received and background signals. The quality of the device’s work is largely determined by the quality of this compensation, its depth, fluctuations in its circuits and control circuits of its parameters.

 The known method allows you to effectively isolate information related to the vital activity of a person, however, it has limited capabilities when conducting search and rescue operations. The method does not limit the range of a person’s search in order to determine his location, has a high sensitivity to the presence of an operator working with the device. The reason for these shortcomings is the emission of a continuous time-unmodulated microwave signal, which, reflecting, summarizes all the information about objects located both in the area of the antenna pattern from its aperture plane to the maximum detection range, and in the area of its side and reverse lobes at close proximity the operator.

 The impossibility of limiting the search zone, that is, setting the minimum and maximum detection range, leads to interference from people and equipment working at the scene of the accident near the search zone, as well as from the operator himself, since the high sensitivity to isolate the modulated component is sufficient to respond to all living objects located in airspace at a considerable distance or respond to the operator due to the presence of side and reverse lobes of the antenna pattern. In addition, when clearing the blockage and removing a living object, it is possible to be injured by the used technical means, since the known method does not allow determining the distance to the location of a living object.

 The closest is a microwave locator containing a modulator and transmitter, consisting of a generator, a power divider, a transmitting antenna connected in series with its signal inputs and signal outputs and configured to emit a radio frequency signal with modulation, a receiver consisting of a receiving antenna, a microwave receiver, a preamplifier / demodulator, a signal processing unit, connected by their signal outputs to the inputs in series, and configured to receive a reflected radio a frequency signal modulated by the component of the pulse and / or respiration of a living object, and the selection of this component at the output of the preamplifier / demodulator, the second signal output of the power divider connected to the control input of the microwave receiver, the first control output of the modulator connected to the transmitter, and the second and third output of the modulator connected to the first and second control input of the preamplifier / demodulator. (US, A, 4958638).

 The advantage of this device compared to the above technical solution is its high sensitivity for determining the parameters of the modulated component due to the absence of a high level of microwave noise inherent noise due to non-ideal compensation at its input, introducing additional fluctuations in the amplitude and phase of the amplified compensated signal, however, this device can be used For non-contact diagnostic purposes only. The device does not provide the ability to arbitrarily select a search zone and determine the distance to a living object, and when probing extended sections of space with an RF signal, it has dead sensitivity zones associated with the single-channel phase detection used.

 The problem solved by the invention is to improve the quality of detection and noise immunity.

 The technical result that can be obtained by implementing the method is the selection of the detection zone in range, compression of the dynamic range of the received signals, as well as a decrease in sensitivity to the presence of other living objects outside the search zone.

 The technical result that can be obtained by performing the device is to fix the emitted radio frequency signal and receive the reflected radio frequency signal at certain time intervals relative to the emitted radio frequency signal, process these signals with reference to the trailing edges to measure the level of the modulated component and the distance to the location of a living object .

The problem is solved in that in a method for detecting the location of a living object, including emitting a radio frequency signal, receiving a reflected radio frequency signal at the site of emission of the radio frequency signal, isolating a component of the received radio frequency signal, modulated in amplitude and phase, corresponding to the pulse rate and / or respiration of a living stationary object , judgment on the selected component about the detection of a living object, according to the invention emit a radio frequency signal with a fixed duration with a T _and receive a reflected RF signal in a fixed period of time T _p equal in duration to a fixed duration T _{and an} emitted RF signal with a delay of τ _s between the end of the emission of the RF signal and the beginning of reception of the reflected RF signal, when it detects a modulated component, measure its level, then the reception time T _{p of the} reflected RF signal is changed until the level of the modulated component decreases relative to its level for the reflected a frequency signal received with a fixed duration T _and until the end of arrival of the reflected radio frequency signal, and the distance to the location of a living object is determined in accordance with the expression
D ≅ c (τ _s + T _pu ) / 2,
where c is the propagation speed of the radio frequency signal,
τ _s - the duration of the delay between the end of the radiation and the beginning of reception of the radio frequency signal,
T _PU - the duration of the reception of the reflected RF signal, at which the level of the modulated component decreased, corresponding to the interval from the beginning of reception of the reflected RF signal to the end of its arrival.

где

коэффициент затухания, а tgδ и ε - соответственно тангенс угла диэлектрических потерь и действительная часть относительной диэлектрической проницаемости преграды на частоте 1 ГГц; d - предполагаемая максимальная толщина преграды, м.There are additional options for implementing the method, in which it is advisable that:
- reduced the duration of the reception of the reflected RF signal at regular intervals;
- changed the duration of the reception of the reflected RF signal by successive approximations;
- the radio frequency signal was emitted with a frequency determined by

Where

attenuation coefficient, and tanδ and ε are the dielectric loss tangent and the real part of the relative dielectric constant of the obstacle at a frequency of 1 GHz, respectively; d is the estimated maximum thickness of the barrier, m

 The problem is also solved by the fact that in a microwave locator containing a modulator and transmitter, consisting of a generator, a power divider, a transmitting antenna connected in series with its signal inputs and signal outputs, and configured to emit a radio frequency signal with modulation, a receiver consisting of a receiver antennas, microwave receiver, preamplifier / demodulator, signal processing unit, connected by their signal outputs to inputs in series, and configured to receive a reflected RF signal, a modulated component of the pulse and / or respiration of a living object, and the selection of this component at the output of the preamplifier / demodulator, the second signal output of the power divider connected to the control input of the microwave receiver, the first control output of the modulator connected to the transmitter, and the second and third output the modulator is connected to the first and second control input of the preamplifier / demodulator, according to the invention, the modulator is made tunable with the possibility of changing the duration of the control important pulses and their fixation, the first pulse modulator of the transmitter and the second pulse modulator of the microwave receiver are introduced, the first signal output of the power divider is connected to the input of the transmitting antenna through the signal input and signal output of the first pulse modulator, and the second signal output of the power divider is connected to the control input of the microwave receiver through the signal input and signal output of the second pulse modulator, the control input of the first pulse modulator is connected to the first control output of the modulator and to fix the time of radiation of the radio frequency signal, the modulator is equipped with a fourth control output connected to the control input of the second pulse modulator for receiving the reflected radio frequency signal by the receiver with a delay relative to the end of the radiation of the radio frequency signal by the transmitter and changing the opening time of the microwave receiver, while the signal processing unit is configured to measuring the level of the modulated component.

 Additional embodiments of the device are described with the disclosure of a better embodiment of the invention.

By linking the time of emission of the radio frequency signal and the time of reception of the reflected radio frequency signal with a delay τ _s between the time of the end of radiation and the time of the start of reception, measuring the level of the modulated component and determining the duration T _{pu of} receiving the reflected radio frequency signal, at which the level of the modulated component decreased, corresponding to the interval from the beginning of the reception of the reflected radio frequency signal until the end of its arrival, it was possible to solve the problem.

 These advantages, as well as features of the present invention will become apparent during a subsequent review of the following best embodiments of the invention with reference to the accompanying drawings.

FIG. 1 depicts a functional diagram of a microwave locator for implementing the inventive method;
FIG. 2 is a timing chart explaining the claimed method, in the case of reducing the length of the reception interval of the reflected RF signal;
FIG. 3 is the same as FIG. 2, in the case of changing the reception interval by the method of successive approximations, when a part of the reflected signal occupies a smaller part of the reception area;
FIG. 4 is the same as FIG. 3, when a portion of the reflected signal occupies most of the reception area;
FIG. 5 is a functional diagram of a microwave locator with two-channel phase detection;
FIG. 6 is the same as FIG. 5, another embodiment with one transceiver antenna;
FIG. 7 is a time diagram of the emitted radio frequency signal (at the output of the first pulse modulator of the transmitter);
FIG. 8 is a timing diagram of a radio frequency clock signal at the output of a second pulse modulator of a receiver;
FIG. 9 is a timing chart of the received RF signals at the input of the microwave receiver;
FIG. 10 is a timing chart of the detected total signal at the outputs of the first and second phase detectors of the microwave receiver;
FIG. 11 is a timing chart of clock pulses supplied from the synchronizer to the first and third low-frequency phase detector;
FIG. 12 is the same as FIG. 11, pulses supplied from the synchronizer, the second and fourth low-frequency phase detector;
FIG. 13 is a functional diagram of an amplifier installed at the output of a subtractor or adder of a low-frequency phase detection unit;
FIG. 14 is the same as FIG. 13, a two-channel option;
FIG. 15 is the same as FIG. 13, a three-channel version;
FIG. 16 is a functional diagram of a measurement unit.

The method can be implemented by the device (Fig. 1), the operation of which is illustrated by timing diagrams (Fig. 2, 3, 4). The transmitter 2 due to the synchronization of the signal by the modulator 1 and the first pulse modulator 11 emits a microwave frequency signal in the radiation interval T _and . The microwave receiver 8 is opened with a delay τ _Z1 through τ time interval from the beginning _of the emission of the RF signal due to synchronize the modulator 1 and the second width modulator 12. Because the obstruction in reality has a limited length, the radiation duration T _and can easily be determined from the equation T _and = 2 (D _max + D _min ) / c, in which D _max , D _min are the far and near borders of the search zone, respectively, and c is the propagation velocity of radio waves in the medium. The delay time is chosen equal to τ _s = 2D _min / s.
The reflected RF signal is received by the microwave receiver 8 in the interval T _p equal to the interval T _and , due to its opening for this duration by the second pulse modulator 12. When choosing such durations of the intervals T _and , T _p , τ _{s, the} microwave cut off part of the received total reflected RF signal the receiver 8, since it is open on the interval T _p (in Fig. 2, 3, 4, the reflected RF signal from a living object is simplified by vertical hatching).

When a modulated component is detected as a result of processing the RF signal by the receiver 6, preamplifier / demodulator 9 and signal processing unit 10, the distance to a living object can easily be determined by the delay time T _x arrival of the reflected RF signal relative to the emitted. However, since the front of the incoming signal is cut off, this delay can be determined from the trailing edges of the emitted and reflected signals. For this, the duration T _{pu of} receiving the reflected RF signal is determined, at which the level of the modulated component corresponding to the interval from the beginning of receiving the reflected RF signal to the time it arrives will decrease (Fig. 2-4).

The duration T _p can be measured in various ways, depending on the algorithm adopted for processing the change in the opening interval of the microwave receiver 6. You can reduce the time T _p for receiving the reflected RF signal at equal intervals Δ (Fig. 2) until the level of the modulated component in the received signal will not decrease. Then Tx ≅ τ _s + T _{s 5} = τ + T _ny distance D = cTx / 2 ≅ (τ ₃ + T _ny) / 2. However, in this case, to obtain a satisfactory error, the discreteness Δ must be chosen sufficiently small in the interval of accuracy of the measurement of the trailing edge, which is a rather lengthy operation and, although it simplifies the processing algorithm, the speed of determining the range of the device decreases.

To increase the speed of determining the range D, it is advisable to change the duration T _{p the} reception of the reflected RF signal by successive approximations (Fig. 3, 4). When a modulated component is detected, the reception interval T _{p is} reduced by half (Fig. 3) and its level is measured on the interval T ₁ . If the levels of the modulated component for T _p and T ₁ are equal, then reduce its duration T ₁ in half, T ₂ = T _1/2 . When reducing the level of the frequency component, increase the reception interval T ₃ = (T ₁ + T ₂ ) / 2. The procedure for halving the interval by equal levels of the modulated component and increasing the reception interval when decreasing the level of the modulated component by adding the duration of the time interval corresponding to an unchanged level of the modulated component for the last interval with the duration of the time interval corresponding to the reduced level of the modulated component and dividing the resulting amount carried out in half until the required specified accuracy is achieved. Practically enough, five to seven measurement steps are needed to determine the interval T _PU corresponding in terms of the measurement error of the range D to one meter, which fully meets the requirements of conducting search and rescue operations and removing the victim from under the rubble.

Upon receipt of the modulated reflected signal from the far detection zone (Fig. 4), the above procedure is also carried out. T ₁ = T _p / 2. With a decrease in the level of the modulated component, T ₂ = (T ₁ + T _p ) / 2. If the level of the modulated component is again less than its previous level, then T ₃ = (T _p + T ₂ ) / 2, etc. Thus, the essence of the claimed method consists in constantly monitoring the level of the modulated component for different ranges D _i , where i is the measurement step, and finding exactly the magnitude of the range D, which corresponds to the border of decrease of the modulated component and its constant value.

 To carry out such measurements, it is necessary to determine the level of the modulated component with high accuracy. As shown by numerous studies, the quality of the selection of the modulated component depends not only on the quality of the receiver, the level of its own noise, the identity of the local oscillator channel of the emitted radio frequency signal, sensitivity and the like, but also on the frequency of the emitted radio frequency signal. So, at different radiation frequencies by antennas with equal effective surfaces for the same sensing object, one can obtain different values of the levels of the selected modulated components depending on the properties of the obstacle. As a result, the dependence is approximated, which makes it possible to isolate those signal frequencies at which the level of the modulated component takes maximum values when using antennas with equal effective surfaces.

где

коэффициент затухания, а tgδ и ε - соответственно тангенс угла диэлектрических потерь и действительная часть относительной диэлектрической проницаемости преграды на частоте 1 ГГц; d - предполагаемая максимальная толщина преграды, м.

Where

attenuation coefficient, and tanδ and ε are the dielectric loss tangent and the real part of the relative dielectric constant of the obstacle at a frequency of 1 GHz, respectively; d is the estimated maximum thickness of the barrier, m

 So, for example, for a blockage formed by reinforced concrete structures at d = 2 m, the best radiation frequency f is 0.7 GHz, and for a brick wall at d = 0.5 m, the best frequency f ≈ 6.2 GHz at any distance to the object to be detected in free space.

 To ensure operation at a frequency corresponding to the maximum detection efficiency, the device may have broadband paths of the transmitter 2 and receiver 6, a generator 3 with frequency switching or tuning and interchangeable transmit and receive antennas 5, 7, for different frequency ranges. In this case, the operating frequency is selected depending on the thickness and electrical parameters of the barrier in accordance with the empirical dependence obtained by the authors.

 To implement the inventive method, the microwave locator (Fig. 1) has a modulator 1 and a transmitter 2. The transmitter 2 consists of a generator 3, a power divider 4, a transmitting antenna 5 connected in series. The transmitter 2 is configured to emit a radio frequency signal with modulation defined by the modulator 1. The receiver 6 consists of a receiving antenna 7, a microwave receiver 8, a preamplifier / demodulator 9, a signal processing unit 10 connected in series. The second signal output of the power divider 4 is connected to the control input of the microwave receiver 8, the first control output of the modulator 1 is connected to the transmitter 2, and the second and third output of the modulator 1 are connected respectively to the first and second control input of the preamplifier / demodulator 9.

 The modulator 1 is made tunable with the ability to change the duration of the control pulses and their fixation. The first pulse modulator 11 and the second pulse modulator 12 are introduced into the device. The first signal output of the power divider 4 is connected to the input of the transmitting antenna 5 through the first pulse modulator 11, and the second signal output of the power divider 4 is connected to the control input of the microwave receiver 8 through the second pulse modulator 12 The control input of the first pulse modulator 11 is connected to the first control output of the modulator 1 to fix the time of radiation of the radio frequency signal. The modulator 1 is equipped with a fourth control output associated with the control input of the second pulse modulator 12 for receiving the reflected RF signal, a receiver 6 with a delay relative to the end of the radiation of the radio frequency signal, the transmitter 2 and the opening time of the microwave receiver 8. The signal processing unit 10 is configured to measure the level modulated component.

 To eliminate the dead zones of sensitivity of the receiver 6, two-channel quadrature phase detection can be applied, which is reflected in FIG. 1 by two connections from the microwave receiver 8 through the preamplifier / demodulator 9 to the signal processing unit 10.

 In the technical implementation of the device (Fig. 1), individual blocks from known technical solutions can be used, however, due to the introduction of new functional elements, new relationships are formed between the functional elements. A power amplifier 13 can be introduced into the transmitter 2 (Fig. 5) and the output of the pulse modulator 11 is connected to the input of the transmitting antenna 5 through the power amplifier 13.

 Circulator 14 (Fig. 6) can also be introduced, the transmitting antenna 5 and the receiving antenna 7 (Fig. 1) are made in the form of a single transceiving antenna 15 (Fig. 6). The first pulse modulator 11 is connected to the transceiver antenna 15 through the first arm and the second arm of the circulator 14 in the circulation direction, and the microwave receiver 8 is connected to the transceiver antenna 15 through the second and third arm of the circulator 14.

The modulator 1 (Fig. 5, 6) is based on the clock generator 16 and the synchronizer 17, connected by its clock input to the output of the clock generator 16. The outputs of the synchronizer 17 respectively serve as the first, second, third and fourth output of the modulator 1 (Fig. 1). The signal processing unit 10 is made of a measurement unit 18, a control unit 19 and an indicator 20. The input of the measurement unit 18 serves as an input to the signal processing unit 10, the information control output of the measurement unit 18 is connected to the input of the control unit 19, and the signal output to the signal input of the indicator 20. The first control output of the control unit 19 is connected to the control input of the synchronizer 17, and the second control output of the control unit 19 is connected to the control input of the indicator 20. The control unit 19 implements all the necessary functions related to by switching individual blocks and setting parameters for changing the reception interval T _p according to the selected algorithm depending on the measured level of the modulated component in the measurement unit 18. Therefore, it is directly connected to the control input of the synchronizer 17.

 To ensure two-channel quadrature phase detection, the microwave receiver 8 (Fig. 5, 6) is made of the first and second phase detectors 21, 22, a quadrature power divider 23 in half, an in-phase power divider 24 in half, the signal input of which is connected to the output of the receiving antenna 7 or transceiver antenna 15 through the circulator 14. The first output of the common-mode divider 24 is connected to the first input of the first phase detector 21, and the second to the first input of the second phase detector 22. The output of the second pulse modulator 12 is connected to stroke quadrature divider 23, which serves as a control input of the microwave receiver 8. The first output of the quadrature divider 23 is connected to a second input of the first phase detector 21, and the second output - to a second input of the second phase detector 22.

 A high-frequency amplifier 25 can be introduced into the microwave receiver 8 (Fig. 5, 6), and the signal input of the common-mode divider 24 is connected to the output of the receiving antenna 7 through the amplifier 25. The amplifier 25 can be made low noise.

 A power limiter 26 can also be introduced into the microwave receiver 8 (Fig. 6) and the signal input of the high-frequency amplifier 25 is connected to the output of the receiving antenna 7 or the transceiving antenna 15 through the power limiter 26.

 In the case of large values of the radiated power necessary to ensure a high detection range, it is advisable to use the option with a receiving antenna 7 (Fig. 5) and a power limiter 26 (not shown in Fig. 5), included between the output of the receiving antenna 7 and the input of the amplifier 25.

 To select a useful signal, the preamplifier / demodulator 9 (Fig. 5, 6) is made of the first and second band-pass filters 27, 28, the first and second clock amplifiers 29, 30, the first, second, third and fourth low-frequency phase detectors 31, 32, 33, 34, the first and second low-frequency amplifier 35, 36, the adder 37 and the subtractor 38. The input of the first bandpass filter 27 is connected to the output of the first phase detector 21, and its output is connected to the input of the first clock amplifier 29. The input of the second band-pass filter 28 is connected to the output of the second phase detector 22, and its output to the input of the second clock amplifier 30. The output of the first amplifier 29 is connected to the signal inputs of the first and second low-frequency phase detector 31, 32, and the signal output of the second amplifier 30 is connected to the signal inputs of the third and fourth low-frequency phase detector 33, 34. The second output of modulator 1 is connected to the control inputs of the second and fourth low-frequency phase detector 32, 34, and the third control output of modulator 1 is connected to the control inputs of the first and third low-frequency phase detector 31, 33. The phase of the control pulse nosti third clock output from the modulator 1 is shifted by a quarter period relative to the phase clock sequence at its second output. The outputs of the first and fourth low-frequency phase detector 31, 34 are connected to the first and second input of the subtractor 38, and the outputs of the second and third low-frequency phase detector 32, 33 are connected to the first and second input of the adder 37. The output of the adder 37 is connected to the input of the first amplifier 35, and the output of the subtractor 38 is connected to the input of the second amplifier 36. The outputs of the first and second amplifier 35, 36 are connected to the signal processing unit 10.

 The device operates (Fig. 5, 6) as follows.

Modulator 1 generates four control pulse sequences with a clock frequency of F = 1 / T. From the first output of the synchronizer 17 to the control input of the first pulse modulator 11 a unipolar sequence of duration T _and (envelope in Fig. 7), from the second and third outputs of the synchronizer 17 to the control inputs of the first, second, third and fourth low-frequency phase detectors 31-34 in accordance with a circuit (Fig. 5, 6) a bipolar sequence of equal amplitude and duration T / 2, with a shift T / 4 (Fig. 11, 12), a sequence supplied to the control inputs of the first and third low-frequency phase detectors 31, 33 ahead of the time equal to T / 4, the sequence supplied to the reference inputs of the second and fourth low-frequency phase detectors 32, 34. From the fourth output of the synchronizer 17 to the control input of the second pulse modulator 12 unipolar sequence with a duration of T _and = T _p with a delay τ _z1 = τ _s + T _and relative to the sequence supplied to the control input of the first pulse modulator 11 (envelope in Fig. 8). The clock frequency is selected in accordance with the expression T = 2D _max / s, where D _max is the limiting range of the search zone boundary, c is the propagation velocity of the electromagnetic wave, T _and = 2D _tr / s, where D _tr is the possible detection range, which can always be judged by the size of the blockage. The selected delay time τ _s = 2D _min / s (Fig. 7, 8) is determined by the necessary deadband near the receiving antenna 7 to eliminate the near signal from the obstacle and the influence of the operator. D _min <D _tr <D _max . T _and <T.

The first sequence with a pulse duration T _and fed to the control input of the first pulse modulator 11 which opens transmitter path 2 at the time of pulse actions and radiates the RF signal U _m1 (FIG. 7). Reflected radio frequency signals U _c from objects located at different ranges (Fig. 9) are received at a receiving antenna 7 (Fig. 5) or a transceiver antenna 15 (Fig. 6) at the input of a high-frequency amplifier 25. The amplified microwave signal is fed to the signal input of the in-phase divider 24 of the microwave receiver 8. The heterodyne signal from the second output of the power divider 4 is received at the signal input of the second pulse modulator. The radio frequency pulse U _m2 generated by the second pulse modulator 12 is received at the signal input of the quadrature divider 23 (Fig. eight). The common-mode divider 24 and the quadrature divider 23 have a phase shift of 90 degrees between the signals at their outputs. The pulse modulator 12 under the control of the second sequence with a pulse duration T _and synchronizer 17 unlocks the local oscillator path after a time τ _s1 equal to τ _s + T _and , after the end of the action of the radio frequency pulse U _{m1 of the} transmitter path 2, the diagram U _m2 (Fig. 8). Moreover, most of the reflected RF signal (Fig. 9) coming from the near zone with the corresponding delay times τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{s1}}$ , τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{h2}}$ for further processing is not received, which is simplistically shown in FIG. 9 and FIG. 10. Form U _ss the detected sum signal on the outputs of the first and second phase detectors 22, 23 has the approximate form shown in FIG. 10. From the diagram it follows that the farther the object is located, the smaller the amplitude of the detected reflected signal, however, its longer. This circumstance leads to a narrowing of the dynamic energy range of the detected signals reflected from objects at different ranges, since the duration of each signal and, therefore, its energy, defined as the product of the detected pulse power and its duration (area), are directly proportional to the distance to the reflecting object. Based on the well-known radar formula, it is easy to show that this dynamic range is approximately equal to the square root of the dynamic range obtained in the case of using a continuous or short-pulse probe signal.

An additional narrowing of the dynamic range can be obtained by introducing a power limiter 26 to limit the amplitude of the pulse signals reflected from objects located directly near the receiving antenna 5 (or transceiving antenna 15), and choosing the delay time τ _s accordingly. The effect of the power limiter 26 on the signals reflected from farther objects will be very small, since they have a longer duration and a smaller amplitude. Thus, the fact of a significant narrowing of the dynamic range of the received signals makes it possible to abandon a significant part of the elements associated with the compensation of the signal in the receiving path and its control, which leads to an increase in the sensitivity of the device by removing an additional noise source and reducing the detection time of the object.

 In the claimed device for eliminating sensitivity dips, which has a range-dependent oscillatory character in single-channel phase detection, two-channel phase detection with reference (heterodyne) microwave signals phase-shifted by 90 degrees is used. At the same time, two band-pass filters are connected to the clock signal path directly to the low-frequency signal outputs of the first and second phase detectors 21, 22: the first band-pass filter 27 and the second band-pass filter 28 (Fig. 5, 6) with the center frequency F of the pulse base and the band required for the required signal-to-noise ratio at the output of the path. The amplitudes of the sinusoidal signals of the pulse repetition rate at the output of the first and second bandpass filters 27, 28 will be approximately directly proportional to the area of their detected pulses. Further, these signals are amplified by the first and second 29, 30 clock frequencies and are fed in pairs to the signal inputs of the first, second, third and fourth low-frequency phase detectors 31-34.

The radio pulses arriving at the signal inputs of the first and second phase detectors 21 and 22 from the output of the common-mode divider 24 of the microwave receiver 8 can be represented as:
u _s = U _s / 2cos (wt + Ф _s ),
and the output of the quadrature divider 23 in the form:
u _g1 = U _g / 2cos (wt + _{f g} ),
u _g2 = U _g / 2cos (wt + Ф _g + 90 ^o ) = -U _g / 2sin (wt + Ф _g ),
where w is the carrier frequency of the radio frequency signal,
F _s , _{f g} - initial phases,
U _with U _g - the amplitude of the pulses.

Since, as a first approximation, phase detectors are signal multipliers, then during the period when the envelopes of the radio pulses of the local oscillator and receiver paths overlap, we obtain signals proportional to the output of the first and second phase detectors 21 and 22
u _c ≅ cos (wt + Ф _c ) cos (wt + Ф _g ),
u _c ≅ cos (wt + Ф _c ) cos (wt + Ф _g +90 ^° ).
Since the radio pulses follow with a repetition frequency F, then after filtering in the bandpass filters 27, 28 and amplifying the amplifiers 29, 30 at the output of the latter, we obtain sinusoidal clock signals:
u _у1 = U _у cos (Ф _г - Ф _с ) cos (2πFt - Ф _у ),
u _у2 = -U _у sin (Ф _г - Ф _с ) cos (2πFt - Ф _у ),
where Ф _у is the sum of the phases of the signal delay in the bandpass filters 27, 28 and the amplifiers 29, 30 of the clock frequency, assuming their parameters are the same for both channels, and the phases of the first harmonic of the clock frequency of the detected complex pulse signal of the form U _ss , shown in FIG. ten.

From the output of the first and second amplifiers 29, 30, these signals are fed to the signal inputs of the low-frequency phase detectors 31-34, from the first amplifier 29 to the signal inputs of the first and second low-frequency phase detectors 31, 32, and from the second amplifier 30 to the signal inputs of the third and fourth low-frequency phase detectors 33, 34. On the other, reference control inputs of these low-frequency phase detectors from the second and third outputs of the synchronizer 17 are received bipolar pulse sequence clock frequency F, the form of which s shown in FIG. 11 and 12. Since the useful information in the sinusoidal signals u _у1 and u _{у2 is} contained in the modulated parameters U _у and Ф _с , and the clock frequency F significantly exceeds the upper frequency of the useful signal modulating these parameters, their selection is carried out in low-frequency phase detectors 31- 34 by multiplying the signals of the first harmonics of the clock frequency from the output of amplifiers 29, 30 and reference signals from the output of the synchronizer 17 with their subsequent low-pass filtering.

Presenting the reference signals in the form of:
u ₀₁ = U ₀ cos (2πFt) at the control inputs of the second and fourth low-frequency phase detectors 32, 34
and u ₀₂ = U ₀ cos [2πF (tT / 4)] at the control inputs of the first and third low-frequency phase detectors,
we obtain the following signal expressions at the outputs of low-frequency phase detectors 31-34:
The output of the first low-frequency phase detector 31:
u _d1 = kU _y cos (F _r - F _c) cos (2πFt - F _y) U ₀ cos (2πFt) = kU ₀ U _y cos (F _r - F _c) cosF _y; The output of the second low-frequency phase detector 32:
u = kU _{g2 y} cos (F _r - F _c) cos (2πFt - F _y) U ₀ cos [2πF (tT / 4)] = kU U _{y 0} cos (F _r - F _c) sinF _y;
The output of the third low-frequency phase detector 33:
u _q3 = -kU _y sin (F _r - F _c) cos (2πFt - F _y) U ₀ cos (2πFt) = -kU U _{y 0} sin (F _r - F _c) cosF _y;
The output of the fourth low-frequency phase detector 34:
_e4 u = -kU _y sin (F _r - F _c) cos (2πFt - F _y) U ₀ cos [2πF (tT / 4)] = -kU U _{y 0} sin (F _r - F _c) sinF _y;
where k is the conversion coefficient of low-frequency phase detectors.

The signals at the outputs of the low-frequency phase detectors 31-34 are described by different expressions, however, they can be converted into two quadrature ones by summing in the adder 37 the signals from the second and third low-frequency phase detectors 32, 33, and subtracting the signal received at the output of the fourth low-frequency phase detector 34, from the signal received at the output of the first low-frequency phase detector 31, in the subtractor 38. In accordance with this procedure, after a simple trigonometric transformation, from the output of the adder 37 we get:
u u + _{q2 q3} = kU U _{y 0} sin (F _c + F _y - F _z).

From the output of the subtractor 38 we get:
u _d1 - u _e4 = kU U _{y 0} cos (F _c + F _y - F _z).

The need for such processing arises due to the fact that the phase of the signal Ф _с + Ф _у , consisting of a random constant related to the distance to the detection object and taking any values in the interval 0 ... 2π + 2πn (n is an integer), and from of a small modulated component, adding up to a constant value of Ф _г , can bring the total phase to the low tangential sensitivity region of low-frequency phase detectors 31-34 in any of the channels. In this case, in another channel, the sensitivity, on the contrary, increases, since the channels are in a quadrature ratio, which makes it possible to isolate the information components of these signals U _у and Ф _с during subsequent quadrature processing.

The signals from the outputs of adder 37 and subtractor 38, as shown in FIG. 5, 6, are supplied to the inputs of the identical first and second amplifier 35 and 36, in which the constant, non-information component is suppressed and the variable is amplified, associated with the modulation of the parameters U _у and Ф _{with the} processes of breathing, heartbeat and human movement. Identical amplifiers 35, 36 can be implemented through various circuitry solutions.

 For example, in FIG. 13-15, embodiments of amplifier 35 are shown for devices that do not require extreme sensitivity. In such devices, the minimum level of the useful signal amplified in the previous stages significantly exceeds 1 / f the noise of the amplifier itself, and their influence during low-pass filtering can be neglected. You can use a single-channel option (Fig. 13), in which a high-pass filter 39, an intermediate amplifier 40, a low-pass filter 41 and a useful signal amplifier 42 are connected in series. A filter 39 with a cutoff frequency corresponding to the minimum detectable respiration rate (of the order of 0.1 Hz) passes only the variable component of the signal, which is amplified by the intermediate amplifier 40. The filter 41 limits the band of the processed signals to one of the higher harmonics of the heartbeat signals or to the upper recorded Doppler frequency, associated with the movement of the object. In the two-channel version (Fig. 14), only the breathing signal is allocated in the first channel, in the second - all the others. The cutoff frequency of the filter 41 is chosen equal to the cutoff frequency of the filter 39 (0.6 ... 0.7 Hz). The signals of the channels are received for further processing separately. In the three-channel version (Fig. 15), the regions of the respiratory, heartbeat, and human movement frequencies are appropriately divided. Separation of the frequency domain of the useful signal is justified both in subsequent analog processing in order to obtain as much information as possible about the object, and in digital processing in order to equalize the dynamic ranges of the signals in the channels by choosing different gain factors in them, which will limit the bit depth of the analog-to-digital converter digital system. For devices with increased sensitivity, it is necessary to introduce additional modulation of the signal with a frequency outside the region of 1 / f noise, and carry out compensation at this frequency. In this case, the circuit of the amplifier 35 is complicated.

 Filtered signals from the outputs of the first and second amplifiers 35, 36 are received for further processing in the signal processing unit 10. Processing can be carried out either by analog means or by a digital processor after analog-to-digital conversion. The result of the processing is the isolation and measurement of the parameters of the information (variable) component of the signal associated with fluctuations of the radar target due to the processes of respiration, heartbeat or human movement. The signal processing unit 10 can also be performed by various circuitry solutions.

For example, the quadrature signals from the outputs of the channels of the first and second amplifier 35, 36 can be detected by amplitude detectors 43, 44 (Fig. 16). Then these signals are summed up in the adder 45 of the detected signal and the summed signal is fed to the inputs of the integrator 46 and the first comparator 47. The output of the integrator 46 is connected to the input of the second comparator 48. The first comparator 47 generates triggering pulses for the waiting multivibrator 49 for each exceeding the summed signal level U _p1 . The waiting multivibrator 49 generates from them pulses of the same duration, the frequency of which is measured by the counter 50 and can be shown on the indicator 20. The signal accumulated in the integrator 46 is fed to the second comparator 48, which for some time, the limit of which is set, compares the accumulated level with threshold voltage U _p2 . If the specified threshold is exceeded for a given time interval, the second comparator 48 gives a signal to the signaling device 51. When the specified time interval has elapsed, the integrator 46 is reset and the process is repeated. The signal levels in all channels can be observed by indicator 20. Such a processing unit is used for each channel of the first and second amplifier 35, 36.

 Since the above scheme is quite complicated, it is advisable to apply digital processing. In digital processing (not shown in the drawings), the signal processing unit 10 should include an analog-to-digital converter, a processor, and an indicator 20 in the form of a display. Functional schemes and processing techniques in this case are known from other technical solutions. In this case, digital narrow-band filtering is used, spectral analysis based on the Fourier transform block with the corresponding representation of the processing result on the display.

 The parameters of the microwave locator are controlled by the control unit 19 in order to fix the search area for quick viewing of the maximum space, detuning from interference, and determining the distance to the detected object. In the case of digital signal processing, you can combine this function with the control function in one device - a computer.

By changing during operation _and the duration T may also, as in the proposed method to measure distance to the detection object on the basis of reduction or loss of signal from it _and with decreasing T. Moreover, to ensure a temporary separation of the processes of radiation, delay and reception, the ratio T / T _and > 2 should be maintained. To reduce the interference introduced by far-located objects, this ratio should be as large as possible. However, with an increase in the ratio, the duty cycle of the received pulses increases, which leads to a decrease in the sensitivity of the device, therefore, the parameter T must be fixed to perform specific tasks.

 The most successfully claimed method of detecting the location of a living object and a microwave locator can be used in technical means of search and rescue services to objectively determine the presence in the rubble of a person with signs of life.

Sources of information
1. U.S. Patent No. 4,967,751.

 2. German patent N 4241664.

 3. The journal "IEEE TRANSACTION ON INSTRUMENTATION AND MEASUREMENT". Bd. 40, Nr. 4, August, 1991, NEW YORK, US, pp. 747-750, CHUANG, CHEN, CHEN, "Automatic clutter-Canceler for Microwave Life-Detection Systems".

Claims (16)

1. A method for detecting the location of a living object, including emitting a radio frequency signal, receiving a reflected radio frequency signal at a place of radiating an RF signal, isolating a component of a received RF signal, modulated in amplitude and phase, corresponding to the pulse rate and / or respiration of a living stationary object, judging by the selected component of the detection of a living object, characterized in that they emit a radio frequency signal with a fixed duration T, receive a reflected radio channel frequency signal in a fixed period of time Tp, equal in duration to a fixed duration Ti of the emitted radio frequency signal with a delay of τ ₃ between the end of the radiation of the radio frequency signal and the beginning of reception of the reflected radio frequency signal, when a modulated component is detected, its level is measured, then the duration of the reception of the reflected radio frequency signal is changed to reduce the level of the modulated component relative to its level for the reflected RF signal received from the fixed bathtub of duration Ti, and until the end of the arrival of the reflected radio frequency signal, and the distance to the location of a living object is determined in accordance with the expression
D ≅ c (τ ₃ + T _PU ) / 2,
where c is the propagation velocity of the radio frequency signal;
τ ₃ - the duration of the delay between the end of the radiation and the beginning of reception of the radio frequency signal;
T _PU - the duration of the reception of the reflected RF signal, at which the level of the modulated component decreased, corresponding to the interval from the beginning of reception of the reflected RF signal to the end of its arrival.  2. The method according to claim 1, characterized in that when detecting a modulated component, the reception time of the reflected RF signal is reduced at regular intervals.  3. The method according to claim 1, characterized in that when the modulated component is detected, the duration of the reception of the reflected RF signal is changed by successive approximations. 4. The method according to claim 1, characterized in that the radio frequency signal is emitted with a frequency corresponding to the expression

Where

attenuation coefficient, tanδ and ε, respectively, the dielectric loss tangent and the real part of the relative dielectric constant of the obstacle at a frequency of 1 GHz;
d is the estimated maximum thickness of the barrier, m  5. A microwave locator comprising a modulator and a transmitter, consisting of a generator, a power divider, connected by their signal inputs to the signal outputs in series, of a transmitting antenna, and configured to emit a radio frequency signal with modulation, a receiver, consisting of a receiving antenna, a microwave receiver, and a preamplifier / demodulator, signal processing unit, connected by its signal outputs to inputs in series, and configured to receive a reflected RF signal, modules the component of the pulse and / or breathing of a living object, and the selection of this component at the output of the preamplifier / demodulator, the first control output of the modulator is connected to the transmitter, and the second and third output of the modulator are connected to the first and second control input of the preamplifier / demodulator, respectively, characterized in that the modulator is tunable with the ability to change the duration of the control pulses and their fixation, introduced the first pulse modulator of the transmitter and the second pulse modulator of the microwave receiver ka, the first signal output of the power divider is connected to the input of the transmitting antenna through the signal input and signal output of the first pulse modulator, and the second signal output of the power divider is connected to the control input of the microwave receiver through the signal input and signal output of the second pulse modulator, the control input of the first pulse modulator is connected with the first control output of the modulator for fixing the time of radiation of the radio frequency signal, the modulator is equipped with a fourth control output associated with the control the input of the second pulse modulator for receiving the reflected radio frequency signal by the receiver with a delay relative to the end of the radiation of the radio frequency signal by the transmitter and changing the opening time of the microwave receiver, while the signal processing unit is configured to measure the level of the modulated component.  6. The microwave locator according to claim 5, characterized in that the microwave receiver is configured for two-channel phase detection.  7. The microwave locator according to claim 5, characterized in that the power amplifier is inserted into the transmitter, and the signal output of the first pulse modulator is connected to the input of the transmitting antenna through the signal input and output of the power amplifier.  8. The microwave locator according to claim 5, characterized in that the circulator is introduced, the transmitting antenna and the receiving antenna are made in the form of a single transceiver antenna, the first pulse modulator is connected to the transceiver antenna through the circulator arm and its second arm in the circulation direction, and the microwave receiver is connected with a transceiver antenna through the second and third arm of the circulator in the direction of circulation.  9. The microwave locator according to claim 5, characterized in that the modulator is made of a clock generator and a synchronizer connected by its clock input to the output of the clock generator and the outputs of which serve respectively as the first, second, third and fourth output of the modulator, the signal processing unit is made of a block measurement, control unit and indicator, and the input of the measurement unit serves as the input of the signal processing unit, the control output of the measurement unit is connected to the input of the control unit, and the signal output to the signal input cator, the first control output of the control unit is connected to the control input of the synchronizer, and the second control output of the control unit is connected to the control input of the indicator.  10. The microwave locator according to claim 6, characterized in that the microwave receiver is made of first and second phase detectors, a quadrature power divider in half, an in-phase power divider in half, the signal input of which is connected to the output of the receiving antenna, the first output is connected to the first input of the first phase detector, and the second with the first input of the second phase detector, the output of the second pulse modulator is connected to the input of the quadrature power divider in half, which serves as the control input of the microwave receiver, the first quad output a power divider in half is connected to the second input of the first phase detector, and the second output is connected to the second input of the second phase detector.  11. The microwave locator of claim 10, characterized in that a high-frequency amplifier is inserted into the microwave receiver, the signal input of the common-mode power divider is connected in half to the output of the receiving antenna through the high-frequency amplifier.  12. The microwave locator according to claim 11, characterized in that a power limiter is introduced into the microwave receiver, and the signal input of the high-frequency amplifier is connected to the output of the receiving antenna through the signal output and the signal input of said power limiter.  13. The microwave locator according to claim 10, characterized in that the preamplifier / demodulator is made of a first and second bandpass filter, a first and second clock amplifier, a first, second, third and fourth low-frequency phase detector, a first and second amplifier, an adder and a subtractor moreover, the signal input of the first bandpass filter is connected to the signal output of the first phase detector, and its signal output is connected to the signal input of the first clock amplifier, the signal input of the second bandpass filter with is dined with the signal output of the second phase detector, and its signal output with the signal input of the second clock amplifier, the signal output of the first clock amplifier is connected to the signal inputs of the first and second low-frequency phase detector, and the signal output of the second clock amplifier is connected to the signal inputs of the third and the fourth low-frequency phase detector, the second output of the modulator is connected to the control inputs of the second and fourth low-frequency phase detector, and a third the control output of the modulator is connected to the control inputs of the first and third low-frequency phase detector, the phase of the control pulse sequence of the third frequency output of the modulator is shifted by a quarter of the period relative to the phase of the sequence of the clock frequency at its second output, the outputs of the first and fourth low-frequency phase detector are connected to the first and second the input of the subtractor, and the outputs of the second and third low-frequency phase detector are connected to the first and second input, the sum ora, the adder output is connected to the input of the first amplifier and the output of the subtractor is connected to the input of the second amplifier, the outputs of the first and second amplifier connected to the signal processing unit.  14. The microwave locator according to item 13, wherein the first and second amplifier, respectively, is made of a high-pass filter circuit, an intermediate amplifier, a low-pass filter, a useful signal amplifier, connected in series.  15. The microwave locator of claim 14, wherein each of said first and second amplifiers is multi-channel, wherein one channel is configured to isolate a modulated component corresponding to breathing of a living object, the second channel is configured to isolate a modulated component corresponding to the heartbeat of a living object, the third - corresponding to the movement of a living object.  16. The microwave locator according to item 13, wherein the measuring unit of the signal processing unit is made of the first and second amplitude detectors, the adder of the detected signal, the integrator, the first and second comparator, the leading multivibrator, counter, signaling device, the signal input of the first amplitude detector is connected with the signal output of the first amplifier, and the signal input of the second amplitude detector is connected to the signal output of the second amplifier, the outputs of the first and second amplitude detector are connected respectively, with the first and second input of the adder of the detected signal, the output of which is connected to the signal input of the integrator and the signal input of the first comparator, the other input of which is threshold, the signal output of the integrator is connected to the signal input of the second comparator, the other input of which is threshold, and its output is connected with a signaling device, the signal output of the integrator is also connected to the first input of the indicator of the signal processing unit, the signal output of the first comparator is connected to the signal input, waiting first multivibrator whose signal output is connected to the counter, and counter output is connected to the second input of the indicator.

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