WO2008041883A1

WO2008041883A1 - Pulsed ultra-wideband sensor

Info

Publication number: WO2008041883A1
Application number: PCT/RU2006/000683
Authority: WO
Inventors: Igor Yakovlevich Immoreev; Sergey Vitalievich Samkov; Sergey Nikolaevich Pavlov
Original assignee: Hauan, Terje
Priority date: 2006-10-06
Filing date: 2006-12-20
Publication date: 2008-04-10
Also published as: RU2321341C1

Abstract

A respiration control sensor comprises a control unit (1) for forming a time delay, a probing signal forming path with a coherent radio pulse generator (2), a transmitting antenna (3) and a receiving antenna (4), a probing signal transmitter path, a return signal receiver path with two quadrature channels for processing of the return signal, a processing block (6) providing recovery of the law of movement of the investigated subject, and a data processing and displaying block (7). The sensor also includes a phase-shifting circuit (14), whose input is coupled to the probing signal forming path and output is coupled to an input of a signal mixer (20) in one of the quadrature channels. The inputs of the processing block (6) are coupled to an output of an analog-to-digital converters (19 and 24). The invention provides an increase in phase sensitivity of the sensor and enables in controlling the respiration parameters of the movable investigated subjects.

Description

PULSED ULTRA- WIDEBAND SENSOR

Field of the invention

The invention relates to medical diagnostic instruments for investigating physiological functions of living organisms, in particular, a radiolocation means for diagnosing of patients' respiration parameters under stationary and field conditions. The sensor implemented according to the claimed invention may be used as a screening examination instrument for early diagnosis of individual's cardiovascular and respiration system diseases.

Background of the invention The employment of an ultra-wideband radar as a radiolocation means allows a number of tasks to be solved, said tasks being intractable when conventional diagnosis means are utilized.

First, the usage of ultra- wideband sensors provides non-invasiveness, i.e., eliminates the necessity of penetration into the organism's internal medium. Such an approach provides safety and eliminates the probability of infecting a patient in the process of performing measurements. In addition, the employment of specially furnished operating rooms and laboratories, special surgical instruments and highly-skilled personnel is avoided.

Second, the given measurement means enables making of contact-free diagnosis for treatment of the patients having extensive burns or heavy cutaneous diseases when usage of contact diagnostic means is impossible. The indicated advantage allows investigations to be performed through the patient's clothing to thereby reduce the time for conducting examinations.

Third, ultra-wideband sensors provide the required safety for the patient owing to spreading of a low-energy electromagnetic signal. The radiation load experienced by the patient is reduced by a number of factors in comparison with X-ray computerized tomography. Moreover, the necessity of thorough cleaning and disinfecting of measurement instruments is eliminated, and the need for replacement of disposable elements of the used technique and expendable materials is omitted. The result is that total expenses for maintaining the diagnostic technique are substantially reduced.

According to the classification used nowadays, radars which may be referred to ultra- wideband radiolocation systems have a signal frequency band defined in compliance with the following condition: 0,25< (f_u - f/)/(f_u + f/ ) <1, where f_u and f_/ are, correspondingly, upper and lower signal frequency band boundaries (see, for example, LYa. Immoreev ""Ultra- wideband radars: new possibilities, unique problems, the features of the system. Journal of Bauman's MGTU, Series "Instrument making", Number 4, 1998; LYa. Immoreev. The possibilities and features of ultra-wideband radio systems. Applied electronics, Kharkov, vol. 1, N° 2, 2002, pages 122 to 140). The application of ultra-wideband radiolocation systems enables a substantial increase in the information content of a signal due to an increase in the distance resolution of a locator.

A variety of structural embodiments of pulsed ultra- wideband respiration control sensors are presently known. As an example, USA Patent No. US 5519400 (McEwan, published 21.05.1996) describes a pulsed ultra- wideband sensor for controlling of a phase-code modulated movement of a subject. Short video pulses are used as a reference signal and an excitation signal for a transmitting antenna.

An apparatus comprises a signal transmitter with a transmitting antenna spreading an ultra- wideband signal at a frequency of from 2 to 10 GHz. A time delay block generates a control signal defining a time delay between a series of pulsed signals issued. A receiver with a receiving antenna provides reception of sampled values of a signal in compliance with a gating signal of the time delay block.

The gating signal provides reception of the issued pulsed signal with a delay equal to the time during which the issued signal reaches the investigated subject and a return signal reaches the receiving antenna. The given time depends on the distance between the sensor and the investigated subject. The time delay of the transmitted signal pulses and the received signal pulses is provided through the time delay block by means of which block the signals are modulated within a range between the first time delay and the second time delay. The difference between the first time delay and the second time delay is selected to be lower than the nominal pulse duration. The time delay difference is preferably selected to be equal to a quarter of an electromagnetic signal oscillation period. A modulating signal is encoded in order to eliminate mutual influence of radiolocation sensors located adjacent to one another.

The signal receiver comprises a synchronization block for synchronization with a modulating signal. The given block generates an output signal defining the parameters of movement of the investigated subject. The receiver may comprise two output quadrature channels, one of said channels being in-phase with respect to a reference signal and into the other of said channels the out-of-phase signal is formed with respect to the reference signal. The data accepted from the quadrature channels of the receiver is used for independent processing of the signals. The quadrature channels are alternately changed-over upon receiving of a signal reflected from the subject, said changing-over being provided by means of a high- speed analog switch controlled by a modulating signal. Each of the receiving channels is equipped with an individual filter and a signal amplifier.

Thus, the prior art radiolocation sensor does not ensure the possibility of simultaneous processing of signals delivered into the quadrature channels. The employment of an essentially single-channel pattern of processing of the return electromagnetic signal eliminates the possibility of simultaneous processing of the signals delivered into the quadrature channels for neutralization of various distortions of the signal received and recovery of a signal indicative of the function of movement of the investigated subject.

In case no possibility exists for simultaneous processing of signals delivered into the quadrature channels or a single-channel signal processing pattern is utilized, no reliable information is to be obtained on physiological parameters of the investigated subject with a required extent of certainty at any point of a working distance. In such a case, the so-called "blind" zones appear at the working distance between the sensor and the investigated subject, wherein a phase sensitivity of the sensor is substantially minimized, though the amplitude of probing signals reflected from the subject may be sufficiently high. The number of such zones and the gap between them depend on the working part of distance of the radiolocation sensor and the wavelength of oscillations filling the probing signal.

The presence of the "blind" zones and small width of the working part of distance of the sensor, which is defined by the duration of the reference signals, enhances the requirements on the accuracy of diagnostic technique and reduces the accuracy of measurements of the patient's physiological parameters in predetermined zones of the working distance. The given circumstances impose substantial restrictions on the field of application of the pulsed ultra- wideband sensor: such a sensor may be used only on the condition that the patient is fully fixed within a strictly fixed designed distance. Any changing in the position of the patient under study needs retuning of the sensor with regard to distance, and in individual cases the position of the sensor relative to the investigated subject should be altered in order to prevent the patient' body from getting into some "blind" zone at the sensor's working part of distance.

Automatic retuning of the sensor with regard to distance will require the employment of an automatic range tracking system, which will substantially complicate the design of an instrument and, accordingly, increase expenses for the manufacture and operation of the sensor. However, the employment of an expensive automatic distance tracking system does not eliminate the possibility of occurrence of the patient in a "blind" zone. In individual cases, even the measurement itself of the patient's physiological parameters becomes impossible. Another embodiment of a pulsed ultra-wideband sensor used for respiration control, is described in USA patent application No. US 2004/0249258 (Tupin J.R. et al, published 09.12.2004). This instrument is a pulsed ultra-wideband low-power radar with a receiving- transmitting antenna. Short video pulses are used as a reference signal. The apparatus comprises a pulse-type constant frequency generator, a transmitter, a receiver, a delayed signal generation block, an analog-to-digital signal data converter, a signal processing block, a data display block, and a control and synchronization block, the outputs of the latter block being connected to all the blocks and units of the apparatus. The signal processing block enables an extensive statistic processing of return signals. The employment of the prior art sensor only allows the return signal to be amplified with regard to its energy value by stepped amplification of the signal amplitude in the receiver before the signal is translated to a digital code. However, the similar disadvantages are inherent in the given sensor, said disadvantages resulting from the impossibility of eliminating three-dimensional zones tending to reduce the information content of the signal reflected from the subject owing to the application of a single-channel signal processing pattern.

It is known from USA Patent No US 5573012 (McEwan, published 12.11.1996) a pulsed radio location instrument for controlling the patient's physiological parameters, including respiration control. Functioning of this prior art apparatus is based on processing of the signals reflected from the investigated subject and generation of a voltage mean value signal, by means of which signal an acoustic generator signal is modulated. A signal converter converts the measured voltage of the return signal to an amplitude-frequency modulated audio signal. The apparatus also comprises a pulse generator which generates delayed signals of the moment a signal receiver input circuit is opened, and a signal accumulator for accumulating signals of the receiver input circuit. The received signal may be individually processed by frequency filtration and amplification for controlling different physiological parameters of the patient, however the design of the sensor and the signal processing circuit do not exclude the possibility for occurrence of "blind" zones at the working parts of distance between the investigated subject and the sensor. The closest prior art of the claimed invention is a pulsed ultra- wideband sensor for respiration control, described in USA Patent No. US 4085740 (Allen, Jr, published 25.04.1978). The apparatus comprises a generator for generation of electromagnetic oscillations with a frequency of 10 GHz. The output signal of the generator is modulated at a frequency of 1 MHz by means of a modulation block. The modulated signal is directed to a transmitter and is further spread by a transmitting antenna toward the investigated subject.

A probing signal reflected from the subject is perceived by the receiving antenna of the sensor and is then branched in two channels of the receiver input circuit. Simultaneously the reference probing signal is directed into an attenuator, an output signal of which attenuator is also branched in two channels. The first in-phase reference signal is sent into a mixer of the first channel of the receiver, and the second reference signal is sent into a phase-shifting circuit to acquire a phase shift by an angle of 90°. The output of the phase-shifting circuit is coupled to the mixer input of the second channel of the receiver. Thus, the sensor receiver comprises two quadrature channels, where in either of the channels the output of the signal mixer is connected in series with a detector designed for demodulation of the signal, a signal amplifier and a filter. In the process of controlling the patient's physiological parameters, sine signals are formed in the receiver quadrature channels at the mixer output. On detecting or demodulating in each channel of a composite signal of two phase-shifted sinusoid, an amplitude of the signal is determined, said amplitude being a function of a relative angular phase-shifting velocity of two input signals fed to the mixer input. The relative phase value of the return signal in each of the channels is indicative of a function of the patient's chest movement or patient's heart rate depending on tuning of the filters and the amplifiers in the quadrature channels. The first quadrature channel is used for separating the signal characterizing a chest movement law, and the second channel is used for separating the patient's heart rate. The respective signals are separated by means of amplifiers and frequency filters tuned to the corresponding amplitude and frequency of the patient's physiological parameter under study.

The quadrature channels of the receiver of the prior art sensor are designed for different functional purposes and are used for controlling of two physiological parameters: the patient's heart rate and the law of the chest movement, respectively. In connection with this, the prior art instrument has the same disadvantages as the above described other prior art instruments, namely: the sensor output signal has low information content owing to the appearance of "blind" zones in the working parts of distance between the investigated subject and the sensor; the application of the sensor is limited by a fixed distance between the sensor and the patient; the possibility of utilizing the sensor is excluded even at slight movement of the investigated subject. The reduced information content of a return signal results from the processes occurring during making the diagnosis. Measurement of signal carrying useful information is performed through evaluation of a phase difference between the reference probing signal and the signal reflected from the patient's chest. Movement of the chest causes changes in the phase incursion of the signal reflected from the investigated subject.

It should be noted that the individual's chest moves in accordance with a complicated law dependent not only on respiration but also on functioning of the heart of patient under study. As an example, during respiration holding the chest continues its movement caused by the movement of the heart. On the whole, the chest movement is of low-amplitude reciprocating character. The maximum amplitude of the chest movement characteristic of respiration is 5 mm, and the amplitude of movement caused by palpitation is from about 0.2 mm to about 2 mm. So, the oscillation frequency of a probing signal should be substantially high, in the order of from 3 to 20 GHz, for enabling accurate measurement of the individual's physiological parameters. In conventional signal processing patterns characteristic of the above prior art apparatuses, a correlation processing system is utilized. The functioning of such systems is based on multiplication of the reference probing signal and the return signal delayed by the time interval during which the signal is spread to the investigated subject and back to the receiving antenna. The probing signal is presented in the form of short video pulses having duration not in the excess of a period of oscillations filling the probing pulse. The output signal of a correlation system is proportional to the phase difference between the probing signal and the return signal.

In case the investigated subject is in a fixed position, the amplitude Z of the output signal after processing is characterized by the following ratio:

Z = ^nT₀ oos(φ), (1)

where Eo is a maximum amplitude of the probing signal; E] is a maximum amplitude of the received return signal; To is a period of oscillations of the probing signal; n is a whole number of periods of oscillations filling the probing pulse. The phase difference value φ in the expression (1) is defined by the time of spreading the electromagnetic waves to the investigated subject and back: o n D φ = ω^ = 4π^ , (2)

where ω₀ = 2τif₀ is a circular frequency of the probing signal; fo is a mean frequency of the probing signal spectrum;

C is a rate of spreading the electromagnetic waves; λ is a wavelength of oscillations filling the probing signal;

R] is a distance between the investigated subject and the sensor.

A normalized chart Z(i?;)/T₀ of a function of the output signal of a correlation meter depending on the distance to the investigated subject is illustrated in Fig. 1. As the represented graphical dependence suggests, "blind" zones exist at a working distance between the sensor and the investigated subject, in which zones the sensor output signal is equal to or approximates a zero value. The presence of such zones does not depend on reflectivity (an effective scattering area) of the investigated subject. The distance between the "blind" zone boundaries is defined depending on the oscillation period of the reference probing signal, in proportion to the value

. The number N of such "blind" zones is in inverse proportion to the period To of oscillations of the probing signal or to the oscillation wavelength of the probing signal:

4R_x _ 4R_x

N =

T C λ

The smaller is the period (the higher the frequency), the greater is the number of such zones within the working distance. In particular, with a mean frequency of the probing signal spectrum of 6 GHz at the working distance of 2 m, the number of such zones will be 160, and the gap between the "blind" zone boundaries will be 12.5 mm. Thus, the probability is very high that the human chest surface reflecting the probing signals during measurement of respiration and heart rates will be in the vicinity of the "blind" zone. In case the investigated subject, whose movement parameters are to be defined, is in the vicinity of the "blind" zone region, the measurement of movement parameters of such a subject, for example of the patient's chest, is extremely difficult with the subject's amplitude of movement less than a quarter of the wavelength of oscillations of the probing signal. The indicated circumstances affect the accuracy of measurement results, which cannot be tolerated in diagnostics of the patient and may lead to irreparable consequences. With great reciprocation amplitudes of the chest, for example at patient's deep breathing, and high values of mean frequency of the probing signal spectrum, a shape of the output signal of the correlation system is substantially distorted in comparison with an actual function characterizing a mechanism of movement of the investigated subject. Due to this it is impossible to define with a required extent of accuracy the parameters of movement of the subject, such as frequency, amplitude and function of movement of the subject.

With the given character of movement of the investigated subject the amplitude Z(t) of the output signal of the correlation system is described by the following expression:

Z(t) = E_m cos{φ(t)+ φ_λ ), (3)

E E where E_1n = ° ' nT₀ is maximum energy of interaction between the return signal and

the probing signal, said energy being released at an output load with an unit resistance; r> n φ_x = 2ω₀ — = 4π—^L is a phase shift determined by the distance between the investigated C λ subject and the sensor;

φ(t)= 2ω₀ — — — - = 4π — F(Ωt) is an instantaneous phase value resulted from the

C A movement of the investigated subject; is the law of movement of the investigated subject; Ω = 2πf is a circular frequency of reciprocation of the investigated subject; / is a frequency of reciprocation of the investigated subject; t is a current time; ΔR is a maximum amplitude of movement of the investigated subject.

Let us assume that the investigated subject is at a distance Rj from the sensor and moves in accordance with a sine law with a circular frequency Ω and an amplitude AR . The expression (3) for the output signal will then assume the following form:

^Z(t)= ^E _1n ^cosf ⁴*3^sin(^Ωθ+⁴* 4^"]. ⁽⁴> The oscillograms of the output signal (variations in the amplitude Z(Y) and the amplitude-frequency spectrum Z(/}) of the output signal) of the processing correlation system are illustrated in Figs 2 to 9. The dependences shown in the charts are presented for various values m, said m value being determined in conformance with the following ratio: m = Aπ . λ

The charts show the character of variations in the output signal at different values ΔR of the oscillation amplitude of the investigated subject and, correspondingly, at various values m.

During conducting of measurements, the oscillation frequency of the investigated subject was 1 Hz. The value f_\ in the charts indicates the frequency spectrum of the signal reflected from the investigated subject.

It is obvious from the dependences presented in the charts that the shape of the output signal substantially differs from a real mechanism of movement of the subject at greater values ΔR of the movement amplitude of the investigated subject, as compared to the wavelength λ. With the values m>0.5 (see Figs 4 to 9, m = 2, 5 and 10), immediate determination of a mechanism of variations in amplitude (a function of movement) and frequency of movement of the investigated subject becomes problematic and in specific cases impossible.

Disclosure of the invention The claimed invention is targeted at elimination of the above disadvantages intrinsic in the prior arts, said disadvantages resulting from the impossibility of simultaneous processing of output signals in the quadrature channels of the receiver and a reduced information content of the return signal.

Solution of the indicated technical tasks provides for achievement of a novel technical result including an increase in a phase sensitivity of the sensor and a possibility of controlling the respiration of subjects under study movable within a working distance of the sensor thanks to the elimination of "blind" zones at the working distance of measurements.

The achievement of the novel technical result is enabled by implementation of a pulsed ultra-wideband respiration controlling sensor which comprises a control unit forming a time delay, a probing signal forming path including a coherent radio pulse generator, and further comprises a transmitting antenna, a receiving antenna, a probing signal transmitter path, and a return signal receiver path with two quadrature channels for processing of a return signal. Each of the quadrature channels includes at least one signal mixer whose input is coupled to the receiving antenna, and an analog-to-digital converter. The receiver path also includes a phase- shifting circuit whose input is coupled to the probing signal forming path and output is coupled to the input of the signal mixer provided in one of the quadrature channels. According to the claimed invention, the sensor comprises a processing block for recovery of the law of movement of the investigated subject, and a data processing and displaying block. The first input of the processing block is connected to the output of the analog-to-digital converter provided in the first quadrature channel. The second input of the processing block is connected to the output of the analog-to-digital converter provided in the second quadrature channel. The output of the processing block is connected to the data processing and displaying block.

In order to eliminate the disadvantages intrinsic in pulsed ultra-wideband sensors equipped with a conventional signal processing circuit, the quadrature channels of the return signal receiver path are used for neutralization of the signal distortions and recovery of the function of movement of the subject to thereby increase an information content of the output signal.

In the first quadrature channel a signal is formed which is in-phase with respect to a reference signal. In the second quadrature channel the reference signal is phase shifted by 90°. At the output of the first channel a signal Z₁(Q is formed, which is in-phase with respect to the reference signal and is described according to the dependence (3):

At the output of the second channel a signal Z₂(O is formed, said signal being described

by the following dependence: Z_τ{t) = — E_m sin(φ{t)+ φ_ι), (5)

An independence variable of a function φ(t)+ φ_ι may be reduced by calculating the ratio of sine and cosine functions of the signals formed in the quadrature channels, followed by determining an arc tangent of the resulting ratio:

Based on prior information on parameters of the probing signal, in particular on a mean frequency of the signal spectrum and, correspondingly, on a wavelength λ, the law F(Ωt) of reciprocating movement of the subject may be calculated at an accuracy of up to the value Rj from the following ratio:

= ΔR sin(Ωt)+R_l5 (7)

In case it is impossible to determine the distance R₁ to the investigated subject, the law F(Ωt) of movement of the subject may be determined at a high extent of accuracy in the following form: F(fit) = AR sin(Ωt) , (8)

All the above operations for recovery of the function of movement of the investigated subject are provided using the processing block performing programmed operations for digital processing of incoming signals formed in the quadrature channels of the receiver. In the general case the conversion of the input signals Z₁(Y) and Z₂(Y) in the quadrature channels, which is carried out by means of the processing block for recovery of the function of the law of movement of the investigated subject, may be described by the following dependence:

F(Qt) = A - BTg[Z₁(O + JZ₂ (O], (9)

4π where J = V-I is an imaginary unit.

Simultaneous processing of sine and cosine signals and generation of the output signal, which defines the recovered function of movement of the investigated subject, allows the occurrence of "blind" zones at the distance between the investigated subject and the sensor to be completely eliminated.

The result is that by using in the receiver of quadrature channels and special digital processing of signals, the function and parameters of movement of the investigated subject, in particular amplitude of movement and oscillation frequency, may be completely recovered, which is of prime importance for solving diagnostic tasks in medicine. Moreover, recovery of the function of movement of the investigated subject enables controlling the respiration of the moving subjects.

In a preferred embodiment, the sensor comprises a controlled electronic switch providing an alternate switching of the probing signal generation path to the transmitter path and to the receiver path. The input of the switch is coupled to the output of the probing signal generation path. The first output of the switch is coupled to the transmitter path. The second output of the switch is coupled to the second input of the signal mixer in the first quadrature channel of the receiver and to the input of the phase-shifting circuit, whose output is coupled to the second input of the signal mixer in the second quadrature channel of the receiver. The control input of the electronic switch is connected to the control unit. The probing signal forming path may comprise a band pass filter and a buffer amplifier.

The output of signal mixer in each of the quadrature channels of the receiver is connected to the input of the analog-to-digital converter through the band pass filter, a low-frequency amplifier, and a low-frequency filter.

The receiver and transmitter paths may include band pass filters and signal amplifiers correspondingly connected to the receiving and transmitting antennas.

Brief description of drawings

The invention is further exemplified by the description of concrete examples of implementation of the pulsed ultra- wideband sensor designed for controlling of human's respiration. The accompanying drawings illustrate the following:

Fig. 1 is a normalized graph Z(i?;)/To of an output signal of a correlator depending on a relative distance R₁A, to the investigated subject which is immovable;

Fig. 2 is a graph of function Z(t) of an output signal of the correlator with m=0,5; Fig. 3 is an amplitude-frequency spectrum Z(/}) of an output signal of the correlator with m =0,5;

Fig 4 is a graph of function Z(t) of an output signal of the correlator with m-2; Fig. 5 is an amplitude-frequency spectrum Z(/})of an output signal of the correlator with m=2;

Fig. 6 is a graph of function Z(Y) of an output signal of the correlator with m=5; Fig. 7 is an amplitude-frequency spectrum Z(/}) of an output signal of a correlator with m=5;

Fig. 8 is a graph of function Z(O of an output signal of a correlator with m=10; Fig. 9 is an amplitude-frequency spectrum Z(/}) of an output signal of the correlator with m=10; Fig. 10 is a structural diagram of the sensor implemented according to the invention;

Fig. 11 is a structural diagram of the control unit forming a time delay; Fig. 12 is a schematic diagram of the sensor implemented according to the invention; Fig. 13 is a time diagram U(t) of synchronization pulses at an output of a driving generator; Fig. 14 is a time diagram U(t) of synchronization pulses at an output of a delay line of a synchronizing pulse forming path of a receiver;

Fig. 15 is a time diagram U(Y) of synchronization pulses at an output of a short pulse generator of a synchronizing pulse forming path of a transmitter; Fig. 16 is a time diagram XJ (t) of synchronization pulses at an output of a short pulse generator of the synchronizing pulse forming path of a receiver;

Fig. 17 is a time diagram U(Y) of synchronization pulses at an output of the control unit;

Fig. 18 is a time diagram U(O of coherent radio pulses at an output of a self-contained microwave generator;

Fig. 19 is a normalized time diagram of the function F(Ωt)/λ of movement of the investigated subject with m=10;

Fig. 20 is an amplitude-frequency spectrum F(f) of the function of movement of the investigated subject with m=10; Fig. 21 is a time diagram Z₁(J) of an output signal from the first quadrature channel with m= 10;

Fig. 22 is a time diagram Z₂(f) of an output signal from the second quadrature channel with m=10;

Fig. 23 is amplitude-frequency spectrum Z₁(Z)) of an output signal from the first quadrature channel with m= 10 ;

Fig. 24 is amplitude-frequency spectrum Z₂(/}) of an output signal from the second quadrature channel with m=10;

Fig. 25 is a normalized time diagram of the recovered function F(Ωt)/λ of movement of the investigated subject with m=10 in case the sensor implemented according to the claimed invention is employed;

Fig. 26 is an amplitude-frequency spectrum F(Ji) of the function of movement of the investigated subject with m=10 in case the sensor implemented according to the claimed invention is employed.

Preferable examples of embodiment of the invention

A pulsed ultra-wideband respiration controlling sensor whose structural diagram is illustrated in Fig. 10 comprises a control unit 1 for forming a time delay, a probing signal forming path with a coherent radio pulse generator such as externally excited a self-contained microwave generator 2, a transmitting antenna 3 and a receiving antenna 4, a probing signal transmitter path, a return signal receiver path with two quadrature channels for processing of a return signal. The sensor further comprises a controlled electronic switch 5, a processing block 6 for recovery of the law of movement of the investigated subject, and a data processing and displaying block 7. The probing signal forming path comprises a buffer amplifier 8 and a band pass filter 9, which are connected in series with the self-contained microwave generator 2, said band pass filter being coupled to the input of the electronic switch 5. The probing signal transmitter path includes a band pass filter 10 and an amplifier 11 which are connected in series with the transmitting antenna 3, the input of the amplifier being coupled to the first output of the electronic switch 5.

The return signal receiver path comprises a band pass filter 12, an amplifier 13 which are connected in series with the receiving antenna 4, the output of this amplifier being connected to the two quadrature channels for processing of a return signal, and a phase-shifting circuit 14. The first quadrature channel includes a signal mixer 15, with a band pass filter 16, a low- frequency amplifier 17, a low-frequency filter 18 and an analog-to-digital converter 19 being connected in series with the output of said mixer. The output of an analog-to-digital converter 19 is connected to the first input of the processing block 6. The first input of the mixer 15 is coupled to the output of the amplifier 13 and the second input to the second output of the electronic switch 5.

The second quadrature channel comprises a signal mixer 20, with a band pass filter 21, a low-frequency amplifier 22, a low-frequency filter 23 and an analog-to-digital converter 24 being connected in series with the output of said mixer. The output of the analog-to-digital converter 24 is coupled to the second input of the processing block 6. The first input of the mixer 20 is coupled to the output of the amplifier 13, and the second input is coupled to the second output of the electronic switch 5 through the phase-shifting circuit 14 providing a phase shift of a probing signal by minus 90°.

The time delay forming control unit 1 whose structural diagram is shown in Fig. 11 comprises a driving generator 25, a synchronizing pulse forming path of the transmitter, said signal being designed for controlling the probing signal forming process, and a synchronizing pulse forming path of the receiver.

The synchronizing pulse forming path of the transmitter consists of a short pulse generator 26 by means of which a short video pulse of a synchronization signal is formed. The synchronizing pulse forming path of the receiver consists of a controlled digital delay line 27 and a short pulse generator 28, and defines the first output of the control unit 1.

Both of the synchronizing pulse forming paths are connected to inputs of an "OR" circuit 29, the output of which circuit defines the second output of the control unit 1. The pulsed ultra-wideband respiration control sensor, whose schematic diagram is illustrated in Fig. 12, comprises an externally excited self-contained microwave generator (see the reference character 2 in Fig. 10) provided on a field-controlled transistor 30. This generator is based on a two-contour circuit with a common source. The generation frequency is defined by the sizes of micro strip lines 31 and 32 and by the nominal parameters of capacitors 33 and 34. At the generation frequency, the micro strip lines 31 and 32 function as unbalanced parallel oscillating contours. In order to excite oscillations, the reactive resistance of these contours should be of inductive character. For this purpose, the micro strip lines 31 and 32 are made shorter than λ/2 and λ/4, respectively. The position of an operating point of the field-controlled transistor 30 is set by means of a resistive potential divider consists of resistors 35 and 36. Functioning of the generator is controlled by synchronization signals delivered from the output of the control unit 1 through the micro strip line 32. A strip line element 37 provides a short circuiting mode at the generation frequency. In this case an imaginary part of an input complex resistance of the line 32 at a junction point of drain of the field-controlled transistor 30, capacitors 33 and 38 and micro strip line 32 is high and is of inductive character. Due to this, decoupling of the self- contained microwave generator and the control unit 1 is effectuated on the basis of high frequency.

The buffer amplifier (see the reference character 8 in Fig. 10) is provided on a field- controlled transistor 39 and connected to the self-contained microwave generator through a blocking capacitor 38. The selected capacity of this capacitor is sufficiently low for reducing the coupling coefficients between the self-contained microwave generator and the amplifier, which is designed for amplifying the power of signals and reducing the effect of subsequent cascades upon operation of the self-contained microwave generator. The operating mode of the transistor 39 in terms of direct current is determined by the rated values of resistors 40 and 41 of a resistive potential divider and a resistor 42 of a drain load. A micro strip line 43 and a strip line element 44 function as a choke filter at a mean frequency of the produced radio pulses to prevent the microwave current flow through the circuit for the development of a bias voltage of the transistor 39. The strip line element 45 functions as a blocking capacitor at a mean frequency of the signals formed.

The frequency band pass filter 9 has a cutoff frequency of 5.5 GHz and is designed for eliminating low-frequency parasitic oscillations. The output of the filter 9 is coupled to an input of an additional amplifier 46 for amplifying microwave power of the probing signal. The amplifier 46 enhances the signal to a desired level in the probing signal forming path.

The signal forming path is coupled to a receiving-transmitting antenna 47 through electronic switches 48 and 49 controlled by the signals delivered from the first output of the time delay generating control unit 1 and through the transmitter path including a power amplifier 11 of the transmitter. In response to the signals from the control unit 1 the switch 48 provides alternate switching of the probing pulse forming path to the probing signal transmitter path and to the return signal receiver path. In response to the signals from the control unit 1 the switch 49 couples the probing signal transmitter path or the return signal receiver path to the receiving-transmitting antenna 47.

The path for transmitting the probing signal to the inputs of the signal mixers 15 and 20 in the quadrature channels for processing of the return signal comprises a power amplifier 50 for amplifying of the probing signal to the level needed for proper functioning of the mixers 15 and 20. The output of the amplifier 50 is connected through a blocking capacitor 51 to an input of a transformer 52 designed for dividing the reference probing signal into two signals equal in power, with one of the signals being phase shifted by minus 90°. The transformer 52 functions as a phase-shifting circuit (see the reference character 14 in Fig. 10). The outputs of the transformer 52 are properly connected with the second inputs of the mixers 15 and 20 whose first inputs are coupled to the return signal receiver path. The return signal receiver path includes a high-frequency filter 12 having a cutoff frequency of 5.5 GHz, a noiseless amplifier 13 for a microwave signal, and a blocking capacitor 53. The filter 12 is designed for suppressing the interferences resulted from various radio systems having lower operating frequencies and rather high signal level. The amplifier 13 neutralizes the losses occurring in the input path of return signal receiver. The outputs of the mixers 15 and 20 in the quadrature channels are coupled through blocking capacitors 54 and 55 and band pass filters 16 and 21 to the low-frequency amplifiers 17 and 22 (a schematic diagram of the amplifier 22 shown in Fig. 10 is illustrated in Fig 12). The filters 16 and 21 are designed for separation of a low-frequency signal proportional to the reciprocating movement of the patient's chest. Each of the amplifiers 17 and 22 consists of two amplification cascades provided on microcircuits 56 and 57, an active low-frequency output filter provided on a microcircuit 58 having a Chebyshev's characteristic, and a high-frequency input filter defined by an amplification cascade with a feedback line including an integrator provided on a microcircuit 59. The low-frequency output filter provides maximum uniformity of an amplitude-frequency characteristic of the signal within a transmission band. The high-frequency input filter is designed for attenuating a parasitic constant component of the signal, said component being resulted from reflection of the probing signals from immovable foreign objects, and is adapted for reducing the drift of the signal constant component.

The outputs of the low-frequency filters 18 and 23 used as parts of the low-frequency amplifiers 17 and 22 are coupled to the inputs of the respective analog-to-digital converters 19 and 24. The outputs of the converters 19 and 24 are connected to the respective inputs of the processing block 6 for recovery of the movement law of the investigated subject, by means of which processing block the digital filtration of the input signals and the programmed operations for recovery of the movement function are performed.

The first control output of the processing block 6 is connected to the input of the control unit 1, and the second data output is connected to the data processing and displaying unit 7 which may be, for example, a personal computer. The pulsed ultra- wideband sensor, whose structural diagram is illustrated in Fig. 10, operates as follows.

A driving generator 25 produces rectangular synchronization pulses with a period of T₀, whose time diagram is represented in Fig. 13. The signal is then branched to be further delivered into two paths: the synchronizing pulse forming path of the transmitter where the synchronizing pulse is formed for controlling the generation of a probing signal, and the synchronizing pulse forming path of the receiver.

By the use of the short pulse generator 26 in the synchronizing pulse forming path of the transmitter, a short video pulse of synchronization signal is formed with a delay time Ui at a front zone of a synchronization pulse, said delay being dependent on a pulse forming time (see the time diagram in Fig. 15). The duration of the pulse produced is defined by the required probing pulse duration.

In the synchronizing pulse forming path of the receiver a delay for a period of td2 of a synchronization pulse is provided in a delay line 27 (see the time diagram in Fig. 14), during which delay the probing signal spreads to the investigated subject back to the sensor. The delay value defines the distance range of functioning of the sensor and is determined from the

2R formula: t_d2

C By the use of a short pulse generator 28 in the synchronizing pulse forming path of the receiver, a short video pulse of synchronization signal is produced with a delay time td₃ along a front zone of the synchronizing pulse, said delay resulting from the signal generation time (see the time diagram in Fig. 16). The synchronization signals formed are combined by means of an "OR" circuit 29 into a single synchronization signal which is a periodic sequence of pairs of video pulses - duplets (see the time diagram in Fig. 17). The time interval of the duplet pulses is defined by the delay time value t_d2. The duplet sequence period T₀ is set by the driving generator 25.

The synchronization signal is then directed through the second output of the control unit 1 to the controlling input of the self-contained microwave generator 2 which generates two coherent radio pulses (see a time diagram in Fig. 18).

The formed duplet of coherent radio pulses is directed through the buffer amplifier 8 and the band pass filter 9 to the input of the electronic switch 5. By the use of the switch 5 the produced signals are commuted. The signals are directed to the probing signal transmitter path or to the return signal receiver path. The switch 5 is controlled by the synchronization signal sent from the first output of the control unit 1.

In the initial state, the switch 5 is in a position illustrated in Fig. 10. In the given position of the switch 5 the first radio pulse of the duplet is delivered to the probing signal transmitter path. The probing signal is amplified in the amplifier 11 to a required level to thereby compensate the signal energy losses in the filters 9 and 10, and also in the switch 5. The filters 9, 10 and 12 have a transmission band of from 3 to 10 GHz and are designed for suppressing out-of-band radiation.

The produced probing signal is sent to the transmitting antenna 3 and is spread into the surrounding space to the investigated subject. In a time interval needed for spreading of the probing signal to the investigated subject and back, a second synchronizing pulse of the duplet is formed, by means of which signal the switch 5 connects the probing signal forming path to the second inputs of the mixers 15 and 20. The reference signal for the mixer 20 additionally passes through the phase-shifting circuit 14 to acquire a phase shift of minus 90°. The result is that the second coherent radio pulse is delivered to the quadrature channels in the return signal receiver path with a changed phase. The iη-phase signal and the changed-phase signal serve as reference signals for the mixers 15 and 20.

The signal reflected from the investigated subject and received by the antenna 4 passes through the filter 12 which reduces the level of interferences from the outer radio systems, and is then amplified to the required level by means of the noiseless amplifier 13. The filtered and amplified return signal is delivered to the quadrature channels through the first inputs of the mixers 15 and 20. As a result of correlation with the reference synchronization signals sent to the second reference inputs of the mixers 15 and 20, two signals are formed in the quadrature channels, namely, the first in-phase signal and the second out-of-phase signal with a phase shifted by 90°.

In each of the quadrature channels, the signal is separated in band pass filters 16 and 21, the signals are amplified by means of low-frequency amplifiers 17 and 22 accompanied by filtering of the signals in low-frequency filters 18 and 23. The signals thus separated and amplified are then digitized in the analog-to-digital converters 19 and 24. The signals formed in the quadrature channels are sent from the converter outputs to the processing block 6 providing digital filtration of incoming signals and recovery of the law of movement of the investigated subject. The given law of movement is described in the generalized form by the

following function: F{Ω.t) = argfa (?) + jZ₂ (t)] .

Aπ At the output of the first quadrature channel (at the input to the analog-to-digital

converter 19) a signal Z_ι(t) = —E_m cos((p(t)+φ_ι) is formed, said signal being in-phase with

respect to the reference probing signal.

At the output of the second quadrature channel (at the input to the analog-to-digital

converter 24) a signal Z₂(i) E_1n sm^' (φ(t)+ φ_λ) is formed.

An independent variable of function φ{t) + φ_χ is determined in the processing block 6 through calculation of the ratio of sine and cosine signals formed in the quadrature channels, accompanied by the calculation of an arc tangent of the resultant ratio in the following form:

{E_m cos(φ{ή+ φj)

On the basis of a prior information on parameters of the probing signal, including a wavelength λ of oscillations filling the probing signal pulse, the law F(Ωt) of reciprocating movement of the subject i§ calculated at an accuracy of up to the value R₁ according to the following dependence:

F(Qt) = — (φ{t) + φ_λ ) = Aπ ^- 1 = AR sin(Ωf) + R₁.

Aπ

) With the possibility of determining the distance R₁ to the investigated subject, the law F(Ωt) of movement of the subject is calculated at a high degree of accuracy in the following form: F(Ωt) = AR sin(Ωt) .

Precise data on the distance to the investigated subject enables the phase shift φi to be balanced to zero. The distance to the subject may be unknown before the beginning of measurements. In such a case it may be determined in the process of measurements. The accuracy of determining the distance Ri has an impact on the extent of balancing the phase shift Cp₁.

The time diagrams describing the law of movement of the investigated subject, the output signals of the quadrature channels and the recovered function of movement of the investigated subject are represented in Figs 19 to 26. The given diagrams are obtained by a mathematical modeling method provided that the investigated subject reciprocates at a

frequency of 1 Hz and is positioned at a distance Ri from the sensor. The value m = 4-π is

X selected to be equal to 10 radians. The movement of the investigated subject is described by a sine function:

F(Ωt) = AR sin(Ωt)+ R_v

A normalized time diagram of the function F(Ωt)/λ of movement of the subject and an amplitude-frequency spectrum Fφoϊ the function are represented in Figs 19 and 20, respectively. Cosine and sine signals Z₁(J) and Z₂(O are directed to the input of the analog-to- digital converters 19 and 24, the time diagrams and amplitude-frequency spectra of which signals are illustrated in Figs 21, 22, and 23, 24, respectively.

As a result of carrying out the above sequence of mathematical operations, a digital signal is produced, said signal being indicative of the recovered function of movement of the investigated subject. The normalized time diagram of the recovered function F(Ωt)/λ of movement of the investigated subject and the amplitude-frequency spectrum F(fj) are shown in

Figs 25 and 26, respectively.

The signal delivered from the output of the processing block 6 and adapted to determine the law of movement of the investigated subject is then directed to the data processing and displaying block 7, wherein useful information on the patient's respiration parameters and the state of respiration system is separated. So, with the use of sensor implemented according to the invention, the digital filtration of incoming signals and the recovery of the law of movement of the investigated subject are performed using the processing block 6. As a result, phase sensitivity of the sensor is increased and the possibility of controlling the respiration of movable subjects is enabled by eliminating the occurrence of "blind" zones at the working distance.

The pulsed ultra- wideband sensor whose schematic diagram is depicted in Fig. 12 operates in the similar manner.

The self-contained microwave generator is controlled in response to the synchronization signals fed from the outputs of the control unit 1 through the micro strip line 32. The control synchronization signals are produced in the control unit 1 as pairs of video pulses with a rectangular envelope. The pulse time interval is determined by the distance between the sensor and the patient. The radio pulses are produced with a duration defined by the duration of the control synchronizing pulses.

In the buffer amplifier provided on the field-controlled transistor 39, the power of the formed signals is increased to thereby reduce the effect of the subsequent cascades on operation of the self-contained microwave generator. The radio signals are then directed through a high-frequency filter 9 designed for eliminating the low-frequency parasitic oscillations to the input of the signal power amplifier 46. The amplified signal is sent to the input of an electronic switch 48. In the initial position, electronic switches 48 and 49 enable passage of the first radio pulse of duplet into the probing signal transmitter path. The signal is directed from the output of the first switch 48 through a signal power amplifier 11 to the input of the second switch 49 in its open position, wherein the probing signal transmitter path is coupled to the receiving-transmitting antenna 47.

Synchronously with the second pulse, the control synchronization signal is fed to the switches 48 and 49 from the output of the control unit 1. In response to this signal, the switch

48 directs the second radio pulse of duplet to the return signal receiver path and the switch 49 couples the receiving-transmitting antenna 47 to this path. The radio signal is amplified in the amplifier 50 to the power level required for proper functioning of the mixers 15 and 20 in the quadrature channels. The amplified reference probing signal is delivered through the blocking capacitor 51 to the input of the transformer 52 dividing the reference probing signal into two signals equal in power, with one of the signals being phase-shifted by 90°.

The produced signals are sent to the second inputs of the mixers 15 and 20. The signal received by the receiving-transmitting antenna 47 is directed through the switch 49 to the high frequency filter 12 having a cutoff frequency of 5.5 Hz and adapted for suppressing the interferences from the outer radio systems. The signal is further delivered into the noiseless amplifier 13 for balancing the losses occurring in the input path of the return signal receiver. The amplified and filtered-out signal is sent through the blocking capacitor 53 to the first inputs of the mixers 15 and 20 in the quadrature channels.

The signals from the outputs of the mixers 15 and 20 are then delivered through the blocking capacitors 54 and 55 to the input of low-frequency filters. The signals formed in the quadrature channels are oscillations of combined shape resulted from multiplying of the received return signal and reference signals in the receiver path. The resulting signals are proportional to a phase difference of oscillations filling the signal pulses and comprise harmonics with summarized and difference frequencies and combinations thereof.

Separation of the low-frequency signal proportional to the movement of the patient's chest is performed by means of filters 16 and 21. The separated signals are then sent to low- frequency amplifiers comprising input band pass filters and output low-frequency filters. The amplified low-frequency signals of the quadrature channels are digitized by means of the analog-to-digital converters 19 and 24. Once digitized, the signals of quadrature channels are directed to the processing block 6 for recovery of the law of movement of the investigated subject in accordance with the sequence of operations described with regard to the above example of embodiment of invention. The data produced are sent to the block 7 for processing and displaying the obtained information. A personal computer may be used as such a block. The block 7 enables in processing, analyzing and recording of the obtained data pertaining to the parameters and state of the patient's respiration system.

Industrial applicability Employment of the pulsed ultra-wideband sensor implemented according to the invention and adapted for controlling the patient's respiration allows the phase sensitivity of diagnostic equipment to be significantly increased and the possibility of controlling respiration during movement of patients to be provided owing to the elimination of "blind" zones from the working distance between the sensor and the investigated subject. The given advantage allows the invention to be utilized in medicinal equipment as a high-sensitivity diagnostic means for controlling patients' respiration parameters. A list of reference characters of the sensor components represented on the structural and schematic diagrams of the sensor (see Figs 10, 11 and 12 of drawings):

1 - control unit;

2 — self-contained microwave generator; 3 - transmitting antenna;

4 - receiving antenna;

5 — electronic switch;

6 - processing block providing recovery of the law of movement of the investigated subject; 7 - data processing and displaying block;

8 - buffer amplifier;

9 - band pass filter of a reference signal forming path;

10 - band pass filter of a probing signal transmission path;

11 - signal amplifier of a probing signal transmission path; 12 - band pass filter of a return signal receiver path;

13 - amplifier of a return signal receiver path;

14 - phase-shifting circuit;

15 - signal mixer of a first quadrature channel;

16 — band pass filter of a first quadrature channel; 17 - low-frequency amplifier of a first quadrature channel;

18 — low-frequency filter of a first quadrature channel;

19 - analog-to-digital converter of a first quadrature channel;

20 - signal mixer of a second quadrature channel;

21 - band pass filter of a second quadrature channel; 22 - low-frequency amplifier of a second quadrature channel;

23 - low-frequency filter of a second quadrature channel;

24 - analog-to-digital converter of a second quadrature channel;

25 — driving generator;

26 - short-pulse generating element for a synchronizing pulse forming path of transmitter;

27 - controlled digital delay line;

28 - short-pulse generating element for a synchronizing pulse forming path of receiver;

29 - "OR" circuit; 30 - field-controlled transistor;

31 and 32 — micro strip lines; 33 and 34 - capacitors;

35 and 36 - resistors of the fist potential divider; 37 — strip line element;

38 — blocking capacitor;

39 - field-controlled transistor;

40 and 41 — resistors of the second potential divider; 42 - resistor 42 of a drain load; 43 - micro strip line;

44 and 45 - strip line elements;

46 - additional amplifier for amplifying microwave power of the probing signal;

47 - receiving-transmitting antenna;

48 - the fist electronic switch; 49 - the second electronic switch;

50 - amplifier of the probing signal;

51 - blocking capacitor;

52 - transformer;

53, 54 and 55 - blocking capacitors; 56 - microcircuit of the fist amplification cascade of the low-frequency amplifier;

57 — microcircuit of the second amplification cascade of the low-frequency amplifier;

58 - microcircuit of low-frequency output filter of the low-frequency amplifier;

59 - microcircuit of high-frequency input filter of the low-frequency amplifier.

Claims

1. An ultra-wideband sensor for respiration control, comprising a control unit (1) generating a time delay, a probing signal forming path with a coherent radio pulse generator (2), a transmitting antenna (3) and a receiving antenna (4), a probing signal transmitter path, a return signal receiver path with two quadrature channels for processing of the return signal, each of said channels including at least one signal mixer (15 or 20), whose input is coupled to the receiving antenna (4), and one analog-to-digital converter (19 or 24), and a phase-shifting circuit (14) whose input is coupled to the probing signal forming path and output is coupled to the signal mixer (20) in one of the quadrature channels, is characterized in that said sensor comprises a processing block (6) providing recovery of the law of movement of the investigated subject, and a data processing and displaying block (7), the first input of said processing block (6) being coupled to the output of the analog-to-digital converter (19) of the first quadrature channel, the second input of said processing block (6) being coupled to the output of the analog-to-digital converter (24) of the second quadrature channel, and the output of the said processing block (6) being coupled to said data processing and displaying block (7).

2. The sensor of the claim 1 is characterized in that it comprises a controlled electronic switch (5) whose input is coupled to the output of the probing signal forming path, the first output of said switch (5) is communicating with the transmitter path, the second output of said switch (5) is coupled to the second input of the signal mixer (15) in the first quadrature channel of the receiver and to the input of a phase-shifting circuit (14), the output of which circuit is coupled to the second input of the signal mixer (20) in the second quadrature channel of the receiver, the control input of said electronic switch (5) being coupled to said control unit (1).

3. The sensor of the claim 1 is characterized in that the probing signal forming path comprises a band pass filter (9) and a buffer amplifier (8).

4. The sensor of the claim 1 is characterized in that the output of said signal mixer (15 or 20) in each of the quadrature channels of the receiver is coupled to the input of said analog-to-digital converter (19 or 24) through a band pass filter (16 or 21), a low-frequency amplifier (17 or 22) and a low-frequency filter (18 or 23).

5. The sensor of the claim 1 is characterized in that the paths of the receiver and transmitter include band pass filters (10 or 12) and signal amplifiers (11 or 13) correspondingly coupled to the receiving antenna (3) and transmitting antenna (4).

6. The sensor of the claim 1 is characterized in that the processing block (6) provides recovery of the law F(Ωt) of movement of the investigated subject in compliance with the following dependences:

Z₂(t) = E₁₁₁ sin (φ(t) + φ_λ),

F(Ωt) = — (φ(t) + (P₁) = ΔR SiIi(Qf) + R₁ ,

Aπ where Z^t) and Z₂(t) are correspondingly output signals of the first and second quadrature channels;

F F E_m = ° ^l TiT_f3 is maximum energy of interaction between the return signal and the

probing signal, said energy being released at an output load with an unit resistance; Eo is maximum amplitude of the probing signal; E] is maximum amplitude of the received return signal; To is the probing signal oscillation period; M is the whole number of periods of oscillations filling the probing pulse;

AR φ\t) = Aπ FyQt) is an instantaneous phase value resulted from movement of the

X investigated subject;

<P_X = 4TV— is a phase shift defined by the distance between the investigated subject and

A the sensor; λ is a wavelength of oscillations filling the probing signal;

Ω - 2πf is a circular frequency of movement of the investigated subject;

/ is a frequency of movement of the investigated subject; t is current time;

ΔR is maximum amplitude of movement of the investigated subject; R] is a distance between the investigated subject and the sensor.