EP0740799A1

EP0740799A1 - Process and device for sensing living bodies

Info

Publication number: EP0740799A1
Application number: EP95906247A
Authority: EP
Inventors: Gerd Jürgen SCHMIDT
Original assignee: Selectronic Vertriebsgesellschaft fur Sicherheitstechnik und Sonderelektronik Mbh
Current assignee: SELECTRONIC GESELLSCHAFT FUER SICHERHEITSTECHNIK U
Priority date: 1994-01-20
Filing date: 1995-01-20
Publication date: 1996-11-06
Also published as: CA2181680A1; EP0740800A1; CN1145665A; AU1452495A; EP0740800B9; CA2181680C; CN1094199C; DE59510894D1; JPH09507648A; RU2162235C2; AU687156B2; CN1090327C; US6122537A; JP3701673B2; JP3433382B2; ATE265691T1; DE19580062D2; WO1995020170A1; DE9400950U1; US5790032A

Abstract

PCT No. PCT/DE95/00065 Sec. 371 Date Jan. 12, 1997 Sec. 102(e) Date Jan. 12, 1997 PCT Filed Jan. 20, 1995 PCT Pub. No. WO95/20171 PCT Pub. Date Jul. 27, 1995An apparatus for detecting vital functions of living bodies by means of electromagnetic signals includes a receiving device for electromagnetic signals. The receiving device for electromagnetic signals includes a device for obtaining frequency components that are characteristic of living bodies, out of received electromagnetic signals. The receiving device includes a direct demodulator that has a non-linear current/voltage characteristic that is frequency-selective for demodulation of frequency components that are characteristic of living bodies.

Description

Live body detection method and apparatus Description

The invention relates to a device according to

Preamble of claim 1, a method according to the

Preamble of claim 13 and uses of the method and / or the device.

In the following description, the detection of living bodies, in particular living human bodies, is understood to determine the presence of bodies in the living state. This detection is important e.g. in the search for buried subjects as a result of natural disasters or in the event of accidents if there is neither visual nor hearing contact with the

Spilled exists. Because the period of survival

is limited, the rapid determination of whether there are still living buried subjects and the recovery of these buried subjects after location is of great importance. Under "Locating" the determination of the

Understood location.

The previously used methods and devices for detecting or locating buried people are generally not able to distinguish buried people from the dead.

The use of search dogs is only possible for a limited time, a concentrated working animal is required

experience shows that after 2 to 3 hours of an extended one

Recovery phase, which leads to the interruption of the search. In addition, the animals are there because of their sense of smell in the foreground, unable to, only after

To search for the living, which is why the recovery of the dead often means that valuable time is lost that is no longer available for the recovery of the living.

Listening devices for taking tapping or

Signs of life fail in the unconscious. In addition, error-free location is often not possible due to the reflection of the sound in the pile.

For improved localization after avalanche accidents, it is known to wear transmission devices on the body which, following the spillage, are based on the emitted electromagnetic signals

Radiation enable localization.

However, such devices do not allow any conclusions to be drawn about the life functions of the porters and are generally not available in the event of accidents or spills due to natural disasters.

There is therefore a need for improved equipment and methods for the detection of living bodies, in particular living human bodies, in order to be able to take faster and more targeted action through a more qualified rescue of the still living.

The invention has for its object a

Device according to the preamble of claim 1 and a method according to the preamble of claim 14 so

to further develop that the desired improved recovery options are provided while avoiding the disadvantages described above.

This task is accomplished by a device with the

Features of claim 1 and a method with the

Features of claim 13 solved.

Further advantageous configurations and uses of the method and the device can be found in the subclaims.

The inventors have found that living bodies, and hence living human bodies, are generally affected by their heartbeat as well as their breathing activity influence high-frequency electromagnetic signals in a surprising way even over large distances. Since in the unconscious heartbeat and in most cases there is also breathing activity, these functions can be regarded as an indication of the presence of life for the purposes of the present invention.

Because these life functions are usually within

known frequency ranges run, which can be at the human heart rate of about 0.5 to 3.4 Hz and

normally around 1 to 2 Hz, breathing can range between 0.1 to 1.5 Hz, this will

defines characteristic frequency intervals that differ significantly from those of other living things, such as the search dogs that are often used on site.

In any case, a frequency range of 0.01 to 10 Hz all appears for the vital functions of a body

frequencies of interest.

It could be shown that living human bodies, which are penetrated by electromagnetic radiation, impart a detectable phase modulation to this radiation with the frequencies described above. This results in sidebands of the mono-frequency radiation

electromagnetic carrier signal, which is essentially at the above frequencies to the radiated fundamental frequency

are moved.

It was surprising to discover that even without

radiated transmission power, only the receiving device, together with the device for obtaining the frequency components characteristic of living bodies, was able to provide the desired detection.

This means that the presence of a living body at least in the vicinity of the receiving device to detectable signal components in the mentioned

Frequency ranges without having to carry out a radiation with a carrier signal. In addition, it is possible to make a statement about the number of people located based on received and also processed signals. The principle of biodiversity and specificity is used here, due to which the heart and respiratory rate patterns of different people differ. If the number of people is four or more, the frequency can be overlaid

Frequencies are no longer clearly differentiated in general. From this number of people only the statement is possible: 'At least four people are present'.

The inventors were already with the receiving device for electromagnetic signals and the device for

Obtaining characteristics of living bodies

Frequency components without additional emitted signals safely in the layer living bodies up to more than 3 m distance or approximately the distance of a building floor

to capture.

In the simplest embodiment of the invention, the direct demodulator described later in the form of a direct diode receiver was sufficient to receive the frequency components characteristic of living bodies.

Later, additional transmitters were used with which the coverage area was radiated, and reflected, transmitted or scattered radiation was received, the examination of which for the above frequency components

Evidence for the presence of living bodies was provided.

To electromagnetic radiation still through dense

To be able to receive heap itself at some distance, frequencies of electromagnetic radiation from a few hundred megahertz to about 10 gigahertz were used, which ensured a high penetration depth.

This radiation was subjected to phase modulation, which shifted the high-frequency carrier signal by a few hertz

Sidebands added. A detection of such closely spaced frequency bands would have been done with conventional ones Reception techniques short-term stable oscillators with deviations of less than 10 requires what was previously considered unattainable with reasonable effort. This problem is exacerbated by the low signal power received.

Below are some of the advantages of using the

Embodiments described subclaims explained.

The transition from detection to location is made possible by a receiving antenna with a defined one

Directional characteristic, which for the optimal adaptation to the spatial search area as small as possible secondary or

Has side lobes, a large forward lobe and a small back lobe as possible.

At first, the usage seems more familiar

Phase demolulers as obvious. Homodyne, heterodyne, PLL (phase locked loop) are known

Loop) method and the excitation of the edge of a local resonant circuit. It has been found, however, that none of the above methods has been able to deliver the desired results with effort that is justifiable for a portable application and inexpensive for a stationary application. Only the use of a direct demodulator, which enables a direct separation of the modulation frequency from the modulated frequency, led to the

desired results. However, it is assumed that the above methods are possible within the scope of the corresponding equipment and improved circuit arrangements

The present invention can be applied.

With a device with nonlinear current /

Voltage characteristic as a frequency-selective element, the demodulation of the frequency components of interest could be achieved. A diode, a bipolar or a field effect transistor could be used successfully as an element with a non-linear characteristic. These components are both inexpensive and uncritical to use. The optimal one

Working range of these components from about 100 kHz to 200 MHz could be achieved by a higher reception frequencies

Demodulator upstream frequency conversion device can be used. This frequency conversion device added tolerable distortions in the time domain to the signal, but only superimposed a small amount of additional noise.

With a transmitter for sending a

electromagnetic carrier signal with a fixed frequency, the signal to be received could be raised; However, the greatest attention had to be paid to the stability of the carrier frequency in order to avoid unwanted modulations in the

exclude the frequency range of interest. A simple quartz-stabilized analog transmission circuit with one

The high-quality resonant circuit was surprisingly found to be a suitable oscillator after a sufficient settling time.

Using a transmitting antenna with a fixed directional characteristic, a kind of cross bearing is achieved together with the receiving antenna and the location not only in one spatial direction, but in a defined three-dimensional direction

Areas possible.

This location can be used successfully with a homogeneous pile or in an open environment. As a result, the inventive method and the inventive

Device can also be used for object monitoring and / or security. The special exemplary embodiments show both a later location of this description

portable as well as a stationary monitoring arrangement.

In contrast to high-frequency digital filters, the use of an analog sampling filter showed no adverse additional frequency components and made a significant contribution to the quality of the signal received. Additional unwanted signal components, such as noise and superimposed interference, have been eliminated by limiting the bandwidth of the electromagnetic Avoid signals before sampling and before A / D conversion to high frequencies.

The use of an analogue was also important

High-pass filter to avoid low-frequency components of the frequency-dependent l / f noise of the transmit oscillator and internal modules.

The unexpectedly good functioning of the device according to the invention and of the method according to the invention also permit its use in other areas.

In prison or psychiatry you can

suicidal persons are monitored without the constant supervision by caregivers.

The invention will now be described by way of example with reference to the accompanying drawings

Embodiments described in detail.

Show it:

Fig. 1 is a schematic representation of the main assemblies

an embodiment of the invention

Contraption,

Fig. 2 is a schematic representation of a simpler

Embodiment of the device according to the invention

with their main components,

Fig. 3 is a schematic representation of the structure of the

Evaluation chain,

4 and 4a are a flow diagram of the implemented

Processing steps,

5 and 6 spectral representations of with the

device according to the invention detected

electromagnetic signals with for living

Body characteristic frequency components,

Fig. 7 shows a direct diode receiver without an upstream

Converter,

8a is a circuit diagram of an analog high-pass filter and an anti-aliasing filter designed as a low-pass filter,

8b is a circuit diagram of the voltage symmetrization, FIG. 9 shows an overview of FIGS. 11 to 14, in which a second transportable device according to the invention

Embodiment is shown

10 shows an overview of FIGS. 15 to 17,

in which a third, in a rectangular one

Trough arranged according to the invention

Embodiment is shown

Fig. 11 is a control panel of the second invention

Embodiment from above,

Fig. 12 is a sectional view taken along line A-A

Fig. 14

Fig. 13 is a sectional view taken along the line B-B

Fig. 14

Fig. 14 is a sectional view taken along the line C-C

Fig. 12

Fig. 15 is a sectional view of the third

Embodiment according to the invention along the

Line F-F of Fig. 16,

Fig. 16 is a sectional view of the third

Embodiment according to the invention along the

Line D-D of Fig. 17,

Fig. 17 is a sectional view of the third

Embodiment according to the invention along the

Line E-E of Fig. 16.

In the following, the invention is first described in more general terms and as a result of more detail using individual embodiments.

1 shows an arrangement with a transmitter 1 and a transmission antenna 2, which transmit on a fixed frequency, which is preferably in the range from a few 100 MHz to about 10 GHz.

The transmission antenna 2 preferably has a lobe-shaped, fixed directional characteristic. The transmitter 1 and the

Depending on the embodiment of the invention, the transmitting antenna 2 is designed as a portable unit or mounted in a stationary manner. The receiving device designated as a whole by 3, which is shown in a simpler embodiment in FIG. 2, comprises a receiving antenna 4 which is connected to a

Direct modulator 5 is connected, which for the living body from the received electromagnetic signal

characteristic frequency components demodulated. This

Demodulation is carried out as phase or frequency demodulation and can already at the output of the

Direct demodulator 5 the desired frequency components

provide.

Compared to the embodiment of the direct demodulator shown in FIG. 7, it can also consist of a

Rectifier bridge of known design exist, which leads to a voltage-doubled or voltage-quadrupled useful signal.

In a further embodiment, the receiving device 3 comprises an upstream of the demodulator 5

Frequency conversion device 6, which receives signals as a converter above approximately 200 megahertz to terrahertz

Converts frequency ranges in which the direct demodulator 5 shows increased reception powers. When using diodes, a bipolar or a field effect transistor, this suitable, down-converted, optimal working range is around 100 kHz to 200 MHz.

There is a downstream of the direct demodulator

Filter device 7 for filtering undesirable

Signal components that determine the bandwidth of the electromagnetic signal before sampling (before analog /

Digital conversion) limited to high frequencies. This filter device 7 also limits the bandwidth to low frequencies. The amplifier 8 connected downstream of the filter 7 increases the voltage or alternatively

Embodiment the current of the received signals and leads them to an analog / digital converter 9 for sampling. After analog / digital conversion, those for living

Body characteristic frequency components by a

Computing device 10 prepared for spectral analysis and displayed spectrally. Here the intensity of the

Frequency components that are characteristic of living bodies, information about the existence of the vital functions of the detected human body.

When the signals are evaluated over time, the digital signal is folded for its equalization with the inverse transfer function of the receiving device 3.

Since the reliable detection of these signals is extremely difficult, the direct receiver with the nonlinear element is described below using a direct diode receiver.

Direct diode receiver

The reflected signal is phase or

frequency modulated. The detection of this modulation is not possible with the usual reception techniques for FM (frequency modulation) and PM (phase modulation) or only under extreme ones

Difficulties possible. For a signal modulated at 0.2 Hz e.g. At 10 GHz to be detected with an accuracy of 0.2 ± 0.02 Hz, short-term stable, synchronized oscillators would be included

Deviations of less than 10 are necessary. So far, this did not seem technically feasible.

A way was therefore sought to directly demonstrate the modulation of the received signal.

For example, components with largely square characteristic curves are suitable for this; These include field effect transistors, components with

exponential characteristics, which can be approximated piece by piece as a square, diodes and transistors. If the voltage received is impressed, the sum of two

When frequencies are applied, higher-order terms are created. If there is a quadratic term, then in addition to the directional current, differential frequencies also occur. To do that

Demodulating phase-modulated signal, which is reflected by the person to be detected, can thus be surprisingly despite the highest demands on the

Frequency behavior can already be used with an ordinary rectifier.

The phase-modulated signal is impressed on the non-linear characteristic curve, and currents arise which are proportional to the phase modulation frequency Ω and its multiples k * Ω. The curve shape of the modulation remains due to the

Demodulation principle not received, but it has been found that these changes in the curve shape are not critical for most applications according to the invention, since the detection of the modulation may be sufficient for these.

The signal-to-noise ratio determines the direct

Evidence of the sensitivity limit. S / N values of over 46 db were achieved for the breathing frequency, values of 26 dB for the heartbeat at a distance of 3 m and with oscillator powers of approx. 5 mW.

Assuming that spherical waves are emitted from the heart, there is an inversely proportional relationship between the transmitted and received power to the second power of the distance

Relationship. For the ratio of the amplitudes of the

Breathing frequency UA for noise UN or heart rate UH for noise can therefore be estimated that the

Reception limit at a transmission power of 1 W is then about 50 m with respect to the heartbeat and typically 160 m with respect to breathing.

Antennas with higher gain and low-noise components can increase these values accordingly in the manner according to the invention. Sufficient reception signals are therefore still to be expected for location, even for layers of soil several meters thick. The ideal diode with regard to saturation current 10 and temperature voltage is the Si power diode 1N4004, whose suitability as a rectifier is, however, restricted to high frequencies by the large junction capacitance. This is followed by the small signal Si diode 1N4148, then the Si Schottky diode BAT 46 and finally the two Ge diodes AA116 and AA144.

A direct diode receiver was tuned for 440 MHz, 1.3 GHz, 2.4 GHz, 5.6 GHz and 10 GHz, respectively. For 4 of the 5 frequencies, receiving antennas with direct diode receivers were built:

440 MHz: half-wave dipole with v = 0.940, Z = 60.5 Ω

and BAT 46

1.3 GHz: half-wave dipole with v = 0.906, Z = 57.4 Ω

and BAT 46

2.4 GHz: half-wave dipole with v = 0.940, Z = 60.5 Ω

and BAT 46

5.6 GHz: whole-wave triangular dipole with v = 0.73,

Z = 140 Ω and BAT 46

Even with this receiver, the sensitivity dropped sharply compared to the 2.4 GHz receiver. At 10 GHz, no usable voltage was detectable, so that a 10 GHz direct diode receiver was not built. The available diodes no longer show a usable rectifier effect at such high frequencies.

Since the signals according to the invention had been classified by experts as below the measurement limit, the

strong attention has been paid to the antenna types used.

Antennas

The forward-backward ratio must be made as large as possible for the location in order not to receive signals which are incident in the opposite direction to the main emission direction. Side lobes must also be minimized for this reason. The entire

The radiation diagram should therefore have the smallest possible main lobe and no side lobes. In accordance with the invention, the input impedance of the antennas can and should be matched to real or complex impedances in such a way that power matching is achieved in transmitters and noise matching in receivers. The

However, meeting these requirements with an antenna design is not possible at the same time.

All antennas used are endfire antennas because

Backfire antennas of comparable dimensions always on

have a worse front-to-back ratio because the waveguide structure must be excited in the reverse direction. The antennas should be as broadband as possible, since an adjustment should be avoided. Broadband antennas with a very good front-to-back ratio are logarithmic

periodic structures known. Through the logarithmic

Grading of the waveguide structures is on the one hand

Broadband and, on the other hand, a pronounced directional effect. The fact that the gain is lower compared to resonant antennas of comparable dimensions does not generally bother the application according to the invention.

The polycon antenna can replace the rotating paraboloid antenna, since deviations from the paraboloid shape that are smaller than a tenth of a wavelength do not have a negative effect on the behavior of the antenna. Even at a fifth of the wavelength, the loss of gain remains below 2 dB and can therefore be neglected in most cases.

The technically complex design of the paraboloid reflector can thus be replaced without disadvantages by the more easily implemented polycone reflector. However, the feeding is comparatively complex, and the front-to-back ratio only improves with reflectors that are large compared to the wavelength and whose illumination is limited to the inner area.

In order to avoid the problems with polarization, our embodiments with the two higher frequencies (5.6 GHz and 10.368 GHz) each use a circularly polarized antenna - once as a receiving antenna, once as a transmitting antenna. Although this typically results in losses of typically 3 dB, these are small in comparison to the losses that can occur with linearly polarized antennas rotated against one another.

In one embodiment with only one common transmitting / receiving antenna, the incoming and outgoing waves could be successfully separated using a circulator.

Due to the difficult metrological conditions to be overcome, special attention was also paid to the high-frequency assemblies.

High frequency assemblies

The required high-frequency modules are listed below. The list takes into account the possible ones

Links that exist between the modules and the peripheral elements. These correspond to the configurations according to the invention that we have implemented.

The direct modulators are used at the higher frequencies, i.e. at frequencies above approx. 200 MHz according to the converters converting to the intermediate frequency of 137.5 MHz

used. At this frequency, both the diodes used and the transistors are functional.

1. Diode mixer

The diode mixer consists of a symmetrical one

Voltage quadruple circuit with a resonant circuit at the input and a low pass at the output.

In contrast to the voltage that can be achieved with the diode as a direct receiver, four times the output voltage can be achieved here, since the sources are now connected in series. The resulting increased internal resistance is for the

Function irrelevant.

In practical operation, it was found that the diode mixer has a different signal-to-noise ratio

known mixer designs is superior. Low frequency assemblies

All modules operated in the low frequency range are equipped with their own power supply. For this purpose, single lead batteries with 12 V / 2Ah were used, which were provided with a voltage monitoring circuit and an on-switch. The strict separation of everyone

Power supply units turned out to be necessary after the use of a power supply led to considerable interference.

The entire arrangement is thus completely isolated on the transmitter side and only connected to the network on the receiver side via the personal computer, which, however, is

portable devices as a battery powered device

is trained .

1. Preamplifier

The preamplifier uses a low noise quadruple operational amplifier. One of the amplifiers is as

Operating voltage balancer switched; the other three are connected as bandpass filters and are coupled to one another via high-pass filters.

A low-pass filter limits the noise in the first stage. An optional resistor was used to supply the direct diode receiver with a bias current from the preamplifier.

A total of two preamp modules were included

different reinforcement used. Since the

A sensitive amplifier of the entire arrangement can overdrive the A / D converter and thus lead to data loss.

2.Sampling filter (anti-aliasing filter)

The sampling of time-dependent signals must be done with a

Frequency that is greater than twice the highest frequency contained in the input signal. Therefore, the input signal must be spectrally limited before the analog-digital conversion. Surprisingly, for the purposes of the present invention, this limitation must be by an analog filter and cannot be replaced by digital processing. If this is not taken into account, a

Undersampling of the spectral components that are above half the sampling frequency. These are mixed in the lower frequency range and falsify the signal

irreversible and therefore the success according to the invention cannot be achieved.

So-called digital anti-aliasing filters that the

Allowing users to believe that the band can be limited after the A / D converter has surprisingly proven to be completely ineffective with regard to the problem; all with the

Undersampled errors occurred. A

Subsequent digital correction was no longer possible due to the destroyed signal content.

In general, it should be noted that experts are so wrong about analog and digital parameters

Conceptions prevail that the design of a measuring system for the digital processing of analog quantities due to the

Information from the manufacturer and the exclusive use of the hardware and software offered by them could not lead to the goal.

The demands placed on the analog anti-aliasing low-pass filter are very high depending on the further processing. The dynamic range must be at least 1 bit better than that of the subsequent A / D converter, and linear and non-linear distortions must also be at least 1 bit better than the A / D converter. Although the dynamic range of an N-bit A / D converter is usually only N-2 bits in practice, these relationships must be taken into account.

Switch-capacitor filters can be used if the sampling theorem is also taken into account there and the dynamic range achieved is sufficient.

The convolution of the input signal with the sampling filter leads to amplitude and phase distortions and, due to the group delay of the filter, to envelope distortion. This If necessary, signal changes can be taken into account by convolving the inverse transfer function of the sampling filter with the sampled signal in the computer. This procedure is only possible if the scanning has been carried out correctly. In the case of undersampling, however, the error continues

enlarged.

Between the upper signal frequency fs, sampling frequency fa, asymptotic slope or order of the sampling filter N and the oversampling factor k there is the following relationship to the achievable accuracy or resolution A in bits:

A = k * N + 1

For a cut-off frequency of fs = 2 Hz with a resolution of A = 13 bits, e.g. following options for implementation:

1st order filter (N = 1) ==> sampling frequency fa = 16384 Hz 3rd order filter (N = 3) ==> sampling frequency fa = 64 Hz

6th order filter (N = 6) ==> sampling frequency fa = 16 Hz

The last combination is ours

Embodiment used arrangement. For low order filters with "good-natured" behavior regarding the

Surprisingly, transfer function must be with extreme

Oversampling rates can be calculated to achieve useful results. Despite the high sampling frequency of over 16 kHz, only the spectral components up to 2 Hz are correctly sampled. (With A = 16 bits, fs = 20 kHz and fa = 44 kHz, filters of the 109th order would be necessary to carry out a scan corresponding to the

Perform sampling theorem.)

Oversampling has another advantage: Every analog-digital converter, even if it is ideal with regard to its characteristic curve, adds this to the signal to be sampled

Add quantization noise so that the signal is not only due to the quantization, ie the discretization of the Amplitude values, is falsified, there is also additional noise.

The noise can be regarded approximately as white, so that with a larger scanning bandwidth, i.e. at

Oversampling, in the signal bandwidth correspondingly less noise falls and thus the signal-to-noise ratio of the converter, but not the signal, can be improved proportionally.

The 6th-order sampling low-pass filter used is achieved by connecting two 3rd-order low-pass filters in series

(asymptotic edge steepness 18 dB / octave or 60 dB per decade) realized. Each low pass consists of an as

Voltage follower switched operational amplifier and an R-C circuit.

The amplitudes, phase and envelope distortion due to the frequency and phase response of all filters as well as the

Group delays can be undone by folding the time function with its inverse transfer functions T-1 (w) of the previous signal path T (w) and thus performing a complete pole-zero compensation. This may be necessary if the original time signal is to be reconstructed and therefore the deformation of the

Time signal through the converter and the elements of the

Transmission chain must be avoided. In one

Use cases in which the significant detection of a spectral line is required can be disregarded.

In the construction according to the invention, in one embodiment, the time signal passes through at least one from the converter (receiving antenna) to the personal computer (A / D converter)

15th order high pass and 21st order low pass, which result from the product of the transfer functions of the individual elements of the measuring chain (direct mixer, preamplifier, 2 * low pass, 2 * high pass, A / D converter).

The dynamic behavior of the analog part of the

Electronics can also be improved by assemblies if necessary that carry out pole zero compensation directly. This can reduce noise, a

unfavorable transmission behavior can be improved or can be optimal according to certain criteria

Transmission properties can be achieved.

3. High pass filter

The spectral limitation of the input signal in relation to the low frequencies is advantageous according to the invention for three reasons:

1. 1 / f noise

The amplitude of the l / f noise increases reciprocally to the frequency. Therefore, with increasing measuring time, noise components with an ever lower frequency appear and falsify the signal to be measured. The main sources of the l / f noise are the transmit oscillator, the converter oscillator, the

Operational amplifier.

2. Slow movements

Movements of the body to be detected lead to a Doppler at constant speed

Frequency shift and thus to spectral components that can fall within the frequency band to be examined. at

a wide additional band occurs in irregular movements. The slower the movements, the lower the frequency of the spectra, which are then increasingly difficult to separate from noise components.

3. Evaluation time

In order to identify a spectral line of frequency f, at least one time t = l / f must be measured, i.e. the lower the frequencies to be detected, the longer it has to be measured. Since it cannot be guaranteed that the measuring time is an integer multiple of the interested

Is a spectral component, a leak effect occurs in the Fourier analysis. This leads to a spectral spread. Therefore, a measurement time that is a multiple of the period must be observed when analyzing low frequencies, the accuracy increasing proportionally with the measurement time. At 10% Errors in the spectral resolution and 0.2 Hz lower frequency must be expected with a typical 50 second measurement time.

Figure 3 shows the general structure of the evaluation chain. Personal computers from the

Office area, type IBM-PC compatible, used because their

Efficiency was sufficient for the task.

The plan shown in FIGS. 4 and 4a gives one

Overview of the implemented processing steps, where F {} denotes the Fourier transform and F-I {} the inverse Fourier transform.

Results

After various preliminary tests, one came up

Sampling rate of 16 Hz with a unipolar resolution of 13 bit (total resolution 14 bit) turns out to be well suited. As

Window width for the spectral analysis were 512 values

correspondingly selected about 33 seconds; as a window that

Hamming window.

FIG. 5 shows the heart rate of a test person when breathing was stopped. The spectral component stands out so clearly from the environment that for the detection of the

Heartbeat of the test subject, further processing is not necessary. The range of amounts is plotted in

arbitrary units over frequency in Hertz. The

Measurement took place at 2.4 GHz, it was the

Direct diode receiver, i.e. the 1/2 dipole used as the receiver, the local oscillator as the transmitter, breathing was stopped.

FIG. 6 shows the spectrum of the signal reflected by a breathing person using the direct diode receiver and the logarithmic-periodic Yagi antenna and the 1.3 GHz transmission oscillator as the source. Both heart rate and breathing rate are available.

At the frequency of 440 MHz, the tests were carried out due to the extreme sensitivity of the entire arrangement as difficult. Show almost all test shots

Overrides and reactions to external events.

The problem of overdriving can be solved by appropriate damping; the evidence of breathing and heart activity is not affected by this.

If a circulator is used, you get how

described with an antenna that transmits and receives simultaneously.

The examples clearly demonstrate that the detection of living people is possible. Neither walls nor distances of a few 10 meters are worth mentioning

Obstacle. 1.3 GHz and 2.4 GHz turned out to be well suited as the working frequency. In the case of antennas that are still handy, the sensitivity is high enough to obtain reproducible results with clear identification of the heartbeat and breathing, without intensive numerical

Processing steps are necessary, since there are already strong reception signals.

Circuit diagram high pass and anti-Alisainq low pass

The circuit diagram of those used for band limitation

Assembly is shown in Fig. 8a and 8b. The third-order high-pass filter suppresses the low-frequency noise components, in particular the l / f noise. The following third order low-pass filter limits the spectrum to higher frequencies. A linear amplifier stage for level adjustment follows. The

Operating voltage is electronically balanced so that a unipolar supply is sufficient. Two of these modules in cascade meet the requirements of the sampling theorem.

Diode demodulator circuit diagram

A diode detector, the circuit of which can be seen in FIG. 7, is used for phase demodulation of the received signal mixed to the intermediate frequency and as a direct demodulator for the developed receiving antennas. The circuit corresponds to a typical power meter; a bias current can come from the output be impressed. The input impedance can be adapted to the IF mixer or the antennas.

Diode direct receiver circuit diagram

The direct diode receivers consist of 1/2 or 1

Wavelengths long, multiplied by the corresponding shortening factor, and are corresponding

upstream. A bias current can be impressed at the output.

In addition, each unit has its own

stabilized power supply and its own on-off switch, so that modules with large

Time constant (local oscillators, preamplifier, low-pass filter) could be operated in continuous operation and were in thermal and electrical equilibrium, while consumers with high current consumption (transmitter output stages, converter) can be switched off between applications.

Preferred special embodiments

In a first preferred embodiment, the device according to the invention does not include one in the figures

Specially shown polycone antenna, which simulates a flat parabolic antenna piece by piece, as a transmit / receive antenna 2, 4. The transmit / receive antenna 2, 4 is provided with a circulator, which provides a decoupling between transmitted and

received signals causes.

A defined search of target detection areas can be carried out using a mechanical swivel head and preferably scales assigned to swivel angles. Motorized tracking of the swivel head around its swivel axes with electronic control for grid-like scanning of the target detection area allows automated recording of data even in areas inaccessible to humans, such as nuclear contaminated areas.

Areas prone to earthquakes or chemical explosions. In addition, a threshold function can define values in the frequency interval described above, Above which the signaling of the detection of a living person is carried out.

In a second version according to the invention, all electronic assemblies up to the analog / digital converter 9 are accommodated in a pilot's suitcase. The case version provides a complete system for capturing living

Persons or living beings.

In a pilot case 14 there are two shortened antennas 2, 4 with angled reflectors and folding dipole exciters. The antenna Tx used as the transmitting antenna 2 is connected to a transmitter which, at an operating frequency of 1300.0 MHz, delivers a power of 6 mW at an equivalent load of 50 Ω. The horizontal opening angle of each antenna is 54 °, the vertical opening angle is 64 °. The profit, determined by comparison with a calibrated

Reference antenna is 6.7 dBi each. The receiving antenna 4 Rx is connected to a receiver, which by means of

Converter 6 converts the incoming signals into the frequency range around 137.5 MHz. This is followed by the demodulator 5, the amplifier 8, the filter 7 and a driver. Four rechargeable lead-gel batteries 15, 16, 17, 18 serve to supply energy. The units are in a frame 19 made of aluminum profiles 20, 21, 22, 23 in two levels

arranged. The upper, third level is formed by the front panel 24 with the controls. The entire insert can be completely removed from the case 14 for service purposes.

The front plate 24 carries four on-off switches 25, 26, 27, 28, which are assigned to the respective components, two 4 mm charging sockets 29, 30, a multipole socket 31 for data transmission on the PC and a manually operated level control 32 to reduce the signal amplitude of the

Output signal.

A PC with a built-in analog-to-digital converter is connected via a flexible cable. The evaluation of the Measured signals are made by a for the application

adapted software program that carries out the method steps shown in FIGS. 4 and 4a.

From the transmitter via the transmitting antenna 2, Tx

unmodulated signal emitted. If the signal hits a living being, breathing and heartbeat cause one

Phase modulation of the corresponding surfaces

reflected waves. The reflected waves are picked up by the receiving antenna Rx, by the receiver onto one

Lower intermediate frequency implemented and phase demodulated in demodulator 5.

The information you are looking for is now in the form of

low-frequency voltage fluctuations. These are amplified and the bandwidth is limited to frequencies between 0.05 Hz and 4 Hz by means of filters. An anti-aliasing filter 7 prevents the creation of aliasing frequencies, caused by the sampling of the signal during the analog-digital conversion. The shielding braid of the transmission cable is driven to avoid external interference. The associated compensation of the cable capacity allows cable lengths of several 100 meters between the personal computer with the analog / digital converter and case. The

Software allows the user to select time intervals for the signal. After selecting a window function, the transformation from the time domain to the frequency domain takes place.

The evaluation of the spectrum by the user is based on a statistical evaluation of the probability of

Support the presence of a living person, which is based on the experience gained so far. Another

statistical approach delivers the expected

Distance interval in which the detected person is staying.

Due to the compact design and mobility, the following areas of application can be found for the case version: For police authorities for portable monitoring in general, as well for monitoring the perpetrator and the hostages in the event of hostage-taking, monitoring of empty buildings, monitoring of empty vehicles, monitoring of tunnel and canal structures, as well as in the fight against terrorism and extremism, at customs and border authorities, for example for checking containers for the presence of a living being, or checking vehicles .

In the third embodiment of the invention, the device is in a fixed and mounted

rectangular tub. There are eight shortened antennas 2, 4 with angled reflectors and folding dipole exciters in a metal trough 33 with a plastic base 34 that is permeable to high frequencies.

Antennas interconnected in four groups are connected as transmit antennas 2 to an amplifier 35 which, fed by a transmitter 1, Tx, delivers an output of 600 mW at an equivalent load of 50 Ω at an operating frequency of 1300.0 MHz. The horizontal opening angle of everyone

Antenna is 54 °, the vertical opening angle is 64 °. The result is the same profit as with the case version. The receiving antenna 4, likewise combined from a group of four antennas, is connected to a receiver Rx, which converts the incoming signals into the frequency range of 137.5 MHz by means of a converter 6. This is followed by the evaluation electronics already described in the second version of the case version according to the invention.

The third embodiment of the invention is used in fixed applications. These include customs and

Border authorities as well as tunnel and hall operators. It is the surveillance of empty buildings, empty vehicles, the monitoring of tunnels and canal structures as well as the use in endangered buildings for terrorism and

Combating extremism possible. A container check for the presence of a living being can be done covertly, so that even blind passengers at border crossings or in Loading area of trains or planes can be captured.

Claims

claims

1. Device for detecting living bodies, in particular for detecting living human bodies, with the help

electromagnetic signals and a receiving device for electromagnetic signals,

characterized,

that the receiving device (3) for electromagnetic signals is a device for obtaining characteristic frequency components for living bodies from the

includes electromagnetic signals.

2. Device according to claim 1,

characterized,

that the receiving device (3) comprises a direct demodulator, which directly from the received electromagnetic

Signal the characteristic of living bodies

Frequency components demodulated.

3. Device according to claim 2,

characterized,

that the direct demodulator (3) is a component with a non-linear current / voltage characteristic

frequency-selective element for the demodulation of the frequency components characteristic of living bodies.

4. The device according to claim 3,

characterized,

that the direct demodulator (3) is a diode, a bipolar or a field effect transistor as a frequency selective

Element includes.

5. Device according to one of claims 1 to 4,

characterized,

that the receiving device (3) comprises a frequency conversion device (6) connected upstream of the demodulator (5).

6. Device according to one of claims 1 to 5,

characterized,

that the device comprises a transmitting device (1) for transmitting an electromagnetic carrier signal with a fixed frequency.

7. The device according to claim 6,

characterized,

that the carrier signal is in a frequency range from approximately one MHz to approximately one THz.

8. Device according to one of claims 1 to 7

characterized,

that the device for obtaining frequency components characteristic of living bodies comprises a filter device (7), a scanning device, an A / D converter (9) and a computing device (10) for spectral analysis.

9. The device according to claim 8,

characterized,

that the filter device (7) at least one analog

Sampling filter includes.

10. The device according to claim 9,

characterized in that the sampling filter limits the bandwidth of the electromagnetic signal to high frequencies before sampling and before A / D conversion.

11. The device according to one of claims 1 to 10, characterized in that

that all electronic assemblies in the signal path before the digital evaluation, including their power supply, are arranged in a portable suitcase.

12. The device according to one of claims 1 to 11,

characterized,

that all the electronic assemblies lying in the signal path before the digital evaluation, including their voltage supply, are arranged in a rectangular, fixed tub.

13. Method for the detection of living bodies, in particular for the detection of living human bodies, with the aid of the reception of electromagnetic signals

characterized,

that characteristic frequency components for living bodies are obtained from the received electromagnetic signals.

14. The method according to claim 13,

characterized,

that the received electromagnetic signal

is directly demodulated.

15. The method according to claim 13 or 14,

characterized,

that the received electromagnetic signal is converted to an intermediate frequency.

16. The method according to any one of claims 13 to 15, characterized in

that the received signal is limited analogously to high and low frequencies.

17. The method according to any one of claims 13 to 16,

characterized,

that the received electromagnetic signal is sampled after the filtering and converted into a digital signal.

18. The method according to claim 17,

characterized,

that the digital signal with a window function in

Time range, and is folded with the inverse transfer function of the receiving device.

19. The method according to claim 16, 17 or 18,

characterized,

that the digital signal before its evaluation and

Representation as output signal from time to

Frequency range is transformed.

20. The method according to claim 19,

characterized,

that the transformed signal is analyzed in a frequency range from approximately 0.01 Hz to approximately 10 Hz, preferably from approximately 0.02 Hz to approximately 3 Hz, for the frequency components of cardiac and / or respiratory activity that are characteristic of living bodies.

21. Use of a device and / or a method according to claims 1 to 20 in the prison system

Monitoring the condition of detainees.

22. Use of a device and / or a method according to claims 1 to 20 for object monitoring and / or security, including persons located therein.

23. Use of a device and / or a method

according to claims 1 to 20 for detecting and / or locating living bodies in disaster protection, in particular in the event of earthquakes, landslides, avalanches, house collapses and / or fires.