DE2331328A1 - MONITORING OR ALARM - Google Patents

Description

surveillance or alarm system

The invention relates to a system for displaying Movements that work according to the Doppler principle and can be used, for example, as an alarm system, and refer to them in particular on a combined ultrasonic and microwave monitoring system for the reliable evaluation of movements.

In a group of systems for displaying movements, a sensitive receiver is connected to a transmitter used to receive and measure an electric field. When an intruder or object triggers the electrical Field interferes, there is a change in the field strength, which is determined by the receiver and triggering a display or Alarm device is used. Another group of systems for displaying movements is room alarm systems which are characterized by the fact that they bring energy into one

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special space to be protected or radiate into the space surrounding an object to be protected and then a part of the emitted energy, which is reflected from the environment. If there is a plague, for example an alarm is triggered if the frequency of the reflected energy changes as a result of an intruder in the area of the room. Any change in frequency of the reflected energy compared to the radiated energy is reflected in the monitored Moving object area. This principle is known as the "Doppler Effect". With this type of equipment the Doppler frequency shift in that of the moving Object detected within a certain range of reflected radiation.

The invention relates to a room alarm system which works according to the Doppler principle and is characterized in that the energy radiated from a set of transducers is ultrasonic energy and that from a transmit / receive antenna (monostatic antenna) microwave radiation is emitted.

The essential parameter in the optimal design of any motion surveillance system is the highest possible Probability of displaying movement with the lowest probability of a false alarm. Even though Numerous systems have been designed with which a Doppler signal can be reliably separated from a received wave

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should be »if the Iranians get false alarms again, Da. see an intruder at a much slower rate ala moves the emitted radiation, the Seeing intruder only a very moving Doppler effect small percentage change in the frequency of the radiation received. For example, if energy has a frequency of 20 kHz is reflected by an intruder moving at a speed of 30 cm per second, so the Doppler effect of the intruder's movement causes the received frequency to deviate from the transmission frequency of only 37 Hz. This is a very small frequency shift that is reliably indicated shall be. An optimal detector will reliably display the Doppler effect and reject external signals that are associated with could be mistaken for a Doppler signal generated by movement.

The monitoring system according to the invention generates a lower number of false alarms than comparable systems to date Effort by sending an alarm signal from a microwave device to the alarm signal from an ultrasound device combined. An alarm device is only activated if an output signal is given by both devices at the same time actuated, which indicates a movement in a certain area of space.

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In many applications, motion monitoring systems should protect a very wide area. There are certain difficulties in doing so. For example, this results in one high probability that an antenna unit will respond to interference in its vicinity if this antenna unit To detect intruders at a great distance from the antenna. On the other hand, it is more likely that a unit that has a more uniform sensitivity ie near and far range, responds to disturbances outside of the The boundaries of the area to be monitored arise. Thus, it is suitable for uniform monitoring of a large area in the it is generally desirable to use a large number of units distributed in the area to be monitored. A disadvantage for many Microwave Doppler detectors exist in the need for expensive and complicated devices with separate ones Transmit and receive antennas to protect large areas, while using a single antenna expensive transmit-receive circuits are required to protect the receiver against the high-power transmission signals to reach.

An advantage of the system according to the invention consists in the use of several ultrasonic transducers for overlap of the large volume of space, the probes being connected in parallel by cheap bandpass circuits. In addition, in

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The microwave device has a single, omnidirectional transmitting / receiving antenna to improve the reliability of the system together with a miniaturized high-frequency circuit to achieve a balanced Doppler mixture used without complicated high frequency facilities.

One point of alarm systems that has received little attention so far is the difficulty of displaying faults within the plant. Many currently available alarm systems can be very easily protected from the intruder the intrusion into the monitored area are rendered ineffective. Furthermore, the failure of one or more converter arrangements lead to a complete ineffectiveness of the system without this being recognized by an operator. In the present invention, both the ultrasonic and the microwave devices of the system can be equipped with automatic Self-test circuits, with intrusion indicator circuits and be provided with external test circuits. The automatic Self-checking and tampering indicator circuitry for the ultrasonic device can operate so that the ultrasonic energy is applied to the two The monitoring signal is transmitted to the lines leading to the transmission element. The microwave device will thereby automatically self-checking that a DC voltage interrogation connection is used in a bridge or push-pull mixer whose output signal is used for automatic Self-examination and intervention notification is used.

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Both the ultrasonic and the microwave device carry the self-checking and tamper-evident signals of a Self-check and tamper-evident logic circuit too. These Signals from the ultrasonic oscillator and the microwave transmitter oscillator do not occur when (1) the microwave energy fails, (2) the ultrasonic energy fails, or (3) the Lines for the supply of ultrasonic energy to the ultrasonic transmitter elements interrupted or short-circuited. The self check and tamper indication logic circuit triggers an alarm if one of the above signals fails.

According to the invention, the ultrasonic microwave monitoring system an alarm means to generate an indication of movement for a particular area. Can do this an ultrasound probe that responds to movements within the specified area and engages with a provides such a movement changing output signal. A microwave probe also speaks to movements within of the specific range and supplies an output signal that changes with such movements. With the ultrasound probe and the microwave probe is connected to a combination circuit which triggers a signal for the alarm device, if the output signal of both probes is simultaneously in is in a state that requires movement within the

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relevant area. There is also a test circuit connected to the ultrasound probe and the microwave probe and speaks to fault conditions within the system to generate a fault indication signal for the alarm device. '

The invention is explained in more detail below with reference to the figures.

Fig. 1 shows a schematic, perspective partial representation an ultrasonic / microwave alarm system according to the invention with three ultrasonic assemblies and a single one Microwave antenna.

Fig. 2 shows a block diagram of the system according to the invention, in which the signals from an ultrasonic probe and a Microwave probe for generating an alarm signal can be combined.

Fig. 3 shows a block diagram of that having the microwave probe Part of the system with a stripline oscillator connected to a bridge or push-pull mixer is.

Fig. Ij shows schematically a stripline oscillator with is coupled to an H-tape conductor mixer.

Fig. 5 shows an equivalent circuit of the microwave part the system from which it follows that an adapted

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Antenna represents an ohmic load when there is no target to be monitored.

FIG. 6 shows a block diagram of the ultrasonic part of FIG System according to FIG. 2, wherein a number of transmitting radiating elements and a number of receiving elements available.

7a and 7b show schematically the circuits for combination the receiver elements or the transmitter elements.

8 schematically shows an oscillator and the distribution and intervention monitoring circuit for the ultrasonic transmission elements .

Fig. 9 shows in a diagram the frequency profile of a typical Ultrasonic emitter as a function of temperature.

Fig. 10 shows schematically an oscillator and driver circuit controlled by the radiator element.

11 schematically shows a test modulator and mixer circuit for the ultrasonic part of the system according to FIG. 2.

The alarm monitoring system shown in Fig. 1 for the protection of a certain area, for example a size of Jl m χ 15 m, has a central detector unit 10 and outer converter units 12 and I ¹ I, all by means of a pipe bracket

16. which also serves as a cable guide, about 1.8 m above the

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Are attached to the ground. The central detector unit 10 contains 4 ultrasonic receiving elements 18, only two of which are shown are, as well as a microwave antenna 20, which both in the transmission ais also works in the receiving business, as this is explained will. Each of the outer transducer units 12 and 14 has ultrasonic transmission elements 22, of which only two are shown. For some small areas to be monitored, one or several ultrasonic transmitting elements 22 and the ultrasonic receiving elements 18 all in a central detector unit be housed so that the outer transducer units are avoided. In this Aüsführungsbeispiel is in the central Detector unit, an ultrasonic transmission element (not shown) is provided which controls an oscillator frequency, as described will. If external transducer units or a composite central detector unit is used, it works the plant in the manner to be described.

The signals to and from the central detector 10 and the outer transducer units 12 and 14 come from and arrive at one, respectively central controller 24, which contains the electronics. A main control switch 26 controls the operation of the system to either to enable protection against intruders or to switch off the system so that movements in the area to be monitored are possible without triggering an alarm. Alarm signals from the central controller 24 are sent to a monitoring console 28, the four rows of alarm indicators each

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usual type contains. Since more than one particular area can be monitored by means of the same console 28, a number of central controllers 2k can be connected to it, one for each indicator when the console is at full capacity.

The Doppler alarm system shown as a block diagram in FIG. 2 According to FIG. 1, the ultrasonic device 30 contains both the transmitting elements 22 and the receiving elements 18, and the microwave device 32 with the microwave antenna 20. Each of the devices 30 and 32 is itself constitutes a complete Doppler alarm system, and these devices are described in turn.

An output alarm signal from each of the devices 30 and 32 is fed to the inputs of a combinational logic circuit J> k in the central controller 2 ¹ I in order to generate an alarm signal on a line 36 to the monitoring console 28. Typically, the outputs of devices 30 and 32 will be logic signals changing between "upper" and "lower" states and applied to a NOR gate in combinational logic circuit J> k to produce a changing logic signal on the line 36 to generate. In accordance with the operation of a standard logic circuit, an alarm signal appears on line 36 when both input

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signals of the combinational logic circuit J> k from the devices 30 and 32 are in the same logic state. The combination logic circuit 3 ^ thus only switches when both devices 30 and 32 give an alarm at the same time and thereby indicate a movement within the area to be monitored. There is therefore a redundancy that reduces the likelihood of a false alarm, which often occurred with previous alarm systems.

Both the ultrasound and the microwave device are constantly monitored for correct operation and for intervention by someone trying to bypass the system or switch it off. The devices 30 and 32 are supplied via a line 38 from the central controller 2k self-test signals. Both the ultrasonic and microwave devices provide self-test and intrusion signals to an automatic self-test and intrusion-test logic circuit 40. These signals are derived from the output signals of the ultrasonic and microwave transmit oscillator and disappear if the microwave power or the ultrasonic energy fails or if the feed line to the ultrasound - Transmitter converter is interrupted or short-circuited. The automatic self-test and intrusion ^{test logic circuit 1} IO delivers an alarm signal to line Ί2 via the monitoring console 28 if the intrusion signals or the self-test signals disappear.

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the. The automatic self-check and intrusion check logic circuit 40 may contain an array of NOT-AND gates or OR gates to generate an alarm signal on line 42 to generate when the self-checking signals or intervention signals disappear.

In Fig. 3 is a block diagram of the microwave device 32, which contains a transmit / receive antenna 20 which is connected to a bridge or push-pull transmit / receive mixer 44 is coupled, which in turn is coupled to a microwave oscillator. A Doppler frequency signal from mixer 44 becomes a Doppler filter / preamplifier 48 fed to the Builds character strength from the mixer and forms the passband for the Doppler frequency. The pass band for the Doppler frequency drops by about 12 dB per octave at the lower end and by about 36 dB per octave at the upper end. This strong one Falling at the high end improves the lockout at 120 Hz, which is the frequency at which false alarms result from Fluorescent tubes generated plasma are caused.

The Doppler filter / preamplifier 48 is ohmic Attenuator 50 is provided to according to a command on the line 38 an external test signal from the central controller 24 to feed. This signal simulates the Doppler frequency effect due to a moving intruder from mixer 44

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and triggers an alarm in a properly functioning system while the test signal is on line 38 to the attenuator 50 reached.

Signals from the filter / preamplifier 48 are passed to a filter / post-amplifier for further amplification of the Doppler frequency signals 52, whose output signals are fed to a rectifier / integrator circuit 54 arrives, which by means of a usual Two-way rectifier circuit rectifies the Doppler signals and these rectified signals to an integrating circuit feeds. The rectified signals are integrated over time, and if a Doppler signal is a has been pending on the integrating circuit for a sufficiently long time, so that an integration up to a predetermined value occurs, a signal is fed to an alarm level detector 56, which switches the detector to give an alarm signal on line 58 to detector combination logic circuit 34 generated.

At the "front" is the microwave device with the mixer 44 and the oscillator 46, as FIG. 4 shows, made of strip conductor elements built up. The mixer 44 has an H-shaped ribbon conductor structure in order to miniaturize the arrangement, the Reduce the number of false alarms, improve reliability and achieve greater profitability.

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A mixer as shown in the illustration produces a double mixing with a single transmitting / receiving antenna 20 without usual circuits with circulators, hybrids, power amplifiers and other complicated elements are required.

Let us first consider the stripline oscillator 46. A transistor 60 has its collector grounded while being The emitter is connected to a coil 62 and its base is connected to a strip conductor 64. With the strip conductor 64 are also a resistor 66 and adjustable capacitors 68 and 70 are coupled. The adjustable capacitor 68 is used for tuning the oscillation frequency of the oscillator 46, and the capacitor 70 allows maximum power coupling between the The oscillator 46 and the mixer 44. Furthermore, a resistor 72, which forms part of the oscillator 46, is connected to the coil 62 and a line capacitance 74 connected to a terminal 76, to provide a DC voltage for the oscillator.

The microwave transmission frequencies from the oscillator 46 are supplied to the H-shaped stripline 78 via the capacitor 70. At the output end of the strip conductor 78 are the transmitting / receiving antenna 20 and a coil 80 are connected. At the connection points of the stub pipe and the main transmission line of the H-shaped strip conductor line 78 are tip

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value detector diodes 82 and 8 * 1 connected. The peak detector diode 82 mixes to apply Doppler frequency signals to a resistor-capacitor network, which has a resistor 8 £ and a capacitor 88. This is the so-called Doppler frequency that is generated by movement is generated within the area to be monitored. The peak de t ect ordiode 8 * 1 causes a mixture to To supply Doppler frequency signals with phase inversion to a resistor-capacitor network comprising a resistor 90 and a capacitor 92 includes. Resistors 86 and 90 are Connected to one another via an output terminal 94, the one Connection to the filter / preamplifier 48 forms. Line capacitance 96 is that connected to resistors 86 and 90 Assigned to the line.

In operation of the oscillator 46 ″ and the bridge or push-pull mixer 44 becomes a relatively low one from the oscillator 46 Operating frequency generated, for example 915 MHz. By using a relatively low operating frequency, the effective frequency reflection cross section of a target within the monitored area becomes small when the target dimensions are small with respect to the operating wavelength of the oscillator 46. Thus, at short wavelengths in the area of the X-band a false alarm from small targets, about cats or mice, while larger ones

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Wavelengths corresponding to 900 MHz the alarm triggering by small targets of this kind is reduced. A second advantage Operating the oscillator 46 at a relatively low frequency is more economical because it is then by a simple transistorized circuit with a strip conductor can be represented. To achieve an equivalent performance in the X-band To achieve this, a cavity diode oscillator must usually be used. Furthermore, those in mixer 44 are considered proportionate low operating frequencies to use diodes and other components much cheaper than corresponding Components for mixers working in the X-band. A third advantage of a relatively low operating frequency of the Oscillator 46 is that indoor installed microwave systems respond to the 120 Hz plasma that generated by fluorescent tubes. Thus it is advantageous to choose a microwave frequency at 120 Hz outside of the Doppler frequency passband for the target velocities of interest.

The transmit frequency of the oscillator 46 is fed to the input terminal of the mixer 44, which is best understood by that one regards a moving target in the area to be monitored as an impedance which changes over time and which on the antenna 20 reflects back. Such an assumption is to be considered admissible as long as the speed of the target

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is negligibly small compared to the speed of wave propagation. For monitoring alarm systems this is hardly a problem. A target produces a weak spatial standing wave ratio pattern (VSWR pattern), that is pulled when moving. This pattern or this distribution is called the time-changing impedance in the Microwave antenna 20 coupled.

Based on the equivalent circuit shown in FIG the microwave antenna 20 represents an ohmic load 20a (Z) in the absence of a target of the transmitted wave is denoted by E and the antenna clamping voltage of the wave reflected by the target is denoted by V, that is Microwave domain equation as follows:

, _r EG X / σ - * ■, ,,, *

^{V = e λ} > ⁽¹⁾

. (ϋπ) χ

where χ = the distance between antenna 20 and a target 98, <f = the microwave cross section of the target 98, λ = the operating wavelength of the system and G = the gain of antenna 20.

The time-changing impedance Z (t) at the terminals of the antenna 20 results from the following equation:

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Ζ _Λ (1 + Γ) ZCt) = (2)

whereby
is.

If the target 98 is moving at a speed S, then is

χ = St
and

e. ~

where the factor 2S / A is the expression for the Doppler frequency is.

If one looks again at the general case of the time-changing impedances, then the high-frequency residual voltage is B. given over the clamping impedance Z (t) (Fig. 5) by the following equation:

u _ 2EZ (t) . ...

^B - [Z ₀ + ZTtTT ⁽⁶⁾

The solution of the equation for the existing impedance Z (t) leads to:

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where ω = 21Γ. Doppler sequence is.

Equation (7) gives a Doppler output frequency from the peak detector diode 82 which generates a voltage proportional to the absolute value of the high frequency voltage B. That The output generated by diode 82 is given by the following formula:

(B [α E [1 + cos tot] ( ₈ ) (ijTr) ^3/2 S ² t ²

This formula contains a DC voltage signal with a superimposed low amplitude modulation of Doppler frequency.

2 2 The modulation intensity is inversely proportional to S t, the normal propagation loss for microwave signals.

In most alarm systems based on the Doppler principle, the Doppler signal must be amplified in the order of 90 dB in order to obtain a usable level. Since the DC voltage level of the peak value detector 82 can be several volts, a capacitive coupling is used between the detector 82 and the Doppler amplifier chain with the preamplifier M8. This avoids direct current saturation of the amplifier chain, but the amplifiers i \ Q and 52 are not

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isolated over time changes in the DC voltage level. Such a change results from the amplitude modulation and the noise of the oscillator 46 and can in the Setup 32 trigger false alarms.

To reduce the effects of the DC voltage level change, the peak detector diode 84 is connected to the stripline circuit 78 and is in communication with the peak detector diode 82. This turns off the DC voltage at terminal 84, resulting in a balanced mix. It follows that the Doppler frequency signals are also switched off unless the Doppler output signal of the detector diode 84 is reversed in phase with respect to the output signal of the detector diode 82. This is achieved in the mixer according to FIG. 4 in that the detector diode 84 over the transformed high-frequency impedance Z ^f (t) according to the equation

Z '(t) = jfo (9)

lies. This transformation is done with a four-pole high frequency circuit what is known as an inversion circuit.

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Two other important features of the mixer 44 represent the RF coil 80 at the output terminal to ground and a DC voltage level interrogation connection at the anode of the Detector diode 82. This interrogation link includes one Resistor 99 and line capacitance 100. The circuit provides an automatic self-test and intrusion test output from the "front" of the microwave device 32. Thus, these test output signals enable a continuous check at the "front end" of the microwave device, while the external test signal fed to the attenuator 50 periodic inspections of the other components of the system are permitted. The high frequency coil 80 serves as a DC voltage feedback for the detector diodes 82 and 84 and as an earth shunt for low frequency disturbances (60 Hz), which are coupled from the environment of the system to the line part 78a could become.

Let us now consider the ultrasonic device 30, which is shown as a block diagram in FIG. 7 and is a complete one An ultrasonic Doppler alarm system showing an alarm signal on line 102 to the detector combination logic circuit 34 generated. The four ultrasonic receiving transducers 18 are coupled to a transducer combination circuit 104, the output signal of which is fed to a filter / preamplifier 106 will. The ultrasonic transmitter transducers 22 of the outer detector

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are coupled to a converter combination circuit 108, which receives transmission energy via a line 110 connected to a monitoring circuit 112 and sends out test signals. In the same way, the ultrasonic ^{transmitter transducers 22 of the outer detector I 1} I are connected to a transducer combination circuit 114 which receives transmission energy via a line 116 connected to the monitoring circuit 112 and sends out test signals. An important feature of the ultrasonic device 30 is the circuit arrangement for the transmission of ultrasonic energy and automatic self-checking and intervention checking signals via the same lines 110 and 116 to the respective combination circuit 108 and 114.

An amplified signal from filter / preamplifier 106 is included a modulation frequency that is generated by an oscillator 118 in a mixer 120. The modulated Signals from mixer 120 are amplified to an appropriate size in a filter / amplifier. The signals from the filter / Amplifiers 122 are fed to a rectifier / integrator circuit 124 where a full wave rectifier takes the Doppler signals converts them into rectified signals and feeds them to a conventional integrating circuit. The integrating circuit integrates the rectified signals over time, and when a predetermined value is reached, an alarm detector is activated 126 triggered to generate an alarm signal on line 102 to combinational logic circuit 34.

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The external self-check and the intervention check of the ultrasonic device 30 is controlled by means of an oscillator * 118 coupled test modulator 128 performed. A self-check control signal on a line 130 triggers the test modulator 128 off so that it is on line 132 to the filter / preamplifier 106 generates a test signal. The external self-test control signal on line I30 cannot be sent directly to the Ultrasonic Doppler filter / amplifier 122 can be coupled in order to reliably test the ultrasonic device 30 to effect. Such a test would bypass the preamplifier 106 and mixer 120 entirely and provide a display for the proper condition of the plant, even if one or both of these elements is faulty Condition would be. Therefore, the ultrasonic signal is modulated at a frequency within the Doppler pass band coupled to the ultrasonic preamplifier 106 to fully test the system.

The test signal on line I30 is a square wave from the central control 2 ^, and the test modulator 128 has a simple switch that generates pulses of ultrasound signals when a test signal waveforms. These impulses that on line 132 are attenuated in a manner suitable for testing the ultrasonic preamplifier are then coupled to the input of amplifier 106.

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■ The amplified test pulses from the preamplifier 106 arrive to mixer 120 which is periodically unbalanced to produce an output for amplifier 122. A The important point is that the ultrasonic test pulses on the Line 132 and the ultrasonic mixer driver signal from oscillator 118 must not be 90 out of phase, otherwise a very small imbalance of the mixer and a small output signal will be generated.

Consider now the converter combination circuits 104, 104 and 114, the combination circuit 104 in FIG Fig. 7a and the combination circuits 108 and 114 are shown in Fig. 7b. The easiest way to combine several converters are connected in parallel. Unfortunately However, a balanced behavior can only very rarely be achieved with converters connected in parallel, because their resonance frequencies and their impedances are seldom matched to one another in practice. Are the parallel-connected If the converter is operated as a transmitter, for example, the converter or the converter uses up their series resonance frequencies closest to the driver frequency, a large part of the power, because the remaining transducers have higher impedances form. Thus, for a successful operation of an alarm system with several converters for monitoring a large one Some type of isolation / broadband circuit is required.

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-25- 2331329

The receiving transducer elements 18 are made by using the circuit of FIG. 7a summarized, which consists of a Basic filter circuit is derived and in which each of the transducers 18 is in a resonance circuit with a resonance inductance 134 is coupled. Thus, the transducers 18 arranged in bandpass filters, and these filters are separated from one another by resistors 136. The impedance ratios are chosen so that the resistors 136 have little effect on the efficiency of the arrangement.

The transmission transducer elements 22 are combined according to FIG. 7b, each transducer 22 being in series with a resonance inductance 138 in order to form a basic filter circuit which in turn contains the transducers in a bandpass filter. The filters are separated from one another by resistors I ¹ JO. The ultrasonic energy source shown in FIG. 7b contains the oscillator II8 from FIG. 6.

8, each of the outer transducer units is 12 and 14 coupled to the monitoring circuit 112, which in turn receives a frequency signal on a line 142 from the oscillator II8. The monitoring circuit 112 distributes ultrasonic energy to the transmitting external units 12 and 14 and receives via the two lines 144 and 146 automatic self-checking and Supervision test information from the external units. the

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in series with the transducers 22 lying coils I38 and resistors 140 form an isolation / broadband circuit of the type mentioned above.

The ultrasonic generator 118 is coupled to the line 144 via a capacitor and is correspondingly above it a capacitor 150 on line 146. Coupling to the transducer side of capacitor 148 provides a fault indication circuit with resistors 152 and 154, with resistor 154 being in parallel with a capacitor 156. A Error indication signal on line 148 is input into the combinational logic circuit 40 coupled according to FIG. At the transducer end of capacitor 150 is a fault circuit with resistors 160 and 162 are connected, and the resistor 162 has a capacitor 164 in parallel. An error indication signal appears on line I66 and is also used in the combinational logic circuit 40 from FIG. 2 supplied.

To the connection of the resistance elements 140 of the converter units A diode I68 is connected to 12 and 14. As there is no DC voltage path from the converter side of the capacitors 148 and 150 to earth, except through the fault circuit resistors 152, 154 or I60, 162, place the diodes of each external unit the corresponding line to a DC voltage value. This value is approaching the top

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controlling the ultrasonic oscillator 180, resulting in a state in which the diodes 168 have little influence on the operation of the transmitting transducer 22 have.

Each of the fault indicator circuits can be viewed as a spike detector with a remote diode 168. The disconnection of the diode 168 from any fault circuit, for example by breaking the lines 144, 146, so that the Case intrusion switch 502 is opened, or by shorting the lines, causes the output voltage to disappear of the DC voltage detector. Be on it indicated that failure of the ultrasonic oscillator 118 will produce the same result.

In the outer converter unit 12, the capacitor 1 * 18 forms the output capacitor of the peak detector for the part of the system with series resistors 152 and 154 which the detector las twiderst and represent. The arrangement of the capacitor 156 above the resistor 154 enables the filtering out of the ultrasonic frequency components. When the DC voltage value disappears at the junction of resistors 152 and 154, this provides a fault condition signal on line 158 Combination logic circuit 40 represents. Likewise, forms the capacitor 150 for the outer converter unit 14 is the output capacitor the peak detector circuit with those in series

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lying resistors 160 and 162, which serve as a detector load resistor. The capacitor 164 also functions as a filter for removing the ultrasonic frequency component. If a DC voltage signal disappears at the connection point of the resistors 160 and 162, this represents an error display signal on the line 166 connected ^{to the combination logic circuit 1 IO.}

The ultrasound elements for both the receiver transducer 18 and the transmission transducer 22 having a frequency / temperature characteristic according to the curve I68 of FIG. 9. Because this curve represents the ideal frequency for the ultrasonic device 30, the maximum sensitivity of the system requires a large temperature range, that the frequency signal from oscillator II8 follows this curve, ie when the temperature increases, the output frequency of oscillator II8 should decrease along curve I68.

In Fig. 10, the oscillator II8 is shown schematically, wherein an additional ultrasonic transducer 170 is provided in the central detector unit 10, which via a resistor I74 for controlling the output frequency occurring at terminal I76 of the oscillator II8 to an input of an amplifier 172 is connected. Besides its frequency control function the converter I70 emits sufficient ultrasonic energy

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the detector unit 10 to the outer units 12 and 14 to make superfluous if the area to be monitored is proportionate is small.

It is also connected to the non-inverting input of the amplifier 172 is connected to a resistor circuit including resistors 178, 180 and 182. A positive feedback loop across amplifier 172 includes a resistor 184 connected to the amplifier output and the non-inverting input of the Amplifier is connected. The driver circuit for the inverting input of amplifier 172 includes one in series with a capacitor 188 lying resistor I86, with a feedback loop a resistor 190 and a capacitor 192 has.

The output of amplifier 172 operates through a Coupling capacitor 198 to a complementary symmetrical power output holder made up of transistors 194 and 196, the lie with their collectors together via a capacitor 200 at the output terminal 176. The emitter of the transistor 194 is grounded and the emitter of transistor I96 is connected via a terminal 202 to a DC voltage source. The base current for transistor 194 is through resistors 204 and 206 and the base current for transistor I96 is provided by resistors 208 and 210.

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The oscillator 118 is an RC wave generator, but bridged converter 117 connects the non-inverting input of the amplifier through resistor 174 to ground. The oscillator is thus blocked against the parallel resonance of the ultrasonic transducer 170, since the bridging effect on the positive feedback occurs at least at this frequency. A feature of the oscillator 118 shown in FIG. 10 is that the ultrasonic signal is not a sine wave, but a square wave with a voltage of 12 volts (peak-to-peak). Measurements show that the ultrasonic energy emitted by the transducer 22 is slightly greater than when a sinusoidal signal with a voltage of 12 volts (peak-to-peak) drives the device.

Fig. 11 shows the test modulator 128 which is connected to the preamplifier 106, which provides an output signal for the bridge or push-pull mixer 120. A frequency signal from the Source 118 connected to terminal 212 is fed to both mixer 120 and test modulator 128. For the latter, the supply takes place via a series connection of resistor 214 and capacitor 216. The capacitor 216 is at a connection point 218, to which the resistors 220 and 222 and the anode of a diode 224 are also connected are. The resistor 220 is connected to a DC voltage source set to a predetermined value. Of the Resistor 222 connects to a test signal input terminal 226

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and receives the self-test control signal via line 130. A parallel circuit is also connected to the resistor 222 connected by resistor 228 and capacitor 230.

If a test signal is fed to terminal 226, diode 224 becomes conductive and feeds an input signal to preamplifier 106 via a series circuit of resistor 232 and capacitor 234. A resistor 236 completes a divider circuit with resistor 232. Also coupled to the input of preamplifier 106 is a sensitivity control circuit which contains a variable resistor 238 connected in series with a grounded resistor 2 ¹ IO. The sensitivity control circuit receives signals from combination circuit 104 at terminal 242. Resistor 240 is in series with variable resistor 238 so that the test circuit is still functional when the control is set for minimum sensitivity.

An output of amplifier 106 becomes the center tap a subdivided secondary winding 244 of a mixer transformer 246 fed to the one via the resistor 250 with primary winding 248 connected to terminal 212. Diodes 252 and 254 are connected to the ends of the secondary winding 244. These diodes are across resistors 256 and 258 and grounded through capacitors 260 and 262. The outcome of the ■

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Amplifier 106 is also connected to ground through resistor 264. An output from mixer 120 occurs at one Terminal 266 is open and fed to filter / amplifier 122.

The test modulator works as follows: The resistors 220, 222 and 228 form a DC voltage ^{divider which biases the diode 22 2} I in the reverse direction as long as no test signal occurs at the terminal 226. Resistor 214, capacitor 216, and resistor 222 form an ultrasonic frequency voltage divider / phase shifter that applies an ultrasonic voltage to the anode of diode 224. However, the magnitude of the ultrasonic voltage is insufficient to overcome the bias and no current flows through the diode 224 to generate an output signal via the load resistor 236. The supply of a test signal via the resistor 228 periodically brings the diode 224 into the conductive state and causes ultrasonic signal pulses across resistor 236. These pulses are coupled to the input of preamplifier 106 via resistor 232 and capacitor 234. The resistor 232 is chosen so that a corresponding attenuation results in connection with the other circuit impedances.

Another important feature of the invention is that the ultrasonic transceiver transducers are chosen so that they have great directivity. This allows certain

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particularly critical sub-areas of the area to be monitored be monitored. For example, a pair of transceiver converters can be placed directly on a cash register, window or other special objects to create a special sensitivity in these areas. on the other hand it is possible to remove the converter from difficult places, such as space heaters, air conditioning outlets and outlets to clear away other possible sources of false signals.

Although the invention has been described above using an exemplary embodiment with modifications, it is not based on this limits, but there are of course other changes possible, all of which fall under the invention.

309885/0936

Claims (1)

Expectations 1.yAlarm or monitoring system to generate a display when a movement occurs within an area to be monitored, characterized by a movement in the area to be monitored responsive ultrasound device, which changes with such a movement Output signal generated by an on movement im to monitoring area responsive microwave device, which changes with the movement output signal generated by a combination circuit connected to the ultrasonic device and to the microwave device for generating an alarm signal if the output signals of the two devices simultaneously move in the monitored area, and by one with the ultrasonic device and the microwave device connected test circuit responsive to fault conditions in the equipment and then a fault indication signal generated. 2. Plant according to claim 1, characterized in that the ultrasonic device has a transmitting transducer for radiation of radio frequency energy in the monitored area, to that of a moving body within the the monitored area, the reflected energy is appealing 3G9885 / 0936 Receiving elements that generate a Doppler frequency signal, a circuit actuated by this Doppler frequency signal for generating a scanning output signal representing the movement and a frequency generator connected to the transmission transducer and an error response circuit contains, in the event of failure of transmission or transmission elements to generate a fault indicator signal " 3. Plant according to claim 2, characterized in that the Transmitter a number of bandpass filters, each with a radiating element for emitting radiation into the have to be monitored area, a number of each resistors connected in series with the bandpass filters. and a connection circuit connecting the band-pass filters and switches the resistors in parallel with the frequency generator. ¹ I. System according to claim 2 or 3, characterized in that the frequency generator contains an RC-driven operational amplifier and a radiation element coupled to a terminal of the operational amplifier, so that the output signal of the generator is adapted to the frequency / temperature characteristics of the radiation element, the latter is used as a sending element. 309885/0936 5. Plant according to claim ^, characterized in that the The frequency generator has a complementary symmetrical power output switch which is coupled to the output of the puncture amplifier. 6. Plant according to one of claims 1 to 5 »characterized in that that the microwave device has a transmitting / receiving antenna, the microwave energy radiates into the monitored area and onto a moving body reflected energy responds, an oscillator for generating a carrier frequency signal, a bridge or push-pull mixer, which is connected to the antenna and the oscillator to generate a reflected signal received by the antenna To demodulate the signal with the output signal of the oscillator, a Doppler amplifier to pick up a signal from the mixer, an integrating circuit connected to the output of the Doppler amplifier for integrating its output signal contains over time and a level detector that picks up signals from the integrating circuit and at exceeding a preset level triggers an alarm signal. 7. Plant according to claim 6, characterized in that the mixer has a high-frequency impedance inverter, one of which End to the antenna and the other end of which is connected to the output of the oscillator, a first peak 309885 / 093G value voltage detector at the end of the antenna facing Inverter for sampling the magnitude of the high voltage at the antenna, a second peak value voltage detector the end of the inverter facing the oscillator for sampling the magnitude of the high-frequency voltage on the oscillator and a combination circuit that converts the energy from the peak voltage detectors to a mixer output signal which is fed to the input of the Doppler amplifier. 8. System according to claim 7, characterized by a high-frequency choke coupled to the transmission line at the antenna end. 9. Plant according to one of claims 6 to 8, characterized in that that the mixer has a DC voltage level sensing connection for generating a fault condition signal for the test circuit contains. 10. Plant according to one of claims 3 to 9, characterized in that that the test circuit has a peak voltage detector with a diode that matches the one with the bandpass filters connected resistors, and having an output capacitor connected to one electrode of the diode and the output of the frequency generator is connected. see below ^{: kö 309885/0936}