DE2331328C2 - - Google Patents

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Publication number
DE2331328C2
DE2331328C2 DE19732331328 DE2331328A DE2331328C2 DE 2331328 C2 DE2331328 C2 DE 2331328C2 DE 19732331328 DE19732331328 DE 19732331328 DE 2331328 A DE2331328 A DE 2331328A DE 2331328 C2 DE2331328 C2 DE 2331328C2
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Germany
Prior art keywords
test
oscillator
connected
line
signal
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
DE19732331328
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German (de)
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DE2331328A1 (en
Inventor
David Nelson Rockville Md. Us Gershberg
Alex Young Arlington Va. Us Lee
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Raytheon E-Systems Inc
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Raytheon E-Systems Inc
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Application filed by Raytheon E-Systems Inc filed Critical Raytheon E-Systems Inc
Publication of DE2331328A1 publication Critical patent/DE2331328A1/en
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Publication of DE2331328C2 publication Critical patent/DE2331328C2/de
Expired legal-status Critical Current

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Classifications

    • GPHYSICS
    • G08SIGNALLING
    • G08BSIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00Burglar, theft or intruder alarms
    • G08B13/22Electrical actuation
    • G08B13/24Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2491Intrusion detection systems, i.e. where the body of an intruder causes the interference with the electromagnetic field
    • G08B13/2494Intrusion detection systems, i.e. where the body of an intruder causes the interference with the electromagnetic field by interference with electro-magnetic field distribution combined with other electrical sensor means, e.g. microwave detectors combined with other sensor means
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/50Systems of measurement based on relative movement of target
    • G01S13/52Discriminating between fixed and moving objects or between objects moving at different speeds
    • G01S13/56Discriminating between fixed and moving objects or between objects moving at different speeds for presence detection
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/86Combinations of radar systems with non-radar systems, e.g. sonar, direction finder
    • G01S13/862Combination of radar systems with sonar systems
    • GPHYSICS
    • G08SIGNALLING
    • G08BSIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00Burglar, theft or intruder alarms
    • G08B13/16Actuation by interference with mechanical vibrations in air or other fluid
    • G08B13/1609Actuation by interference with mechanical vibrations in air or other fluid using active vibration detection systems
    • G08B13/1645Actuation by interference with mechanical vibrations in air or other fluid using active vibration detection systems using ultrasonic detection means and other detection means, e.g. microwave or infra-red radiation

Description

The invention is based on an alarm or monitoring system according to the preamble of claim 1.

From DE-OS 19 29 145 such an alarm or Monitoring system with an ultrasound device and a microwave device known. A Disadvantage of this system, however, is that their failure or one by intruders destruction of one or more parts of the Alarm system neither interference signals nor alarm signals are triggered so that no optimal security is guaranteed.

An alarm system is known from US-PS 35 73 817, their sensor arrangements in the absence of reception emit signals control signals that their flawless Confirm the operating status without doing so detailed information on the corresponding implementation the necessary orders are then made.

It is an object of the invention to provide an improved alarm or to create surveillance system for Achieving optimal security even if one fails or multiple parts or manipulation and interventions triggers alarm by intruders.

This task is carried out by the Claim 1 specified features solved.

Advantageous embodiments of the invention are specified in the subclaims.

An embodiment of the invention is described below with reference to the Figures explained in more detail.

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

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 are combined to generate an alarm signal.

Fig. 3 shows a block diagram of the microwave probe pointing part of the system with a stripline oscillator, which is connected to a bridge or push-pull mixer.

Fig. 4 shows schematically a stripline oscillator which is coupled to an H-stripline mixer.

Fig. 5 shows an equivalent circuit of the microwave part of the system, from which it follows that a matched antenna represents an ohmic load if there is no target to be monitored.

FIG. 6 shows a block diagram of the ultrasound part of the system according to FIG. 2, a number of transmitting radiator elements and a number of receiver elements being present.

Fig. 7a and 7b schematically show the circuits for combining the receiver elements and the transmitter elements.

Fig. 8 shows schematically an oscillator as well as the distribution and intrusion monitoring circuit for the ultrasonic transmitting elements.

Fig. 9 is a diagram showing the frequency response of a typical ultrasonic radiator as a function of temperature.

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

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

The alarm monitoring system shown in FIG. 1 for protecting a specific area, for example a size of 31 m × 15 m, has a centrally arranged ultrasound receiving unit 10 and external ultrasound transmitter units 12 and 14 , all of which are provided by means of a pipe holder 16 , which also serves as a cable guide , about 1.8 m above the floor. The centrally located ultrasound receiving unit 10 includes 4 ultrasound receiving elements 18 , only two of which are shown, as well as a microwave antenna 20 , which operates in both the transmitting and receiving modes, as will be explained. Each of the outer ultrasonic transmitter units 12 and 14 has ultrasonic transmitter elements 22 , of which only two are shown. For some small areas to be monitored, one or more ultrasound transmitter elements 22 and the ultrasound receiver elements 18 can all be accommodated in a central ultrasound receiver unit, so that the external ultrasound transmitter units are avoided. In this exemplary embodiment, an ultrasonic transmitting element (not shown) is provided in the central ultrasonic receiving unit, which controls an oscillator frequency, as will be described. If external transducer units or a composite central detector unit is used, the system operates in the manner to be described.

The signals to and from the centrally arranged ultrasound receiving unit 10 and the external ultrasound transmitter units 12 and 14 come from or reach a central controller 24 which contains the electronics. A main control switch 26 controls the operation of the system to either provide protection against intruders or to shut down 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 fed to a monitoring console 28 which contains four rows of alarm indicators of any common type. Because more than a particular area can be monitored using the same console 28 , a number of central controls 24 can be connected to it, one for each alarm indicator when the console is fully utilized.

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

An output alarm signal from each of devices 30 and 32 is provided to the inputs of a combination logic circuit 34 in central controller 24 to generate an alarm signal on line 36 to monitoring console 28 . Typically, the outputs of devices 30 and 32 represent logic signals that change between an "upper" and a "lower" state and are supplied to a non-and gate in the combination logic circuit 34 to provide a changing logic signal on line 36 produce. According to the operation of a standard logic circuit, an alarm signal appears on line 36 when both input signals of the detector combination logic circuit 34 from devices 30 and 32 are in the same logic state. The detector combination logic circuit 34 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 redundancy, which reduces the likelihood of a false alarm that often occurred with previous alarm systems.

Both the ultrasound and microwave devices are constantly monitored for proper operation and intervention by someone who tries to bypass or switch off the system. The devices 30 and 32 are supplied with self-test signals from the central controller 24 via a line 38 . Both the ultrasound and microwave devices provide self-test and intervention signals to an automatic self-test and intervention test logic circuit 40 . These signals are derived from the output signals of the ultrasonic and microwave transmitter oscillator and disappear when the microwave energy or the ultrasonic energy fails or when the feed line to the ultrasonic transmitter transducer is interrupted or short-circuited. The automatic self-test and intrusion test logic circuit 40 provides an alarm signal to the line 42 through the monitoring console 28 when the intrusion signals or the self-test signals disappear. The automatic self-test and intrusion test logic circuit 40 may include an array of non-AND gates or OR gates to generate an alarm signal on line 42 when the self-test signals or intrusion signals disappear.

FIG. 3 shows a block diagram of the microwave device 32 which contains a transmission / reception antenna 20 which is coupled to a bridge or push-pull transmission / reception mixer 44 , which in turn is coupled to a microwave oscillator 46 . A Doppler frequency signal from mixer 44 is fed to a Doppler filter / preamplifier 48 which builds up the character strength from the mixer and forms the pass band 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 sharp drop at the high end improves the blocking at 120 Hz, which is the frequency at which false alarms are caused due to plasma generated by fluorescent lamps.

The Doppler filter / preamplifier 48 is provided with an ohmic attenuator 50 in order to supply an external test signal from the central controller 24 in accordance with a command on line 38 . This signal simulates the Doppler frequency effect as a result of a moving intruder from mixer 44 and triggers an alarm in a properly functioning system, while the test signal on line 38 reaches attenuator 50 .

Signals from the filter / preamplifier 48 are fed to a filter / repeater 52 for further amplification of the Doppler frequency signals, the output signals of which reach a rectifier / integrating circuit 54 which rectifies the Doppler signals and these rectified signals by means of a conventional two-way rectifier circuit feeds an integrating circuit. The rectified signals are integrated over time, and if a Doppler signal has been present on the integrating circuit for a sufficiently long time so that integration takes place up to a predetermined value, an alarm level detector 56 is supplied with a signal which switches the detector, so that it generates an alarm signal on line 58 to the detector combination logic circuit 34 .

On the input side, the microwave device 32 with the mixer 44 and the oscillator 46 , as shown in FIG. 4, is made up of strip conductor elements. The mixer 44 has an H-shaped stripline structure to miniaturize the arrangement, reduce the number of false alarms, improve reliability and achieve greater economy.

A mixer as shown effects back-mixing for the signal with a single transmit / receive antenna 20 without the need for conventional circuits with circulators, hybrid circuits, power amplifiers and other complicated elements.

Let us first consider the stripline oscillator (= oscillator in strip line technology) 46 . A transistor 60 is grounded with its collector, while its emitter is connected to a coil 62 and its base to a strip line 64 . With the strip line 64 , a resistor 66 and adjustable capacitors 68 and 70 are also coupled ge. The adjustable capacitor 68 is used to tune the oscillation frequency of the oscillator 46 , and the capacitor 70 enables maximum power coupling between the oscillator 46 and the mixer 44 . Furthermore, a resistor 72 forming part of the oscillator 46 is connected to the coil 62 and a line capacitance 74 at a terminal 76 in order to supply a DC voltage for the oscillator.

The microwave transmission frequencies from the oscillator 46 are fed to the H-shaped strip line 78 via the capacitor 70 . The transmission / reception antenna 20 and a coil 80 are connected to the output end of the strip line 78 . At the connection points of the stumps and the main transmission line of the H-shaped strip line 78 , peak value detector diodes 82 and 84 are connected. The peak detector diode 82 mixes to supply Doppler frequency signals to a resistor-capacitor network having a resistor 86 and a capacitor 88 . This is the so-called Doppler frequency, which is generated by movements within the area to be monitored. The peak detector diode 84 mixes to supply phase-inverted Doppler frequency signals to a resistor-capacitor network that includes a resistor 90 and a capacitor 92 . The resistors 86 and 90 are connected to one another via an output terminal 94 , which forms a connection to the filter / preamplifier 48 . A line capacitance 96 is associated with the line connected to resistors 86 and 90 .

In operation of the oscillator 46 and the bridge or push-pull mixer 44 , the oscillator 46 generates a relatively low operating frequency, for example 915 MHz. By using a relatively low operating frequency, the effective frequency reflection cross-section of a target within the area to be monitored becomes small if the target dimensions are small with respect to the operating wavelength of the oscillator 46 . Thus, a false alarm could be triggered by small targets, such as cats or mice, at short wavelengths in the area of the X band, while the triggering of alarms by small targets of this type is reduced at longer wavelengths corresponding to 900 MHz. A second advantage of operating the oscillator 46 at a relatively low frequency is economical because it can then be implemented by a simple transistorized circuit with a stripline. A cavity diode oscillator must usually be used to achieve equivalent performance in the X band. Furthermore, the diodes and other components to be used in the mixer 44 for relatively low operating frequencies are considerably cheaper than corresponding components for mixers operating in the X- band. A third advantage of a relatively low operating frequency of the oscillator 46 is that indoor microwave systems are responsive to the 120 Hz plasma generated by fluorescent tubes. It is therefore advantageous to choose a microwave frequency at which 120 Hz lies outside the Doppler frequency pass band for the target speeds of interest.

The transmission frequency of the oscillator 46 is fed to the input terminal of the mixer 44 , which is best made clear by considering a target moving in the area to be monitored as a time-changing impedance that reflects back on the antenna 20 . Such an assumption can be considered admissible as long as the speed of the target is negligible compared to the speed of the wave propagation. This is hardly a problem for monitoring alarm systems. A target produces a weak, spatial standing wave ratio pattern (VSWR pattern) that is drawn during movement. This pattern or this distribution is coupled into the microwave antenna 20 as a time-changing impedance.

Based on the equivalent circuit of FIG. 5, the microwave antenna 20 at nichtvorhandenem target a resistive load 20 a (Z 0). If it is the antenna terminal voltage of the transmitted wave with E and the antenna terminal voltage of the light reflected from the target wave V, so is the microwave range equation as follows:

in which
x = the distance between the antenna 20 and a target 98 , σ = the microwave cross section of the target 98 , λ = the operating wavelength of the system and G = the gain of the antenna 20 is.

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

in which

is.

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

x = St (4)

and

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

Looking again at the general case of the temporally changing impedances, the high-frequency residual voltage B over the clamping impedance Z (t) ( FIG. 5) is given by the following equation:

Solving the equation for the existing impedance Z (t) leads to:

where ω = 2 π . Doppler frequency 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. The output signal generated by diode 82 is given by the following formula:

This formula contains a DC voltage signal with a superimposed low amplitude modulation of Doppler frequency. The modulation intensity is inversely proportional to S ² t ², 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 level of the peak detector 82 can be several volts, a capacitive coupling between the detector 82 and the Doppler amplifier chain is used with the preamplifier 48th This avoids DC saturation of the amplifier chain, but amplifiers 48 and 52 are not isolated from changes in the DC voltage level over time. Such a change results from the amplitude modulation and the noise of the oscillator 46 and can trigger false alarms in the device 32 .

To reduce the effects of the DC level change, the peak detector diode 84 is connected to the stripline circuit 78 and is connected to the peak detector diode 82 . This switches off the DC voltage at terminal 94 , so that a balanced mixture results. It follows that the Doppler frequency signals are also turned off unless the Doppler output of the detector diode 84 is reversed in phase with the output 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 '(t) according to the equation

lies. This transformation is done with a four-pole radio frequency circuit reached, which is known as an inversion circuit.  

Two other important features of the mixer 44 filters the high frequency coil 80 at the output terminal to earth and a DC voltage level query compound at the anode of detector diode 82. This query compound contains a resistor 99 and a line Capacity 100. The circuit provides an automatic self-test and intrusion test output signal from the input side of the microwave device 32 . These test output signals thus enable a continuous check at the input of the microwave device, while the external test signal supplied to the attenuator 50 allows periodic checks of the other components of the system. 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 could be coupled from the area around the system to the line part 78 a .

It is now considered the ultrasonic device 30 , which is shown in Fig. 6 as a block diagram and represents a full permanent ultrasonic Doppler alarm system that generates an alarm signal on line 102 to the detector combination logic circuit 34 . The four ultrasonic reception transducers 18 are coupled to a transducer combination circuit 104 , the output signal of which is fed to a filter / preamplifier 106 . The ultrasonic transducer end 22 of the outer ultrasound transmitter unit 12 are coupled to a transducer combination circuit 108 which receives the transmission signal, connected to a monitoring circuit 112 line 110 and sends test signals. In the same way, the ultrasound transducers 22 of the outer ultrasound transmitter unit 14 are connected to a transducer combination circuit 114 , which receives the transmission signal via a line 116 connected to the monitoring circuit 112 and transmits test signals. An important feature of the ultrasound device 30 is the circuit arrangement for emitting ultrasound signals and automatic self-test and grip test signals via the same lines 110 and 116 to the respective combination circuit 108 and 114 .

An amplified signal from the filter / preamplifier 106 is mixed with a modulation frequency that is generated by an oscillator 118 in a mixing circuit 120 . The modulated signals from mixer 120 are amplified to a suitable size in a filter / amplifier 122 . The signals from the filter / amplifier 122 are fed to a rectifier / integrating circuit 124 , where a two-way rectifier converts the Doppler signals 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 126 is triggered to generate an alarm signal on line 102 to the combination logic circuit 34 .

The external self-test and the intervention test of the ultrasound device 30 is carried out by means of a test modulator 128 coupled to the oscillator 118 . A self test control signal on line 130 triggers test modulator 128 so that it generates a test signal on line 132 to filter / preamplifier 106 . The external self-test control signal on line 130 cannot be coupled directly to the ultrasound Doppler filter / amplifier 122 to effect a reliable test of the ultrasound device 30 . Such a test would completely bypass preamplifier 106 and mixer 120 and provide an indication of the proper condition of the plant, even if one or both of these elements were in a defective condition. Therefore, the ultrasound signal modulated at a frequency within the Doppler pass band is coupled to the ultrasound preamplifier 106 to fully test the system.

The test signal on line 130 is a square wave from central controller 24 , and test modulator 128 has a simple switch that generates pulses of ultrasound signals when a test signal is generated. These pulses, which are generated on line 132 , are attenuated in a manner suitable for testing the ultrasound preamplifier and are then coupled to the input of amplifier 106 .

The amplified test pulses from preamplifier 106 go to mixer 120 , which is periodically unbalanced to produce an output signal for amplifier 122 . An important point is that the ultrasound test pulses on line 132 and the ultrasound mixer driver signal from oscillator 118 must not be out of phase by 90 °, otherwise a very low mix imbalance and a small output signal will be generated.

The converter combination circuits 104, 108 and 114 are now considered, the combination circuit 104 being shown in FIG. 7a and the combination circuits 108 and 114 in FIG. 7b. The simplest way to combine several converters is to connect them in parallel. Unfortunately, with converters connected in parallel, it is very seldom possible to achieve balanced behavior, since their resonance frequencies and their impedances are seldom matched in practice. If the converters connected in parallel are operated, for example, as a transmitter, the converter or converters whose series resonance frequencies are closest to the driver frequency consumes a large part of the power, since the other converters form higher impedances. Thus, some type of isolating / broadband switching is required for successful operation of an alarm system with multiple transducers to monitor a large area.

The receiving transducer elements 18 are combined by using the circuit according to FIG. 7a, which is derived from a basic filter circuit and in which each of the transducers 18 is coupled to an inductor 134 in a resonance circuit. Thus, the transducers 18 are 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 transmitter transducer elements 22 are combined as shown in FIG. 7b, each transducer 22 being in series with an inductor 138 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 140 . The ultrasonic energy source shown in FIG. 7b contains the oscillator 118 from FIG. 6.

Referring to FIG. 8, each of the outer converter units is coupled to the monitoring circuit 112 12 and 14, in turn, receives on a line 142 a frequency signal from the oscillator 118th The monitoring circuit 112 distributes ultrasound energy to the transmitting outer units 12 and 14 and receives automatic self-test and monitoring test information from the outer units over the two lines 144 and 146 . The coils 138 and resistors 140 lying in series with the converters 22 form an isolating / broadband circuit of the type mentioned above.

Ultrasonic generator 118 is coupled to line 144 via a capacitor 148 and is accordingly connected to line 146 via a capacitor 150 . The coupling to the converter side of the capacitor 148 represents an error display circuit with resistors 152 and 154 , the resistor 154 being in parallel with a capacitor 156 . An error indication signal on line 158 is coupled to the combination logic circuit 40 of FIG. 2. To the transducer end of the capacitor 150, an error circuit having resistors 160 and 162 is connected, and the resistor 162 is a capacitor 164 in parallel. An error indication signal appears on line 166 and is also supplied to the combination logic circuit 40 of FIG. 2.

A diode 168 is connected to the connection of the resistance elements 140 of the converter units 12 and 14 . Since there is no DC voltage path from the converter side of capacitors 148 and 150 to ground, except through fault circuit resistors 152, 154 or 160, 162 , diodes 168 of each external unit route the corresponding line to a DC voltage value. This value approaches the peak control of the ultrasonic oscillator 118 , resulting in a state in which the diodes 168 have little influence on the operation of the transmitter transducers 22 .

Each of the fault indicator circuits can be viewed as a peak detector with a remote diode 168 . Disconnecting the diode 168 from any fault circuit, such as a break in the lines 144, 146 , so that the intrusion switch 502 is opened, or by a short circuit in the lines, causes the output voltage of the DC voltage detector to disappear. It should be noted that a failure of the ultrasonic oscillator 118 produces the same result.

In the first outer ultrasonic transmitter unit 12 , the capacitor 148 forms the output capacitor of the peak detector for the part of the system with the series resistors 152 and 154 , which represent the detector load resistance. The arrangement of the capacitor 156 over the resistor 154 enables the ultrasonic frequency components to be filtered out. When the DC voltage value at the junction of resistors 152 and 154 disappears, this is an error condition signal on the line 158 to the combinational logic circuit 40. In the same manner, the capacitor 150 forms the second outer transducer unit 14 to the off-type capacitor, the peak detector circuit with the series resistors 160 and 162 , which serve as a detector load resistor. The capacitor 164 also acts as a filter to remove the ultrasonic frequency component. If a DC voltage signal disappears at the connection point of the resistors 160 and 162 , this represents an error indication signal on the line 166 connected to the combination logic circuit 40 .

The ultrasonic elements for both the receiver transducer 18 and the transmitter transducer 22 have a frequency / temperature characteristic according to curve 168 ' from FIG. 9. Since this curve represents the ideal transmission frequency for the ultrasonic device 30 , the maximum sensitivity of the system requires over a wide temperature range, that the frequency signal from the oscillator 118 follows this curve, ie when the temperature rises, the output frequency of the oscillator 118 should decrease along the curve 168 ' .

In Fig. 10, the oscillator 118 is shown schematically, wherein an additional ultrasonic transducer 170 is provided in the central detector unit 10 , which is connected via a resistor 174 to control the output frequency of the oscillator 118 occurring at the terminal 176 to an input of an amplifier 172 . In addition to its frequency control function, the converter 170 emits sufficient ultrasound power from the detector unit 10 to make the external units 12 and 14 superfluous if the area to be monitored is relatively small.

Also connected to the non-inverting input of amplifier 172 is a resistance circuit that includes resistors 178, 180 and 182 . A positive feedback loop across amplifier 172 includes a resistor 184 connected to the amplifier output and the amplifier's non-inverting input. The driver circuit for the inverting input of amplifier 172 includes a resistor 186 in series with a capacitor 188 , a feedback loop having a resistor 190 and a capacitor 192 .

The output signal of the amplifier 172 works via a coupling capacitor 198 to an output power switching stage with complementary-symmetrical transistors 194 and 196 , which are collectively connected to the output terminal 176 via a capacitor 200 . The emitter of transistor 194 is grounded and the emitter of transistor 196 is connected to a DC voltage source via a terminal 202 . The base current for transistor 194 is provided by resistors 204 and 206 and the base current for transistor 196 is provided by resistors 208 and 210 .

Oscillator 118 is an RC toggle generator, however converter 170 bypasses the non-inverting input of the amplifier through resistor 174 to ground. The oscillator is thus locked against the parallel resonance of the ultrasound 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 ultra sound signal is not a sine wave, but a square wave with a voltage of 12 volts (peak-to-peak). Measurements show that the ultrasound energy radiated by the transducer 22 is somewhat greater than if a sinusoidal signal with a voltage of 12 volts (peak-peak) drives the device.

Fig. 11 shows the Prüfmodulator 128, which is coupled to the preamplifier 106 which provides an output signal for the bridge or push-pull mixer 120th A frequency signal from source 118 connected to terminal 212 is supplied 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 located at a connection point 218 , at which the resistors 220 and 222 and the anode of a diode 224 are also closed. Resistor 220 is connected to a DC voltage source set to a predetermined value. The resistor 222 is connected to a test signal input terminal 226 and receives the self-test control signal via line 130 . A parallel connection of resistor 228 and capacitor 230 is also connected to resistor 222 .

If a test signal is fed to the terminal 226 , the diode 224 comes into the conductive state and supplies the preamplifier 106 with an input signal via a series connection of resistor 232 and capacitor 234 . Resistor 236 completes a divider circuit with resistor 232 . Also coupled to the input of preamplifier 106 is a sensitivity control circuit that includes a variable resistor 238 in series with a grounded resistor 240 . The sensitivity control circuit receives signals from the combination circuit 104 at a terminal 242 . The resistor 240 is in series with the changeable counter stood 238 , so that the test circuit is still functional when the control is set for minimal sensitivity.

An output signal from amplifier 106 is fed to the center tap of a divided secondary winding 244 of a mixer transformer 246 , which has a primary winding 248 connected to terminal 212 via resistor 250 . At the ends of the secondary winding 244 diodes 252 and 254 are connected. These diodes are grounded through resistors 256 and 258 and capacitors 260 and 262 . The output of amplifier 106 is also connected through a resistor 264 to ground. An output signal from mixer 120 occurs at terminal 266 and is supplied 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 224 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 which supplies 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 across 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 via the resistor 236 . These pulses are coupled through resistor 232 and capacitor 234 to the input of preamplifier 106 . The resistor 232 is selected so that a corresponding damping results in connection with the other circuit impedances.

Another important feature of the invention is that the ultrasonic transceiver transducers are selected that they have a great directivity. This allows certain  critical sub-areas of the area to be monitored in particular be monitored. For example, a pair of send / Receiver converters directly to a cash register, a window or other special items to be directed into these Areas to create a special sensitivity. On the other hand is it possible to convert the transducer from difficult places such as space heating, air conditioning outlet openings and other possible sources of false signals.

Claims (8)

1. Alarm or monitoring system for generating a display when a movement occurs within an area to be monitored
  • with an ultrasound device ( 30 ) which responds to movement within the area to be monitored and which generates an output signal which changes with movement,
  • - With a in the area to be monitored microwave emitting microwave device ( 32 ) which responds to waves reflected from a body and generates an output signal, and
  • - With both the ultrasonic device ( 30 ) and the microwave device ( 32 ) connected detector combination circuit ( 34 ) for generating an alarm signal when the output signal of the ultrasonic device ( 30 ) and the output signal of the microwave device ( 32 ) simultaneously a movement in the monitored Display value,
characterized by
  • - That the ultrasonic device ( 30 ) has the following elements:
    a number of ultrasonic transmitter transducers ( 22 ) of a first ultrasonic transmitter unit ( 12 ) coupled to a first transducer combination circuit ( 108 ),
    a number of ultrasonic transmitter transducers ( 22 ) of a second ultrasonic transmitter unit ( 14 ) coupled to a second transducer combination circuit ( 114 ), the transducer combination circuits ( 108, 114 ) each having a line ( 110, 116 ) both for receiving transmission energy and for delivering self-testing and intervention test signals are connected to a monitoring circuit ( 112 ) connected via a line ( 142 ) to an oscillator ( 118 ) for emitting an output signal via lines ( 158, 166 ) to a test logic circuit ( 40 ) arranged outside the ultrasound device ( 30 ),
    a number of ultrasound reception transducers ( 18 ) coupled to a third transducer combination circuit ( 104 ) of an ultrasound reception unit ( 10 ) arranged spatially between the two ultrasound transmitter units ( 12, 14 ),
    an ultrasonic evaluation logic ( 106, 120, 122, 124, 126 ) connected to the third transducer combination circuit ( 104 ) and the oscillator ( 118 ) for evaluating the signals received by the ultrasonic receiving transducers ( 18 ) and for forwarding an output signal via a line ( 102 ) to the detector combination circuit ( 34 ) and
    a test modulator ( 128 ) connected to the oscillator ( 118 ) and supplied with a self-test input signal by a central control unit ( 24 ) outside the ultrasonic device ( 30 ) via a line ( 130 ), for generating a test modulator ( 128 ) via a line ( 132 ) to the ultrasound evaluation logic ( 106, 120, 122, 124, 126 ) forwarded test signal for testing the ultrasound evaluation logic ( 106, 120, 122, 124, 126 ), which in the fault-free state when a test signal emitted by the test modulator ( 128 ) is present emits an intrusion-induced alarm signal via the line ( 102 ) to the detector combination circuit ( 34 );
  • - That the microwave device ( 32 ) has the following elements:
    a transmitting / receiving antenna ( 20 ),
    a further oscillator ( 46 ) in stripline technology
    and a mixer ( 44 ) connected to the transmitting / receiving antenna ( 20 ) and the oscillator ( 46 ), the output signals of which are passed on to a microwave evaluation logic ( 48, 52, 54, 56 ) and which has a DC voltage level interrogation connection ( 99, 100 ) for emitting automatic self-test and intrusion test signals, which are connected to the test logic circuit ( 40 ) arranged outside the microwave device ( 32 ), the output signals of the microwave evaluation logic ( 48, 52, 54, 56 ) being connected via a line ( 58 ) the detector combination circuit ( 34 ) are supplied, and
    An attenuator ( 50 ), which is supplied with an external test signal via a line ( 38 ) and has an external test signal generated by the central control unit ( 24 ) arranged outside the microwave device ( 32 ), for outputting an attenuator to the microwave evaluation logic ( 48, 52, 54, 56 ) forwarded test signal for testing the microwave evaluation logic ( 48, 52, 54, 56 ), which emits an alarm signal via line ( 58 ) to the detector combination circuit ( 34 ) in the error-free state in the presence of a test signal generated by the attenuator ( 50 ) ; and
  • - That coupled with the ultrasonic device ( 30 ) via the lines ( 158, 166 ) and with the microwave device ( 32 ) via a further line connected test logic circuit ( 40 ) in the event of failure of the output signal of the monitoring circuit ( 112 ) and / or of the DC voltage level interrogation connection ( 99, 100 ) emitted signals via a signal line ( 42 ) an alarm signal to the central control unit ( 24 ), which is also fed via a line ( 36 ) to the output signal of the detector combination circuit ( 34 ).
2. Installation according to claim 1, characterized in that the ultrasonic device ( 30 ) a number of frequency filters ( 138 ) for parallel operation of several transmitters, each of which has a number of ultrasonic transmitter transducers ( 22 ), a number of resistors ( 140 ), the are each connected in series with one of the frequency filters ( 138 ) and has means for connecting the frequency filters ( 138 ) and the resistors ( 140 ) in series therewith in parallel with the oscillator ( 118 ).
3. Installation according to claim 1 or 2, characterized in that the test logic circuit ( 40 ) has a peak voltage detector with a diode ( 168 ) which is connected to the common connection of the resistors ( 140 ), and an output capacitor ( 148 ) has, which is connected to an electrode of the diode ( 168 ) and to an output of the oscillator ( 118 ).
4. Installation according to one of claims 1 to 3, characterized in that the oscillator ( 118 ) has a resistor ( 182 ) and a capacitor ( 188 ) which are connected to an operational amplifier ( 172 ), and in that an ultrasonic transducer ( 170 ) is connected to a terminal of the operational amplifier ( 172 ) to bring the output frequency of the oscillator ( 118 ) to the frequency-temperature characteristic of the ultrasonic transducer ( 170 ), which is also used as a transmitting element in the system.
5. Plant according to claim 4, characterized in that the oscillator ( 118 ) has an output power switching stage ( 194, 196 ) which is connected to the output of the operational amplifier ( 172 ).
6. Installation according to claim 5, characterized in that the mixer ( 44 ) has an RF impedance inverter ( 78 ) which has one end to the transmitting / receiving antenna ( 20 ) and the other end to the output of the oscillator ( 46 ) is connected; that a first peak voltage detector ( 82 ) at the antenna-side end ( 78 a) of the RF impedance inverter ( 78 ) for detecting the RF voltage amplitude at the transmitting / receiving antenna ( 20 ); that a second peak voltage detector ( 84 ) is located on the oscillator end of the RF impedance inverter ( 78 ) for detecting the RF voltage amplitude on the oscillator ( 46 ); and that switching elements ( 86, 88, 90, 92, 96 ) are provided, by means of which the signal levels detected by each of the peak voltage detectors ( 82, 84 ) are combined to form a DC-free push-pull mixer output signal which is sent to an input of the microwave processing circuit ( 48, 52, 54, 56 ).
7. Plant according to claim 6, characterized in that the RF impedance inverter ( 78 ) has an RF choke ( 80 ) which is connected to the antenna-side end ( 78 a) .
DE19732331328 1972-07-20 1973-06-20 Expired DE2331328C2 (en)

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US (1) US3801978A (en)
JP (1) JPS5754837B2 (en)
CA (1) CA1005876A (en)
DE (1) DE2331328C2 (en)
GB (1) GB1386223A (en)
IL (2) IL42676A (en)

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Also Published As

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JPS5754837B2 (en) 1982-11-19
CA1005876A (en) 1977-02-22
IL42676A (en) 1976-07-30
IL42676D0 (en) 1973-11-28
DE2331328A1 (en) 1974-01-31
JPS4960193A (en) 1974-06-11
US3801978A (en) 1974-04-02
CA1005876A1 (en)
GB1386223A (en) 1975-03-05

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