GB2383485A

GB2383485A - Testing microwave detector

Info

Publication number: GB2383485A
Application number: GB0130322A
Authority: GB
Inventors: John Konstandelos
Original assignee: Pyronix Ltd
Current assignee: Pyronix Ltd
Priority date: 2001-12-19
Filing date: 2001-12-19
Publication date: 2003-06-25
Also published as: GB0130322D0

Abstract

In order to test a microwave Doppler intruder detector, traffic or employee monitoring system, or interrogator system, a transponder receives the transmitted signal and returns a test signal which simulates a correct return. The system then analyses this to determine if it working correctly. The transmitted signal may be radiation scattered from internal surfaces of the system housing, ie the transponder may be outside line of sight. The transponder may modify incoming radiation, and may use a single antenna for both transmission and reflection.

Description

DETECTOR DEVICE Field of the Invention The present invention relates to a detector device and, more particularly, to such a device comprising a self-diagnosis capability.

Background to the Invention Present day motion detector devices rely upon the Doppler principle to detect the presence of a moving object within a protected volume or volume to be surveyed. Conventionally, such motion detector devices use at least microwave technology, that is, typically CBand, X-band or K-Band signals transmitted and received via a transceiver. Post-reception, the received signals are suitably processed to identify the presence of a Doppler signal that can be attributed to movement within the protected volume.

Relatively sensitive devices such as, for example, the mixer, which typically takes the form of a mixer diode, can be easily damaged by inappropriate handling or excessive signal strengths. Therefore, care needs to be taken in the fabrication and the installation of motion detector devices. Notwithstanding any such care, the mixer diodes may be, post-installation, inappropriately exposed to signals or handling that may cause damage to them. It will be appreciated that any such damage may, in the worst case, prevent the motion detector device from operating correctly in that, from the perspective of the output of the mixer diode, there will be no change in

the signal due to any Doppler shifted received signal.

It is an object of the present invention at least to mitigate some of the problems of the prior art.

Summary of Invention Accordingly, a first aspect of the present invention provides a detector device comprising a transmitter for generating and radiating an electromagnetic signal, a receiver for receiving and processing electromagnetic signals and a transponder for generating and radiating a test electromagnetic signal having at least one predetermined characteristic for receipt by the receiver or at least an element thereof.

A preferred embodiment provides a detector device further comprising a housing containing at least the transponder; the transponder being arranged to receive energy scattered within the housing and to generate the test electromagnetic signal using that scattered energy.

By relying on energy that is scattered within the housing or leaked from components housed within the housing, a compact motion detector device can be realised which has a self-diagnosis capability.

Preferred embodiments provide a motion detector device in which the housing additionally contains at least one of the transmitter and receiver and, preferably, contains both.

In preferred embodiments, the transponder detects or

receives electromagnetic radiation emanating from the transmitter and/or associated circuit elements, applies a modulating signal to the received electromagnetic radiation and re-radiates the modulated signal, as the test electromagnetic signal, to be received by the receiver.

A preferred embodiment provides a detector device in which the transponder comprises at least a transceiver comprising a receiver for receiving a portion of the scattered or transmitted electromagnetic signal ; an oscillator for modulating the portion of the received electromagnetic signal to produce the test electromagnetic signal and a transmitter for radiating the test electromagnetic signal.

A preferred embodiment provides a detector device further comprising a signal analyser for monitoring the characteristics of the modulated or test electromagnetic signal to determine the correct operation or otherwise of at least one element of the detector device. Suitably, a fault condition can be raised indicating a fault with the operation of the device in the event of the test signal characteristics being other than expected.

In preferred embodiments, the frequency of the test electromagnetic signal is arranged to emulate the Doppler shift that would be produced by a body moving at a speed of between 0.5 m sec-1 and 1 m sec' which, at a transmitter frequency of lO. 5GHz, for example, corresponds to Doppler frequencies of between 35Hz and 75Hz.

It will be appreciated that the output from the mixer can be used by a signal analysis system comprising, for example, a microprocessor and associated software, to determined whether or not a mixer of the device and/or the device as a whole is functioning correctly.

Suitably, an embodiment additionally comprises a signal analyser for analysing the test electromagnetic modulated signal to determine whether that modulated signal has predetermined characteristics. In preferred embodiments, the predetermined characteristics comprise at least oscillations having a frequency associated with the frequency of the input signal.

To test the operation of the detector device an appropriate input signal is applied to the transponder.

Suitably, an embodiment provides a signal generator for generating the modulating signal to be applied to the transponder for producing the test electromagnetic signal. In preferred embodiments, the input signal represents an enable/disable test mode signal which controls whether the transponder is operable or not.

Brief description of the drawings Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawing in which: figure 1 illustrates schematically a motion detection apparatus having a self-diagnosis capability in accordance with a first embodiment of the present invention.

Description of the preferred embodiments

Referring to figure 1, there is shown schematically a motion detector apparatus 100 comprising a motion detector device 102 containing a signal processor 104 to detect relative motion between the device and a body 106 within a monitored volume 108. In the presence of relative motion, the motion detector device 102 produces a corresponding alarm signal 110. The alarm signal 110 may be output to a control panel (not shown) for further processing such as, for example, output via an audiovisual output device.

The detector device 102 comprises an oscillator 112 for generating C, K or X-band microwave signals that are radiated into the monitored or protected volume 108 via an antenna 114 of a transmitter. A portion of the output of the oscillator signal 112 is directed to a mixer 116. Signals received by an antenna 120 of a receiver are also directed to the mixer 116 where they are mixed with the oscillator signal 116.

Typically, in the presence of relative motion between the device 102 and the body 106, the input signal 122 is a reflected and Doppler shifted version of the transmitted signal 124. The degree of Doppler shift varies according to the speed and direction of the body relative to the detector 102. Movement of between 0.5 m sec' and 1 m sec' produces a Doppler shift of between 35 Hz and 75Hz at a transmitter frequency of 10.5GHz.

The output of the mixer 116, that is, the IF signal 126, is input to the signal processor 104 which, if appropriate, can instruct an alarm-fault generator 130 to

generate an alarm condition signal 110 to be output via the audio-visual output device (not shown) or to raise at least an alarm condition signal.

The detector device also comprises a transponder 132 for generating a test electromagnetic signal 134. The test electromagnetic signal 134 is received at the input port of the mixer 116, that is, the port to which the conductor 118 is connected.

Preferably, the transponder 132 takes the form of a transceiver comprising an antenna 132a, a mixer 132b and an oscillator 132c. Energy emanating from the transmitter antenna 114 is transmitted to the monitored volume 108.

However, a significant proportion is scattered, that is, reflected, refracted and diffracted, within the housing.

The scattered energy 124', received by the antenna 132a, and the signal generated by the oscillator 132d are combined in the mixer and the resulting modulated signal is radiated via the antenna 132a. In effect, the signal presented to the input of the mixer 116 has characteristics which substantially follow those of a Doppler shifted version of the transmitted signal, even in the absence of the moving body 106 within the protected or monitored volume 108.

The oscillator 132c of the transponder is operable, in response to an applied input signal, to produce oscillations at predeterminable frequencies. The predeterminable frequency will vary according to the anticipated speed of the objects to be detected within the protected volume. In preferred embodiments, the predetermined frequencies may be between about 30 Hz to

75 Hz.

The signal processor 104 uses the signal analyser 128 to monitor the IF output 126 to determine whether or not an intrusion into the protected volume 108 has been detected during conventional operation of the detector device 102. In the event that the signal analyser 128 determines that an intrusion into the protected volume 108 has been detected, the signal analyser 128 instructs an alarm-fault signal generator 130 to produce an alarm condition signal 110 for output via an output device (not shown) or to output the alarm condition signal 110 for further processing by, for example, a central control centre.

However, during a test mode of operation of the detector device 102, the signal analyser 128 supplies an appropriate test signal to the transponder. The test signal takes the form of an enable/disable signal that controls the operation of the transponder local oscillator 132c. The enable signal allows the transponder local oscillator 132c to produce an output signal whereas the disable signal prevents the transponder local oscillator 132c from producing an output signal.

The signal analyser 128, again, monitors the IF output 126 and, in the absence of the IF output signal meeting predetermined criteria, the signal analyser 128 instructs the alarm-fault generator 130 to produce a fault indicator signal 138. The fault indicator signal 138 may be output via a fault indicator output device (not shown). Alternatively, the fault indicator signal

may be raised and output for further processing or for transmission to a control centre or control panel.

It will be appreciated that the testing preferably takes place in the absence of motion of the body 106 within the protected volume 108. The predetermined criteria include the magnitude of the IF signal being disposed above or below a particular threshold.

Advantageously, the correct operation or otherwise of the detector device 102 can be monitored in a predetermined and controlled manner and also in the absence of external test equipment that is conventionally used to monitor such operation.

It will be appreciated that even though the above embodiment uses a single antenna to generate the electromagnetic field 134, embodiments of the invention are not limited to such an arrangement. It will be appreciated that embodiments can be realised in which separate receive and transmit antennas are used to generate and radiate the test electromagnetic signal 134.

Although the above embodiments have been described with reference to detecting movement within a protected volume, the present invention is not limited to such an application. It will be appreciated by those skilled in the art that the invention is equally applicable to detecting relative motion between the detector device and a body whether the body is stationary and the detector is moving or both the body and detector are moving relative to each other.

The self-diagnosis capability of the embodiments of the present invention is not the conventional line-ofsight testing. The transponder relies upon non-line-ofsight electromagnetic energy.

The self-diagnosis capability of the embodiments of the present invention may find other applications. For example, in a system that monitors employees or traffic using transmitted and received signals, the transponder may be incorporated within such a system. If such a system used codes, that is, each employee or vehicle carried a device that issued, upon interrogation, a corresponding code, the transponder could be operated to produce a test code. In effect, the predetermined characteristic, rather than being a Doppler shift in the transmit frequency, would be a code. The code may be produced by switching the oscillator on and off as appropriate.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS 1. A detector device comprising a transmitter for radiating a first electromagnetic signal; a receiver for receiving electromagnetic signals; and a transponder, responsive to an input signal, to generate and radiate a test electromagnetic signal having at least one predetermined characteristic for receipt by the receiver or at least a portion thereof.
2. A detector device as claimed in claim 1, further comprising a housing containing at least the transponder; the transponder being arranged to receive energy scattered within the housing and to generate the test electromagnetic signal using that scattered energy.
3. A detector device as claimed in either of claims 1 and 2, in which the transponder comprises at least a transceiver comprising a receiver for receiving a portion of the first electromagnetic signal; a modulator for modifying the portion of the first electromagnetic signal and a transmitter for radiating the modified electromagnetic signal as the test electromagnetic signal.
4. A detector device as claimed in claim 3, in which the receiver and transmitter are formed using a common antenna.
5. A detector device as claimed in any preceding claim, further comprising a signal generator for generating

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the input signal.
6. A detector device as claimed in any preceding claim, further comprising a signal analyser for monitoring the characteristic of the test signal to determine the correct operation or otherwise of at least one element of the detector device.
7. A detector device as claimed in any preceding claim, in which the transponder is arranged to radiate the test electromagnetic signal in response to the input signal.
8. A detector device as claimed in any preceding claim, in which the transponder is operable as a non-line of sight device to receive the scattered energy.
9. A detector device substantially as described herein with reference to and/or as illustrated in the accompanying drawings.