Communications: directive radio wave systems and devices (e.g. – Directive – Beacon or receiver
Patent
1992-12-18
1994-10-11
Issing, Gregory C.
Communications: directive radio wave systems and devices (e.g.,
Directive
Beacon or receiver
342 98, 342437, 455136, 455258, G01S 504, G01S 1300, H04B 1702, H04B 106
Patent
active
053551419
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a channelised bearing processor which determines the direction and characteristics of an unknown signal source. Such a processor has application wherever it is necessary to locate the positions of transmitters which emit pulsed or continuous wave (CW) signals at frequencies for example typically in the range of 0.5 to 18 GHz.
BACKGROUND ART
It is known to use wideband receivers for direction finding. Typically a system comprises a circular array of wide angled antennas, each of which is coupled to a respective wideband receiver. At the detection of a signal within the frequency range of the wideband receiver, an output proportional to the amplitude of the signal as received is produced. The respective amplitude signals are supplied to a bearing processor which determines the bearing of the source of signals. If it is desired to measure characteristics of the received signal, such as its frequency, then for example an instantaneous frequency measuring device is coupled to either an omni-directional antenna or a combination of the bearing array antennas so arranged as to give omni-coverage. The use of wideband receivers for direction finding has a number of limitations. In particular, they are not suitable for measuring characteristics (or emitter parameters) in increasingly dense scenarios in which simultaneously occurring signals have different characteristics and relatively short durations.
DISCLOSURE OF INVENTION
It is an object of the present invention to be able to resolve the directions and determine the characteristics of two or more simultaneously occurring short duration signals.
According to the present invention there is provided a channelised bearing processor characterised by a channelised receiver formed by a plurality of receivers covering respective predetermined frequency ranges, a local oscillator coupled to each of the receivers, a plurality of receiving channels for producing an amplitude signal, each said receiving channel having an input for receiving an input signal and a tunable receiver having an input for a local oscillator signal, and local oscillator selecting means responsive to an output from one of the plurality of receivers to connect the local oscillator connected to that one of the plurality of receivers to the local oscillator signal inputs of the tunable receivers.
The present invention provides a channelised bearing processor characterised by a plurality of signal inputs coupled to respective frequency down-conversion stages, each of which stages provides in use an i.f. output, delay means for delaying the respective i.f. outputs, a tunable receiver coupled to each of the delay means, each tunable receiver having a local oscillator signal input, a plurality of local oscillators, each producing a different frequency, selector means for selecting one of the outputs produced by the plurality of local oscillators and supplying it to the local oscillator signal inputs of the tunable receivers, a channelised receiver comprising a plurality of i.f. receivers, each operative to receive signals in respective predetermined frequency ranges, each said i.f. receiver having means for providing an indication that it has received a signal in its respective predetermined frequency range, said indication being supplied to the selector means for use in selecting the local oscillator to be connected to the local oscillator signal inputs of the tunable receivers.
The channelised bearing processor is able to resolve the bearings of two or more simultaneously occurring signals since only one amplitude sample is required to calculate the bearing. Thereafter the tunable receiver can be retuned after one sample period in order to measure the bearing of another signal. In this way bearings of simultaneously occurring signals can be calculated subject to the proviso that they are present for more than one sampling period.
The channelised receiver may comprise a plurality of integrated i.f. receivers and each of the tunable receivers may compr
REFERENCES:
patent: 3886556 (1975-05-01), Lowman
Graham Stephen P.
Keeping Michael W.
Issing Gregory C.
Thorn EMI Electronics Limited
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