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AssigneeNorthrop Grumman Corporation
InventorDavid T. Carrott
Estimating the term…
The location of a cellular telephone handset relative to the sites of two pairs of fixed cellular transceivers is determined by responding to the phase difference of radio waves the handset emits, as coupled to the sites. The phase difference is detected by supplying replicas of the waves received at the first and second sites to first and second electro-acoustical transducers at opposite ends of a Bragg cell. One Bragg cell is thus associated with each pair of cellular transceivers. A laser beam incident on each Bragg cell is deflected by a moving optical grating resulting from the interaction of acoustic waves applied by the electro-acoustical transducers to the particular Bragg cell. The laser beam deflection angle for each Bragg cell determines the relative phase angle of the acoustic waves in that cell. Indications of the deflection angles, positions of the transceivers and propagation speeds of replicas of the radio waves propagating in communication links between the sites are combined to indicate the handset location.
Apparatus for deriving a signal indicative of a possible position of a radio wave source relative to a pair of receiver sites having known positions, the radio wave source being arranged for emitting a radio wave to which receivers at the sites are arranged to be responsive, the apparatus comprising an optically diffractive medium capable of having a moving optical grating induced therein in response to acoustic waves propagating therein, first and second electro-acoustic transducers coupled to the optically diffractive medium for launching first and second acoustic waves toward each other in the optically diffractive medium in response to electric excitation of the first and second transducers by replicas of the radio waves to which the pair of receivers are responsive, the transducers being positioned and arranged so that the first and second acoustic waves interact with each other in the medium, an optical source for illuminating the medium, and a detector arrangement arranged to be responsive to optical energy from the source and modulated by the moving grating for deriving a signal indicative of the relative phase angle of the radio wave replicas exciting the first and second transducers, the transducers and medium being arranged so the acoustic waves propagate in a direction between the transducers, the detector arrangement including plural individual optical detector elements positioned in an array that extends in the same direction as the direction the acoustic waves propagate, the signal indicative of the relative chase angle being derived in response to an indication of the location of the detector element which has the greatest intensity of optical energy incident on it.
Apparatus for deriving a signal indicative of a possible position of a radio wave source relative to a pair of receiver sites having known positions, the radio wave source being arranged for emitting a radio wave to which receivers at the sites are arranged to be responsive, the apparatus comprising an optically diffractive medium capable of having a moving optical grating induced therein in response to acoustic waves propagating therein, first and second electro-acoustic transducers coupled to the optically diffractive medium for launching first and second acoustic waves toward each other in the optically diffractive medium in response to electric excitation of the first and second transducers by replicas of the radio waves to which the pair of receivers are responsive, the transducers being positioned and arranged so that the first and second acoustic waves interact with each other in the medium, an optical source for illuminating the medium, and a detector arrangement arranged to be responsive to optical energy from the source and modulated by the moving grating for deriving a signal indicative of the relative phase angle of the radio wave replicas exciting the first and second transducers, the detector arrangement being arranged to derive a signal indicative of the angle of the maximum intensity of the modulated optical energy relative to the propagation direction of the acoustic waves in the medium, the signal indicative of the relative phase angle being derived in response to the signal indicative of the angle of the maximum intensity of the modulated optical energy relative to the propagation direction of the acoustic waves in the medium.
A system for deriving a signal indicative of a possible position of a radio wave source relative to a pair of sites having known positions, the system comprising a receiver at each of the sites for receiving the radio wave, an optically diffractive medium capable of having a moving optical grating induced therein in response to acoustic waves propagating therein, first and second electro-acoustic transducers coupled to the optically diffractive medium for launching first and second acoustic waves toward each other in the optically diffractive medium in response to electric excitation of the first and second transducers by replicas of the radio waves to which the pair of receivers are responsive, the transducers being positioned and arranged so that the first and second acoustic waves interact with each other in the medium, an optical source for illuminating the medium, and a detector arrangement arranged to be responsive to optical energy from the source and modulated by the moving grating for deriving a signal indicative of the relative phase angle of the radio wave replicas exciting the first and second transducers, the detector arrangement being arranged to derive a signal indicative of the angle of the maximum intensity of the modulated optical energy relative to the propagation direction of the acoustic waves in the medium, the signal indicative of the relative phase angle being derived in response to the signal indicative of the angle of the maximum intensity of the modulated optical energy relative to the propagation direction of the acoustic waves in the medium.
A method of deriving a signal indicative of a possible position of an emitted radio wave source relative to a pair of receiver sites having known positions, the method comprising receiving the emitted radio wave at the pair of sites, processing replicas of the radio waves received at the pair of sites by supplying to an optically diffractive medium acoustic replicas of the received radio waves, the acoustic replicas propagating toward each other and meeting in the optically diffractive medium, causing an optical beam to be incident on the acoustic replicas propagating in the medium, the acoustic replicas meeting in the medium causing modulation and deflection of the optical beam, and responding to an indication of the deflection angle of the optical beam to derive a response determined by the relative phase of the replicas of the radio waves received at the pair of sites.
The method of claim further comprising determining the location of the radio wave source relative to at least three sites having known positions, each site including a receiver for the emitted radio wave, receiving the emitted radio wave at receivers at a second pair of the sites, processing replicas of the radio waves received at the second pair of sites by supplying to a second optically diffractive medium second acoustic replicas that propagate toward each other and meet in the second optically diffractive medium, the second acoustic replicas meeting in the second medium causing modulation and deflection of the second optical beam, responding to an indication of the deflection angle of the second optical beam to derive a second response determined by the relative phase of the replicas of the radio waves received at the second pair of sites, and combining both responses to derive an indication of the radio wave source location.
Apparatus for determining the location of a radio wave source relative to at least three receiver sites having known positions, each of the sites being arranged to be responsive to the radio wave, the apparatus comprising an optically diffractive medium arrangement capable of having several optical gratings induced therein in response to acoustic waves propagating therein, electro-acoustic transducers connected to be responsive to replicas of the radio wave at the sites and coupled to the optically diffractive medium arrangement for launching several acoustic waves in the optically diffractive medium arrangement, the acoustic waves being replicas of the radio waves at the sites, a pair of said electro-acoustic transducers being coupled with the optically diffractive medium arrangement to cause a pair of acoustic waves to be launched toward each other so the pair of acoustic waves interact with each other in the optically diffractive medium arrangement, an optical source arrangement for illuminating the optically diffractive medium arrangement, the several acoustic waves in the optically diffractive medium arrangement causing deflections of optical energy from the optical source arrangement, the deflection angles of the optical energy being indications of the relative phases of the replicas of the radio waves at the at least three receiver sites, an optical-electric detector arrangement arranged to be responsive to optical energy from the optical source arrangement, and a processor arrangement connected to be responsive to the optical-electric detector arrangement and indications of the known positions and the deflection angles for deriving a signal indicative of the location of the radio wave source.
A method of determining the location of a wave emitted by a wave source comprising the steps of receiving the wave at three or more sites having known positions, launching in an optical diffracting medium arrangement several acoustic waves that are replicas of the wave, as received at the sites, the acoustic waves being launched while the optical energy is incident on the diffracting medium, the waves being launched so that pairs of them propagate toward each other and meet in the medium arrangement to cause deflection of the optical energy incident on the medium arrangement, the deflection angles of the optical energy being indications of the relative phases of the replicas of the radio waves at the at least three receiver sites, and indicating the position of the wave source in response to the indication of the deflected angles.
Apparatus for deriving a signal indicative of a possible position of a radio wave source relative to a pair of receiver sites having known positions, the radio wave source being arranged for emitting a radio wave to which receivers at the sites are arranged to be responsive, the apparatus comprising an optically diffractive medium capable of having a moving optical grating induced therein in response to acoustic waves propagating therein, first and second electro-acoustic transducers coupled to the optically diffractive medium for launching first and second acoustic waves toward each other in the optically diffractive medium in response to electric excitation of the first and second transducers by replicas of the radio waves to which the pair of receivers are responsive, the transducers being positioned and arranged so that the first and second acoustic waves interact with each other in the medium, an optical source for illuminating the medium, the optical source and medium being arranged so that a beam from the source incident on the medium is deflected by the medium by an angle indicative of the phase difference of the first and second acoustic waves, and a detector arrangement arranged to be responsive to the deflected beam for deriving a signal indicative of the deflection angle of the deflected beam.
Dependencies are inferred from the claim text.
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From the US filing history. Foreign family members aren’t listed.
By combining or switching between measurements derived from different systems: at least one of the measurements being a non-radio measurement
Using radio waves: position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega…
Radio direction-finding
Term ended 30 Aug 2021 (estimated)
The present invention relates generally to an apparatus for and method of enabling the location of a radio wave source to be determined and, more particularly, to such an apparatus and method wherein replicas of waves transmitted from a radio wave source and received at receiver sites having known locations are applied to transducers which apply acoustic waves in opposite directions to a diffraction grating for modulating an optical wave.
Time difference of arrival (TDOA) is a well-documented method of locating a radio frequency source. TDOA works by detecting the difference in phase of an RF wave emitted by an RF source and received by receivers having known locations. Replicas of the waves received by the receivers are supplied to an electronic phase detector. If the receivers are exactly the same distance from the RF source the phase of the RF signal at the receivers is the same, causing the phase detector to derive a null output level. If the RF source moves relative to a line equi-distant from the two receivers, one receiver is closer to the source than the other, causing a phase difference between the signals at the receivers so that the phase detector derives a signal having an amplitude and polarity indicative of the phase difference.
A problem with this typical TDOA arrangement employing phase detectors is that when the phase detector derives a null output level it is not possible to determine on which side of the two receivers the RF source is located. This problem can be resolved by including a second pair of receivers to derive a second TDOA output signal. The two pairs of receivers frequently include a common receiver. However, use of two pairs of receivers does not resolve the problems associated with relying on phase detectors deriving signals having very small amplitudes, as occurs when the two receivers are approximately equi-distant from the RF source.
FIG. 1 is a schematic diagram of a preferred embodiment of a system in accordance with the invention for detecting possible locations of a cellular telephone handset;
FIG. 2 is a schematic diagram of a preferred embodiment of a system in accordance with the invention for unambiguously detecting the location of a cellular telephone handset; and
FIG. 3 is a block diagram of a preferred embodiment of equipment included at each of the cellular transceiver sites in the system of FIG. 2.
Reference is now made to FIG. 1 of the drawing, an illustration of a system for determining possible positions of cellular telephone handset 10 relative to the sites of cellular transceivers 12 and 14, having known fixed positions. Cellular telephone handset 10, when in use, periodically emits a radio wave having known frequency and initial phase characteristics, such as a constant frequency having an initial phase of zero degrees modulating a carrier. Handset 10 transmits the radio wave having known frequency and initial phase characteristics to the sites of cellular transceivers 12 and 14.
Each of cellular transceivers 12 and 14 includes a receiver segment responsive to the radio wave cellular telephone handset 10 emits. The receiver segment of each of cellular transceivers 12 and 14 responds to the radio wave it receives from cellular telephone 10 to derive a replica of that portion of the wave having the known frequency and initial phase characteristics; for example, the constant frequency modulating the carrier. Each of transceivers 12 and 14 couples the replica it derives to electro-acousto-optical processor 16 which derives an output signal indicative of the time difference of arrival (TDOA) at the sites of cellular transceivers 12 and 14 of the radio wave that cellular telephone 10 emits. To this end, transceivers 12 and 14 are connected to processor 16 by communication links 18 and 20 having known characteristics, particularly signal propagation time between the sites of transceivers 12 and 14. Communication links 18 and 20 can be of any known type, such as land-based wire or fiber optic lines, or wireless paths.
Processor 16 can be located at a central station, but is preferably located at the site of one of cellular transceivers 12 and 14. If processor 16 is located at the site of one of cellular transceivers 12 or 14, the processing is performed at the site receiving the greatest signal strength of the radio wave that cellular telephone 10 emits. In such an event, the site of each of cellular transceivers 12 and 14 includes identical processors of the type illustrated by processor 16. In a typical cellular system, each cellular transceiver includes a detector arrangement for the strength of the signal received at the site of the transceiver. These detectors are coupled to each other to determine the site receiving the greatest signal strength from the radio wave a cellular telephone handset emits, to assure transmission of telephone signals between the cellular telephone handset and only one transceiver in the vicinity of the handset. Consequently, virtually no additional equipment is required at the sites of the cellular transceivers 12 and 14 to determine the site which is to perform the processing.