Communications: directive radio wave systems and devices (e.g. – Directive – Beacon or receiver
Patent
1995-02-01
1996-06-11
Issing, Gregory C.
Communications: directive radio wave systems and devices (e.g.,
Directive
Beacon or receiver
342450, G01S 504, G01S 302
Patent
active
055260012
ABSTRACT:
Bearing rate of change, or equivalently bearing differences, are used to estimate emitter geolocation, in contrast to using such rates or differences to estimate only range. In using the bearing differences, it is not necessary to maintain the same relative bearing to compensate for DOA dependent errors. Nor does the invention require a precise fully resolved and calibrated interferometer to generate DF measurements. Furthermore, it can be used with currently implemented amplitude DF systems that employ no phase interferometry at all. By making minimal changes, these systems will produce accurate geolocation. The invention will also work with any system that can be modified to produce an accurate bearing rate-of-change. Therefore, it can be used with time-difference-of-arrival (TDOA) systems also. If bearing measurements are also produced by such systems, the magnitude of the bias on that bearing measurement is not important. The effect of angle bias errors in performing bearings-only geolocation are greatly reduced or eliminated. Bias and random components of the measurement error are separated, an estimation of bias error in azimuth or AOA measurements can also be generated. Bearings differences are uniquely associated with curves, e.g. circles, on which the emitter must lie. A plurality of circles are generated to unamibiguously determine emitter geolocation. Multiple platforms may be used to generate the bearing differences. It is also possible to utilize existing bearings-only emitter location software by generating psuedo bearings. The new pseudo bearing measurements use bearing differences, rather than AOA. Geolocation is thus derived strictly from bearing differences, thus eliminating the effects of bias error.
REFERENCES:
patent: 3691560 (1972-09-01), Hammack
patent: 3866229 (1975-02-01), Hammack
patent: 3922533 (1975-11-01), Royal
Dangle Kurt M.
Rose Conrad M.
Issing Gregory C.
Lett Gerald L.
Litton Systems Inc.
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