Communications: directive radio wave systems and devices (e.g. – Determining velocity – Combined with determining distance
Patent
1994-06-30
1995-08-15
Sotomayor, John B.
Communications: directive radio wave systems and devices (e.g.,
Determining velocity
Combined with determining distance
342 26, 342115, 342137, 342162, 342189, G01S 13526, G01S 1353, G01S 13538, G01S 1395
Patent
active
054423597
ABSTRACT:
A method and apparatus for resolving Doppler frequency shift ambiguities in pulse Doppler radar systems provides a radiated signal that is modulated with a periodic waveform having a plurality of pulses within a period, the interpulse intervals between pulses in the period being unequal. Radar target returns are autocorrelated for a plurality of lags, which may include the interpulse intervals and linear combinations thereof. The calculated arguments .theta..sub.Ci of the autocorrelation function are unwrapped by adding 2k.sub..pi., k=0, .+-.1, .+-.2, . . . , to the phase .theta..sub.C1 obtained for the shortest lag T.sub.1 and determining an integer m.sub.k2 from .vertline.(.theta..sub.C2 +2m.sub.k2 .pi.)-(T.sub.2 /T.sub.1).theta..sub.C1 .vertline. <.pi. and then setting .theta..sub.2 =.theta..sub.C2 +2m.sub.k2 .pi.. Phase angles .theta..sub.3, .theta..sub.4, . . . , .theta..sub.m are unwrapped in a similar manner, the integer m.sub.ki being determined from .vertline.(.theta..sub.Ci +2m.sub.ki .pi.)-(T.sub.i /T.sub.i-1).theta. .sub.Ci .vertline.<.pi.. The unwrapped phase angles and the point (0,0) are least mean square fitted to lines of phase angle vs lag for each value of k. The root mean square error of the phase angle offset from each line is determined and the slope of the line with the minimum RMS error is chosen as the Doppler frequency shift from which the velocity of the target is extracted.
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Levine Seymour
Sotomayor John B.
Starr Mark T.
Unisys Corporation
Weinstein Stanton D.
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