Communications: directive radio wave systems and devices (e.g. – Determining velocity
Patent
1984-04-20
1987-10-06
Tubbesing, T. H.
Communications: directive radio wave systems and devices (e.g.,
Determining velocity
342109, 342 6, 342 97, G01S 1360
Patent
active
046986367
ABSTRACT:
A ground speed determining radar system for take off roll and landings and roll out maneuvers has a ground based modulating radar reflector and a carrier based radar. The radar transmits microwave energy to the reflector where it is modulated by rotating spaced reflectors and returned to the radar receiver. The receiver is a heterodyne receiver having a log IF stage and a fast time control (FTC) circuit for attenuating clutter and an acquisition loop circuit, lock-on circuit and tracking loop circuit. The acquisition loop circuit includes a center, gate, modulation bandpass filter, switch, acquisition sweep generator and gate generator; the lock-on circuit adds a delay line and a good data indicator to the loop acquisition circuit, and the track loop circuit includes early/late gates, early/late gate low pass filters, subtractor, integrator, the switch and gate generator. Prior to acquisition or upon loss of lock-on, the modulation band pass filter has zero output to the switch and the switch switches in the acquisition sweep generator and a ramp voltage is applied to the early/late gates. During the time the early/late gates are swept over the desired modulated frequency from the ground reflector the modulated band pass filter outputs a signal to the switch which switches in the integrator of the tracking loop. The lock-on circuit's delay means delays the modulation band pass output a time sufficient for the integrator to settle down and spurious noise to the disappear before activiting the data indicator. At times, the early/late gates are not centered on an echo return; thus more echo energy is in one (late) gate than in the other (early gate), for example. The subtractor outputs the difference to the integrator which output a dc voltage proportional to the range to the reflector. A differentiator and range indicator and the switch are connected to the integrator for receiving its dc output and, respectively, outputting velocity and range information and feed back to center the early/late gates on the echo.
REFERENCES:
patent: 2580921 (1952-01-01), Iams
patent: 3321757 (1967-05-01), Crow et al.
patent: 4104634 (1978-08-01), Gillard et al.
patent: 4283725 (1981-08-01), Chisholm
patent: 4594676 (1986-06-01), Breiholz et al.
Marlow Raymond
Nelson, Jr. John L.
Sotomayor John B.
Tubbesing T. H.
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