Abstract: A radar system comprising an RF transmitter and receiver means for mounting in a moving carrier for transmitting RF energy and receiving RF energy returns and a non-rotating modulating radar reflector which has a lens means for focusing incident impinging RF energy onto a spot opposite the incident side and a plurality of solid state modulating radar reflectors positioned at the spot locations for selectively reflecting the RF energy and dissipating the RF energy for providing RF energy returns modulated with a lens identification code and frequencies for determining true ground speed, range, glide slope, and azimuth position.

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.