The Efect of Antenna Patterns on the Performance of Dual-Antenna Radar Airborne Moving Target Indicators

A dual antenna radar airborne moving target indication (AMTI) system is a scheme for eliminating or sharply reducing residual ground clutter fluctuation and stationary target residue so that moving target returns are easier to detect. Successive pulse transmissions are alternately transmitted from the two antennas, each of which is connected to its own receiver. The two antennas are arranged longitudinally (in the flight path of the airplane) in such a relative position that the rear antenna occupies the same position as the forward one after one repetition period. The pulse from the first (forward) antenna is delayed after square-law detection, and subtracted from the square law detected second pulse return. If the two antennas have identical antenna patterns and transmitted pulse shapes, and if there are no position errors, the returns from stationary objects will be perfectly cancelled (except for a noise residue, neglected in this paper). This paper derives clutter cancellation and moving target enhance ment formulas in terms of the antenna patterns and position errors. The formulas are complicated, so certain approximations are suggested for rough-cut calculations.