Abstract: An active retrodirective antenna array having central phasing from a reference antenna element through a "tree" structured network of transmission lines utilizes a plurality of phase conjugate circuits (PCCs) at each node and a phase reference regeneration circuit (PRR) at each node except the initial node. Each node virtually coincides with an element of the array. A PCC generates the exact conjugate phase .phi.*.sub.1 of an incident signal .phi..sub.1 in accordance with the relation R (2.phi..sub.0 -.phi..sub.1) where R is equal to the reciprocal of 1-2/n, and n.gtoreq.4, using a phase locked loop which combines the phases .phi..sub.1 and .phi.*.sub.1 in an up-converter, divides the sum by 2 and mixes the result with the phase .phi..sub.0 in a down-converter for phase detection by the phase .phi.*.sub.1 from the loop oscillator divided by n. The PRR extracts the phase .phi..sub.0 from the conjugate phase .phi.*.sub.1 by mixing .phi.*.sub.

Abstract: An active retrodirective antenna array wherein a reference array element is used to generate a phase reference which is replicated at succeeding elements of the array. Each element of the array is associated with a phase regeneration circuit and the phase conjugation circuitry of an adjacent element. In one implementation, the phase reference circuit operates on the input signal at the reference element, a voltage controlled oscillator (VCO) output signal and the input pilot signal at the next array element received from a transmission line. By proper filtering and mixing, a phase component may be produced to which the VCO may be locked to produce the phase conjugate of the pilot signal at the next array element plus a transmission line delay. The same phase conjugation process occurs at the next element where the proper phase reference is regenerated by mixing samples of the input pilot and transmitted signal.