Frequency translating phase conjugation circuit for active retrodirective antenna array

In an active retrodirective array of antenna elements for transmitting a beam at one frequency in the direction of an incident signal of a source operating at a different frequency, wherein a chosen one of said elements is selected as a reference for generating the conjugate phase of the signal phase received by each of the other elements, and where the other elements are divided into a plurality of elements, the improvement comprising

• a first plurality of separate means associated with each of a number of said antenna elements of a first group, each connected to receive a signal directly from said reference element as a phase reference, .phi..sub.0, and to receive a signal from an associated element of an incident phase .phi..sub.1 for generating a signal transmitted to the associated element of conjugate phase .phi.*.sub.1 equal to R(2.phi..sub.0 -.phi..sub.1), where R is equal to the reciprocal of 1-2/n and n.gtoreq.4, and
• a second plurality separate means connected to each phase conjugate generating means by a separate transmission line for extracting from the conjugate phase .phi.*.sub.1 the reference phase .phi..sub.0 and applying the regenerated reference phase to a second plurality of phase conjugate generating means associated with each of a number of said antenna elements of a second group, each of said second plurality of phase conjugate generating means being identical to corresponding means of said first group of antenna elements.

A phase conjugation circuit for receiving an incident signal of phase .phi..sub.0 from an element of an antenna array and an incident signal of phase .phi..sub.1 from another element of an array antenna, and producing a signal of conjugate phase .phi.*.sub.1 equal to R(2.phi..sub.0 -.phi..sub.1), where R is equal to the reciprocal of 1-2/n and n.gtoreq.4, comprising

• a voltage controlled oscillator for producing said signal of phase .phi.*.sub.1
• means for combining the output of said oscillator and said signal of phase .phi..sub.1 to obtain a signal of phase .phi..sub.1 +.phi.*.sub.1,
• means for dividing said signal of phase .phi..sub.1 +.phi.*.sub.1 by two, to obtain a signal of phase 1/2 (.phi..sub.1 +.phi.*.sub.1),
• means for combining said signal of phase .phi..sub.0 with the output of said means for dividing by two to obtain a signal of a phase difference 1/2 (.phi..sub.1 +.phi.*.sub.1)-.phi..sub.0
• means for phase detecting said signal of phase difference 1/2 (.phi..sub.1 +.phi.*.sub.1)-.phi..sub.0 with the output of said oscillator divided by n, and
• means for loop filtering the output of said phase detector to obtain a control signal for said voltage control oscillator, whereby said oscillator produces said phase conjugate signal .phi.*.sub.1.

An active retrodirective array for electronically pointing a microwave beam back in the direction of an incident beam at one frequency from a remote source, said array having a plurality of antenna elements spaced from each other for receiving said incident beam, all of said elements being effectively connected by transmission lines to one reference element which provides a reference phase, .phi..sub.0, for distribution to all other elements, directly through separate phase conjugation means and diplexing means for a predetermined number of antenna elements at a first distribution level, and indirectly through phase conjugation means, diplexing means, and phase reference regeneration means for antenna elements at subsequent levels of distribution of the phase reference, .phi..sub.0, each phase reference regeneration means providing a plurality of phase conjugation means with the reference, .phi..sub.0, for phase conjugation of a signal at a second frequency transmitted from an element, thereby to electronically point the microwave beam transmitted from the array back to the source, each phase conjugation means for an antenna element comprising a voltage controlled oscillator in a phase locked loop, wherein said loop both conjugates the phase and translates the first frequency to the second frequency, said phase locked loop comprising means for mixing the output signal of said oscillator and a signal received from one array element connected to the phase conjugation means by a transmission line to obtain a sum signal whose frequency and phase is the sum of the signals mixed, means for dividing said sum by two, means for mixing the output signal of said divide-by-two means with a phase reference signal to obtain a difference signal whose frequency and phase is the difference between the signals mixed, means for dividing the output of said voltage controlled oscillator by an integer n, means for phase detecting said difference signal with the output of said divide-by-n means to obtain a phase error signal for control of said oscillator, thereby to produce a signal that is a conjugate of the signal received from said one array element, and means for coupling the output of said oscillator to said transmission line connecting said one array element to the phase conjugation means.