The drawback of conventional Pon retrodirective antenna systems is the requ
irement of a local oscillator (LO) working at approximately twice the recei
ve frequency. This limits the use of these systems to rather moderate frequ
encies where such an oscillator can be obtained, To overcome this problem,
a new phase conjugate mixer topology is proposed, whereby the use of a harm
onic mixer instead of the conventional fundamental type effectively halves
the LO frequency requirement. Another significant problem of conventional P
on phase conjugate mixers is the small spacing in frequency, typically only
a few 0.1% of the carrier frequency, between RF, LF, and LO frequency. In
this paper, we have overcome this problem by introducing a double balanced
structure with a novel phasing strategy. The phasing circuit automatically
cancels the RF and LO signal at the system's output port, giving 36-dB RF/I
F, and 34-dB LO/IF isolation for a 970-MHz IF and 990-MHz RF signal. The ne
w mixer structure proposed here is an attractive proposition for use in ret
rodirective antenna arrays significantly enhancing their potential for appl
ication in the millimeter-wave frequency range.