A 40 GHz communication link with IF-assisted self-heterodyne direct down conversion

A 40 GHz communication link was demonstrated using a combination of super-heterodyne mixing and self-heterodyne direct down conversion. The broadcast carrier and modulated signals inherent in self-heterodyne transmission were first mixed down from 40 GHz to an IF of 1.5 GHz using a 10.375 GHz LO and a novel, low LO power 4/sup th/ harmonic diode mixer. These IF signals passed through an amplifier chain with a total gain of G=75 dB and noise figure of NF=1.21 dB prior to direct down conversion with a self-mixer. It was shown analytically and experimentally that the phase noise cancellation inherent in self-heterodyne detection is preserved independent of the phase noise of the additional LO signal. The input and output IF signals had the same phase noise up to 100 kHz carrier offset for a transmission distance of 2 meters.