60-GHz dual-conversion down-converter using Schottky diode and dual-band rat-race coupler in standard 0.18-μm CMOS process

A 60 GHz dual-conversion down-converter with a microwave mixer in the first conversion and analog mixers in the second conversion is demonstrated in 0.18-μm CMOS technology. The first down-converted sub-harmonic mixer consists of a rat-race coupler with the dual-band Chebyshev response and Schottky diodes in anti-parallel configuration. The high cut-off frequency of a Schottky diode helps lowering the conversion loss and noise figure of a microwave mixer. A double balanced resistive mixer is used at the second down-converted mixer. As a result, the conversion gain is about 6 dB in the frequency range of 45~67 GHz and the IF bandwidth is over 1 GHz. IP_1dB is about -5-dBm and IIP3 is about 5-dBm at 45~67 GHz. The single sideband noise figure is 21 dB at 60 GHz. The total power consumption is 71 mW at 2.5 V.