60-GHz SiGe BiCMOS dual-conversion down-converter: Schottky diode RF mixer and analog Gilbert IF mixer with microwave quadrature generator

A 60 GHz dual-conversion down-converter using 0.35 μm SiGe BiCMOS process is demonstrated in this paper. A Schottky diode ring mixer with wideband Marchand balun works as the 60-GHz RF mixer while two analog Gilbert micromixers with LO port pumped by two quadrature couplers work as IF mixers. The cut-off frequency of a Schottky diode makes a fundamental RF ring mixer possible because the series resistance of a Schottky diode is effectively reduced by the n+ buried layer in SiGe BiCMOS process. A Gilbert micromixer with an IF buffer is used to accommodate the single-ended output of the RF ring mixer. By combining these advantages, a dual-conversion down-converter is achieved. The converter has about 8 dB conversion gain, 10 GHz RF bandwidth of 50-60 GHz, 100 MHz IF bandwidth when LO₁ power is 8 dBm and LO₂ power is 2 dBm.