A wideband single-balanced down-mixer for the 60 GHz band in 65 nm CMOS

This paper presents a single-balanced direct down conversion mixer for the unlicensed 60 GHz band. It is based on a differential pair employing the current bleeding technique. An integrated 60 GHz wideband passive balun allows the use of a single ended local oscillator (LO). The circuit is fabricated using the 65 nm bulk CMOS technology of ST Microelectronics. The mixer´s baseband reaches from DC to 2 GHz. The measured radio frequency (RF) bandwidth exceeds 11 GHz, ranging from 54 GHz to at least 65 GHz. The measured RF, IF (intermediate frequency) and LO port return losses lie below -20 dB, -15 dB and -10 dB, respectively, within this entire band. A maximum conversion gain of 9.1 dB at 100 MHz from the carrier is achieved, while typical values measured at 1 GHz IF lie around 6 dB throughout the entire band. The mixer delivers these optimum results for LO powers as low as -5 dBm. The output referred 1 dB compression point reaches -5 dBm for -1 dBm of LO power. The simulated single sideband (SSB) noise figure is of 9dB. Including the differential IF buffer that can drive two single-ended 50Ω loads, the circuit draws 16.8 mA from a 1 V supply. The pad-limited die size is only 0.52 × 0.49 mm².