A 26GHz CMOS 3× Subharmonic Mixer with a Fundamental Frequency Rejection Technique

A 26GHz up-conversion 3× sub-harmonic mixer is designed using a 65 nm CMOS process. The reasons for the lack of research on the 3× subharmonic mixer are investigated and a solution called a fundamental frequency rejection technique is presented. The fundamental frequency rejection technique allows the cancellation of the fundamental LO and boosting of the third-order harmonic. The proposed 3× subharmonic mixer consists of an octet-phase generator, 3× subharmonic mixer core, output transformer balun, and LO buffers. The octet-phase generator, which consists of a transformer balun and a two-stage polyphase filter, provides the 8-phase LO for the fundamental frequency rejection technique. The mixer core consists of three Gilbert-cell active sub-mixers to implement the fundamental frequency rejection technique. The measured conversion gain of the 3× subharmonic mixer is -5.1±1.5 dB at the RF of 19.5-31.5 GHz. The measured OP 1dB and OIP3 are -15.4 dBm and -7.6 dBm, respectively. The LO-RF isolation and 3LO-RF isolation are >42 dB and >46 dB, respectively, at the operating frequency. The proposed 3× subharmonic mixer consumes DC power of 55.65 mW and occupies a die area of 0.267 mm2.