A 47 GHz to 70 GHz Frequency Doubler Exploiting 2nd-Harmonic Feedback with 10.1 dBm Psat and ntotal of 22% in 65 nm CMOS

A wideband millimeter wave (mm-wave) frequency doubler (FDB) architecture is proposed, where a feedback network is employed to increase the 2
^nd
-harmonic signal at the output. Unlike traditional approaches where the 2
^nd
-harmonic is nulled at the input, common-mode/differential-mode signals are exploited to create frequency-dependent networks at fo and 2 fo. The stand-alone FDB in 65-nm CMOS achieves a saturated output power (P
sat
) of > 10.1 dBm. A wideband power amplifier (PA) follows the FDB to achieve a total P
sat
of 15 dBm with a maximum DC-to-RF efficiency (ntotal) of 24.5%, demonstrating the applicability of the FDB for mm-wave radar.