A wideband W-band receiver front-end in 65-nm CMOS

A 75-to-91 GHz receiver front-end, consisting of a three-stage cascode low-noise amplifier (LNA), a double-balanced Gilbert-cell mixer and a differential DC-to-9 GHz IF buffer, is reported in 65-nm general purpose (GP) CMOS technology. The noise and input-impedance matched LNA employs a cascode input stage with shunt-series, transformer feedback. A theoretical and experimental comparison with a conventional inductor-feedback LNA indicates; 0.5-1 dB higher gain, 0.3-0.6 dB lower noise figure and better input return loss for the transformer feedback LNA. The receiver has a differential down-conversion gain of 13 dB, an input P-1dB of -16.2 dBm, and a double-sideband noise figure of 8.5 to 10 dB at an IF of 1 GHz. Because of the transformer feedback, the input return loss is better than -20 dB from 80 to 92 GHz and remains below -10 dB from 70 GHz beyond 95 GHz. The circuit occupies an area of 460 pm x 500 mu m and consumes 89 mW (47 mW in the LNA and mixer) from a 1.5 V supply. An LO-to-RF isolation of 60 dB was measured for LO signals in the 80-to-85 GHz range. Measurements of the mixer breakout, which includes transformers at the RF and LO ports, show a record NFDSB of 8 to 10 dB over the 74-to-91 GHz band. The 50-Omega noise figure of the LNA is 6.4 to 8.4 dB in the 75-to-88.5 GHz range. The LNA can also be employed as a transmitter output stage with a saturated output power of +4 dBm.