A CMOS Two-Element 170-GHz Fundamental-Frequency Transmitter With Direct RF-8PSK Modulation

A CMOS 170-GHz fundamental-frequency transmitter (TX) realizing the 8PSK modulation scheme directly in the RF domain is presented. The use of direct RF modulation obviates the need for high-resolution high-speed mixed-signal blocks. The proposed architecture extends the conventional quadrature modulation by performing additional phase modulation on I and Q components of the LO signal, which helps increase modulation order. The TX employs high-speed switchable phase shifters to achieve LO phase modulation and fundamental-frequency over-neutralized power amplifiers to drive an integrated two-element tapered dipole antenna array. Fabricated in a 65-nm CMOS process ( fT/fmax = 230/260 GHz), the RF-8PSK TX prototype occupies 3.2 × 2.8 mm
²
of die area. The free-space wireless measurement of the TX over a 10-cm link range yields 15 Gb/s data rate at an error vector magnitude (EVM) of -14.8 dB. The TX achieves an EIRP of 4 dBm while consuming 560-mW power.