CMOS Transceiver Pixels for Terahertz Imaging

Pixels integrating a transmitter and a coherent receiver in an area of half-wavelength square are proposed for terahertz active imaging. 300- and 427-GHz transceiver pixels are demonstrated using a 65-nm CMOS process. The 300-GHz pixel employs a push-push stacked cross-coupled VCO, which doubles as a transmitter and an LO, and a pair of diode-connected NMOS transistors for mixing. The pixel occupies an area of 450×580µm2, and provides −21.3-dBm total radiated power and −79.5-dBm sensitivity for a 1-kHz noise bandwidth at 260GHz. The 426-GHz pixel using a star-type triple-push Colpitts oscillator works as a transmitter and a self-oscillating mixer. The pixel occupies an area of 380×470µm2. The radiated power is −17.9 dBm and the sensitivity is −89.6 dBm for a 1-kHz noise bandwidth. Link-budget analyses suggest that camera-like reflection-mode imaging of targets 5m away should be possible using the pixel and a 4.6cm×4.6cm reflector.