A 300-GHz-Band 40-Gb/s 2D Phased-Array CMOS Transmitter with Near-Half-Wave Antenna Pitch

The free-space wavelengths in the 300-GHz band are so short that it is extremely challenging to realize phased arrays with a half-wave antenna pitch, required for preventing grating lobes. This paper presents a CMOS 2D phased-array transmitter (TX) with a near-half-wave antenna pitch. The 3 × 3 near-half-wave pitch antenna array prototype consists of four main antennas at the corners and five auxiliary antennas. The main antennas are fed directly by a 2 × 2 array of CMOS TX elements (upconversion mixers), disposed with a near-full-wave pitch. Each of the auxiliary antennas is fed with leaked signals from two or more neighboring TX elements. The superposition of leaked signals gives the right phase for each auxiliary antenna. This interpolated feeding architecture relaxes the area reduction requirement for the arrayed TX elements and still enables near-half-wave phased arrays. The 2D phased-array TX, prototyped using a 40-nm CMOS process, operates in the frequency range of 263–279 GHz, and the antenna pitch is approximately 0.54 times the wavelength. It achieves a maximum EIRP of –6.9 dBm and a highest data rate of 40 Gb/s with 16QAM over a link distance of 0.05 m. The beam steering range is r30q in the E- and H-planes.