A Multiport Chip-Scale Dielectric Resonator Antenna for CMOS THz Transmitters

The practicality of terahertz (THz) CMOS radiating transmitters is limited by the power produced by CMOS circuits above the transistor fmax and the efficiency of on-chip antennas due to silicon substrate conductance and dimension sensitivity. In this article, we propose a new way of designing CMOS transmitters at THz frequencies by considering the silicon substrate as a dielectric resonator antenna. It is shown that sizing the substrate is the main contributor to determine the transmitter directivity and efficiency. We further propose a dense multiport approach to increase the radiated power from the silicon chip. To demonstrate the validity of this approach, a 1.45 x 1.45 mm² 65-nm CMOS chip was designed with a 5 x 6 dense array of excitation ports implemented using injection-locked third-harmonic voltage-controlled oscillators with digital control. The measured chip achieves a record radiated power of +9 dBm, an equivalent isotropic radiated power (EIRP) of +24 dBm, and the total power efficiency of 1.9% at 0.28 THz.