Abstract
A high-efficiency power amplifier (PA) and a high-conversion-gain (Gc) upconverting mixer (UCM) were developed using 75-nm InP-based MOS HEMTs to enable sub-THz beamforming with a sufficiently large equivalent isotropic radiated power (EIRP) and effectively suppressed grating lobes. The chip sizes of both millimeter-wave monolithic integrated circuits (MMICs) were minimized to less than 1 mm, facilitating their integration into a sub-THz phased-array (STPA) transmitter with an antenna pitch of one wavelength or less, specifically less than 1 mm at 300 GHz. The PA MMIC demonstrated superior performance compared with conventional PAs in the 300-GHz band owing to advanced manufacturing technologies, including the use of a modulated passivation film alongside the gate oxide and epitaxial structures. A peak power-added efficiency (PAE) of 9.3% was achieved, with an associated output power of 9.2 dBm and a linear gain of 18.6 dB at 300 GHz. To the best of our knowledge, the achieved PAE is the highest reported to date. Moreover, the UCM MMIC, which comprised a third-order subharmonic resistive mixer, an on-chip band-pass filter, and an RF amplifier, operated with a 5-dBm local (LO) signal at 90 GHz. The MMIC demonstrated a high Gc of -1.9 dB, a 3-dB bandwidth spanning 39 GHz (270-309 GHz), and a 1-dB gain-compressed RF power of -10.4 dBm, with a power consumption of 84 mW. The observed 3LO leakage power was -26.5 dBm. These findings indicate that a higher EIRP can be achieved with reduced power consumption through the use of an STPA transmitter that integrates a Si CMOS IC and an InP-based MMIC based on the circuits described here.
