A 120-to-142-GHz Compact Balanced Power Amplifier Utilizing Novel Slow-Wave Coupled Line in 40-nm CMOS

This manuscript introduces an integrated power amplifier (PA) meticulously designed for the D-band, addressing the interconnect challenges between power amplifiers and transmitting antennas operating in the millimeter-wave and terahertz frequency ranges. The proposed PA design is founded on a 2-way combined, low-loss balanced amplifier technology. The low-loss balanced amplifier technology utilizes a four-stage differential common-source amplifier unit, featuring the lossy over-neutralization technique as foundational building blocks. Simultaneously, the combining network integrates a quadrature coupler designed with a novel slow-wave coupled line. In contrast to conventional coupled line structures, the novel slow-wave coupled-line structure excels in low loss, high coupling coefficient, and the demand for high characteristic impedance while maintaining a high phase constant, contributing to a more compact form factor. Fabricated utilizing a 40-nm CMOS process, the amplifier showcases a total area of 0.34 mm2 (
$0.074\lambda ^{2}$
), with a core area of 0.11 mm2 (
$0.024\lambda ^{2}$
). At 130 GHz, it attains a peak gain of 23 dB, a saturated output power of 13.2 dBm. Moreover, the entire D-band exhibits outstanding matching characteristics. To the best of our knowledge, this is the first published CMOS balanced power amplifier designed in D-band.