A Compact 90–180 GHz, 15–18 dBm Power Amplifier With Novel Self-Shielding Load-Open Balun and Broadband Fourth-Order LC Ladder Power Combiner in 28-nm CMOS

This article presents a compact four-way six-stage power amplifier (PA) operating in the 90–180 GHz range with 15–18 dBm saturated output power ( $P_{\text {sat}}$ ) in 28-nm bulk CMOS. A compact neutralized amplifier core utilizing a modified MOS capacitor is proposed, achieving a fourfold size reduction. The output network features a three-conductor self-shielding load-open (SSLO) balun-based dual LC-tank, and a slow wave coplanar waveguide (CPW) based 4th-order LC ladder, achieving a total loss of less than 2.5 dB. Staggered transformer-based broadband matching is employed to achieve a flat gain of 20 dB. At input, a parallel winding balun-based 1-to-8 power splitter is introduced to provide balanced power distribution. Measurements indicate that the PA achieves a maximum small-signal gain of 21 dB and delivers $P_{\text {sat}}$ more than 15 dBm, peaking at 18 dBm at 140 GHz. Compared to the state-of-the-art, this PA offers the widest operating band among F-band and D-band silicon-based PAs with comparable $P_{\text {sat}}$ , making it a promising candidate for high data rate and long-distance communication in D-/F-bands.