A 123-GHz Power Amplifier Utilizing Adaptive Gain and Linearity Compensation Achieving 31.6-dB Gain With 12.05-dBm <i>P</i> _sat and 10.18-dBm OP _1 dB

This article presents a high-gain, high-linearity power amplifier (PA) operating in the D band, applying a novel adaptive power gain and linearity compensation structure (AGLC). The proposed structure significantly enhances linearity while concurrently providing gain improvement. On the basis, this work also employs a strongly coupled and low-insertion-loss transformer to further enhance the gain. In the measurement, the proposed PA achieves a gain of 31.6 dB with a saturation output power (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\mathrm {sat}}$</tex-math> </inline-formula>) of 12.05 dBm and an output power at 1-dB compression point (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm {OP}}_{\mathrm {1~dB}}$</tex-math> </inline-formula>) of 10.18 dBm at 123 GHz. By activating the AGLC, the small-signal gain and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm {OP}}_{\mathrm {1~dB}}$</tex-math> </inline-formula> are improved by up to 1.33 and 2.83 dB, respectively. Meanwhile, the measurement results show that AGLC can significantly reduce the AM–AM and AM–PM distortions of PA and greatly improve the output referred third-order intermodulation intercept point (OIP3). When a 64-quadrature amplitude modulation (QAM) signal is applied, the proposed PA achieves a minimum error vector magnitude (EVM) of −24 dB under a power backoff of only 5.03 dB. To the best of the authors’ knowledge, the proposed PA achieves remarkably prominent gain and linearity performance in the D band.