A Compact 140-GHz CMOS Power Amplifier With 10.5-dBm Output Power and 27.6-dB Power Gain Supporting up to 128-QAM Modulation

A compact 140-GHz power amplifier (PA) with an employed multilayer stacked transformer (MLST) matching network is implemented in a 65-nm CMOS process. The employed MLST matching network adopts two metal layers as the primary coil and one single layer as the secondary coil to increase the coupling factor and decrease the insertion loss (IL) of the matching network at the D-band frequency range. Besides, a gain-boosting unit (GBU) is further introduced in the first stage of the PA to enhance the power gain. The proposed 140-GHz PA achieves a measured power added efficiency of 6.9%, a
${P_{\textrm {sat}}}$
of 10.5 dBm, and an
${OP_{\textrm {1dB}}}$
of 7.03 dBm with a maximum power gain of 27.6 dB when the GBU turns off. By turning on the GBU, the power gain managed to increase from 27.6 to 31 dB with stability. Furthermore, modulation measurement shows that the proposed D-band PA supports 24-Gb/s 64-QAM and 11.2-Gb/s 128-QAM modulated signals with error vector magnitudes (EVMs) of −23.1/−22.87 dB at the output power of 7 dBm, respectively. The core chip area and dc power consumption of the PA are only 0.0275 mm2 and 170 mW.