20–26-GHz CMOS PA With High <i>P</i> _out and OP_{1 dB} Using a 1:2 Capacitance-Ratio-Equivalent Power Combiner

We demonstrate a four-way wide-band power amplifier (PA1) with a 1:2 capacitance-ratio-equivalent power combiner (PC) and a dynamic-threshold-voltage MOSFET with a resistor (DTMOS-R) using a 90-nm CMOS. Another PA (PA2) without a DTMOS-R using low-loss micro-strip line inductors replaced with a PC is demonstrated for contrast. A low-loss PC is realized using equal <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula>/4 spiral transmission line inductors based on a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula>/9 one (with a 1:2 capacitance ratio involving Cp1 and Cp2) for low-loss output-stage matching. The output power of the output stage of PA1, with low-threshold voltage (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm { th}}$ </tex-math></inline-formula>) due to the DTMOS-R and low Rds based on the parallel four-way output, is enhanced using a PC. Between 20–26 GHz, PA1 achieves a prominent S21 of 23.2 dB, peak power-added-efficiency (PAE) between 20.8%–29.7%, and saturation output power between 19.9–21.2 dBm. Moreover, the output 1-dB compression point (OP1dB) is 16–20.4 dBm between 20–26 GHz. Using the PC and DTMOS-R yields the bulk CMOS PA’s high performance (Pout, PAE, and OP1dB), comparable to recent state-of-the-art millimeter-wave PAs, i.e., SOI/SiGe processes.