A Hybrid ΔΣ/Nyquist Rate Switched Capacitor Power Amplifier in 65nm CMOS

This paper presents a new hybrid-mode SCPA that segments a traditional SCPA into two segments. An LSB C-2C sub-array is modulated using a $\Delta \Sigma $ modulator (DSM) connected in parallel with a Nyquist-rate unary MSB array. This technique enables a hybrid SCPA (H-SCPA) that can achieve a higher bandwidth than a traditional DSM DAC, while achieving a higher resolution than a traditional Nyquist DAC. A prototype design is implemented in 65nm CMOS and post-extracted simulation results validate the performance of the H-SCPA. The H-SCPA achieves a peak output power of 23.5 dBm and a peak system efficiency of 48% at an operating frequency of 2.8 GHz. When amplifying a 20 MHz, 64 QAM, OFDM signal, the average output power and system efficiency at 2.8 GHz are 17.4 dBm and 24.9 %, respectively, while achieving an error vector magnitude (EVM) of 1.9 %-rms and meeting the spectral mask requirements.