A Broadband Injection-Locking Class-E Power Amplifier

This paper presents a fully integrated two-stage injection-locking class-E power amplifier (PA) using a GaAs 0.5-μm enhancement- and depletion-mode pseudomorphic high-electron mobility transistor (E/D-mode PHEMT) process. The injection-locking concept is used in this design, and the PA works as an oscillator whose output voltage is tuned at the input frequency. The proposed PA achieves high power-added efficiency (PAE) and high power gain. An autonomous circuit is also employed for the stability analysis, and the design procedure is summarized for the circuit implementation. By employing this design technique, the proposed injection-locking class-E PA under continuous-wave signal achieves a peak PAE of 59% at an output power of 26.6 dBm from a 6-V dc supply voltage. With a Gaussian minimum-shift keying (GMSK) modulation input signal at 3.5 GHz, the measured maximum PAE is 57% at an output power of 26.7 dBm. The measured error vector magnitude is within 2.2% over all of the output power level, and the adjacent channel power ratio is better than - 40 dBc. Under a 64-QAM modulation signal with class-AB operation, the proposed PA achieves a peak PAE of 55% with an output power of 27 dBm.