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초록

This paper presents a wideband Class-EF2 power amplifier (PA) based on a multiple series resonance (MSR) circuit. The proposed PA consists of a shunt capacitor, a series LC network in shunt, the MSR, and an impedance matching network, enabling simultaneous achievement of high efficiency, high output power, and wide bandwidth. In particular, the MSR is composed of multiple series resonance circuit with different resonance frequencies, which minimizes variations in output power and efficiency across the frequency band. To validate the wideband performance of the proposed MSR, Class-EF2 amplifier at a center frequency of 13.56 MHz was designed using an LDMOSFET. Using a continuous-wave (CW) signal, the implemented PA delivers a maximum output power of 59.2-60.0 dBm with a drain efficiency (DE) of from 79.3 to 86.7% over the 12.2-14.9 MHz band. Using a pulse with a duty cycle of 0.5, the output power and DE are increased to 59.6-60.2 dBm and 82.8-92.0% across the band, respectively. Thermal scan showed that the temperature maintained below 70 °C even for very high output power of more than 1 kW.

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