Fundamental study on drain efficiency of EDSM/EPWM transmitter
using class-EM amplifier <Abstract> Drain efficiency of EPWM (envelope pulse width modulation) transmitter composed of a class-EM amplifier is evaluated by circuit simulation, and the pulse modulation method to the constant envelope RF signal by PWM pulses is studied. The EM amplifier, which is composed of a class-E amplifier and a auxiliary circuit reducing its switching loss during turn-off, is designed normally for continuous wave. Simulation results show that the conventional PWM switching method gating the input RF signal produces unnecessary transient responses making the drain voltage rise and the output signal distorted; the efficiency is degraded. Another method that gates the DC supply voltage by the PWM pulses works as expected and intended, and the result shows the drain efficiency as high as that of an EM amplifier in case of CW signal. |