High efficiency pulse width modulation transmitter

A high efficiency Class E transmitter that produces variable output power using pulse width modulation (PWM) to maintain high efficiency is descibed. Agilent's Advanced Design System (ADS) was used to design the Class power amplifier. The system consists of a Class E power amplifier and a PWM generator. To reduce matching losses, high-Q inductors are used in the resonator. Low second and third harmonic distortion is achieved with a harmonic filter in the output matching network. The 165.57 Hz pulse signal and 13.56 MHz oscillator out put signal are fed to the NAND gate to form the PWM signal. The measured inductance and Q-factor of the custom-made series inductor at the output matching network are 1.3 and 300 μH, respectively. The high-Q inductor in the series resonance circuit and the shunt harmonic filter also provide matching at the fundamental frequency. The second and third harmonic distortion levels are significantly suppressed. It exhibited a high PAE of 90.5 percent at an output power of 10.1 W and 80 percent at a low output power of 1.5 W.