High efficiency 88–108MHz, 25W class-E PA for transmitters in smart cities

Abstract

In this paper a low power high efficiency Class-E RF power amplifier (Pa) for broadcast FM band (88∼108MHz) application is presented. This PA suitable for low power transmitter's used in smart cities. Traditionally switching PAs are not used for FM broadcast application due to high emissions in side bands. Double tuning networks and harmonic traps are used at the input and output of the amplifier to achieve adjacent channel purity (ACP) more than −80dBc in order to conform to the limits imposed by the Federal Communication Commission (FCC) for Low Power FM (LPFM) transmitters. This power amplifier has output power of 25W (43.9dBm) and power added efficiency (PAE) of 80.3% with the gain of l5dB. This class-E power amplifier is driven by a class-A RF amplifier with output power of 2W (33dBm) and 50Ω impedance. The amplifier is characterized for input RF power sweep, Frequency sweep and adjacent channel power ratio (ACPR). The proposed Class-E RF power amplifier also provides 50Ω input and output impedance matching for seamless interfacing with standard FM antennas or power combiners. The typical applications are low power FM transmitters for educational, civic, health, emergency and disaster services.