Amplifier Powers an Octave with 80% Average Efficiency (.PDF Download)

Efficiency is one of the most sought-after parameters in RF power amplifier (PA) design, since it translates directly to power consumption and operating cost. In continuous inverse Class F (CCF⁻¹) PAs, the current waveform factor, δ, plays a major role in achieving high drain efficiency. With a modified lowpass output matching network (OMN), it is possible to constrain δ to a limited range high drain efficiency even when operating a PA with broadband frequency coverage. The approach was demonstrated in a an easy-to-implement PA design that operates from 1.0 to 1.9 GHz (a fractional bandwidth of 62%) that achieves +39.8 to +42.0 dBm output power across the frequency band with drain efficiency of 75.8 to 84.5% (average drain efficiency of 80%).

High-efficiency PAs are important components in modern communications systems, particularly when broadband frequency coverage and high-data-rate performance are required. Classic harmonic tuned PAs, such as Class E amplifiers or those operating in Class F mode or inverted Class F (F⁻¹) mode typically operate with high efficiency but limited bandwidths. To extend the bandwidth of high-efficiency amplifiers, a continuous working mode was proposed by Steve Cripps in 2009, with additional concepts introduced more recently, including Class B/F mode, continuous Class F mode,4 and continuous Class F⁻¹ mode.