Filtering Power Amplifier With Wide Bandwidth Using Discriminating Coupling

This paper presents a filtering power amplifier (PA) with wide bandwidth. A bandpass filter (BPF) using discriminating coupling is first proposed to be utilized as the output matching network (OMN) of PA. Discriminating coupling means that the fundamental and the harmonics of the proposed structure have different coupling coefficients. Thus, the input impedances of the fundamental, second and third harmonics could meet the requirements of the extended continuous mode theory, respectively. Also, good frequency selectivity is obtained. The working principle of discriminating coupling, the filter synthesis theory and the equivalent circuit are utilized to guide the design of the filtering PA. To demonstrate the proposed structure, a compact filtering PA operating at 1.8 GHz is designed. The measured results exhibit good frequency selectivity and high power added efficiency (PAE). More importantly, comparing to the previous filtering power amplifiers (PAs) with good frequency selectivity, the proposed design possesses wide bandwidth of 31.1% with PAE higher than 60%.