Dual-band filtering power amplifier with extended passband bandwidths and wide stopband rejection

This article presents a dual-band filtering power amplifier (DB-FPA) with extended passband bandwidths and wide stopband rejection, which is helpful in reducing the number of microwave components in the dual-band radio frequency front end, resulting in compact circuit size and low loss. In the designed DB-FPA, a wideband low-pass filter is applied as the input matching network (IMN) to provide wideband impedance matching and good stopband rejection, while a dual-band filtering impedance transformation is adopted as the output matching network (OMN) to provide dual-band impedance matchings and filtering responses simultaneously. Specifically, the IMN is constructed by high-impedance transmission-line sections and low-impedance open-circuit stubs. The OMN is designed based on the specific external quality factors and coupling coefficients during two bands, resulting in dual-band impedance transformations and dual-band filtering responses. Then, based on the above IMN and OMN, the design procedure of the presented DB-FPA is summarised. To verify the proposed idea, a novel DB-FPA has been fabricated and measured. During the two frequency bands, the measured maximum power added efficiencies are 55.11% and 47.78% within 33.0 dBm input power, while the measured peak gains are 15.4 and 14.0 dB within 15.0 dBm input power.