Investigating broadband filtering power amplifier using multi-mode resonator-based bandpass filter

This paper presents an innovative approach to addressing the challenges of multifunctional and broadband sub-6 GHz applications by proposing a high-efficiency, wideband filtering power amplifier (FPA) with superior filtering selectivity. The proposed method focuses on the integration of the power amplifier (PA) and bandpass filter (BPF) into a single, co-designed structure, eliminating the conventional output matching network (OMN) by directly connecting the BPF to the transistor's drain. This integration significantly reduces circuit size, minimizes signal loss, and enhances overall performance. The BPF design utilizes a multi-mode resonator featuring four transmission zeros and five poles, constructed with series-coupled lines and a shunt stepped-impedance open stub. Closed-form equations for the transmission zeros are derived using even-odd mode analysis and scattering parameter theory. This configuration offers numerous benefits, including highly selective bandpass characteristics, wideband efficiency, and a compact footprint. The proposed technique is validated through the design and implementation of an FPA incorporating this filtering structure, with optimal performance results and a comparative analysis against recent high-efficiency FPAs from the literature. The proposed FPA, operating within the 2.0–4.0 GHz frequency range, demonstrates a peak drain efficiency between 49.4% and 72%, with a corresponding peak output power of 38–41.9 dBm at saturation. This operational bandwidth covers several significant wireless standards, including 5G new radio (NR) n78 ( 3.3 − 3.8 GHz), WiMAX (3.5 GHz), WLAN (WiFi) at 2.4 GHz, LTE (4G) at 2.6 GHz, and Bluetooth at 2.4 GHz. By covering these widely adopted communication bands, the proposed FPA addresses the increasing demand for wideband, multifunctional devices in next-generation wireless networks, offering an effective balance among enhanced power efficiency, broadband functionality, high-quality filtering performance, and high selectivity. • Innovative FPA Design: High-efficiency, wideband solution for sub-6 GHz. • Integrated Architecture: Combines PA and BPF, eliminating traditional OMN. • Advanced Filtering: Multi-mode resonator with four zeros and five poles. • Precision Analysis: Transmission zeros derived using advanced theoretical methods. • Peak Performance: Achieves up to 41.9 dBm saturation power and 72% peak drain efficiency over 2.0–4.0 GHz. • Multistandard Coverage: Supports 5G NR n78, WiMAX, WiFi, LTE, and Bluetooth bands.