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This article presents the design, simulation, implementation, and experimental results of a highly efficient, concurrent dual‐band, gallium nitride (GaN), class‐AB power amplifier (PA) at two frequencies: 1.84 and 3.5 GHz. It proposes a novel dual‐band bandpass filter (DBBPF) with quad‐section stepped‐impedance resonators (SIRs) capable of rejecting the annoying frequencies of the second and third harmonics in the dual‐band. The proposed DBBPF was applied in the design of a dual‐band PA using a packaged 10 W GaN transistor. The PA prototype maintained a peak power‐added efficiency (PAE) of 75.3% at the 1.84 GHz frequency and 64.5% at the 3.5 GHz frequency. For a continuous wave output power of 40.9 dBm, the measured gain was 13 dB in the two frequency bands. Linearized modulated measurements, concurrently using 10 MHz quadrature amplitude modulation (16 QAM) signals and worldwide interoperability for microwave access (WiMAX) signals, showed an average PAE of 48.5% and 39.8% and an adjacent channel leakage ratio of −46 and −45 dBc with an average output power of 37.8 and 36.8 dBm at the two frequency bands, respectively. This PA is used for wireless systems. It is especially useful in standard simultaneous global system for mobile (GSM) and WiMAX wireless systems.

In this paper, a different dual-band asymmetric Doherty power amplifier (ADPA) with a novel dual-band bandpass filter (DBBPF) with quad-section stepped impedance resonators (SIRs) is presented. This specific DBBPF rejects the annoying frequencies of the second and third harmonics in the dual-band and contributes considerably to performance improvement of ADPA. This structure is confirmed with the design, simulation, implementation and testing of a 10 W GaN-based ADPA for global system for mobile communications (GSM) and worldwide interoperability for microwave access (WiMAX) applications at 1.84 and 3.5[Formula: see text]GHz, respectively. In the measurement results, the ADPA defines a drain efficiency (DE) of 63.7% with an output power of 35[Formula: see text]dBm and power gain is 14.2[Formula: see text]dB, and a DE of 47.5% with an output power of 34.5[Formula: see text]dBm and power gain is 10.4[Formula: see text]dB at the 9[Formula: see text]dB output power back-off (OBO) from the saturated output power in the two frequency bands. Linearity effects, applying 10[Formula: see text]MHz 16 QAM signal and a 5[Formula: see text]MHz WiMAX signal, display an adjacent channel leakage ratio of [Formula: see text] and [Formula: see text][Formula: see text]dBc with the average output power of 36.8/36[Formula: see text]dBm at 1.84/3.5[Formula: see text]GHz, respectively.