A Dual-Band Balanced Amplifier With Intrinsic Diplexing and Filtering

Abstract

This article presents a high-efficiency dual-band balanced power amplifier (PA) that compactly integrates intrinsic diplexing and filtering functions, where the filtering function refers to the built-in interband isolation and undesired-band suppression generated by the path-interference mechanism of cascaded dual-band couplers. The proposed architecture combines dual-band couplers with PA stages, achieving interband isolation and diplexed power combining at two target frequencies of 1.4 and 2.5 GHz. This integration reduces the need for cascaded filters and diplexers typically used in conventional architectures, thereby reducing additional passive insertion loss. For validation, a prototype targeting 1.4 and 2.5 GHz was fabricated. At 1.4 GHz, the PA delivers a saturated output power ( $P_{\mathrm {sat}}$ ) of 43.6 dBm, a drain efficiency (DE) of 76.4%, and a saturated gain of 14.3 dB. At 2.5 GHz, it achieves a $P_{\mathrm {sat}}$ of 43.7 dBm, a DE of 72.8%, and a saturated gain of 12.6 dB. The measured small-signal gains are 20.2 and 15.4 dB at the two bands, respectively, and the measured undesired-band suppression exceeds 23 and 22 dB for the 1.4- and 2.5-GHz input paths, respectively, while the interport isolation exceeds 30 dB near 1.9 GHz. Under a 10-MHz 5G NR signal with a peak-to-average power ratio (PAPR) of approximately 8.8 dB, the averaged ACLR values without digital predistortion (DPD) are −28.41/−27.52 dBc at 1.4/2.5 GHz. These results validate that the proposed architecture offers an effective solution for achieving high efficiency, high output power, and high integration in dual-band RF front-end modules.