A Dual‐Band Filtering Power Amplifier Based on Three‐Line Coupled Structure

ABSTRACT This letter proposes a novel filter structure based on the three‐line coupled structure (TLCS) and designs a dual‐band filtering (DBF) power amplifier (PA) using this structure. The output matching network (OMN) of the PA integrates a suppressing network and a TLCS filter, delivering excellent filtering performance and effective out‐of‐band suppression. To validate the feasibility of the proposed structure, a dual‐band filtered PA covering 2.4–2.8 GHz and 3.78–4.08 GHz was designed, fabricated, and measured. The measured peak drain efficiency (DE) values are 65.1% and 54.8%, respectively, with peak output power (P out ) of 40.9 and 40.3 dBm. The measured fractional bandwidths (FBWs) of the two frequency bands are 15.4% and 7.6%. Compared with existing dual‐band PA designs reported, the proposed PA has a wider passband bandwidth. Besides, using a 20‐MHz long‐term evolution (LTE) signal with a 7‐dB peak‐to‐average power ratio (PAPR) and applying the digital predistortion (DPD), the adjacent channel power ratios (ACPRs) of the PA are −47.03 and −47.68 dBc, corresponding to the two frequency bands.