Miniaturized Dual-band Matching Technique Based On Coupled-line Transformer And Application In Dual-band Power Amplifiers Design

In recent years, the design theory of the dual-frequency microwave devices more and more important. It became a hot research field. The impedance matching is an indispensable part in the microwave design. The dual-band matching network can transform the impedance in two different frequencies at the same time. The dual-band matching technique based on coupled-line transformer can satisfy this demand and achieve miniaturization and DC-block function.This study presents a novel miniaturized dual-band coupled-line impedance transformer. This dual-band matching technique uses the characteristics of coupled-line and dual-band stubs to realize matching arbitrary complex impedance to arbitrary complex impedance at two arbitrary uncorrelated frequencies. Especially, it satisfies the demand of dual-band matching at two relatively closed operating frequencies (n=f2/f1≤1.2), and occupy a5.5cm2circuit area with inherent DC-Block function. The proposed synthesis approach is validated by the design and fabrication of a30W gallium nitride (GaN)-based class-AB power amplifier (PA) for GSM and WCDMA at1800MHz and2140MHz. The PA’s output matching network based on the proposed structure can accurately match50Ω to the ideal load impedances of the transistor at two designed frequency simultaneously and has20%and15%bandwidth for which the reflection coefficient magnitudes are less than0.1, respectively.The proposed dual-band coupled-line impedance transformer takes the advantages of coupled-line to solve the problem of complexity, narrow-band, low frequency rate and small impedance range. Dual-band coupled-line impedance transformer has a wide range of application prospects in dual-band microwave device and concurrent dual-band communication system.