Dual-band impedance transformer using coupled line for arbitrary complex loads

This study presents a novel impedance transformer that can realize a dual-band (i.e. dual-characteristic) arbitrary complex load matching which consists of two transmission lines and one coupled-line section. The theoretical analysis and the closed-form mathematical equations of the designed circuit parameters are completely described and solved. To demonstrate the proposed impedance matching performances, several examples are simulated with different complex loads at two unrelated frequencies. Besides, one corresponding load-matching model is designed, simulated and fabricated on printed circuit board (PCB). As a result, good agreements between simulated and measured results validate the proposed transformer and its design approach.