Dual‐Band Impedance Transformer Using Four‐Section With a Wide and Flexible Frequency Ratio

In this paper, a dual‐band RF rectifier with flexible frequency ratios is presented. To achieve this flexibility, a four‐section transformer is proposed that covers a wide range of the Smith chart impedance, including the region closest to the open‐circuit impedance of the diode. Additionally, a new dual‐band short stub is introduced, designed to ensure proper current feedback without compromising in‐band performance. By combining the dual‐band matching circuit with shorted stubs, a wide frequency ratio is achieved. Two different dual‐band circuits, with frequencies of 0.7/1.2 and 0.7/2.45 GHz, were fabricated and tested to demonstrate the flexibility of the proposed topology. The designs were based on the SMS‐7630 Schottky diode and tested at frequencies below 6 GHz. Experimental results show that the first dual‐band circuit (0.7/1.2 GHz) achieves efficiencies of 70% and 60.5%, while the second dual‐band circuit (0.7/2.45 GHz) has efficiencies of 88.5% and 50%. The maximum voltages reached were 3.8 and 3.45 V, respectively.