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.