This letter presents an efficient dual-band rectifier using stepped impedance stub matching circuit. Theoretical analysis of the dual-band impedance matching circuit comprising a stepped impedance stub is carried out, which plays a key role in designing the resultant dual-band rectifier. The proposed dual-band matching circuit can achieve wide frequency ratio which is analyzed and predicted by simulation. For demonstration, a dual-band rectifier working at 0.915 and 2.45 GHz is fabricated with dimensions of 21.47 mm ×18.93 mm. The measured results show that with a 1500 Ω load, the maximum efficiencies of the rectifier reach 74% and 73% at 0.915 and 2.45 GHz, respectively. Due to the simple but efficient structure of the dual-band matching network, the dual-band rectifier in this work exhibits merits of compact size and high efficiency.

This letter presents a substrate integrated waveguide (SIW) diplexer using the dual-mode resonator. By enhancing the perturbation strength, the resonant frequencies of the dual-mode square cavity can be assigned to required frequencies. Thus, the cavity can be employed as the common resonator to replace the T-junction. The coupling aperture between the common resonator and the triangular resonator is parallel to one resonant mode's magnetic field and perpendicular to the other's. As a result, the isolation between the two channels is increased. Furthermore, the cavities are vertically stacked to realize a compact size. A diplexer with lower and upper channels centered at 8 and 9 GHz, respectively, is designed to verify the proposed concept. The simulated and measured results agree with each other.

In this letter, a multioctave voltage doubler rectifier using a T-type matching network is demonstrated. The voltage doubler topology is used to flatten the load impedance, which makes it easier to achieve broadband impedance matching. The T-type matching network is used for the broadband input impedance matching. The design procedure of the proposed broadband rectifier is provided and discussed. For validation, a rectifier prototype is fabricated, and the performance is evaluated. The measured results exhibit power conversion efficiency (PCE) of more than 50% over a frequency band of 0.2–3.2 GHz at 15 dBm input power and 70% from 1 to 2.7 GHz. Moreover, the peak PCE is 78.2% at 1.9 GHz when the input power is 18 dBm.

In this letter, a circular dual-mode substrate integrated waveguide (SIW) filter with two controllable transmission zeros is proposed. Two vias situated on a diameter line are employed to perturb two modes in a circular substrate integrated waveguide resonator. Taking advantage of the modal orthogonality of multiple cavity modes, transmission zeros are created. By moving the vias along the diameter line, the transmission zeros can be adjusted. The coupling matrix is employed to analyze the design concept. A three-pole filter with the center frequency at 8 GHz and two transmission zeros at 8.6 and 9.2 GHz is designed and fabricated. Experimental and simulated results are presented which validate the design concept of the proposed filter.

A microstrip diplexer with very high isolation is presented. The diplexer consists of two compact filters with quarter-wavelength resonators coupled by the metallised vias. Each metallised via is inductive and behaves as a K-inverter. This type of filter has two adjustable transmission zeros on each side of the passband, which can be shifted by changing the coupling coefficient between the source and load. By locating the transmission zero of one channel at the passband of the other channel, very high isolation of the diplexer can be achieved. Simulated results of the fabricated diplexer agree well with measured results.

A self-biased adaptive reconfigurable rectenna, consisting of a microstrip patch antenna and a self-biased reconfigurable rectifying circuit, is proposed. To eliminate the need of bias networks, a DC power routing structure is introduced to link the reconfigurable matching stub and the load. Hence the output DC current obtained by the rectifier can be divided/split, thereby letting a part of the DC current flow back to the matching stub for providing a bias voltage. According to the input power level, the states of the PIN switch can be automatically changed in order to connect/disconnect the matching stub to the rectifying circuit for achieving improved matching performance at different power levels. Simulated and measured results show that the proposed rectenna reaches more than 50% conversion efficiency over a broadened input power range from 0~20 dBm with the peak efficiency of 68% at 9 dBm. It is evident that the proposed self-biased reconfigurable matching scheme is a promising and effective solution to facilitate the less-complicated reconfigurable rectenna integration and realize high efficiency at higher operating frequency bands (e.g. > 5 GHz).