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A single-layer broadband circularly polarized reflectarray with subwavelength double-ring elements is presented in this article. Compared to conventional λ/2 elements, the subwavelength one can obtain a better circular polarization performance. Then, by using angular rotation technique, a reflectarray with this type of elements is designed and implemented. The fabricated reflectarray demonstrates excellent performance of 40% 3-dB axial ratio bandwidth and 19.1% 1-dB gain bandwidth, respectively. Moreover, the highest aperture efficiency can reach as large as 50%. [ABSTRACT FROM AUTHOR]

In this paper, a microstrip tri-band bandpass filter (BPF) utilizing square ring loaded resonator is proposed. A pair of bent perturbation stubs is installed to the ring resonator so as to control resonant modes of the ring. The first three modes are used for tri-band BPF design. In order to control the second and third resonant modes, two pairs of square patches and loaded open stubs are added, and then two asymmetric resonators are cascaded for tri-band operation. Based on the transmission line theory, even- and odd-mode analysis method is used to deduce the resonant frequencies. According to the resonant conditions, a kind of tri-band BPF can be flexibly designed. Finally, two filters are designed as examples in a comprehensive way for demonstration, and one design with passbands located at 2.4, 3.5 and 5.2 GHz is fabricated. Measured results agree well with the simulated ones. [ABSTRACT FROM AUTHOR]

A compact electronically tunable dual-bandpass filter (BPF) with harmonic suppression is investigated in this paper. The BPF is composed of a step-impedance resonator, aT-stub with a varactor diode and a filtering network. The second passband can be independently tuned by varying the bias voltage across the varactor, whereas the first passband is fixed. The proposed filter exhibits wide stopband due to the introduction of the filtering network suppressing harmonics. A prototype of a tunable dual-band BPF, in which the second passband is tuned from 1.58 to 2.21?GHz and the first passband is fixed at 0.98?GHz, is designed and fabricated. The simulated and measured results are in good agreement with each other. [ABSTRACT FROM PUBLISHER]