This article presents a dual‐band/dual‐polarized microstrip patch antenna.For a dual‐band retrodirective array system, the dual‐band/dual‐polarized microstrip patch antenna operating at 11 and 12.2 GHz is designed and tested. The antenna consists of one rectangular microstrip patch and a square ring outside of the patch. Two different feeding locations are used for vertical and horizontal polarizations. The vertical polarization is used for a receiving mode and the horizontal polarization for a transmitting mode. The antenna shows a measured gain of 5.2 and 6.8 dBi at 10.9 and 12.2 GHz. The isolation between the two feeding ports is measured to be greater than 15 dB at each center frequency. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2781–2784, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27217

A piezoelectric transducer (PET)-controlled tunable hairpin bandpass filter (BPF) is introduced. A dielectric perturber is attached to a PET cantilever beam and suspended above the hairpin BPF. The PET actuator vertically lifts up or pulls down the attached dielectric perturber using a DC bias voltage. The dielectric perturber changes the effective permittivity, causing a variation in the BPF's effective capacitance. This changes the centre frequency and passband of the BPF. The hairpin BPF is designed at 5.8 GHz with a fractional bandwidth (FBW) of 0.414%. The fabricated BPF shows a measured insertion loss of less than 2.5 dB and a return loss of greater than 12 dB in the frequency tuning range.

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A microstrip dumb-bell-shaped slot resonator (DSSR) is proposed for a miniaturised bandpass filter (BPF) design. An equivalent circuit model of the DSSR is also presented and validated through circuit and EM simulations. The proposed DSSR does not employ ground slots, so the fabrication process is simple. This ultimately results in an easy analysis and design which minimises fabrication errors. Using the DSSR, a miniaturised 7.35 GHz BPF is designed and tested. The filter dimensions are 0.37l g × 0.27l g , where l g is the guided wavelength at the centre frequency of 7.35 GHz.

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