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In this paper, a new dual-band bandpass (BPF) filter with multi-spurious suppression is proposed, which is composed of stepimpedance resonators (SIR) and grounded-step-impedance resonators (GSIR). It is shown that the resonant frequencies of GSIR can be obtained similar to SIR. Then, by determining the dimensions of SIR to have a specified resonant frequencies ratio, the dimensions of GSIR can be calculated. It is also shown that the coupling lengths between SIR and GSIR can create several transmissions zeros and can be used to suppress the unwanted higher order resonant frequencies. A third-order filter is designed and fabricated to operate at two WLAN frequencies of 2.45 GHz and 5.8 GHz. The measured results show a rejection level of 24 dB up to more than 17 GHz (7f 1). Simulation and measurement results are in good agreement with each other.

In this paper, a wideband, circularly polarized patch antenna is proposed that leverages the unidirectional resonant modes of a circular patch mounted on top of a grounded dielectric‐ferrite substrate. The proposed antenna is fed via the proximity coupling method and several parasitically coupled patches are placed on a dielectric superstrate to enhance the impedance bandwidth of the antenna. The resonant modes of the structure rotate only in the clockwise or counter clockwise directions. In the frequency range where the effective permeability of the ferrite layer is negative, the resonance frequencies of these modes differ significantly, which produces a large axial ratio (AR) bandwidth. For the proposed antenna, the numerical results show the 10 dB impedance bandwidth to be around 44% and the 3 dB axial ratio bandwidth to be higher than 64%.

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