A broadband circularly polarized (CP) leaky‐wave antenna fed by spoof surface plasmon polaritons (SSPPs) is proposed in this paper. The antenna consists of SSPPs transmission line and the periodic open rings. The periodic open rings are loaded at both sides of the transmission line with 90° phase shift to obtain CP responses. Meanwhile, the antenna can obtain a wide‐angle beam scanning due to the dispersion characteristics of SSPPs. The simulated results indicate that the antenna has a wide CP impedance bandwidth of 44.9% from 3.8 to 6 GHz with a return loss smaller than −10 dB and the antenna axial ratio (AR) lower than 3 dB. Also, the antenna has a wide scanning angle that ranges from −54° to +10°. For validation, the antenna was fabricated and the measured results agreed well with simulated ones.

In this article, a low profile wideband metasurface filtering antenna with tunable radiation nulls is proposed. Metasurface structure is used to excite adjacent resonant modes to obtain broadband responses. A U-shaped slot is introduced into the microstrip line to generate a radiation null in the lower stopband. Complementary split-ring resonators (CSRRs) are etched on the metasurface unit to produce another radiation null in the upper stopband edge to improve the filtering effect. The radiation nulls position can be flexibly controlled by changing the size of U-shaped slot and CSRRs. For verification, the corresponding antenna is fabricated and tested. The antenna size is 0:556λ0 Â 0:556λ0 Â 0:044λ0 (30 Â 30 Â 2.4 mm 3 ). The measured results agree well with the simulated. The antenna operates from 4.9 to 6 GHz with a flat gain (5.5 dBi), a sharp passband skirt and stable radiation patterns.

A compact dual-band balanced bandpass filter with high frequency selectivity and adjustable passband based on the perturbed circular substrate integrated waveguide cavity is firstly proposed in this paper. Two pairs of metallic vias are located at 45°direction of cavities to separate a pair of degenerate modes (TM110 modes) to achieve the differential-mode (DM) dual-band response. Moreover, the perturbation vias can also be used to control the center frequency of the second DM passband while the first one still stays unaffected. The introduction of source-load coupling makes the filter exhibit excellent selectivity. And four controllable transmission zeros appear near two DM passbands. Finally, good common-mode suppression has been got owing to the proposed balanced structure. The measured results are in accordance with the simulated ones well.