An electronically controllable microstrip leaky-wave antenna (LWA) to steer the radiations at a fixed frequency is presented. The proposed LWA is composed of a corrugated microstrip line loaded by the varactor diodes with triangular-modulated surface impedance. Due to the periodical modulation of the surface impedance, the guided waves can be converted into the leaky-wave radiations efficiently with frequency-scanning property. Furthermore, the surface impedance of the LWA can be reconfigured by changing the capacitance of the varactor diode through dc bias voltage, which will make the radiation beam steer in a large angle range accordingly at a fixed frequency. Both numerical simulations and experimental results show that the radiation beams can be controlled for continuously steering at each frequency from 5.5 to 5.8 GHz by changing the dc bias voltage from 0 to 20 V, in which the scanning angle can reach as high as 45°.

We propose a supercompact and ultrawideband (UWB) bandpass filter for spoof surface plasmonic polariton (SSPP) mode. By using meander-line technology, the electrical size of the proposed SSPP structure is reduced dramatically, which is only about 1/4 of the traditional rectangular-groove structure with the same geometry. Based on the proposed SSPP structure, we construct a supercompact UWB bandpass filter working in the frequency range of 0.25-4.5 GHz, whose geometric size is only 87.5 x 12.8 mm². The upper cutoff frequency of the passband can be controlled by changing the meander-line design of the SSPP unit, and the lower cutoff frequency of the passband is determined by the capacitive coupling of the feeding structure. Both the simulation and experimental results show that the UWB SSPP bandpass filter is centered at 2.4 GHz with an extremely wide relative bandwidth of 174%, whose electrical size is only 0.7λ x 0.1λ at the central frequency.

A leaky-wave antenna (LWA) is proposed on the basis of an ultrathin spoof surface plasmonic (SSP) waveguide, which can convert SSP waves into spatial multi-polarized radiation waves. The SSP waveguide is composed of a metallic strip line with periodic unit cells, and each unit consists of two orthogonally bevelled slots. The feature of single-conductor SSP waveguide determines that the leaky-wave radiation pattern is omnidirectional in the azimuth direction around LWA. Due to the design of orthogonally bevelled slots, different polarized radiations can be achieved along the azimuth direction. Simulation results show that lefthanded circularly polarized (LHCP), right-handed circularly polarized (RHCP) and linearly polarized (LP) radiations are achieved in different azimuth directions simultaneously, which are further validated by the experimental measurement. We also demonstrate a purely single polarized radiation by placing a metal reflector close to LWA, and the polarization is reconfigurable among LHCP, RHCP and LP by mechanically rotating LWA.

Spoof surface plasmon polaritons (SSPPs) can be converted to leaky-wave radiations by a spoof surface plasmon (SSP) waveguide with periodically modulated surface impedance, which is also known as a SSPP leaky-wave antenna (LWA). However, most of the reported SSPP LWAs can only radiate electromagnetic (em) waves with linear polarizations parallel to the SSP waveguide due to the limitation of perpendicular grooving structures, and the polarizations of LWA radiations are difficult to arbitrarily design. We propose an efficient method to achieve the leaky-wave radiations with arbitrarily customizable polarizations based on an alternative SSPP LWA, which is made of a periodically modulated SSP waveguide with bilateral 45°-tilted grooves to generate two orthogonally polarized em waves. The grooves on both sides of the SSPP LWA can be designed with proper displacement to provide the required phase difference between two orthogonally polarized radiation waves in order to customize the polarization of the leaky-wave radiations. Both simulation and experimental results are provided to validate the feasibility of tailoring arbitrary polarizations for the radiation waves based on the proposed SSPP LWA.