In this paper, an ultra-wideband and polarization-independent metasurface for radar cross section (RCS) reduction is proposed. The unit cell of the metasurface operates in a linear cross-polarization scheme in a broad band. The phase and amplitude of cross-polarized reflection can be separately controlled by its geometry and rotation angle. Based on the diffuse reflection theory, a 3-bit coding metasurface is designed to reduce the RCS in an ultra-wide band. The wideband property of the metasurface benefits from the wideband cross polarization conversion and flexible phase modulation. In addition, the polarization-independent feature of the metasurface is achieved by tailoring the rotation angle of each element. Both the simulated and measured results demonstrate that the proposed metasurface can reduce the RCS significantly in an ultra-wide frequency band for both normal and oblique incidences, which makes it promising in the applications such as electromagnetic cloaking.

A compact dual-notched balanced ultra-wideband (UWB) bandpass filter (BPF) is designed by using the folded triple-mode slotline resonators and differential microstrip-slotline transitions. Two differential-mode transmission zeros near the passband edges are created to improve the selectivity, due to a cross-coupling between two microstrip open stubs beyond the cross-junction position as well as between the input and output. Good matching in the whole passband can be achieved by properly choosing the width of the microstrip open stubs. The inverse QWRs coupling stepped-impedance microstrip stub loaded in the 50 Ω microstrip feedlines can generate multiple transmission zeros to suppress the common-mode resonance and realise dual-notched bands in the UWB passband. Good agreement can be obtained between the measured results and simulated ones.

Plasmonic metallic nanoparticles are coupled to the organic solar cells to overcome the trade-off between the light absorption and carrier collection. They are usually located inside or outside of the active layers. However, no detailed comparison was reported on the light absorption difference when nanoparticles are located inside or outside of the active layers. In this paper, we compare light-trapping abilities of Ag nanospheres in organic solar cells when they are located inside and outside of the photoactive layer. We show that large-sized nanoparticles are preferred when they are placed outside of the active layer while small-sized nanoparticles are favored in the case of embedding nanoparticles in the homogenous active layer.

A compact dual-band bandpass filter (BPF) with a slotline resonator (SR) and a short stub centre-loaded microstrip resonator (SMR) is proposed for wideband and wireless local area network (WLAN) applications. The high-impedance microstrip feedlines for the filter with the SMR can function as the quarter-wavelength resonators for the filter with the SR to realise a wideband passband. Owing to the source-load coupling, the loaded short stub and the intrinsic characteristics of the SMR, three transmission zeros can be created to improve selectivity and isolation. Compact size can be obtained by adopting the folded SR and folded SMR inserted between the arms of the SR. A compact dual-band BPF for wideband and WLAN applications is simulated and measured, and good agreement can be obtained between the measured and simulated results.

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