This paper presents a highly compact frequency-selective surface (FSS) that has the potential to switch between the X-band (8 GHz–12 GHz) and C-band (4 GHz–8 GHz) for RF shielding applications. The proposed FSS is composed of a square conducting loop with inward-extended arms loaded with curved extensions. The symmetric geometry allows the RF shield to perform equally for transverse electric (TE), transverse magnetic (TM), and 45° polarizations. The unit cell has a dimension of 0.176 ${\lambda }_0$ and has excellent angular stability up to 60°. The resonance mechanism was investigated using equivalent circuit models of the shield. The design of the unit element allowed incorporation of PIN diodes between adjacent elements for switching to a lower C-band spectrum at 6.6 GHz. The biasing network is on the bottom layer of the substrate to avoid effects on the shielding performance. A PIN diode configuration for the switching operation was also proposed. In simulations, the PIN diode model was incorporated to observe the switchable operation. Two prototypes were fabricated, and the switchable operation was demonstrated by etching copper strips on one fabricated prototype between adjacent unit cells (in lieu of PIN diodes) as a proof of the design prototypes. Comparisons among the results confirmed that the design offers high angular stability and excellent performance in both bands.

A comprehensive novel framework for retrofitting Frequency Selective Surface (FSS) shields to any glass surface using low cost copper foils has been proposed in this work. The realization technique is demonstrated through a novel tri-band FSS shield. GSM-1800, Wi-Fi 2.5 GHz, and WLAN 5.6 GHz spectrum, with -10 dB bandwidth of 680 MHz, 190 MHz, and 1300 MHz respectively, are suppressed by the shield. The unit cell is made up of a combination of square and circular concentric loops with some alterations. The design is entirely polarization-insensitive and has a steady frequency response for oblique angles up to 60°. The unit element is highly miniaturized for triband operation measuring λ ₀ /9 at 1.8 GHz frequency. An equivalent circuit model is also derived to better elaborate the working mechanism of the shield. The pattern is chemically etched on low-cost copper adhesive foil and affixed to ordinary glass as a sticker. The design retains visual transparency of 72 % allowing enough light to enter through windows while rejecting the intended frequencies by at least 28 dB or more in all three bands. The design exhibits a very high shielding efficiency of above 98 % for all three bands. Experimental demonstration for single layer glass, sandwiched glass, as well as air filled double glazed glass, is carried out. The thermal stability of the proposed design is measured and found intact up to the ambient temperature of 50°C.

This study reports on a highly miniaturised polarisation selective surface (PSS) for dual‐band Wi‐Fi and WLAN applications. The proposed unit cell consists of two independently tuneable square loops. The outer loop is split with a gap of 0.2 mm to introduce polarisation selectivity and miniaturisation for lower‐frequency band of 2.5 GHz. The inner square loop is inductively loaded with arms to suppress 5.45 GHz frequency band. These configurations have resulted in a unit element size of at 2.5 GHz, which is not presented before to the best of the authors' knowledge. A wide rejection bandwidth ( ) of more than 600 and 1180 MHz is obtained around 2.5 and 5.45 GHz, respectively. Furthermore, the proposed PSS exhibits an excellent polarisation selective characteristic by generating two stopbands at 2.5 and 5.45 GHz when illuminated by horizontal (TM) incident waves, whereas vertically (TE) polarised incident waves result in the generation of passbands for these two frequencies. Numerical validation through equivalent circuit modelling of the proposed PSS has also been carried out. A finite prototype containing elements is fabricated and tested. The measured results demonstrated that the PSS has excellent potential for applications that employ polarisation separators and wave generators.

This paper reports on a novel technique of switching radiation characteristics electronically between E-and H-planes of planar Substrate Integrated Waveguide Leaky Wave Antennas (SIW-LWAs). The leaky wave mode is achieved through increasing the pitch of bounding metallic via posts on one side of SIW transmission section. The radiation switching is achieved by extending the top and bottom metallic planes to a distance of 1 mm along the leakage side. The extended section acts as a parallel plate section which is conveniently connected or disconnected from the leaking side of SIW through PIN diodes. The ‘ON’ state of PIN diodes extends the metal guides and results in the H-plane leakage whereas ‘OFF’ state of PIN diodes truncates the extended metal earlier and alter the leakage line boundary condition towards E-plane. The whole concept is validated by series of simulations followed by the realization and testing of the SIW-LWA. The measured radiation pattern scans about 54° in the E-plane between 10.0 GHz to 11.7 GHz, and 58° in the H-plane from 9 GHz to 10.6 GHz. The proposed topology is a suitable candidate for remote sensing and airborne applications.