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A novel 2D simple low cost frequency selective surface was screen printed on thin (0.21 mm), flexible transparent plastic substrate (relative permittivity 3.2). It was designed, fabricated and tested in the frequency range 10-20 GHz. The plane wave transmission and reflection coefficients agreed with numerical modelling. The effective permittivity and thickness of the backing sheet has a significant effect on the frequency characteristics. The stop band frequency reduced from 15GHz (no backing) to 12.5GHz with polycarbonate. The plastic substrate thickness beyond 1.8mm has minimal effect on the resonant frequency. While the inner element spacing controls the stop-band frequency, the substrate thickness controls the bandwidth. The screen printing technique provided a simple, low cost FSS fabrication method to produce flexible, conformal, optically transparent and bio-degradable FSS structures which can find their use in electromagnetic shielding and filtering applications in radomes, reflector antennas, beam splitters and polarizers.

Convoluted elements on a frequency selective surface (FSS) allow for low frequency elements to be contained in physically smaller unit cells. Smaller unit cells give the FSS greater angular stability, especially where a curved FSS is required, and so unwanted grating effects are avoided. A convoluted element FSS with a frequency rejection band centred at 2 GHz and unit cell area of 15 mm by 15 mm (0.10 λ x 0.10 λ) has been developed. To test its usefulness, the full structure FSS is used as a parabolic reflector in a dual band FSS reflector antenna operating at 1 GHz and 2 GHz. Simulated and measured results are close at both bands. The reflector antenna has high gain at 2 GHz of 12.7 dBi (simulated) and 11.7 dBi (measured). To observe the angular stability of the FSS and therefore its effectiveness as a reflector, it was compared with a copper test reflector at both bands. Simulation of the reflector antenna with test reflector produced a 2 GHz gain of 13.3 dBi which is very close to that with the FSS reflector. The simulated 2 GHz gain plot of the reflector antenna with FSS reflector is very similar to that with the test reflector indicating that the FSS has good angular stability. The gain at 1 GHz is also high with 9.3 dBi (simulated) and 8.7 dBi (measured). Simulation of the reflector antenna with no FSS and only a rear test reflector produced a 1 GHz gain of 10 dBi which is very close to that with the FSS reflector in place indicating that the FSS causes no significant attenuation at that frequency. The convoluted element FSS would be useful as a curved reflector in the creation of high gain, multiband, conformal antennas.

The Resonator is one of the techniques widely used to determine the dielectric properties of a material. It is due to the accuracy of the resonator technique as compared to the other methods such as open wave guide sensor, transmission method, and coaxial probe. The accuracy plays an important role in any measurement devices as this is one of the features to show that the device is competent enough to perform a specific task. So, as to cope with accuracy issues, two microstrip ring resonators were designed and prototyped to detect the dielectric properties of Material Under Test (MUT) in this study. Both utilize Rogers Duroid 4003C as the substrate for the dielectric sensor and is meant to resonate at 4 and 5 GHz in which the substrate possesses 3.38 dielectric properties and 0.0027 loss tangent. Several features in designing the resonator such as the coupling gap, d, and radius of the ring, R were taken into consideration. Those parameters were verified and validated through software simulation and measurement using Vector Network Analyzer (VNA) to achieve the expected sensor prototype to operate in the real environment. The measurement was made to test two known dielectric properties of MUT to demonstrate the sensitivity of the sensors. The outcome from the measurement was evaluated in terms of S-21 parameter. The dielectric measurement leads to a change in frequency response against different MUT. The measurement was extended to study the performance of the resonator through the R and d of the resonator in which these parametric studies were made by varying the R and d of the resonator with the presence and the absence of MUT. The outcomes from the measurement suggest the best R and d for the resonator in terms of dielectric permittivity.

A ring type frequency selective surface (FSS) can provide transmission stop-band characteristics in rooms. This allows adjacent rooms to be isolated for one LAN for frequency reuse while other frequencies pass through the walls with minimal attenuation. The FSS was screen printed on a thin flexible plastic substrate of permittivity 3.2 with a stop band at 12.3GHz and 10dB bandwidth of 3.5GHz. The variation in bandstop characteristics was investigated for various wall materials. The centre frequency varied by more than 3 GHz for common wall materials which means significant transparency for some building materials. The technique is a low cost method of confining LAN picocells in one room.