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A new adaptive frequency selective surface (AFSS) has been presented for electromagnetic (EM) shielding applications. Passive EM shields lack reconfigurability which severely limits their application. Moreover, active EM shields involving PIN diodes and other active elements consume power all the time. This paper incorporates a novel adaptive approach with frequency selective surface (FSS) to create a smart environment. The unit cell of the designed FSS has the shape of an octagon loop; each loop includes a pin diode at 180° intervals. An envelope detector has been used to trigger the microcontroller whenever an incident RF signal has been detected. The PIN diodes are switched ON or OFF automatically based on the requirements using a microcontroller to save power. When the PIN diodes are OFF, the FSS is in the shielding mode and when they are ON it is in the transmission mode. A prototype has been built for measurements. A good agreement between theory and experiment has been observed. The proposed AFSS can also be programmed as a time-based event and remote-controlled for on-demand EM wave shielding applications.

A rectangular dielectric resonator antenna (DRA) has been excited using a unique conformal H-shaped metal strip. Using this excitation, the degenerate mode pair of first higher orderTEδ13x and TE1δ3y has been excited for bandwidth improvement and high gain. A broadband circular polarization (CP) over a bandwidth of ~20% (3.67-4.4 GHz) in conjunction with a wide impedance-matching bandwidth of ~27.7% (3.67-4.73 GHz) has been achieved. A CP beamwidth of 89° has been offered by the antenna in Φ = 0° plane and ~32° in Φ = 90° plane. A high gain of ~6.8 dBic has been provided by the antenna, which is a significant improvement to those circularly polarized rectangular DRAs reported in the literature for similar applications. This broad CP bandwidth and beamwidth can be considerably beneficial for the worldwide interoperability for microwave access (WiMAX) and satellite applications. Furthermore, the proposed antenna has been fabricated to validate the simulated results. The measured results have been observed to agree well with the simulated results.

In this paper, a novel wideband circularly polarized multiple-input multiple-output (MIMO) dielectric resonator antenna (DRA) has been proposed for worldwide interoperability for microwave access (WiMAX) applications. The mutual coupling (MC) between closely placed DRA units at 0.5λ has been significantly reduced by using a new hybrid technique. The exclusive features of the proposed MIMO antenna include wide impedance matching bandwidth (BW), broadband circular polarization (CP), and suppressed MC between the radiating elements. The first step of hybrid technique is the employment of parasitic patch at an optimized distance beside the conformal metal strip of the two identical rectangular DRAs in order to generate CP wave along with a wide impedance matching BW over the same frequency range. In the final step, the MC is suppressed significantly along with the broadband CP by placing the DRAs diagonally at an optimized position. The proposed MIMO antenna is the hybrid of the parasitic patch and the diagonal position of radiating elements. The CP BW offered by the proposed antenna is ~20.82% (3.58-4.40 GHz) in conjunction with an impedance-matching BW of ~38.51% (3.50-4.95 GHz). Moreover, MC less than -28 dB is achieved over the entire band and -26 dB at 3.89 GHz (minimum of the AR) through the hybrid technique. The prototype of the proposed antenna geometry is fabricated and measured. A good agreement has been attained between the simulated and measured results.

A wideband circularly polarized rectangular dielectric resonator antenna (DRA) fed by single feeding mechanism has been studied theoretically and experimentally. The study has been carried out to find out the effect on different antenna parameters when a parasitic strip is attached to the wall beside the conformal metallic feed. The DRA is excited by an E-shaped metal strip. The novel feed produces a narrow impedance matching |S11|