Frequency-reconfigurable antenna using ellipse-shaped patch with defected ground structure

Abstract

Recently, there has been an increased demand for single systems that can handle different wireless communication applications simultaneously. Often, it is impractical to allocate multiple antennas to the same system, so multifunctional antennas are a critical necessity. Also, most existing frequency-reconfigurable antennas (FRA) are made from non-transparent materials, but a transparent antenna may be useful in scenarios where the antenna should not impair visibility. Furthermore, wideband-to-narrowband reconfigurability has potential for use in future cognitive radio systems. This thesis focuses on FRAs with wideband-tonarrowband reconfigurability that use transparent and non-transparent materials. The ultra-wideband antenna design uses an ellipse-shaped patch, thereby yielding a 7.77 GHz impedance bandwidth from 2.83 GHz to 10.66 GHz. The first FRA is obtained by introducing a pair of annular ring slots defected ground structure (DGS) resonator with metal switches. Its initial wideband operation mode from 3 GHz to 6 GHz can be reconfigured into six additional bandwidth modes with a dual-band operation centred at 3.7 GHz and 5.8 GHz and five single-band modes resonating at 4.2 GHz, 4.58 GHz, 4.86 GHz, 5.7 GHz and 6 GHz. Meanwhile, a FRA for the Wireless Local-Area Network applications is reconfigured from a pair of rectangular DGS resonators integrated with PIN diodes. The antenna is able to switch between a narrowband operation centred at 5.8 GHz and a wideband operation in the range of 3.5 - 5.97 GHz. Finally, a semi-transparent antenna with a wideband-to-narrowband frequency mode is achieved by integrating an E-shaped DGS resonator and PIN diodes to disrupt the current flow. The antenna exhibits an impedance bandwidth from 3 GHz to 6 GHz in the wideband mode and a resonance at 4.75 GHz when operated in the narrowband mode. All prototypes are fabricated and measured to verify the simulated results. The gain of antenna fabricated using the AgHT-4 transparent material is about 59% lower compared to FR-4 due to the electrical loss of the transparent film.