Basit Ali Zeb

Wideband High-Gain EBG Resonator Antennas With Small Footprints and All-Dielectric Superstructures

A novel method is presented to design single-feed high-gain EBG resonator antennas (ERAs) with significantly wider bandwidths. Dielectric contrast is introduced to 1-D EBG superstructures composed of unprinted dielectric slabs, and the thicknesses of each of these slabs is optimized to achieve a wideband defect mode in a unit-cell model. Next, antennas are designed and their superstructure areas are truncated to increase the antenna bandwidth and aperture efficiency while decreasing antenna footprint. We demonstrate that a small superstructure area increases the 3-dB bandwidth of ERAs significantly. A prototype ERA designed with a single feed and superstructure area as small as 1.5 λ0 ×1.5 λ0 has a measured 3-dB directivity bandwidth of 22% at a peak gain of 18.2 dBi. This prototype antenna was made out of three slabs of different dielectric constants, two of them touching each other. This prototype demonstrates more than 85% reduction in the ERA footprint alongside a drastic improvement in bandwidth over the 3%-4% measured bandwidth of the classical single-feed ERAs with unprinted slabs.

A Simple Dual-Band Electromagnetic Band Gap Resonator Antenna Based on Inverted Reflection Phase Gradient

A simple method is presented to obtain a high-gain dual-band electromagnetic band gap (EBG) resonator antenna. The antenna is based on a one-dimensional EBG structure, made out of two low-cost unprinted dielectric slabs. The EBG structure is implemented as the antenna superstrate, which has been designed to provide a locally-inverted, positive reflection phase gradient with high reflectivity, in two pre-determined frequency bands. A composite dual-band antenna has been designed and tested with a stacked patch feed. Experimental results confirm the dual-band performance of the prototype antenna. Measured peak gains of 14.5 dBi and 15.1 dBi, and 3-dB gain bandwidth of 4.5% and 4.6%, are achieved at 10.6 GHz and 13.2 GHz, respectively. Measured 10-dB return-loss bandwidths are 6.4% and 3.9% in lower and upper bands, respectively. Potential enhancements of antenna radiation characteristics are studied using small 2 × 2 patch array feeds. It was found that such feeds can lead to lower side lobes, higher peak gains and larger gain bandwidths.

Dielectric Phase-Correcting Structures for Electromagnetic Band Gap Resonator Antennas

A novel technique to design a phase-correcting structure (PCS) for an electromagnetic band gap (EBG) resonator antenna (ERA) is presented. The aperture field of a classical ERA has a significantly nonuniform phase distribution, which adversely affects its radiation characteristics. An all-dielectric PCS was designed to transform such a phase distribution to a nearly uniform phase distribution. A prototype designed using proposed technique was fabricated and tested to verify proposed methodology and to validate predicted results. A very good agreement between the predicted and the measured results is noted. Significant increase in antenna performance has been achieved due to this phase correction, including 9-dB improvement in antenna directivity (from 12.3 dBi to 21.6 dBi), lower side lobes, higher gain, and better aperture efficiency. The phase-corrected antenna has a 3-dB directivity bandwidth of 8%.

A High-Gain Dual-Band EBG Resonator Antenna with Circular Polarization

A dual-band circularly polarized (CP) electromagnatic band-gap (EBG) resonator antenna (ERA) is presented. The antenna employs an all-dielectric superstructure, which consists of two identical unprinted dielectric slabs, and a dual-band corner-truncated patch feed. A prototype antenna is fabricated and tested using a superstructure made out of 3.175-mm-thick Rogers TMM10 material. Measured peak gains are 16.1 dBic [left-hand circular polarization (LHCP)] and 16.2 dBic [right-hand circular polarization (RHCP)], measured radiation efficiencies are 93% and 91%, and the boresight axial ratios are 1.9 and 1.5 dB at 9.65 and 11.75 GHz, respectively. This dual-band antenna is easy to fabricate, making it suitable for high-gain low-cost CP applications.

A new technique to design 1-D dual-band EBG resonator antennas

This paper describes a novel technique to design a dual-band electromagnetic band gap (EBG) resonator antenna by engineering the reflection phase characteristics of a simple superstrate composed of two uniform dielectric slabs. The working principle is explained using the unit-cell analysis and a composite antenna design is presented with a simple EBG superstrate made out of two low-cost FR4 sheets. Antenna simulations and computed radiation patterns confirm the directivity enhancement and dual-band operation of this simple 1-D EBG resonator antenna.

Wideband high-gain EBG resonator antenna employing an unprinted composite superstrate

A single-feed high-gain EBG resonator antenna with extremely wideband performance is presented. The bandwidth is enhanced through a novel composite superstrate made from a combination of unprinted dielectric slabs with uniform thickness. The composite superstrate leads to wide defect-mode bandwidth and offers slowly increasing reflection phase profile over a wide frequency band. A single slot is used to excite the cavity. Peak antenna gain of 17.17 dBi with half-power gain bandwidth of 33.9% centered at 12.6 GHz is predicted. More than 100% increase in 3-dB directivity bandwidth with 55% reduction in aperture size is obtained as compared to conventional designs.

A simple EBG structure for dual-band circularly polarized antennas with high directivity

A simple electromagnetic band gap (EBG) structure is used as a superstrate to enhance the directivity of circularly-polarized (CP) corner-truncated microstrip patch antennas in two frequency bands. The EBG structure is composed of two simple unprinted identical dielectric slabs and its symmetry is exploited to transform the less directive CP beam of the patch to a highly directive CP beam. Computed results confirm the concept of this simple and novel dual-band circularly polarized EBG resonator antenna and its ability to generate CP with good axial ratio in two discrete frequency bands.

Effect of truncating the superstructures in broadband Fabry-Pèrot cavity antennas

Fabry-Perot cavity antennas, while offering design simplicity and high directivity, are promising candidates for microwave and millimeter wave communication links. Recommendations for effectively truncating the 1-D/2-D periodic structures, designed to act as superstructures in such antennas, are presented. It is shown that the aperture size in such antennas contributes, in part, towards the directivity-bandwidth product. A simple Fabry-Perot cavity antenna which uses a two layered 1-D Electromagnetic Band Gap (EBG) structure as its superstructure is studied to quantify the effects of aperture size on peak directivity and half-power directivity-bandwidth. Conventional aperture size for such antennas ranges from 5-6λ02, which results in over-dimensioning as well as narrowband behavior. It is shown that comparable performance with existing designs can be achieved by using much smaller aperture sizes and thus reducing the antenna footprint. This work serves as a guide to effectively choose and fine-tune aperture sizes for Fabry-Perot cavity antennas, thus reducing the redundant computational load in the full-scale design process.

A partially reflecting surface with polarization conversion for circularly polarized antennas with high directivity

This paper presents the design of a Fabry-Perot/EBG resonator antenna which uses a self-polarizing partially reflecting surface (PRS). The PRS, consisting of an array of rectangular patches, is designed for self-generation of circular polarization. The PRS is designed for highest possible reflectivity and the best axial ratio performance for narrowband applications. Numerical simulations of the proposed antenna configuration predict a peak directivity of 22 dBic and the best axial ratio of 0.85 dB at 9.7 GHz.

A Method to Realize Robust Flexible Electronically Tunable Antennas Using Polymer-Embedded Conductive Fabric

A new approach to realize robust, flexible, and electronically tunable wearable antennas is presented. Conductive fabric is used to form the conducting parts of the antenna on a polydimethylsiloxane (PDMS) substrate. Then the antenna and the lumped (active and passive) elements, required for electronic tuning and RF choking, are fully encapsulated with additional layers of PDMS. As a concept demonstration, a new frequency-reconfigurable antenna has been designed and fabricated. The details of the prototype manufacturing process are described. Two UWB human muscle equivalent phantoms were also fabricated for testing purposes. Furthermore, the antenna was subjected to several investigations on its RF performance (both in free space and on a flat phantom) and mechanical stability. The latter includes bending tests on several locations on a human-body shaped phantom and washing in a household washing machine. Good agreement between predicted and experimental results (both in free space and on the phantom) is observed, validating the proposed concept. The tests demonstrated that lumped components and other antenna parts remained intact and in working order even under extreme bending (to a bending radius of 28 mm) and after washing, thus maintaining the overall antenna performance including good frequency reconfigurability from 2.3 to 2.68 GHz. To the best of our knowledge, all these features have never been demonstrated in previously published electronically tunable antennas.