Chandrakanta Kumar

Higher Order Mode Excitation for High-Gain Broadside Radiation From Cylindrical Dielectric Resonator Antennas

A resonant mode (HEM12δ), other than those ( HEM11δ and TM01δ) conventionally excited and used in a cylindrical dielectric resonator antenna (CDRA) has been examined with a view for using it as another radiating mode with broadside radiation patterns. Excitation of the mode, being the most challenging aspect, has been discussed and resolved by employing an innovative technique. The proposed concept has been successfully verified and experimentally demonstrated for the first time. More than 8-dBi peak gain with excellent broadside radiation has been obtained from a prototype shaped from a commercially available low-loss dielectric material with relative permittivity 10.

Reduction in Cross-Polarized Radiation of Microstrip Patches Using Geometry-Independent Resonant-Type Defected Ground Structure (DGS)

A new method of suppressing cross-polarized (XP) radiation using resonant-type defected ground structure (R-DGS) on microstrip antenna has been proposed in this communication. A linearly shaped full wavelength R-DGS has been proposed and experimentally verified for different microstrip geometries. The design is supported by thorough investigations on the physical interaction between R-DGS and XP generating fields. Unlike previously explored nonresonant-type defects, this new approach is independent of patch geometry. A consistent suppression of the H-plane XP fields well below -30 dB for different patch geometries has been experimentally demonstrated.

New Approach in Designing Resonance Cavity High-Gain Antenna Using Nontransparent Conducting Sheet as the Superstrate

A resonance cavity antenna (RCA) has been explored employing nontransparent solid metal sheet as superstrate which, to the best of our knowledge, is reported for the first time. The proposed configuration is much advantageous in terms of design, simplicity, structural stability, fabrication, and cost without compromising in gain, efficiency, and bandwidth. A probe-fed dielectric resonator antenna (DRA) with εr = 10 has been used as the primary radiator. Proposed RCA bearing overall size 1.1λ × 1.1λ × 0.6λ promises for large impedance bandwidth (~23%) with considerably high gain (11.8-12.2 dBi). The superstrate size is relatively compact compared to its semitransparent versions, investigated earlier. Present design has been experimentally validated indicating as much as 12 dBi peak gain with more than 96.5% efficiency.

Dielectric Resonator Working as Feed as Well as Antenna: New Concept for Dual-Mode Dual-Band Improved Design

A new and physically realizable feed employing a dielectric resonator (DR) has been conceived and demonstrated for HEM12δ mode in a cylindrical dielectric resonator antenna (CDRA). This indeed enables in realizing an improved version of dual-band dual-mode dielectric resonator antenna (DRA) with attractive broadside radiation along with wide bandwidth characteristics. It comprises of a two-element stacked geometry, where the lower element is excited by an aperture and the upper element is excited by the lower DR. The upper element is responsible for generating the higher mode (HEM12δ,) whereas the lower mode (HEM11δ) resonates in the entire composite mass. The conjecture has been verified with an S/C-band design using simulated and measured results indicating three different variants. The most improved geometry comprising of a “cone on top of a cylinder” promises 6.5 and 10.3 dBi gains in the lower and upper operating bands with, respectively, 8.3% and 13% matching bandwidth. This newly addressed technique can be of potential use for newer innovations in DRA feed and design.

Asymmetric Geometry of Defected Ground Structure for Rectangular Microstrip: A New Approach to Reduce its Cross-Polarized Fields

A shaped defected ground structure (DGS) that is asymmetric in a specific radiating plane of a microstrip element has been explored with a view to addressing the cross-polarization (XP) issues. The asymmetric configuration has been conceived from an insight of the inherent asymmetry of the modal fields underneath a probe-fed microstrip patch and has been experimentally demonstrated as the best possible design compared to its predecessors in terms of the reduction in XP fields, angular span of suppression around boresight, and the space occupied by the defects. Different orientations of the defects with reference to the patches of different aspect ratio values have been thoroughly examined. More than 28-dB isolation between co-pol and cross-pol has been achieved over 190° angular range, which is indeed 140° more if compared with a conventional ground plane. Its superior characteristics with respect to the earlier designs have also been documented.

Wideband High Gain Antenna Realized From Simple Unloaded Single Patch

A wideband antenna has been conceived and realized from a single metallic patch with air as the substrate. The patch has been strategically folded to achieve dual resonances resulting in S11 ≤ 10 dB over a wide matching bandwidth. Basic design concept has been discussed and experimentally verified. As much as 26% bandwidth covering almost the full X-band with about 9.6 dBi peak gain has been experimentally demonstrated from a 20.3 mm × 13 mm patch folded to realize 13 mm × 13 mm footprint.

Perturbation Technique to Improve Purity of Modal Fields in Dielectric Resonator Antenna Resulting in Reduced Cross-Polarized Radiation

Metallic perturbation in a body of a dielectric resonator antenna (DRA) has been explored with a view to improve the purity of modal fields leading to considerable reduction in unwanted cross-polarized (XP) radiations. A coax-fed cylindrical DRA (CDRA) has been examined with a pair of horizontally oriented metal pins protruded symmetrically face to face through it. The concept behind the design has been discussed and established using simulated results followed by a series of experimental verifications. As much as 10 dB reduction in principal plane XP values without affecting the primary radiation has been demonstrated. Purity in the modal fields is accounted for in terms of achieved isolation between co- and cross-polarized radiations, which attains 25-40 dB over 100° beamwidth.

Design Guidelines for the Cylindrical Dielectric Resonator Antenna Using the Recently Proposed HEM12d Mode [Antenna Designer's Notebook]

Excitation of the higher-order HEM12d mode in a cylindrical dielectric resonator antenna (CDRA) was a big challenge, which was recently resolved by the present authors, nearly 30 years after the invention of the dielectric resonator antenna (DRA). Significantly, the radiation characteristics of this mode closely follow those due to the HEM11d mode, but with relatively higher gain. This breakthrough was made possible by introducing a new concept of feeding, and this was experimentally verified using a single prototype. Here, we have thoroughly investigated the design opportunities and limitations in terms of the material properties and dielectric resonator antennas dimensions. Based on acquired knowledge, a comprehensive design guideline is provided to facilitate future designers estimating the best possible configuration for any specified application. As a significant part of this, the feed design has also been addressed. For practical verification, a customized dielectric resonator antenna was fabricated and measured, indicating excellent agreement with the proposed guidelines.

Synthesizing Aperture Fields Over the Superstrate of Resonance Cavity Antenna for Modifying Its Radiation Properties

Modification and improvement in the radiation characteristics of a resonance cavity antenna (RCA) have been addressed from a new approach of aperture field synthesis over the superstrate. This concept has been established through a series of systematic studies, which are based on the exciting observations reported very recently by these authors. A process of modification or engineering on the superstrate has been conjectured in view of obtaining reduced sidelobe level (SLL) and/or increased gain. The same has been successfully designed and experimentally demonstrated indicating as much as 10 dB suppression in SLL along with 3 dB improvement in gain compared to its nearest contender. This study promises a potential technique in RCA design along with several attractive features.

Theory of Controlled Aperture Field for Advanced Superstrate Design of a Resonance Cavity Antenna With Improved Radiations Properties

An insight based on a new theoretical approach has been developed to facilitate the design of a superstrate which plays a key role in realizing a high gain resonance cavity antenna (RCA). The work is aimed to address a profound theoretical basis of controlling the aperture fields by proper shaping of superstrate and to apply it to alleviate the earlier shortcomings along with further improvement in radiation characteristics. This demonstrates an interesting transformation of a metal superstrate from rectangle to an ellipse or an ellipse-circle combination to achieve significant improvements in the aperture fields and hence the sidelobe level (SLL). The antenna characteristics have been verified using simulated data followed by experiments using different sets of prototypes. About 50% reduction in size along with an improvement in the SLL by 5–17 dB compared to its immediate predecessor has been experimentally demonstrated. Proposed theory should find the potential applications in conceiving efficient RCA designs in the future.