Chandrakanta Kumar

Bio: Chandrakanta Kumar is an academic researcher from Government of India. The author has contributed to research in topics: Microstrip antenna & Microstrip. The author has an hindex of 20, co-authored 94 publications receiving 1310 citations. Previous affiliations of Chandrakanta Kumar include Indian Space Research Organisation & Department of Space.

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

Abstract: 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.

Nature of Cross-Polarized Radiations from Probe-Fed Circular Microstrip Antennas and Their Suppression Using Different Geometries of Defected Ground Structure (DGS)

Abstract: Experiments with probe-fed circular patches using conventional and defected ground planes flashed some interesting features relating to cross-polarized (XP) electric fields and associated radiations before the present authors. Those led to a series of new investigations for understanding the nature of XP fields and to deal with them using defected ground structure (DGS) for improved XP performance. In the first phase of investigation, the XP radiations of a probe-fed circular patch with conventional ground plane have been critically studied as a function of the radial probe location. Remarkably significant effect is experimentally demonstrated. New information about orthogonal resonant fields and its importance in designing an antenna is provided. In the second phase of investigation, limitations of dot-shaped DGS in reducing XP level are experimentally studied. As its improved variants, two new DGS geometries such as annular ring and circular arcs have been explored. The arc-DGS appears to be highly efficient in terms of suppressing XP fields. Suppression by 10-12 dB has been experimentally demonstrated. Each design has been experimented in both C- and X-bands to earn confidence on the measured data.

Control of Higher Harmonics and Their Radiations in Microstrip Antennas Using Compact Defected Ground Structures

Abstract: Controlling higher order modes up to third harmonic of the fundamental operating frequency in a microstrip line-fed patch antenna has been successfully demonstrated. Harmonic rejection in the antenna has been achieved at its feed level using highly compact design of defected ground structure (DGS). Rejection characteristics have been improved adding an open stub to the feed line. All possible higher order modes occurring in between the fundamental and the 3rd harmonic have been identified. Relative suppression of radiated fields with and without DGS-control has been quantitatively measured and effective control of harmonics has been experimentally ensured. The area occupied by the proposed DGS has been compared with earlier designs and over 40-90% reduction in size has been documented.

Improved Cross-Polarization Characteristics of Circular Microstrip Antenna Employing Arc-Shaped Defected Ground Structure (DGS)

Abstract: Application of defected ground structure (DGS) to suppress cross-polarized (XP) radiation from a microstrip patch antenna has been reinvestigated using a new DGS geometry for much improved characteristics. Arc-shaped defect has been used in pair, symmetrically located under a circular patch. A number of optimization parameters have been examined using simulated results, leading to a design indicating improved XP behavior. A set of identical prototypes, with and without DGS, have been experimentally studied. The presence of the DGS shows as much as 30 dB isolation of the XP level from its peak radiation, and that compared to an identical patch without DGS indicates an improvement by as much as 12 dB. The relative suppression in XP values are found to be around 7-12 dB over ±75° elevation around the boresight of the patch.

Defected ground structure (DGS)-integrated rectangular microstrip patch for improved polarisation purity with wide impedance bandwidth

Abstract: Defected ground structure (DGS)-integrated rectangular microstrip patch has been experimentally investigated with an aim to improve polarisation purity in radiated fields. Width to length ratio (aspect ratio) of a patch attributes different characteristic features. Therefore present experimental studies have been executed for four different aspect ratio values like 1.6, 1.3, 1.0 and 0.8. Folded defects have been employed in H-plane. Possibility of achieving high polarisation purity (over 25 dB isolation between co- to cross-polarised fields) with improved impedance bandwidth has been demonstrated. The variation in XP fields as a function of the patch aspect ratio has been investigated and a strong physical insight into the modal fields with and without DGS has been developed.

Gain enhancement methods for printed circuit antennas

Abstract: Resonance conditions for a substrate-superstrate printed antenna geometry which allow for large antenna gain are presented. Asymptotic formulas for gain, beamwidth, and bandwidth are given, and the bandwidth limitation of the method is discussed. The method is extended to produce narrow patterns about the horizon, and directive patterns at two different angles.

Defected Ground Structure: Fundamentals, Analysis, and Applications in Modern Wireless Trends

Abstract: Slots or defects integrated on the ground plane of microwave planar circuits are referred to as Defected Ground Structure. DGS is adopted as an emerging technique for improving the various parameters of microwave circuits, that is, narrow bandwidth, cross-polarization, low gain, and so forth. This paper presents an introduction and evolution of DGS and how DGS is different from former technologies: PBG and EBG. A basic concept behind the DGS technology and several theoretical techniques for analysing the Defected Ground Structure are discussed. Several applications of DGS in the field of filters, planar waveguides, amplifiers, and antennas are presented.

Dielectric antenna and antenna module

Abstract: A dielectric antenna includes at least one dielectric unit. Each dielectric unit is separated into a first region and a second region, and the second region could have a bending portion. A conductor covers a surface of the second region of the dielectric unit to form a waveguide structure. The waveguide structure has a first endpoint connected to the first region and a second endpoint serving as a signal feeding terminal for feeding or receiving signals.

Dielectric Resonator Antennas: Basic Concepts, Design Guidelines, and Recent Developments at Millimeter-Wave Frequencies

Abstract: An up-to-date literature overview on relevant approaches for controlling circuital characteristics and radiation properties of dielectric resonator antennas (DRAs) is presented The main advantages of DRAs are discussed in detail, while reviewing the most effective techniques for antenna feeding as well as for size reduction Furthermore, advanced design solutions for enhancing the realized gain of individual DRAs are investigated In this way, guidance is provided to radio frequency (RF) front-end designers in the selection of different antenna topologies useful to achieve the required antenna performance in terms of frequency response, gain, and polarization Particular attention is put in the analysis of the progress which is being made in the application of DRA technology at millimeter-wave frequencies

MoS 2 Functionalized Multicore Fiber Probes for Selective Detection of Shigella Bacteria Based on Localized Plasmon

Abstract: Present study demonstrates the fiber-optic localized surface plasmon resonance (LSPR) based sensitive biosensor for detection of Shigella bacterial species. The proposed sensor is comprised of multi-core fiber (MCF) having seven cores arranged in a hexagonal shape and spliced with single-mode fiber (SMF) for efficient detection. An increase in evanescent waves (EWs) and coupling of modes between MCF cores was achieved by etching process in a controlled manner. The etching process also increases the refractive index sensitivity (RIS) of the proposed sensor. Further, coating with nanomaterials like gold nanoparticles (AuNPs) and molybdenum disulfide (MoS2) helps in the excitation of localized plasmons. Here, Shigella specific oligonucleotide probes are used as a recognition element. The results demonstrate that the proposed sensor can successfully and efficiently detect the Shigella bacterial species with high sensitivity. Shigella in the range of 10 – 100 CFU/mL (colony-forming unit/mL) can cause serious intestinal infection and therefore, its detection in this range is critical. The proposed sensor demonstrates a linearity range from 1 to 109 CFU/mL with a detection time of 5 min and a limit of detection (LoD) of 1.56 CFU/mL. The proposed sensing methodology can be a potential alternative to the commercially existing ones in the near future.