|
Differentially-Fed Half-Cylindrical Dielectric Resonator Antenna
for Dual-Mode Applications
--A V Praveen Kumar
Differentially-fed half-Cylindrical Dielectric Resonator Antenna (CDRA) enables two different
modes to be excited at the proper phase difference between the two feed lines. For a
differential phase of 00, TE0 mode is excited, while for a phase of 1800, HEM12 mode is
excited. The cut-plane of the half-CDRA is so placed on the ground plane-backed substrate
that the above modes obey the respective boundary conditions. With minor design changes,
the DRA can be operated either in single mode or in dual mode. In dual-mode operation, the
maximum directivities are 6.9 dB and 4.3 dB, respectively for a differential phase of 00 and
1800, respectively.
© 2016 IUP. All Rights Reserved.
Parasitic Metal Loading to Purify the Higher-Order Mode
of a Cylindrical Dielectric Resonator Antenna
--A V Praveen Kumar
The paper shows that a metallic strip placed at certain planes of a Cylindrical Dielectric Resonator Antenna (CDRA) improves the purity of the co-polarized fields of its Higher Order Mode (HOM) when excited by a microstrip line. The metallic boundary suppresses the spurious field components of the HOM which are responsible for a distorted radiation pattern. A directivity of about –30 dB in the broadside direction and about 5.5 dB at ±500 elevation to the broadside has been demonstrated at the HOM frequency of 4.63 GHz. The metal loading also retains the fundamental broadside mode of the CDRA allowing dualband and dual-mode operation.
© 2016 IUP. All Rights Reserved.
Study, Design and Analysis of U-Shaped Metamaterial Absorber
for X-Band Application
--Chandrakant R Rana, Kirti Inamdar and A H Lalluwadia
Electromagnetic microwave absorber is one of the major applications of metamaterials where effective permittivity and permeability can be modified to minimize both transmittance and reflectance at resonant frequency to obtain high absorption through resistive and dielectric loss. Metamaterial absorber can be made ultrathin and highly absorptive ranging from microwave to optical frequency regime. They have proven their potential in comparison to alternate conventional absorbers due to their ultrathinness, near unity absorption properties, simple manufacturing procedures and increasing effectiveness. This paper presents the design, development and working of a novel ultra-wide band, ultrathin metamaterial absorber. The proposed structure is based on simple U-shaped metamaterial printed on a metal-backed dielectric substrate. The numerical simulation carried out in HFSS shows that the proposed design behaves as quad-band EM absorber in X-band. Further, this design has been tested under different angles of incidence. The results gave an affirmation that the proposed design is valid as an absorber for a wide range of incident angles for both TE and TM polarization. The designed absorber can be used for many potential applications like cavity resonance reduction, near field absorbers, loads, anechoic chambers, bolometer, image sensing and processing.
© 2016 IUP. All Rights Reserved.
Bandwidth Enhancement Using Stacked Configuration
in Microstrip Antenna Array for Millimeter Wave Applications
--Soni Goel, Ashmita Kamal and Priyanka Choudhary
In this paper, three millimeter wave antennas are presented for 60 GHz. Each antenna is an array of 2 x 2 microstrip antennas. All three antennas utilize thin substrate of RT Duroid 5,880 having permittivity Er = 2.2. The basic design of 2 x 2 array antenna utilizing RT Duroid is extended for two superstrate loaded antennae designs. The first design uses foam and the other design uses RT Duroid with air gap as superstrates. 2 x 2 array patch engraved on RT Duroid above ground plane acts as driven patch, while the patch incised upon the superstrate acts as a parasitic patch. Optimization of the basic design achieves highest gain in millimeter wave region, whereas the superstrate loaded design results in a much wider bandwidth. A comparison of all design configurations is carried out through the sensitive study of the simulation results, including return loss, polarization and radiation patterns, which validates the designs for millimeter wave region.
© 2016 IUP. All Rights Reserved.
An Eco-Design of Dielectric Resonator Antenna
for Wideband Applications
--Jitendra Kumar and Navneet Gupta
A systematic study on an eco-design of Dielectric Resonator Antenna (DRA) is done for the first time by considering the environment. The developed DRA is an eco-designed antenna which uses less material and energy; due to this the environmental impact is reduced. The proposed DRA geometry decreases the DRA dielectric material by 52% as compared to conventional rectangular DRA with compact volume of 6.48 cm3. The antenna covers most of the wireless system like 5.2 and 5.8 GHz WLAN/Wi-MAX applications.
© 2016 IUP. All Rights Reserved.
Face Recognition Technology: A Review
--Jagdish Chandra Joshi and K K Gupta
The paper reviews face recognition techniques—an actively researched area in the field of biometrics, pattern recognition and computer vision. Maiden attempts were made in the early 1960s or so, but significant progresses were made only around 1988, in synchronization with a massive increase in computational power. The first widely accepted algorithm was the Principal Component Analysis (PCA) or Eigenface method, which even today is used as the most significant tool for dimensionality reduction. Today, many scientists agree that the case of any two simple facial images, under well-controlled conditions of environmental constraints/variables, for comparison is practically known to be a solved problem. Even with minimal variations in such images, apart from facial expression, the problem is insignificant by today’s standards with a recognition accuracy of around 90-98% reported across many papers. This is arguably even better than human performance in the same conditions provided, when humans are tested on the images of the unknown persons. However, when variations in images caused by pose, aging or extreme illumination and pattern recognition conditions are introduced, the ability of human beings to recognize faces is still remarkable as compared to computers.
© 2016 IUP. All Rights Reserved.
|
