Chandra Charu Tripathi

A polarization insensitive compact ultrathin wide-angle penta-band metamaterial absorber

Abstract In this paper, the design, fabrication, and measurements of a compact ultrathin five-band metamaterial absorber with wide-angle stability have been presented. The unit cell of the absorber consists of five concentric metallic circular rings printed as the top layer of a grounded dielectric substrate of thickness 1 mm. The radii and the intermediate gap between the rings are optimized such that the proposed absorber exhibits five distinct absorption peaks at frequencies of 5.28, 7.36, 9.52, 12.64, and 16.32 GHz with absorptivities of 92.03, 90.46, 95.10, 91.65, and 91.10%, respectively. The proposed absorber is polarization insensitive for both TE and TM incident wave and results high absorption for wide incidence angle up to 60°. The proposed structure is compact with its unit cell size of 0.54 λ0 and ultrathin with thickness of ~λ0/19 corresponding to the highest frequency of absorption. Surface current and field distributions are studied to understand the absorption mechanism. A prototype of the proposed absorber is fabricated and experimentally tested for different polarization and incident angles. The measured results are observed to be in agreement with the simulated ones. The proposed absorber is suitable for potential applications due to its multi-band absorption.

Potential challenges and issues in implementation of MIM diodes for rectenna application

Metal-Insulator-Metal (MIM) diodes are one of the widely explored diodes for high frequency applications. The tunneling based transport mechanism in such diodes provides an ultra-fast switching speed which makes it a promising candidate for high frequency rectification in rectennas (Antenna coupled diode). However, despite of a lot of headway in the innovation of MIM diodes, the desired performance has not been achieved yet. This paper brings forward the various challenges and issues confronted in the successful implementation of MIM diodes for rectenna energy harvesting system.

Terahertz Detectors (THzDs): Bridging the Gap for Energy Harvesting

It is indispensable to integrate electronics with environment for better lives. Huge amount of solar energy, dark energy, and unused microwave energy is untapped till now due to insufficient availability of high frequency THz detectors. The difference between THz wave detection and THz electric field detection must be clear. THz wave detection connects the detection of explosives, drugs, astronomy, metals, and imaging applications, etc. On the other hand, THz electric field detection involves the conversion of electromagnetic (EM) radiations to usable DC power. The optimum choice of detectors for energy harvesting is a highly diverse area. The latter part is concentrated on the non‐ linear behavior of the incoming radiations and has been highlighted also. In this chapter, metal‐insulator‐metal (MIM) diode detectors have been explored to become a best choice for high frequency detectors.

Development of compact inductive coupled meander line RFID tag for near-field applications

The development of compact radio frequency identification (RFID) tag is the key requirement for wireless tracking of precious small size goods/packages in transport. A design of compact meander line tag antenna having inductive coupling feed is presented for RFID system operating at ultra high frequency band of 865–867 MHz. The size of the proposed tag antenna is 43 mm × 10 mm, and is designed using Higgs 4 IC chip (made Alien Technology, USA) having impedance of 20.55 − j191.45 Ω at centre frequency 866 MHz. The antenna characteristics such as impedance, radiation pattern, bandwidth, and effect of ground on gain and tag size are analyzed and found to closely match with the simulated values. The observed value of reading range varies from 87.5 to 35 cms depending on mounting on non-metal and metal packages, respectively.

Fabrication and characterization of Al/PMMA/Cr metal-insulator-metal diode

Metal-Insulator-Metal (MIM) diodes are a promising candidate for rectenna based energy harvesting application owing to its tunneling based ultra-fast conduction mechanism. A number of material combinations have been explored in quest of developing such high frequency devices. Recently, organic insulator based MIM diodes are also under investigation. In the present work an organic polymer poly(methyl methacrylate) (PMMA) has been used as insulating layer to fabricate an Al/PMMA/Cr MIM structure. The Al and Cr metal electrodes were thermally evaporated while PMMA was deposited by spin coating technique. Electrical behavior of the diode was measured. The as fabricated device exhibited current in the range of 40 μA at ±0.6 V of applied bias with acceptable non-linearity and asymmetry.