In recent years, hybrid absorption systems have been implemented which achieve high sound absorption over a broad frequency range. This work is an experimental study of a broadband hybrid absorption system which is comprised of a layer of sound-absorbing material ~the passive component! positioned at a distance from a movable wall ~the active component! inside an impedance tube. The movable wal...

This paper investigates low cost matching network for high impedance ultrasonic transducers. Matching the output transmitter impedance to high impedance transducer is important to maximize the transfer of power and improve the transmitting efficiency of the transducer, and so achieve better signal-to-noise ratio. In NDT ultrasonic applications based on piezoelectric transducers it is usual to i...

Plasma characterization and impedance matching are an integral part of any radio frequency (RF) based plasma source. In long pulse operation, particularly in high power operation where plasma load may vary due to different reasons (e.g. pressure and power), online tuning of impedance matching circuit and remote plasma density estimation are very useful. In some cases, due to remote interfaces, ...

For high quality factor magnetically coupled resonator wireless power systems, constant wireless power transfer efficiency can be achieved over a greater range and higher efficiency than an inductively coupled system. However, as the distance varies between two near-field resonators, the input and output impedances to the resonators change. Therefore, in order to achieve constant efficiency, th...

On the basic of fractal theory and folded technique, a miniature antenna for 2.45 GHz radio frequency identification (RFID) tag applications is designed and analyzed in the present paper. In order to realize the miniaturization of tag antenna, a Hilbert fractal structure is used. Impedance matching between antenna and IC chip is of great importance for improving tag performances. A folded techn...

Impedance matching at the surface of left-handed materials (LHM) is required for certain applications including a perfect lens. In this study, we present the experimental and theoretical verification of an impedance-matched LHM to free space. Reflection characteristics of both one-dimensional and two-dimensional LHM were investigated. The reflection was observed to be very low at a narrow frequ...

Objective of this study is to enhance radius of curvature of return loss, input impedance & explore SWR and radiation pattern. Hollow CDRA has been used instead of single-element CDRA to achieve the above mentioned goal. The impedance bandwidth of a high permittivity hollow cylindrical dielectric resonator antenna excited by micro-strip lines was significantly improved by modifying the feed geo...

Broadband noise absorption, including low frequencies, may be obtained by a hybrid passive-active two-layer system. A porous layer in front of an air layer provides passive absorption, at medium and high frequencies. Active control of the input impedance of the two-layer system yields absorption at low frequencies. The active control system can implement either pressure-release or impedance-mat...

Reducing unwanted reflections through impedance matching, called anti-reflection, has long been an important challenge in optics and electrical engineering. Beyond trial and error optimization, however, a systematic way to realize anti-reflection is still absent. Here, we report the discovery of an analytic solution to this long standing problem. For electromagnetic waves, we find the graded pe...