D. V. B. Murthy

Complex permittivity measurements using cavity perturbation technique with substrate integrated waveguide cavities

Cavity perturbation technique is widely used in the measurements of complex dielectric permittivity of materials due to its accuracy and ease of configuration. This paper presents the theoretical formulas for the evaluation of complex permittivity of materials using cavity perturbation technique with substrate integrated cavity resonators. With the proposed formulas, the use of various planar cavities is possible by taking into account the dielectric characteristics of the substrate in which the cavity is implemented. Simulations and measurements are performed on various dielectric samples to validate the proposed theory. The maximum deviation in the measured dielectric permittivity values is below 6% compared to the literature values. The implemented substrate integrated cavity is then analyzed in terms of sensitivity, showing a good performance.

Permittivity Measurements at Microwave Frequencies Using Epsilon-Near-Zero (ENZ) Tunnel Structure

A planar epsilon-near-zero (ENZ) tunnel structure implemented on substrate integrated waveguide (SIW) technology is used to evaluate the complex dielectric permittivity of various materials. Design, optimization, and fabrication of the ENZ tunnel structure are explained. Simulations and measurements on various dielectric samples using the cavity perturbation technique of the proposed structure are presented. Measured values of the permittivity are in good agreement with standard values. Sensitivity analyses are performed on the ENZ structure and the conventional SIW cavity techniques. The proposed structure has very high sensitivity, which yields more accurate results when compared to other techniques, such as perturbation of conventional cavities.

Multi-pole microstrip directional filters for multiplexing applications

Theory and experiment of multi-pole microstrip directional filters for multiplexing networks are presented in this paper. Conventional microstrip directional filters present only a single-pole filter response. By applying stopband filter theory, two Butterworth microstrip directional filters are designed and tested. The desired multi-pole filter response is achieved by cascading two or more similar single stages connected by immitance inverters. These types of directional filters are ideal candidates for multiplexing applications since they present the characteristics of easy implementation and the capacity of a modular concept. Moreover, a flat response is obtained along the passband due to the multi-pole filter behavior.

Experimental dielectric sensing of materials using Epsilon-Near-Zero tunnel in SIW technology.

A planar Epsilon-Near-Zero (ENZ) structure implemented on substrate integrated waveguide technology is used for the characterization of material dielectric permittivity. The proposed structure has very high sensitivity which yields more accurate results when compared to other techniques, such as perturbation of conventional cavities. This prototype presents a low profile, low cost, ease of fabrication and ease of integration, which add important characteristics for portable material analysis systems. Measurements are in good agreement with standard values.

Passive Millimeter-wave imaging using a Substrate Integrated Waveguide antenna

A millimeter-wave imaging system for concealed object detection at the frequency of 24 GHz with total power radiometer configuration has been designed and tested. We added to the system a microwave lens to focus the target to the antenna and a nipkow disc to scan the image under surveillance. We also incorporated the substrate integrated waveguide (SIW) technology in the receiver antenna.

Miniaturized Forced-Mode Ring Resonator with Capacitive Loading

The miniaturization of conventional ring resonators is demonstrated by forcing a voltage minimum at one end of the resonator. In addition, the resonator is loaded with a capacitance to achieve further miniaturization and reducing its sensitivity to substrate thickness tolerance. The flnal resonator is 73% smaller than a conventional ring resonator and has a tenfold decrease in sensitivity to substrate thickness variations. Using this resonator a 4-pole quasi- elliptic fllter is fabricated showing good agreement between simulation and experimental results.

Compact ultra wide band antenna with filtering structure using metamaterial (MTM) and substrate integrated circuit (SIC) technologies

In this paper we present an ultra compact monopole UWB antenna integrated with a filtering structure based on SIC technology and metamaterial transmission line. Preliminary simulation results of the filtering structure and experimental results of the antenna are presented along with design procedure.

Ultra wide band filter with notch at WiMax using Epsilon Near Zero (ENZ) methodology

In this article an ultra wide band filter with a notch at WiMax band using Epsilon Near Zero (ENZ) approach is presented. It is shown that great miniaturization is achieved as the ENZ tunnel length is independent of frequency. This filter is investigated numerically and experimentally. Measured results show a good agreement with the simulated analysis.

A wideband bandpass filter with improved out-of-band performance

A novel compact wide bandpass filter is proposed by cascading two square-ring resonators, a quarter wave length short-stub and a quarter wavelength open-stub. This filter offers wide passband, with high out-of-band rejection and suppression of second spurious harmonic. Design procedure of a filter at 1GHz with 50% fractional bandwidth is presented showing good agreement between simulation and experimental results.