A. V. Praveen Kumar

MICROSTRIPLINE FED CYLINDRICAL DIELECTRIC RESONATOR ANTENNA WITH A COPLANAR PARASITIC STRIP

The paper discusses the experimental analysis on a cylindrical dielectric resonator antenna (DRA) with a parasitic conducting strip, loaded coplanar with the 50Ω microstripline feed. The antenna offers an impedance bandwidth as high as 17.33% at a centre frequency of 2.77 GHz, as a result of the enhanced coupling produced by the coplanar strip. The return loss, impedance, polarization and radiation characteristics of the antenna are studied. The radiation patterns are broad and the low cross-polarisation levels confirm that the antenna is linearly polarised over the entire impedance bandwidth.

A Wideband Conical Beam Cylindrical Dielectric Resonator Antenna

The letter proposes a novel cylindrical dielectric resonator antenna (DRA) geometry with low radiation Q-value facilitating wide band operation with conical radiation patterns. The DRA is fed by a microstrip transmission line with a vertical strip that is attached to the DRA surface. At optimum dimensions and position of the vertical strip on the horizontal microstrip, the DRA exhibits an impedance bandwidth (

Polyaniline and polypyrrole with PVC content for effective EMI shielding

\vert {\rm S}_{11}\vert < - 10

A Novel Technique for Localizing the Scatterer in Inverse Profiling of Two Dimensional Circularly Symmetric Dielectric Scatterers Using Degree of Symmetry and Neural Networks

dB) of

Synthesis of Dielectric Resonators for Microwave Filter Designing.

{\sim}35\hbox{\%}

Qualitative Analysis of Human Semen Using Microwaves

at the centre frequency of 3 GHz. Measured radiation patterns are conical in shape and are stable with moderate gain across the matching band.

Microstripline fed cylindrical sector dielectric resonator antenna

Conducting polymers are characterized by attractive features like high anticorrosion property, controlled conductivity, high temperature resistance, low cost and ease of bulk preparation. These properties make conducting polymers as good shielding materials for electromagnetic interference. Poly aniline and polypyrrole with different proportion of PVC are prepared and studied at the S-band microwave frequencies. Dielectric parameters such as dielectric constant, dielectric loss, conductivity and S-parameters are evaluated. Suitability of these materials for EMI shielding is discussed.

Coaxial fed hexagonal dielectric resonator antenna

A novel technique for localizing the scatterer in microwave imaging of two-dimensional circularly symmetric dielectric scatterers using degree of symmetry and neural networks is presented. The degree of symmetry for a transmitter position is computed as a function of the difference between the first half and the spatially reflected second half of the measured scattered field vector. A Probabilistic Neural Network (PNN) classifier is trained with the degree of symmetry vectors for the different object configurations. It classifies the degree of symmetry vector of the unknown circularly symmetric scatterer presented to it into one of the classes that indicate the radius and location of the centre of the scatterer. Thus the scatterer is localized in the imaging domain. This not only reduces the degrees of freedom in the inversion for the unknown object, thereby aiding the global convergence of the solution, but also results in a reduction in computation time. The technique has been tested on synthetic data and the results are promising.

A Dielectric Resonator Inspired Displacement Sensor

In this paper, synthesis of cylindrical dielectric resonators, for the design of transmission mode filters is presented. Dielectric constants of these resonators are calculated from the TE01δ resonant mode of the DR using Hakki-Coleman method. Microwave band pass filter characteristics are studied by measuring the reflection and transmission characteristics of the dual mode HEM11.

Higher order mode of a microstripline fed cylindrical dielectric resonator antenna

Microwave engineering now a days plays a vital tool in diagnostic and therapeutic medicine. A quality evaluation of human semen at microwave frequencies using the measurements made at different intervals of time by cavity perturbation technique in the S-band of microwave spectrum is presented in this paper. Semen samples were also examined in the microscopic as well as macroscopic level in clinical laboratory. It is observed that conductivity of semen depends upon the motility of sperm and it increases as time elapses, which finds applications in forensic medicine. Accurate information about the dielectric properties of tissues and biological liquids is important for studies on the biological effects at radio and microwaves frequencies. In macroscopic level, these electrical properties determine the energy deposition patterns in tissue upon irradiation by an electromagnetic field. In microscopic level, they reflect the molecular mechanisms, which underlie the absorption of electromagnetic energy by the tissue or liquids. Knowledge of the microwave dielectric properties of human tissues is essential for the under- standing and development of medical microwave techniques. Microwave thermography, microwave hyperthermia and microwave tomography all rely on processes fundamentally determined by the high frequency electromag- netic properties of human tissues. Tissue temperature pattern retrieval in the microwave thermography is achieved using models of the underlying tissue structure, which depend particularly on the dielectric properties of the tissue (1). A recent review of published data on animal and human dielectric parameters shows that for most tissue types animal measurements are good substitute for human tissues (2). Gabriel etal., Cook and Land etal., reported the dielectric parameters of various human tissues at different RF frequencies.(3-6). Microwave study of human blood using coaxial line and wave-guide methods was carried out by Cook (7). Tissue samples of human brain at microwave frequencies were analysed using sample cell terminated transmission line methods (8). Open-ended coaxial line method allows measurements of tissue samples over a wide range of frequencies (9). Microwave medical tomography is emerging as a novel non-hazardous method of imaging for the detection of fracture, swelling and diagnosis of tumors. Active and passive microwave imaging for disease detection and treatment monitoring require proper knowledge of body tissue dielectric properties at the lower microwave frequencies (10-12). Studies on the variation of dielectric properties of body fluids and urinary calcifications at microwave frequencies have revealed that diagnosis is possible through cavity perturbation technique (13-15). The present paper reports dielectric properties of semen at microwave frequencies as well as the quantitative analysis in the clinical laboratory. It is observed that conductivity of semen depends upon the motility of sperm as well as the time elapses after ejaculation. 2. Materials and Methods The experimental set-up consists of a transmission type S-band rectangular cavity resonator, HP 8714 ET network analyser. The cavity resonator is a transmission line with one or both ends closed. The resonant frequencies are determined by the length of the resonator. The resonator in this set-up is excited in the TE10� mode. The sample holder which is made of glass in the form of a capillary tube flared to a disk shaped bulb at the bottom is placed into the cavity through the non-radiating cavity slot, at broader side of the cavity which can facilitate the easy movement of the holder. The resonant frequency fo and the corresponding quality factor Qo of the cavity at each resonant peak with the empty sample holder placed at the maximum electric field are noted. The same holder filled with known amount of sample under study is again introduced into the cavity resonator through the non-radiating slot. The resonant frequencies of the sample loaded cavity is selected and the position of the sample is adjusted for maximum perturbation (i.e., maximum shift of resonant frequency with minimum amplitude for the peak). The new resonant frequency fs and the quality factor Qs are noted. The same procedure is repeated for other resonant frequencies.