http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/443 2013-06-19T15:41:05Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/2984 Dielectric properties of ionomers at microwave frequencies Mathew, K T; Biju Kumar, S; Anil, Lonappan; Joe, Jacob; Jacob, Samuel; Thommachan, Xavier; Thomas, Kurian Ionic polymers (ionomers) with interesting characteristics are emerging as important commercial polymers. Ionomers have the unique ability to behave as cross-linked materials at ambient temperatures and to melt and flow at elevated temperatures like thermoplastics. The complex permittivity and conductivity of a class of ionomers at microwave frequencies are determined using the cavity perturbation technique and the results are presented. 2002-10-01T00:00:00Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/2983 Buried-object detection using free-space time-domain near-field measurements Biju Kumar, S; Aanandan, C K; Mathew, K T The detection of buried objects using time-domain freespace measurements was carried out in the near field. The location of a hidden object was determined from an analysis of the reflected signal. This method can be extended to detect any number of objects. Measurements were carried out in the X- and Ku-bands using ordinary rectangular pyramidal horn antennas of gain 15 dB. The same antenna was used as the transmitter and recei er. The experimental results were compared with simulated results by applying the two-dimensional finite-difference time-domain(FDTD)method, and agree well with each other. The dispersi e nature of the dielectric medium was considered for the simulation. 2001-10-05T00:00:00Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/2982 Dielectric properties of certain biological materials at microwave frequencies. Biju Kumar, S; Mathew, K T; Raveendranath, U; Augustine, P In the medical field, microwaves play a larger role for treatment than diagnosis. For the detection of diseases by microwave methods, it is essential to know the dielectric properties of biological materials. For the present study, a cavity perturbation technique was employed to determine the dielectric properties of these materials. Rectangular cavity resonators were used to measure the complex permittivity of human bile, bile stones, gastric juice and saliva. The measurements were carried out in the S and J bands. It is observed that normal and infected bile have different dielectric constant and loss tangent. Dielectric constant of infected bile and gastric juice varies from patient to patient. Detection and extraction of bile stone with possible method of treatment is also discussed. 2001-01-01T00:00:00Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/2981 Broadband coaxial cavity resonator for complex permittivity measurements of liquids Raveendranath, U; Bijukumar, S; Mathew, K T A novel cavity perturbation technique using coaxial cavity resonators for the measurement of complex permittivity of liquids is presented. The method employs two types of resonators (Resonator I and Resonator II). Resonator I operates in the frequency range 600 MHz-7 GHz and resonator II operates in the frequency range 4 GHz-14 GHz. The introduction of the capillary tube filled with the sample liquid into the coaxial resonator causes shifts in the resonance frequency and loaded Q-factor of the resonator. The shifts in the resonance frequency and loaded Q-factor are used to determine the real and imaginary parts of the complex permittivity of the sample liquid, respectively. Using this technique, the dielectric parameters of water and nitrobenzene are measured. The results are compared with those obtained using other standard methods. The sources of errors are analyzed. 2000-12-01T00:00:00Z