Mathew, K T; Biju Kumar, S; Anil, Lonappan; Joe, Jacob; Jacob, Samuel; Thommachan, Xavier; Thomas, Kurian(Elsevier Science, October , 2002)
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Abstract:
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.
Biju Kumar, S; Aanandan,C K; Mathew, K T(John Wiley & Sons, October 5, 2001)
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Abstract:
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.
Biju Kumar, S; Mathew, K T; Raveendranath, U; Augustine,P(lnternational Microwave Power Institute, 2001)
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Abstract:
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.
Raveendranath, U; Bijukumar, S; Mathew, K T(IEEE, December , 2000)
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Abstract:
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.
Sebastian, Mathew; Joe, Jacob; Joseph, V P; Bijukumar, S; Raveendranath, U; Mathew, K T(John Wiley & Sons, March 5, 1999)
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Abstract:
This paper presents the design of a new type of corner reflector (CR) antenna and the experimental investigation of its radiation characteristics. The design involves the addition of planar parallel periodic strips to the two sides of a CR antenna. The position, angular orientation, and number of strips have a notable effect on the H-plane radiation characteristics of the antenna. Certain configurations of the new antenna are capable of producing very sharp axial beams with gain on the order of 5 dB over the square corner reflector antenna. A configuration that can provide symmetric twin beams with enhanced gain and reduced half-power beam width (HPBW) is also presented.