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The ionosphere is the topside of the atmosphere that contains high concentration of ions and can reflect radio waves due to refraction. The ionospheric region of interest is located above the equatorial region at longitude 1?? 52' and latitude 103?? 48' (Parit Raja, Johor). The observations of the ionospheric critical frequency were made from 2005 to 2007. The critical frequency is determined by using...
There has been much interest recently in developing reconfigurable reflectarray antenna for tunable microwave applications. Liquid crystal (LC) has been given much attention due to its dielectric anisotropy property which allows the change in the frequency and hence the phase of reflection. In this paper, the phase tunability of the periodic array using K15 nematic liquid crystal as the dielectric...
The existence of the F3-layer has been observed at Brazilian equatorial stations. This paper reports on a 1-year observations at Parit Raja, Malaysia (Lat. 1°52′N, Long. 103°48′E). The greatest number of appearances of the F3-layer is around local noon while the least is after local dawn. Its occurrence is more pronounced during winter and the equinoxes. The mean height of reflection for the layer...
In this paper, the phase agility of the patch antenna periodic array using K15 nematic liquid crystal as the dielectric medium is presented. Numerical and experimental results at X-band are used to compare the plane wave scattering parameter from a two patch antenna reflectarray cell of 500 mum. The dependence of reflection phase versus frequency and gradient on loss tangent is characterized. A tunable...
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