The microstrip reflectarray antenna is a microstrip patch element planar array, which reflects the incident fields radiating from a feed antenna. Each patch element introduces a phase change to the scattered fields. In this paper, the scattering of the incident plane wave to a microstrip infinite array which performed by similar microstrip patch elements has been investigated. Determination of the reflected fields phase shift is desired. Finite Difference Time Domain (FDTD) method has been employed to calculate the phase shifts. At first, the infinite array configuration is converted to an equivalent unit cell configuration consisting only one radiator element using PEC and PMC walls around it. Then, a TEM plane wave excitation has been introduced for this equivalent waveguide structure and the reflected fields phase shift is determined by discretization of time domain Maxwell's equations and applying FDTD method.
In this paper, design of a turnstile antenna in UHF band (465 MHz) is carried out. In this design the initial values for monopole lengths and their distances have been considered / 4 λ and for antenna mounting angles to be 90 degree respect to ground plane (satellite body). The effects of monopole lengths, distances and mounting angle variations studied by antenna modeling with Finite Elements Method (by HFSSV10). The results show that increasing monopole lengths, achieving sharper saddle shaped pattern and decreasing antenna mounting angles, making smoother radiation pattern. For monopoles distances, variation about 10 % around / 4 λ does not affect the radiation pattern, obviously. In this article, optimum values for aforementioned main parameters obtained by search method. The designed antenna with optimum values parameters fabricated and tested. The results represent a good agreement between simulation and measurement.
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