In this paper, compact microstrips patch Antenna (MIPA) whose size is reduced via the use of metamaterials is presented. When CSRR are placed, the shift in the resonant frequency to a lower value is promising because it suggests a reduction in patch size. Complementary Split-Ring Resonator (CSRR) is used instead of Split-Ring Resonator (SRR). Equivalent circuit model to characterize the complementary Split Ring Resonator in metamaterials is presented. By using the circuit model, it is shown that the use of a metamaterial can indeed greatly miniaturize the dimensions of the patch antenna.
There is a very tricky problem in Antenna design. Common designs are sensitive to only a narrow range of frequencies, and if they are smaller than a quarter of the wavelength, they are not efficient. This is a problem for small, portable antennas such as those on cellular phones. Fractal antenna designs can be used to overcome some of the these problems. Researches have shown that antennas built with only a small number of iterations of a fractal process can exhibit sensitivity at several frequencies. As the number of iterations increases, the lowest frequency of the antenna gets lower, and additional higher frequencies are added. There are several common fractal for square loop antenna miniaturization using fractal geometry, such as Koch & Minkowski fractal. In this paper, for more miniaturization, we present a fractal model that allows an increase in the total electric length without occupying more space. This led to an easily matched compact loop antenna, but with a small sacrifice of the gain.
This paper addresses conformal array synthesis as a constrained multiobjective optimization problem. Simultaneous reduction of side lobe level (SLL) and cross-polarization (XPL) level is aimed with a constraint on main beam direction. A hybrid of weighted alternating reverse projection (WARP) and two local best multiobjective particle swarm optimization (2LB-MOPSO) is proposed to optimize the pattern. First, the WARP method finds a moderate and feasible solution. Second, 2LB-MOPSO begins with an initial population including the solution of WARP and penalty functions for constraint handling. Involving WARP result in the initial population of 2LB-MOPSO leads to higher convergence rate, avoiding local extermum traps and less sensitivity to penalty functions. Compared to WARP method which stagnates rapidly, the proposed hybrid method gives better SLL and XPL after adequate iterations. In addition, as 2LB-MOPSO offers a set of optimum solutions (Pareto front) instead of a single solution, this method provides more degrees of freedom in selection of proper practical arrays. Finally, to examine the mutual coupling consideration in array design, the same procedure was applied ignoring the mutual coupling between elements. The results show that the SLL and XPL strongly depend on mutual coupling.
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