No abstract

A two-sided frequency selective surface (FSS) is proposed to shield two bands of the mobile frequencies (EGSM-900 and DCS-1800). The FSS consists of an array of square concentric-rings cells printed on both sides of the substrate to offer better shielding of the two mobile frequencies. The CST Microwave suit is used for the simulations. The equivalent circuit model for the two-sided FSS is analysed and the transmission frequency in terms of the two stop frequencies is estimated. The obtained shielding is better than 40 dB across the two bands. The proposed FSS can be used to reduce mobile radiation or to isolate halls from nearby mobile base stations. The bandwidth of the FSS cell can be increased by using ring pairs of unequal sizes on the two sides of the substrate.

In this paper, the possibility of synthesizing a linear antenna array for multiple objectives with the thinning approach is demonstrated. The thinning space is constrained to three cases (side, central, and random) parts instead of a fully filled linear array. In the case of the side part, a set of elements located on both edges of the array are removed with the optimized elements close to the center remaining unchanged. As in the case of the central part, only a set of elements close to the center are removed. In the case of a random selection of elements, the cancellation process is carried out randomly within the sides and the center. Since the amplitude weights of the elements located on the edges of the array have a small amplitude excitation, the method of side thinning gives better results than the other two cases. Moreover, in cases of side and random thinning, the last element of each side is excluded from the thinning process to maintain the aperture size. The convex algorithm (CA) is used to perform such thinning optimization. CA optimization efficiently computes a multi-objective function in coordination with the thinned array technique, such as preserving the main beamwidth in all cases with the reduction of sidelobe levels, generating one or more nulls, and steering the main beam in a certain direction. The simulation results, in all cases, show that 30%-40% of the array elements can be turned off with achieving a multi-objective radiation pattern.

As a result of the rapid growth in wireless communications and the increase in the number of users of cellular phones around the world, massive multi-output, and multi-input (massive MIMO) systems have been used. The main drawback of such a system is the increase in the number of antennas and the amount of energy consumed. To mitigate that the number of active antennas can be reduced to save some energy. In this paper, we will study different algorithms for choosing the suitable antennas in MIMO systems, subject to keeping an acceptable level of bit rate and energy efficiency in the system. The study will also consider the amount of complexity for each algorithm based on the consumed time to perform each algorithm in MATLAB.

No abstract