Abstract
An aperiodic reconfigurable microstrip antenna array is designed to serve as a DVB-T base station antenna operating in a single broadcasting channel. The antenna array is optimized at 698 MHz (center frequency of DVB-T channel 49) to concurrently achieve a particular radiation pattern shaping with high forward gain, main lobe tilting and null filling inside the service area, as well as low sidelobe level outside the service area, and low standing wave ratio at the inputs of all the array elements. To concurrently satisfy all the above requirements, both the geometry dimensions and the array feeding weights (amplitudes and phases) are optimized, thus leading to a complex multi-variable and multi-objective problem. The problem is solved by applying a recently developed particle swarm optimization (PSO) improved variant, called PSO with velocity mutation, in conjunction with the CST software package, which is employed by the PSOvm every time a full-wave analysis is required. Furthermore, all the optimization methods found in the CST environment are compared with the PSOvm. The results show that the PSOvm is capable of producing an antenna array geometry, which is closer to the predefined requirements than the geometries derived by the rest of the optimizers, in the least amount of computational time.
Highlights
Microstrip antenna arrays are very popular as they are low cost and fabricated antennas, and can be used as base station antennas for broadcasting
N =1 where forward gain (FG) is the array gain at θ = 93◦ which ensures gain maximization and the desired main lobe tilting by 3◦, Gmin is the minimum gain inside the service area, SLL1 represents the sidelobe level (SLL) inside the angular sector from θ = 0◦ to θ = 80◦, SLL2 is the SLL inside the sector defined from θ = 150◦ to θ = 360◦ and SWRn represents the standing wave ratio (SWR) at the input port of the nth element
It must be stressed that the optimization algorithm is tasked to achieve 13 objectives in total, FG maximization and main lobe tilting by 3◦, null level −20 dB, SLL reduction in two sectors SLL1 and SLL2, and 8 SWR values by optimizing 26 parameters solving a highly complex multi-objective and multi-variable problem
Summary
Microstrip antenna arrays are very popular as they are low cost and fabricated antennas, and can be used as base station antennas for broadcasting. An improved PSO algorithm has been used in Reference [12] to design an aperiodic antenna array with low SLL, minimum half power beamwidth (HPBW) and nulls in desired directions. The AMAA has been fully modelled and simulated in CST Studio Suite (CST on) and the mutual coupling and the element pattern of each array element is considered since full wave analysis is performed This is really important as it makes the results quite realistic. For each fitness evaluation the antenna array model is updated and a full wave analysis is performed by applying the time domain solver of CST. This solver uses the finite integration technique [18] to solve the electromagnetic problem. To the best of the authors’ knowledge, evolutionary algorithms have never been applied so far to design an AMMA for broadcasting applications in conjunction with CST
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