Lucas S. Pereira

Synthesis of the radiation pattern of retrodirective antenna arrays using the Particle Swarm Optimization algorithm

This paper presents a study of radiation pattern synthesis for retrodirective arrays for mobile communication services in a scenario using high altitude platforms (HAPs). For this purpose, a dual-band and dual-polarization microstrip antenna array has been designed, whereby the array should receive the signal in one band and resend it in the other operating band. The radiation pattern in the receiving mode has been synthesized with the Particle Swarm Optimization (PSO) algorithm, which allowed steering the main beam and controlling the side lobe level. In order to assess the performance for practical implementation, a study on the impact of the magnitude discretization due to the use of digitally controlled variable-gain amplifiers on the radiation properties of the array in receiving mode was carried out. The results show that the performance is slightly affected by limitations on the RF circuitry for practical implementation.

Beam-shaped radiation pattern for uniform radiated power distribution

This paper presents the application of optimization methods for the synthesis of antenna arrays. The desired pattern shall exhibit a shape that allows uniform distribution of the radiated power on the Earth. Besides beamshaping, the optimization methods allow controlling the level of the sidelobes. The synthesis technique is used to calculate the excitation coefficients for arrays composed of cavity-backed circularly polarized annular slot antennas.

Annular slot antenna for high-precision GPS applications

This paper presents the design of a printed antenna with annular slot geometry for GNSS applications. Two prototypes were built in order to meet the requirements of these systems. Different feeding techniques have been proposed in order to obtain the right-hand circular polarization. Electrical walls were added in the prototypes to avoid losses by parallel plate modes, to improve the radiation efficiency, gain and axial ratio. The proposed geometries were designed and built with two different feeding schemes: the first one is based on a series feed, whereas the other is based on the integration of a 90°-hybrid. The results showed that the synthesized antenna has all features required to operate in the Global Navigation Satellite Systems (GNSS).