Microwave beam forming using frequency selective surfaces

Abstract

Phased Array radars revolutionized the defense sector which has drawn its strength from the phase array technology. The concept is based on beam forming and beam steering techniques using antenna arrays and phase shifters. The performance of phased array and microwave beamformer is realized in the design approach presented in this paper. A low loss one-to-four ports power splitter is designed in order to feed each antenna element. Targeted region can be illuminated by varying angles and precise contour of signal’s energy by use of phase shifters in between power divider and antenna array in order to form a beam. Cost effective FR-4 Epoxy substrate is used. A filter is placed behind each array element of beamformer, whose response is not sensitive to angle of arrival. Proposal technique also presents a new idea which replace band pass filters with frequency-selective surface (FSS), placed directly over the antenna array to perform the desired filtering. Feed network and phase shifter is designed in Advance Design System (ADS) whereas HFSS is used for designing and optimization of antenna and FSS. This methodology has enhanced the antenna performance characteristics such as gain, directivity, radiation efficiency and provided the beamforming features for high-speed communication applications. In transmitting systems, beamformers are used to “shape” the radiated electromagnetic field by antenna array in terms of its instantaneous field intensity in three dimensional spaces. By employing beamforming, relative spatial sensitivity of the receiver is affected to focus the receiver on a specific region or targeted area. The biggest advantage observed is swift movement of resultant beam from antenna array using electronic beam steering. The proposed beamforming technique is network-aware, and designed to increase transmission power efficiency, improve receiving signal sensitivity, mitigate interference/multipath effects, and to extend the communication range for cellular systems being used in Relay stations. The simulated and measured results are in good match.