Design of a Low Cost 4 4 Butler Matrix Fed Antenna Array Partially Loaded with Substrate Integrated Waveguide (SIW)

A low cost 4  4 butler matrix fed antenna array has been proposed for Ku band applications. At high frequencies, the ohmic and dielectric losses are high and also the undesired feed radiation is more in the case of microstrip line feed, therefore substrate integrated waveguide (SIW) has been used to feed the antenna elements. The implementation of SIW technology improved the radiation performance of the antenna array system. More directive beams have been achieved than the conventional design. The gain improvement of 1.63 dB and 0.9 dB have been achieved for 2L and 2R beams respectively and the first nulls of all the four major beams have improved considerably. The proposed design is not realized completely either by microstrip or by SIW technique but it combines both the techniques to minimize the design complexity of SIW technique and to improvement in the radiation performance which degrades at high frequency for microstrip feeding network. The design also leads to symmetricity in the maximum gain values of the radiated major beams. FR-4 epoxy has been used as dielectric to build up the whole antenna array system, which makes the system less costly. The single layer implementation also makes the fabrication process simple. The measured results are in good agreement with the simulation.