Comprehensive Study on Phased Antenna Array Based on Conventional and Shielded Butler Matrix for 2.4 GHz Applications

In this work, a phased antenna array based on 4×4 Butler matrix is designed and simulated for 2.4 GHz applications using Roger RT 5880 as a substrate layer. CST SUIT STUDIO is used for this purpose. Two different designs of phased antenna array are simulated; the first one was based on microstrip technology, which is used to design both the feeding network (Butler matrix) and antenna array. The objective is achieved by switching the main beam to ±14̊ and ±40̊. The side lobe levels of -9.4dB and -8.2dB were obtained while the directivities were 12.4dBi and 11.5dBi when different input ports were applied. The physical size of the overall structure is about 621 cm2. An enhancement on antenna radiation pattern is obtained by using a strip line instead of microstrip line in the design of the Butler matrix. The antenna array is shielded at the top layer of the structure from the spurious radiation of Butler matrix radiation effect. The radiation pattern is obtained by making square slits on the top layer of the ground plane. The side lobe levels are reduced by 2.8dB and 0.3dB while the directivity is increased. The proposed design has deeper nulls and smaller physical size. The overall structure size is about 436.6 cm2. The scanning angle directions does not change compared with the conventional design based on microstrip technology since the spacing between antenna elements is the same in both cases. Keywords: Phased Antenna Array, Butler Matrix, Strip line, Shielded Antenna.