Size Reduction of 4 × 4 Butler Matrix Using Defected Microstrip Structure
The paper presents a design of a 4 × 4 planar Butler matrix for an operating frequency of 2.4 GHz which can be used for WLAN applications. Defected Microstrip Structures (DMSs) have been introduced with conventional microstrip line for the design of compact phase shifter. The parametric study of different size DMSs for the desired length of microstrip line has been done. Then the optimized dimension of microstrip line with DMS is calculated and simulated to obtain the required phase shift at the operating frequency. The proposed Butler matrix has been designed using glass epoxy (FR4) substrate with height 1.59 mm and dielectric constant 4.4 and simulated by method of moment (MoM) based IE3D electromagnetic simulator. The errors in phase distribution are between 2° and 7°, couplings are in the range −6.53 to −7.84 dB and various losses of the matrix are within tolerable range.
KeywordsButler matrix Crossover Coupler DMS Phase shifter Slow wave factor
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