A compact 4 × 4 butler matrix on double-layer substrate

ABSTRACT A novel 4 × 4 Butler matrix (BM) on double‐layer substrate is presented. The design of the multilayered BM configuration successfully removes the need for a crossover component by utilizing a double‐layer substrate structure. With the elimination of the crossover, space consumption by the microwave circuit of the BM is reduced significantly. The BM is developed by means of four proposed 3‐dB compact couplers using dual transmission lines on a double‐layer substrate and two 45° phase shifters. The proposed BM components are designed using CST Microwave Studio 2010 and fabricated using inexpensive FR‐4 substrate to operate at 2.45 GHz. The simulated and measured performances in terms of S‐parameters and phase differences for each 3 dB coupler, 45° phase shifter, and BM are presented. Good agreement in beam direction results between the MATLAB (matrix laboratory) simulator and measurement is accomplished with a deviation of ±8°. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:223–229, 2014