Modelling and Validation of a Compact Planar Butler Matrix by Removing Crossover

In this work a compact planar butler matrix is presented by removing the 0 dB crossover. The proposed butler matrix consists of 45 degrees and 90 degrees phase shifter, and four branch line coupler miniaturised by employing open stubs in each transmission line. As the crossover is removed from the circuit, the circuit size is reduced and the performance is enhanced compared to the conventional Butler matrix. The response obtained from the newly designed butler matrix is comparable to the conventional butler matrix which is operated at 2.5 GHz. The size occupied by the proposed butler matrix is 2.01 lambda(g) x 1.13 lambda(g). A phase difference of +/- 45 degrees and +/- 135 degrees is obtained between the output ports with a maximum of differential phase tolerance of 3 degrees and S-parameter magnitude with a leeway of +/- 1.5 dB from the theoretical results. As the phase tolerance is within the acceptable limit of bandwidth region, so the interference in beams is found negligible. The measured result and simulated result is in accord. The planar circuit of very low cost with good performance can be used to provide feed to an antenna array system.