Design of 2 x 8 Filtering Butler Matrix With Arbitrary Power Distribution

This brief reports a novel 2x8 filtering Butler matrix with arbitrary power distribution. The filtering Butler matrix, composed of coupled resonators, provides arbitrary power division and 0 degrees and 180 degrees phase differences as well as a fifth-order bandpass filtering characteristic. The detailed design process and synthesis method for the 2 x 8 filtering Butler matrix are reported. To validate the analysis, a 2 x 8 filtering Butler matrix with unequal power division, operating at 2.4 GHz, is devised, manufactured, and measured. The results of the simulation and experimentation are matched very well. According to the measurement results, the array factors have been calculated to further verify the performance of the Butler matrix, which show a lower sidelobe level.