A Compact mmWave Butler Matrix for Wireless Power Transfer

A compact $4\times 4$ butler matrix at 30 GHz is designed, fabricated and measured for wireless power transfer applications in microstrip configuration. The 90°hybrid coupler is designed with two cross slots of different lengths. The crossover is realized using a ring and cross junction. The coupler and crossover are designed and analyzed. The butler matrix is verified by both the simulated and measured results.