Abstract: A kind of novel 8×8 Butler matrix based on multilayer substrate structure is presented and realized. A bilayer substrate structure is adopted to distribute components into the up and down layer to replace crossover. Two approximate λ_g/8 stepped coupling microstrip Schiffman phase shifter is used to realize wideband phase shift. A threebranch line coupler is employed as wideband bridge. An 8×8 Butler matrix sample working in C band frequency is designed and fabricated. The measured results indicate that in the frequency range over (4.2~5.3) GHz, the return loss of each port is better than -10dB, the isolation is better than 17dB, the distribution error is less than ±1dB, the phase error is less than ±12° and the measured average insert loss is about 2.5dB. Compared with conventional structure with crossover, the novel Butler matrix has lower loss and better adaptability to large scale multibeam forming network.

Key words: Butler matrix, Multi-layer substrate, Schiffman phase shifter, Wide-band