Wideband Hybrid Using Three-Line Coupled Structure and Microstrip-Slot Transitions

The design of a wideband microwave hybrid using a combination of microstrip-slot transitions and three-line parallel coupled microstrip structure is presented. The fundamentals of operation and design of the hybrid are explained. The device requires only a single substrate to achieve an enhanced isolation, almost ideal phase performance, and a balanced power division between its ports. The simulated and experimental results of the developed hybrid show 100% fractional bandwidth assuming 20 dB of isolation as a reference and 67% fractional bandwidth assuming 10 dB of return loss as a reference. The isolation between the difference and summation ports is more than 45 dB across the band from 3 to 9 GHz. The phase characteristics are close to the ideal 180^° and 0^° with only ±1.5^° deviation across the band from 3 to 9 GHz.