Broadband Compact Single-Layer Magic-T Junction with Separation of DC Signals between All Ports

Abstract

A novel structure for a four-port microstrip magic-T junction is presented. The device is composed of microstrip and slotline circuits etched onto two sides of a dielectric substrate. The device is extremely compact and occupies an area more than three times smaller than similar structures recently reported in the literature. The novelty of the device lies in the use of microstrip/slotline transitions for both input ports: summation (in-phase) port and difference (out-of-phase) port. This ensures electrical separation for DC signals between all four ports, a wide operation band and a very small size for the device. The fabricated prototype operates in a 95% fractional bandwidth with reflection losses better than 10 dB and isolation between input ports better than 35 dB. The insertion losses for the excitation at the summation port are about 0.8 dB and for the excitation at the difference port are about 1.4 dB. In the operation band of the device, the maximum amplitude imbalance is equal to +/-0.3 dB, whereas the maximum phase imbalance is equal to +/-4 deg.