Broadband Compact 180∘ Hybrid Derived From the Wilkinson Divider

A novel 180° hybrid is proposed. This hybrid is derived from the Wilkinson divider, where the resistor is simply replaced by a fourth port of equal characteristic impedance, which acts as the ¿ port of the hybrid, while the input port of the original Wilkinson divider acts as the ¿ port. Due to this structure, including only two quarter-wavelength transmission lines, this hybrid has a greatly reduced size compared with the conventional hybrid rat-race and miniaturized variants of it. Furthermore, it exhibits a significantly improved bandwidth. The measured 0.5-dB insertion loss bandwidth is over 200% for ¿ power division and 66% for ¿ power division (with 50-¿ load). Due to its perfectly symmetric configuration, the proposed hybrid features frequency-independent power-dividing balance performance. The 0.5-dB amplitude imbalance for both the ¿ and ¿ port divisions has essentially unlimited bandwidth, and the measured phase imbalance is within 3°over all frequencies. The proposed hybrid also shows excellent ¿ - ¿ port isolation with a measured result exceeding 30 dB over all frequencies.