Broadband Compact 180 Hybrid Derived From the Wilkinson Divider

摘要

A novel 180$^{circ}$ 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 $Delta$ port of the hybrid, while the input port of the original Wilkinson divider acts as the $Sigma$ 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 $Sigma$ power division and 66% for $Delta$ power division (with 50-$Omega$ 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 $Sigma$ and $Delta$ port divisions has essentially unlimited bandwidth, and the measured phase imbalance is within 3$^{circ}$ over all frequencies. The proposed hybrid also shows excellent $Sigma-Delta$ port isolation with a measured result exceeding 30 dB over all frequencies.