Balanced ring hybrid with arbitrary power division ratio

Abstract

A balanced ring hybrid with arbitrary power division ratio is proposed. By embedding four half-wavelength microstrip lines in the traditional single-ended ring hybrid, the functions of differential-mode power division, common-mode suppression, arbitrary power division ratio and port isolation can be achieved at the same time. Higher power division ratio also can be obtained compared with traditional single-ended design for the achievable maximum characteristic impedance of 120 &x3a9;. A simplified analysis process is proposed by making the balanced port equivalent to a new single-ended port. To verify the theoretical prediction, one prototype with a power division ratio of 4 : 1 and a size of 0.59 &xd7; 0.56<italic>&x3bb;</italic>_g (<italic>&x3bb;</italic>_g is the guided wavelength at the centre frequency) is measured and compared with the reported designs. The measured results exhibit the minimum insertion loss of &x223c;0.2 dB and the operating bandwidth for |<italic>S_dd</italic>_AA| &lt; &x2212;15 dB of 20.9%.