Balanced ring hybrid with arbitrary power division ratio

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 Ω. 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 × 0.56λ g (λ 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 ∼0.2 dB and the operating bandwidth for |Sdd AA| < −15 dB of 20.9%.