Bandwidth comparison of various types coplanar microwave ring hybrids

The paper deals with some parameters of microwave ring hybrids mainly from their attainable frequency bandwidth. Selected parameters are especially coupling (C), insertion loss (IL), isolation (I), input VSWR and corresponding bandwidth. We investigated various planar ring hybrids realized in microstrip, coplanar waveguide (CPW), conductor-backed coplanar waveguide (CB-CPW), and CPW-slotline technology, respectively. All couplers are designed for center frequency of 3 GHz and 3 dB coupling. Various hybrids were simulated and compared with measured experimental results.