Miniaturized and enhanced bandwidth Marchand balun using CSRR

Abstract A novel and miniaturized Marchand balun is proposed using two quarter‐wave edge coupled transmission line and two complementary split‐ring resonators (CSRR) unit cell in the ground plane. These coupled lines are joined with the help of an uncoupled microstrip line. The short circuit and open circuit terminations are assigned at the specified ports. Two rectangular shaped CSRR cells improve the circuit performance. A step impedance technique has been applied at the balanced ports to enhance the bandwidth. This proposed design produces a fractional bandwidth of 18.75% at the centre frequency with a maximum magnitude and phase imbalance of 0.56 dB and 0.85°. This design occupies a total circuit area of 0.515 λg (30.72 mm) × 0.279λg (16.63 mm). The circuit has been designed at 2.4 GHz centre frequency using low‐cost FR4 substrate material. The simulated and measured results are in acceptable accord in terms of magnitude and phase response.