Size reduced Marchand balun with integrated microstrip to CPW transition

A new technique for the size reduction of a Marchand balun in conjunction with the integration of additional functions is proposed in this paper. The balun is implemented using two microstrip/coplanar waveguide coupling sections of λ/8 electrical length at its center frequency. This results in a smaller size, innovative integration of microstrip to CPW transition, and the elimination of via holes to ground. For demonstration purposes, a compact broadband balun is designed for operation at 2.5 GHz, and is measured to have excellent performance over a 40% bandwidth.