Impedance Transforming Tandem Couplers With Increased Bandwidth and Transformation Ratio

A novel concept of impedance transforming directional couplers for applications in balanced networks has been proposed. The proposed networks consist of a tandem connection of two asymmetric directional couplers having different coupling coefficients. Theoretical analysis of the proposed networks has been shown and the maximum achievable transformation ratio versus the required reflection coefficient has been given in a tabular form. The concept has been verified by measurements of an impedance transforming directional coupler operating at the center frequency 1 GHz, in which impedance transformation ratio equal R = 5 has been assumed.