Design of a branch line coupler with arbitrary impedance for unequal power division

In this paper design and analysis of a balanced branch line coupler is presented with arbitrary impedance. Branch line coupler is configured by four quarter wavelength transmission line. The design achieved desired functions of branch-line coupler for differential-mode and common-mode signal with the merits of a simple configuration and a design method, low insertion loss, and low cost. Design parameters present in the equations provides two degree of freedom. In this paper, power at the output ports is considered as a known parameter. The power division is obtained at the output using impedance values. Isolation achieved for the unequal power division is less than 20dB. A good agreement is obtained between numerical and full wave electromagnetic simulation results.