A dual-band tandem coupler with an arbitrary coupling coefficient

A novel dual-band tandem coupler with an arbitrary coupling coefficient is proposed and experimentally proved in this paper. The coupler consists of a typical tandem coupler and an additional transmission line placed between the two pairs of coupled lines. The coupler has a simple structure and can realize arbitrary coupling coefficients over two designated frequencies. Design equations are derived for designing the parameters of the proposed coupler. A prototype of the proposed coupler which operates at 0.9/1.5 GHz with -6dB coupling coefficient is designed, fabricated and measured. The measured results agree well with the EM simulated results.