Dual Band Complex to Real Impedance Matching Through Dual Band Quarter Wave Transformer

In this paper, a novel technique to match Frequency Dependent Complex Loads (FDCLs) to real source impedance at uncorrelated dual frequencies is presented. The impedance transformation occurs in two steps. In the first step, the load susceptances are cancelled through stubs. The left behind unequal real loads are then transformed to Z0 through dual band quarter wave transformer. In this article, the strength of a combination of open-short stubs and T-section branched stub to cancel any two arbitrary susceptances at two frequencies is thoroughly studied. Also a novel technique to transform two unequal real loads to the port impedance, Z0 is proposed. The scheme allows concurrent operability. The complete mathematical description of all the proposed structures with closed form solutions are provided. Two prototype matching networks for frequency ratios 2.875 and 4.8 are designed and implemented on ROGERS RO4003 substrate having dielectric constant of 3.38 and substrate height of 20 mils. The simulated and the measured results are in a good accordance.