Design of Wideband Impedance Transformers with Different Number and Different Mounting Positions of the Shunt Stubs

Abstract

In this paper, a novel design method of wideband transmission line impedance transformers is proposed. All the circuit parameters are determined by a self-coded optimization program based on our derived formulas and an appropriately defined objection function. Three microstrip impedance transformers using different number and different mounting positions of the shunt short-circuited stubs are designed with a center frequency of 4.0 GHz and a Chebyshev equal-ripple fractional bandwidth of 80.0%. The measured results agree well with the predicted ones, showing that the proposed design method has adequate freedom in choosing both the number and the mounting positions of the short-circuited stubs, and novel wideband transmission line impedance transformers can be developed with many different configurations.