Dual-Frequency Impedance Transformer with Ultra- High Impedance Transformation

A new dual-band impedance transformer with ultrahigh impedance transformation ratio (UHITR) at the two uncorrelated frequencies is proposed in this paper. The impedance transformer is equipped with two open/short shunt stubs which enhance the impedance transformation capability. The analytical expressions make it quick to design and then the presented design cases with ultrahigh impedance transformation demonstrate the easy microstrip line realization of the prototype. Finally, the proposed technique has been validated through a prototype developed on RO4003C for a high-frequency ratio of 4 and an impedance transformation ratio of 5. The measured return loss of approximately 20dB with good bandwidth at both the design frequencies is in good agreement with the simulation results.