Transmission Zero Embedded Dual-Band Impedance Transformer With Three Shunt Stubs

This letter presents a dual-band impedance transformer with three shunt stubs. The considered load has frequency-dependent complex impedance at two uncorrelated frequencies. The functions of the three shunt stubs are compensating for susceptances at two frequencies simultaneously, generating an additional transmission zero at the desired frequency, and eliminating the need to use transmission lines with extremely high or low impedance. The required circuit parameters are all obtained using the derived analytical design formula. Simulations agree closely with measurements and validate the developed structure as well as the design process.