Continuously tunable concurrent dual-frequency impedance matching network

A concurrent dual-band resistive impedance matching network is presented that allows simultaneous tuning of both its matching frequencies. The structure is based on single shunt stub based impedance transformer, wherein, a tuning element is appended to the stub's open end. The concept is established through an experimental prototype for an arbitrary resistive load of 22-Ω with an RF varactor diode as the tuning device. The fabricated circuit exhibits fractional frequency tuning of 20% and 6% in the lower and the upper matching bands, respectively.