Differential dual-band impedance inverter with common mode suppression based on composite right/left handed (CRLH) transmission lines

In this work, a differential dual-band impedance inverter with common mode rejection operating at f
₁
=1.8GHz (GSM band) and f
₂
=2.4GHz (ISM band) is presented. The designed impedance inverter is based on a Π-type differential composite right/left handed (CRLH) transmission line implemented in microstrip technology through semi-lumped resonators; that is, stepped impedance resonators (SIRs) for the shunt branch, and interdigital capacitors series connected to inductive strips for the series branch. The device exhibits its functionality at the design frequencies, with a common mode rejection ratio (CMRR) better than 35dB. The total occupied area of the common mode suppressed differential dual-band impedance inverter is 0.37λ×0.27λ (where λ is the guided wavelength at f
₁
).