Patent ID: 8072291

Claim:
An apparatus, comprising: a ring of composite right/left-handed (CRLH) transmission line (TL) material having both right handed (RH) and left handed (LH) characteristics; a plurality of lumped elements comprising inductances and capacitances within said LH portions of said CRLH TL; and a plurality of ports, including a sum port and a difference port, on said ring separated along a periphery of said ring by either phase delays Ï† 1 , or phase advances Ï† 2 , to form a hybrid ring coupler; wherein dual frequency characteristics of each segment of said CRLH TL arise in response to an anti-parallel relationship between phase and group velocities below a transition frequency Ï‰ 0 , within left handed material (LH) within the CRLH TL, and a parallel relationship between phase and group velocities above transition frequency Ï‰ 0 within the right-handed material (RH) within the CRLH TL; wherein said ring is compacted into a compact ring in response to constraining phase delay contributions to |Ï† 1 |, |Ï† 2 |â‰¦270Â°, and configured to operate in at least two frequency bands comprising a first frequency band f 1 and a second frequency band f 2 ; and wherein said LH portion further comprises stepped impedance sections in the TL segment corresponding to phase Ï† 2 , said stepped impedance sections tuned toward compensating for self-resonant effects of the lumped elements.