Coupling characteristics between composite right-/left-handed transmission line and conventional transmission line

The coupling characteristics between a composite right/left-handed transmission line (CRLH TL) with lumped-elements and a conventional right-handed transmission line (RH TL), is studied. It is theoretically shown that tight coupling is obtained when the product of the average permittivity and average permeability is negative (epsiv macr ldr mu macr < 0), at the same time the CRLH TL is still in its left-handed region ( epsiv
_L
< 0 , mu
_L
< 0 ). ADS S-parameter simulations are demonstrated to confirm our theoretical results.