"Novel Zeroth-Order Resonance
in Composite Right/Left-Handed Transmission Line Resonators," Asia-Pacific Microwave Conference, 2003.
The dispersion diagram shows that zeroth-order resonance occurs at 2.45 GHz.
The proposed CRLH unit cell is measured at only 0.12[[lambda].sub.0] x 0.098[[lambda].sub.0] x 0.007[[lambda].sub.0], where [[lambda].sub.0] is the free-space wavelength at the zeroth-order resonance. In addition, the antenna footprint is measured at 0.12[[lambda].sub.0] x 0.278[[lambda].sub.0] for prototype (A) and 0.12[[lambda].sub.0] x 0.196[[lambda].sub.0] for prototype (B), which are extremely compact.
For the zeroth-order resonance of an open-ended boundary condition, the input impedance is given by 
Because [Z.sub.in] can be expressed by the impedance of the LC anti-resonant tank, the zeroth-order resonance frequency is given as
Therefore, zeroth-order resonance occurs when the MTL has zero permittivity at non-zero frequency.
Lee, "Omnidirectional circularly polarized antenna utilizing zeroth-order resonance
of epsilon negative transmission line," IEEE Trans.
It should be noted that stop band of the ENG or DNG TL element can also be engineered for antenna design in the case of an open circuit (infinitely large series impedance) or a resonance of the shunt branch (often referred to as the zeroth-order resonance
(ZOR)) in the equivalent circuit model, which will be discussed in the upcoming section.