Compact Coplanar Filters Using Resonators with Left-Hand Characteristics

Recently many designs on the left-handed transmission lines and resonators have been reported whose equivalent circuit is composed of series capacitors and shunt inductors. Using this concept, this paper introduces a method to miniaturize coplanar resonators. The size of a filter using such resonators can be significantly reduced, while the usual ways to miniaturize resonators can still be applied at the same time. To demonstrate the theory, a four-pole filter is designed and tested. The experimental results agree with the theoretical ones very well. The equivalent circuit of the resonator is also extracted to explain the left-handed characteristics of the resonators, and the analytical results agree very well with the simulated and measured responses