Zeroth-Order and TM<formula formulatype="inline"><tex Notation="TeX">$_{10}$</tex></formula> Modes in One-Unit Cell CRLH Mushroom Resonator

Abstract

In this letter, the zeroth-order and ${{\rm TM}_{10}}$ modes of composite right/left-handed (CRLH) mushroom resonator are investigated with regards to the number of cells. It is shown that in addition to $2N - 1$ metamaterial resonance frequencies in an $N$ -cell mushroom resonator, there is also a resonance which belongs to ${{\rm TM}_{10}}$ mode of the unit-cell. This ${{\rm TM}_{10}}$ mode is the fundamental mode of the patch which occurs at a frequency above metamaterial resonance frequencies. These two types of resonance frequencies yield $2N$ resonances in an $N$ -cell CRLH mushroom resonator. This is beneficial especially in one-unit cell case due to dual-band operation. To investigate this feature, three types of mushroom resonant antennas with different number of cells ( $N = 3,2,1$ ) are designed and implemented. Based on theoretical investigation, a single-cell dual-band CRLH mushroom resonant antenna is proposed. At the zeroth-order mode (2.88 GHz), the proposed antenna has a dimension of approximately $0.19\lambda \times 0.09\lambda \times 0.014\lambda$ while achieving a gain and an efficiency of $ - 0.82~\hbox{dBi}$ and 46%, respectively.