Zeroth-Order and TM$_{10}$ Modes in One-Unit Cell CRLH Mushroom Resonator

In this letter, the zeroth-order and 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 TM
₁₀
mode of the unit-cell. This 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 0.19λ×0.09λ×0.014λ while achieving a gain and an efficiency of -0.82 dBi and 46%, respectively.