Planar metamaterials with spiral elements are suggested in this paper to support multiple left-handed (LH) modes. Compared with previously proposed split-loop metamaterial, spiral arrays are found to support hybrid TE and TM LH modes. Dispersion diagrams and field distributions are carried out to demonstrate the existence of the hybrid LH modes. Array with double-spiral elements can be viewed as a spiral split-loop array, which leads a very interesting dual-LH-band feature. It can be explained as a combination of spiral and split-ring arrays has similar mechanism with the multiband frequency selective surfaces (FSS), which have multiple resonators in a single unit cell. The two LH modes are TE and TM modes respectively. Validations of the multiple LH modes are presented by means of full-wave simulation using commercial software (Ansoft HFSS).
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