as well. With the increase of li, f 2 and f 3 fall gently, and so BW 3 widens as well. However, BW 2 narrows gradually as li increases. When we desire to keep f 1 and BW 1 unchanged and want alter f 2 =f 3 and BW 2 =BW 3 , we can adjust li conveniently. Figure 10 shows that the cutting depth can affect the performances of the FSS significantly. The resonant frequencies all decline as the depth rises, although the falling tendency of f 1 are much more gentle than that of f 2 and f 3 . As for bandwidths, BW 1 presents a dropping trend as the depth rises, while BW 3 displays an opposite trend. With the increase of C d , BW 2 falls when C d is quite small ( 3.4 mm), and after that, it keeps quite stable around 2.5 GHz. Figure 11 demonstrates that the change of C w can hardly influence f 1 , yet f 2 and f 3 are impacted slightly and the bandwidths are affected sharply. While BW 1 reduces gradually and BW 3 experiences a fluctuant ascend, BW 2 jumps monotonously with the increase of C w . Thus, if we want to adjust f 2 and f 3 , but keep f 1 stable, regulating the size of the meandered strip is a good choice. The Cutting Depth of the Gap (C d ) The Cutting Width of the Gap (C w ) CONCLUSIONA novel FSS with multiband is proposed and a FSS radome with desired characteristics is manufactured in the article. Simulated results calculated by CST show that in the working band ranges, the transmission has low insert loss and presents a sharp falling down property from the in-band to out-of-band. The three pass-bands are achievably wide and has the potential to be applied to multiband antennas to sharpen the selectivity. The measured results of the fabricated prototype show good agreements with the simulated ones, which verifies the effectiveness of the proposed structure. Moreover, under horizontally and vertically polarized TE wave, the Rx antenna locates in the near field and far field to test its performances. Results validate that the FSS radome accommodates well both in near field and far field. Parametric studies show that the resonant frequencies can be adjusted conveniently by altering some certain parameters. In the later work, the structure can be altered to increase the angular insensitivity in complicated applications. ACKNOWLEDGMENTSThis work is supported by the National Science Foundation of China under Grant No. 61302017. The authors would like to thank the editor, the associate editor, and the anonymous reviewers for their valuable comments and suggestions that greatly improved this article. ABSTRACT: In this letter, the left-handed metamaterial (LH-MTM) which has a negative refractive index (NRI) is employed to improve the performance of microstrip patch antenna. The LH-MTM used in this work is a 3D periodic structure which consists of split ring resonators and thin wires (SRR/TW). The LH-MTM is placed in front of the microstrip patch antenna and due to the NRI property of the LH-MTM; the radiated electromagnetic beam size reduces which results in a highly focused beam. The proposed antenna has been designed ...

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