диафрагмированные волноводные фильтры / 0f3a5702-9a20-41ab-9046-ed352fa9947d

Fig. 20. Modified design of the FSS shown in Fig. 14 and simulated -pa- rameter results. (a) Side view of a unit cell. (b) Equivalent circuit model.

(c) -parameter results.

at low frequencies decreases because a full power transmission occurs at zero frequency. Fig. 20(a) shows a further improved design of the FSS shown in Fig. 14, where one end of the air path is connected to the top PEC by a strip/wire. Its equivalent circuit model is illustrated in Fig. 20(b), where the shorted end of the air path is represented by an inductor . This inductor can be calculated by [26]

(11)

where and denote the length and width of the short-circuited strip/wire. The thickness of this strip/wire is ignored. Based on the width 3.2 mm and length

results using CST-MWS as well as those from the equivalent circuit model. It is seen that a transmission zero at zero frequency is introduced besides two transmission zeros around 3 and 13.5 GHz.

VI. CONCLUSION

Two 3-D bandpass FSS have been presented based on a 2-D periodic array of shielded microstrip lines and metallic structures (such as rectangular metallic plates and “T-type” metallic pieces). When the -field of an incident wave is perpendicular to the strips, multiple resonators are constructed in these FSSs. Unlike many traditional 2-D FSSs, these 3-D FSSs can provide

more transmission zeros in the operating band, leading to high selectivity and wide out-of-band rejection.

Although the proposed FSSs are only for single polarization, the presented concept may be readily extended to realize a dual-polarized FSS. This can be achieved by placing two orthogonally oriented strip lines in a square unit cell. The thickness of our proposed structure can also be reduced further by using stepped-impedance line resonators and lumped components [19].

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Zhongxiang Shen (M’98–SM’04) received the B.Eng. degree from the University of Electronic Science and Technology of China, Chengdu, China, in 1987, the M.S. degree from Southeast University, Nanjing, China, in 1990, and the Ph.D. degree from the University of Waterloo, Waterloo, ON, Canada, in 1997, all in electrical engineering.

From 1990 to 1994, he was with Nanjing University of Aeronautics and Astronautics, Nanjing, China. He was with Com Dev Ltd., Cambridge, Canada, as an Advanced Member of Technical Staff in 1997. He

spent six months each in 1998, first with the Gordon McKay Laboratory, Harvard University, Cambridge, MA, USA, and then with the Radiation Labora-

Jun. 1991.

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[26]F. E. Terman, Radio Engineering’s Handbook. New York, NY, USA: McGraw-Hill, 1945.

Bo Li was born in Hunan, China, in 1984. He received the B.S. and Ph.D. degrees from Nanjing University of Science and Technology, Nanjing, China, in 2006 and 2011, respectively, both in communication engineering.

Currently, he is a Research Fellow with Nanyang Technological University, Singapore. His research interests include RF/microwave power dividers and frequency-selective surfaces.

sistant Professor and then as an Associate Professor with the School of Electrical and Electronic Engineering since January 2004. He has authored or coauthored more than 110 journal papers and another 100 conference papers. His research interests include the design of small and planar antennas for various wireless communication systems, analysis and design of frequency-selective structures, and hybrid numerical techniques for modeling RF/microwave components and antennas.

Dr. Shen is a member of the IEEE Antennas and Propagation Society (IEEE AP-S) and the IEEE Microwave Theory and Techniques Society (IEEE MTT-S). He served as Chair of the IEEE MTT/AP Singapore Chapter. He currently serves as the Chair of the IEEE AP-S Chapter Activities Committee.