| In recent years, mobile communication systems are being developed more and more rapidly. To meet the demand of multi-frequency wireless communication systems, there are more and more studies focus on the compact multi-frequency or broadband antenna. Microstrip antenna become a desirable candidate because of its compact size, low profile, low weight, and ease to fabricate and be integrated with other microwave circuits Therefore, dual-band microstrip antennas have been intensively investigated in this thesis .First, we analyze the basic principles of microstrip antenna and the cavity-mode theory. Then, some typical structures of dual-frequency microstrip antenna technology have been studied extensively to figure out dual-frequency radiation mechanism and corresponding characteristics.Next, a dual-band structure with a bending slot along the non-radiation side has been investigated in detail. Parametric analyses have been conducted to study the dual-band radiation mechanism and obtain the relationship between desirable operating frequencies and dimension parameters. Based on above analysis, a dual-band microstrip antenna and a broadband microstrip antenna have been elaborately designed and fabricated. The dual-band antenna operates at 12GHz and 14GHz with the bandwidths of 3.3% and 2.85%, respectively. The bandwidth of broadband microstrip antenna even exceeds 9%.Finally, a design of dual-band PIFA has been provided for application in mobile communication systems. For given dimensions, a slot in ground grooves and a parasitic meander line are introduced to achieve broadband characteristic with two bands: 815MHz-945MHz and 1540MHz-1990MHz. With further improvement, the antenna can be utilized in mobile communication terminal systems for both transmitting and receiving. |
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