| With the development of the wireless communication, more and more challenges have been brought to antenna designs. In domains of mobile communication and satellite communication, compact and multi-frequency antennas are popular in order to decrease the cost and increase the integration level. While the required integration level is so high that multi-frequency antenna couldn't satisfy the band requirement of the communication terminals, ultra-wideband antennas are attracting more and more research. Microstrip antenna has lots of strengths, such as small size, low cost, easy fabrication and easy integration, and these strengths promise that microstrip antenna is suitable to be used to design compact, multi-frequency and UWB antennas, so microstrip antenna wins more and more research and applications.First, this article introduces some theoretical methods and numerical methods to analyze microstrip antenna and sum up some techniques for miniaturization, multi-frequency and broadening the band. Then, by doing research on multi-frequency principle of an H-shaped microstrip antenna, this article gives a set of formulas to compute the resonant frequencies of the microstrip antenna with perfect symmetrical structure. With the help of the formulas, two dual-frequency microstrip antennas are designed, including an H-shaped antenna suitable for TD-SCDMA communication and a double-E antenna suitable for WiMAX/WLAN application. At last, a compact UWB planar antenna with triple band-notched performances is designed to satisfy the ultra-wideband communication. This UWB antenna could accord with the UWB standard established by FCC in 2002 with impedance band from 3.05GHz to 23.8GHz. In addition, the triple band-rejection performances of 3.4 to 4.0 GHz, 4.92 to 6.0 GHz and 7.8 to 8.6 GHz could avoid the interference from 3.4-3.7GHz in WiMAX, 5.15-5.825GHz in WLAN and 8.025-8.4GHz in satellite communication issued by ITU, so this antenna is valuable for industrial application. |
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