| The antenna is widely used since the mobile communication is developing rapidly. In majority of the antennas, microstrip antenna is becoming the most popular antenna because of its light weight, low section, low cost, easy to conformal with the carriers and can be integrated with active circuits, and a lot of new microstrip antennas are appeared. At present, the microstrip antenna is applied in lots of areas such as plane, mobile communication, medicine, and so on.In recent years, the resource of spectrum is becoming more and more seldom as the development of mobile communication. The antenna can enlarge new band and is compatible with multi-antenna is required to increase the number of channel. The size of traditional half-wavelength microstrip antenna is still large while the mobility termination has to be much smaller. Narrow band is still a disadvantage which needs to be resolved in microstrip antenna. So the researching emphases of this paper are miniaturization, double-frequency and broad band technology.The first two sections introduce the history, characteristic, application and the developing situation of microstrip antenna, and describe the basic concept, analyze method, simulation software and testing instrument, too. The third section introduces three popular technologies of microstrip antenna which are the implementing of miniaturization, double frequencies and broad band technology. Three double-frequency microstrip antennas are designed on the basis of foregoing theory in the 4th and 5th part of this paper. The first dual-frequency antenna is a loaded U-slot Inverted-F antenna, which can work on the frequencies of GSM 900/DCS 1800. In the design of PIFA, with the adoption of the technologies, such as surface slotting and loaded short-circuit wall, the bandwidth enhancement and size reduction of the antenna were realized. At the same time, depending on the simulation software HFSS, the effects of different dimensions of the slot and short-circuit wall on the return loss were discussed in detail, and the parameters of the antenna were determined. The antenna covers the frequency bands of 855-935MHz of GSM 900 and 1720-1900MHz of DCS 1800. Another two antennas are microstrip slot antennas which can operate at the dual frequencies of WLAN. The first rectangular slot loop antenna at upper-frequency bandwidth obtained wide bandwidth(4.50GHz-5.50GHz), but it was at low-frequency matching and bandwidth were not ideal, we optimized the design, and another microstrip slot antennas operating at the dual-frequency bands of WLAN was presented in this paper. Through the simulation of the antenna, it is found that the antenna's bands are 2.40-2.57GHz in the lower band and 5.12-5.36GHz in the upper band, and which cover the bands of the IEEE 802.11a and IEEE 802.11b protocols of WLAN. According to the design of those double frequencies terminal microstrip antennas, the miniaturization, double frequencies and broad band technology are analyzed and validated, which provide theory and practice data to the design of project.At last, the design of microstrip antenna were all produced and tested in this paper, the outcomes of test and simulation were compared and analyzed concretely. |
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