| In recent years, with the rapid development of wireless communication systems, the antenna which can receive and transmit wireless signal has been a qualitative development. In the course of development, increasingly broad range of applications of the antenna, such as smart home system, wearable wireless communication devices, smart mobile devices, as well as the number of wireless communication users quickly growth and frequency range was developed with the use of different communication. These make the antenna direction of development close to the broadband and dual-band or multi-band. With the development of the portable communication device at the same time, also requires the size of the antenna can be as small as possible. Because of the advantages such as: low profile, small size, easy to integrate and easy to realize multi-frequency, the microstrip antenna has because one of the most important one in the family of antennas, and also became one of hot researches at present. But the bandwidth of the microstrip antenna is too narrow and it cannot be used to meet some of the specific situation. In order to solve the narrow bandwidth and using at different situations, this paper mainly studies compact wide-band and dual-band microstrip antenna. Firstly, this article introduces the history and current development of microstrip antenna in domestic and foreign, and also learn the methods to research and design the microstrip antenna. Then it introduces the basic theory of microstrip antenna. It also describes several analytical methods and some of the basic parameters that including radiation parameters and electrical parameters to design a microstrip antenna. And this article outlines some ways to realize the compact wide-band and dual-band microstrip antenna. Finally, this paper designed two compact wide-band and dual-band microstrip antennas, respectively, aiming at the WLAN band. Then using High Frequency Structure Simulator(HFSS) to simulate and optimize them, and also using Network Analyzer to measure them.Based on the above analysis, this paper designed two wide-band microstrip antennas: for the first one, its rectangular patch has slot and corner, so it can realize compact and broadband; for the second one, it reduces the antenna size by load short-wall for E-shaped microstrip antenna, and using U shaped ground-plane to increase the antenna’s gain. These two antennas operate in 2.45 GHz and 5 GHz frequency band, respectively. The simulated results showed that the antenna impedance matching is good, and the simulated 10 d B bandwidth for return loss is from 2.2864GHz~2.73GHz(443.6MHz,19%) and 4.83GHz-6.92GHz(2090MHz,40%), respectively. The simulated gain is about 7d B and 4d B respectively.In order to meet the requirements of WLAN band, this article designed two dual-band microsrtip antennas. For the first one, its patch has two symmetrical Uslot, so the antenna can operate in two different modes. The simulated and measured results show that its operating bandwidth are WLAN 2.45/5.8/5.5 GHz, and the 10 d B bandwidth for return loss is 14.69%(2.27~2.63 GHz) and 7.22%(5.47~5.88 GHz) for the low and high resonant frequency band, respectively. For the second one, it realizes dual-band by loading resonant branches. Its operating bandwidth are WLAN 2.45/5.2/5.8 GHz and Wi MAX 2.5/3.3/5.5 GHz. The 10 d B impedance bandwidth are 2.33~2.69 GHz(360MHz, 14.4%) and 3.34~5.87 GHz(2530MHz, 55%), respectively, having wide frequency bandwidth. The measured results and simulation results are basically consistent.Through the simulation and measurement results of these two types of antennas, it can indicate that these antennas can be very well used in WLAN band. |
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