Study On Miniaturized Microstrip Antenna

With the rapid development of wireless communication technology, the wireless devices with compact size and broad bandwidth are becoming more and more attractive. The wireless electronic products which have the feature of light-weight, low-profile and small-volume will be the mainstream of the future wireless communication. As a "gateway" of the wireless communication systems, the antennas have the most direct impacts on their performances. Though the traditional dipole antennas have a good transmission property, they can not meet the requirement of miniaturization. Microstrip antennas have the merits of small-volume, light-wight, low-cost, easy to be fabricated and integrated with microwave integrated circuits. It has considerable potential value in communication applications and is one of the most popular topics in antenna designs.This dissertation makes a research on the analysis and design of miniaturized microstrip antennas. By the means of theoretical analysis, numerical simulation and experimental verification, several novel miniaturized microstrip antennas are proposed, which can work at 900MHz ISM band, 2.4/5GHz WLAN band and UWB band respectively.Firstly, the antenna designs operating at 900MHz ISM band are investigated. Based on the analysis and investigations of rectangle microstrip slot antenna, a novel cavity-backed circularly polarized slot antenna is presented considering the application prospects of indoor embedded antennas. It uses L-style slot to reduce the antenna size. With the design of feeding network at the top side, circular polarization can be realized. Using electromagnetic simulation software and vector fitting method, an accurate equivalent circuit model of the antenna is presented. It provides a reasonable physical explanation of the antenna and a precise model to the joint simulation and design with other RF front-end circuits.Secondly, the dual-band antennas for WLAN applictions are studied. Based on the analysis and investigations of dual-band microstrip annular ring slot antenna, a novel miniaturized dual-band annular ring slot antenna for WLAN applications is presented. It utilizes two rectangle notches to overcome the problem of resonant effects caused by the distance between inner and outer ring slots. In addition, it also presents an inverted T-style dual-band microstrip slot antenna for WLAN operations. It is compatible with the PCMIA standard PC wireless cards and easily integrated with other RF front-end circuits. The simulated and experimental results indicate that both antennas can wholly cover the WLAN band with satisfactory radiation characteristics.Lastly, the UWB antenna designs are studied. Based on the analysis and investigations of disc patch antenna, a miniaturized UWB microstrip antenna is proposed. In order to avoid interference with other communication systems operating at 5-6GHz band, a band-notched UWB antenna is also presented by introducing an inverted T-style parasitic structure. The simulated and experimental results show that both antennas can wholly cover the UWB band with satisfactory radiation characteristics.