Research On The Miniaturization And Broadband Of Multilayer Microstrip Antenna

With rapid development and applications of the wireless communication technology, in order to meet the increasing requirements of the new wireless communication system, such as satellite communication, WLAN etc, the wireless and electronic devices with compact size and broadBand are becoming more and more attractive. As the device of receiving and transmitting electromagnetic wave, antenna is a very important component for wireless communication system. The radiation properties of the antenna affect the communication quality and efficiency directly. The main issue to minimize the size of wireless communication system is how to reduce the antenna size. Microstrip patch antennas are widely required for the features such as low profile, light weight, low cost, easy fabrication and ease of integration into radio frequency circuit etc. Therefore the microstrip patch antenna with compact size and wideband has considerable potential value in communication applications and is one of the most popular topics in wireless communication.The latest domestic and international research status and research trends of bandwidth microstrip antenna with small size are introduced in this thesis. The methods for microstrip antenna analysis are presented. Several techniques to achieve compact and broadband microstrip antenna have been summarized. Three broadband multilayer patch antennas with small size are proposed, which are designed based on1/8wavelength antenna. By taking the numerical simulation and analysis, how antenna performances are affected by changing main antenna parameters is analyzed and concluded. The antenna designs are optimized. The bandwidths, radiation patterns, gains and other antenna characteristics are discussed in detail. All three kinds of antennas’size are40mm×40mm which include the ground plane, the center frequencies are about1.55GHz and relative bandwidths are around8%. The real antennas are made and measured by vector network analyzer. The measured bandwidths of the antennas are surprisingly similar with simulation results.The miniaturization designs of ultra-wideband antenna are studied in the paper. Three kinds of half size quarter wavelength microstrip antennas for UWB application are proposed. The half size L slot multilayer antenna for UWB application with the size of18mm><7.5mm can work from4.3GHz to6.4GHz in simulated result, the absolute bandwidth of2.1GHz and relative bandwidth of39.3%are achieved. The measured results show that the relative bandwidth of50.53%from3.86GHz to6.47GHz is obtained. It also show that the antenna has a relative bandwidth of82.6%from3.55GHz to8.5GHz when bandwidth standard is VSWR=3. And then a new structure which is modified from L slot antenna is proposed. The length of improved antenna is reduced about17%from the original18mm to15mm. The measured result shows that a bandwidth of4.77GHz from3.73GHz to8.5GHz is obtained; the relative bandwidth is increased to78%. The antenna which has one slot and a folded patch with size of15mm×7.5mm is also present. It can work from4.65GHz to9.4GHz, the absolute bandwidth of4.7GHz and the relative bandwidth of67.6%are obtained. The measured results match well with the simulated ones.At last, the genetic algorithm, combined with the Finite Element Method is employed to optimize the antenna with multiple parameters. By programming the genetic algorithm VB script of the3D electromagnetic numerical simulation software to optimize the multiple parameters of antenna automatically and by extracting antenna performance parameters after numerical software calculation to complete the fitness assessment, the computing time are reduced and the possible mistakes due to repetition of modeling antenna structure are also avoided. By the optimization two kinds of the multilayer miscrostrip antenna, the feasibility and accuracy of this method are verified.