Research On Miniaturization Of Wideband Planar Monopole Antennas

Antenna has become an indispensable part of our daily life,such as cellular phone,wireless LAN,Bluetooth,and so on.How to squeeze the antenna into small-sized portable devices with required bandwidth and gain is a challenge in modern antenna design.The present thesis studied the size miniaturization and wide bandwidth by designing,fabricating,and analyzing a series of planar monopole antennas.It is of significance both in theory and application.For the single-band application,a miniaturized planar monopole antenna,with a central frequency of 868MHz and 10%relative bandwidth,is simulated by using a meandering line structure.For multi-band applications,a miniaturized planar monopole antenna operating in both WiFi and WiMAX bands,is designed and fabricated by using double L-shaped structures,combined with L-shaped loading.The antenna bandwidth is 592 MHz at 2.5 GHz and 2,520 MHz at 5.6 GHz.The measurement and simulation results are consistent on the whole.For the broadband application,a miniaturized wideband planar monopole antenna is designed and fabricated with a U-shaped structure and an improved U-shaped structure.The working frequency range of the antenna is about[3.3-5.86]GHz,the bandwidth is about 63%,the size is miniaturized to 21*32.5 mm2,and the peak gain is 3.2 dBi.The measurement results are in agreement with the simulation results.For the ultra-wideband(UWB)applications,a miniaturized UWB planar monopole antenna is designed and fabricated by combining the L-type with S-type structures;using anti-U-shaped loading,and introducing ground pins to improve the antenna performance.Antenna size is 28*28.1 mm2.The measured results validate the design.At the same time,the presented UWB planar monopole antenna is used to analyze the specific absorption rate(SAR)for human brain tissue.Simulation results give the safe distance for the antenna use.It provides a new way to design antenna to ensure the EM safety of the human body.