The Researches On Novel Microstrip Antenna

With the rapid development of wireless communication technology,the wireless devices with low cost,compact size and broad bandwidth are becoming more and more attractive.As a "gateway" of the wireless communication systems,the antennas have the most direct impacts on their performances.Microstrip antennas have the merits of low cost,small volume,light weight,low profile,easy to be fabricated and conformed onto aircraft.But the specifications of microstrip antennas are different for each communication system.So it is necessary to design novel microstrip antenna for specific communication systems.By the means of theoretical analysis,numerical simulation and experimental verification,three novel microstrip antennas are proposed for airborne multi-mode satellite navigation system,portable UHF RFID reader and terrestrial digital TV transmission system applications,respectively.This work is supported by the High Technology Research and Development Program of China and other projects.Firstly,a novel proximity-coupled probe-fed stacked patch antenna is proposed for airborne multi-mode satellite navigation system applications.The key features of the design are the proximity-coupled probe feeds to increase impedance bandwidth,a high-permittivity substrate encapsulating the patch to increase the gain at low angles and the integrated broadband orthogonal feed network to achieve RHCP reception.In order to afford better fabrication tolerances,the length of the shunted open and short microstrip lines used in the broadband 90 degree phase shifter are different.The experimental results show that the antenna has the merits of low return loss,broad pattern coverage,and high gain at the low angles.Secondly,a low cost miniaturized CP antenna is proposed for UHF RFID(Radio Frequency Identification) reader applications.The antenna is composed of a vertical ground and a square-ring patch with truncated corners.And a novel capacitively coupled feed structure is proposed for good impedance matching and low cross-polarization levels.The final antenna exhibits small volume,good CP performance,broad pattern coverage,and high gain at the low angles.Lastly,a low cost probe-fed stacked patch antenna with stub is proposed for terrestrial digital TV transmission system applications.The bandwidth of the antenna is broadened by the stacked patches.To compensate for the large input inductance stemming from the long probe,a conducting stub is used as a broadband impedance matching network.A gradient-based adjoint-variable approach is used to optimization of the antenna using sensitivity analysis.The experimental results show that the design is capable of achieving a VSWR＜1.1 impedance bandwidth of about 7.6%,and suitable for terrestrial digital TV transmission system applications.