The Research Of Terahertz Fresnel Zone Plate Lens Antenna

Terahertz(THz)frequency range(0.1-10THz)lies in the transition area between the high frequency radio waves and the far infrared.It has been found that THz waves have great potential in medical diagnosis,material test,imaging and so on.The application of THz waves in wireless communication especially has brought significant reform to the wireless communication technology.As an integral part of any wireless communication system,the research of terahertz antenna is of great value.The THz Fresnel lens antennas are designed in terahertz atmospheric transmission I window(320GHz-380GHz)by applying the Fresnel zone plate lens originated from the optics into the THz frequency range.In order to improve the gain property and the directionality of the terahertz wireless communication antenna,three kinds of Fresnel zone plate lens antennas which are the square grooved-dielectric type,the cross-like dielectric type and the conical ring type respectively are proposed.Firstly,the scalar diffraction theory and the structure of the Fresnel zone plate lens are introduced.The focusing field characteristics of the Fresnel lens which is illuminated by the incident plane waves are studied by using the Kirchhoff's diffraction formula.Secondly,the nominal diagonal horn antenna is selected as the feed antenna according to the requirements of the lens antenna for its primary feed.Then the square grooved-dielectric Fresnel lens antenna is designed.The effects of the full-wave period,the focus-distance ratio,the number of sub-regions and the dielectric substrate thickness on radiation characteristics of the lens antenna are studied.The simulation results show that the gain of the lens antenna is over 26.4dB and the 3dB main lobe beamwidth is less than 5.1? across the operation band.Based on the square Fresnel lens,the cross-like Fresnel lens antenna is proposed and analyzed.The effects of the main structural parameters such as the full-wave period,the focus-distance ratio and the dielectric substrate thickness on radiation characteristics are studied.The simulation results show that the gain of the lens antenna is over 26.9dB and the 3dB main lobe beamwidth is less than 5.5? throughout the whole operation bandwidth.After that,the conical ring Fresnel lens antenna is proposed.The radiation characteristics of the lens antenna are simulated and the effects of the half cone angle,the focus-distance ratio and the full-wave period on the far field radiation are studied.The conical ring Fresnel lens antenna is further compared with the classic planar Fresnel zone plate lens antenna in terms of gain and directionality.The simulation results indicate that the gain over 28.8dB and the 3dB main lobe beamwidth less than 4.4? are achieved within the operation bandwidth.All three proposed terahertz Fresnel lenses are fabricated and experimentally tested.The experimental results and the simulation results are compared,and the test error is analyzed thoroughly.In the end,the three kinds of Fresnel lens antennas are compared and further contrasted to the other THz antennas.In summary,the high gain and the great directionality of the proposed Fresnel zone plate lens antennas indicate that the designed lens antennas are qualified for applications in THz wireless communication systems.