Research And Design Of Broadband Flexible Antenna

Flexible antennas are appealing in foldable terminal devices,wearable equipment,flexible sensors.etc.,due to their virtues of small size,low profile,light weight and easy fabrication,etc.For flexible devices using ultrawideband(UWB)or Wireless Fidelity(WiFi)communication technique,antennas are required with wideband and low profile.In this thesis,omni-directional and directional antennas are designed by using 0.07 mm-thick polyimide as substrate.The main work of this thesis is given in the following.(1)A flexible UWB antenna with omnidirectional radiation has been proposed.The antenna radiation patch is a combination of rectangular patch and circular patch,which uses coplanar waveguide feed and unequally high ground plane to obtain wide bandwidth.The antenna size is 38×40 mm~2,and the measured bandwidths cover3.06-13.58,2.8-13.55,3.1-12.8 GHz in case of flat state and bent state of a cylinder with radii of 20 mm and 10 mm respectively.Measured radiation patterns show the antenna is omnidirectional,and the efficiency is higher than 60%in the frequency range of UWB bandwidth.Compared with the published flexible UWB antenna,the proposed antenna exhibits virtues of lower profile and better bending performance.(2)A flexible triple-band WiFi antenna with omnidirectional radiation performance has been proposed.The proposed antenna is a half cut of a symmetric CPW antenna with a rectangular patch.Two slots are etched on the patch and the antenna ground is surrounded around the patch to reduce antenna size and enhance bandwidth.The antenna size is 44×38 mm~2.The measured bandwidth covers three frequency bands of WiFi 2.4,WiFi 5.8 and WiFi 6 in the flat state and the bending with radii of 22.5mm and20 mm.Measured radiation patterns show the antenna is omnidirectional.Compared with the published flexible WiFi antenna,the proposed antenna exhibits virtues of lower profile,wider bandwidth and better bending performance.(3)Two flexible WiFi antennas with directional radiation performance have been proposed.Design of artificial magnetic conductor(AMC)surface printed on very thin substrate has been solved and used in the antennas.Antenna I has a"?"shaped radiation patch and an"F"symmetric ground plane fed by CPW.A circular combined shaped AMC surface is arranged 15 mm below the antenna to obtain directional radiation.The measured bandwidth covers WiFi2.4 GHz,WiFi5.8 GHz and WiFi6GHz band in the flat state.The measured maximum gain is 7.2 d B,and the measured efficiency is higher than 65%.Antenna II is a half-cut of a CPW fed antenna with an“E”shaped patch and ground surrounding around the patch.A hybrid shape AMC surface is arranged 10 mm below the antenna to obtain directional radiation.The measured bandwidth covers WiFi2.4 GHz,WiFi5.2 GHz,WiFi5.8 GHz and WiFi6GHz band in the states of flat and bending with radii of 17.5 mm,20 mm,and 22.5mm.The measured maximum gain is 9.76 d B.Based on Antenna II,a 1×3 array antenna has been proposed.The measured bandwidth of the antenna covers WiFi2.4GHz,WiFi5.2 GHz,WiFi5.8 GHz and WiFi6 GHz bands in the cases of flat and the bending with radii of 45 mm and 35 mm.Measured efficiency is higher than 60%.The AMC surfaces proposed in this thesis is printed on 0.07 mm-thick polyimide are thinner,lighter and more flexible than the published ones.