Antenna Pattern Design Based On FZP

Fresnel Zone Plate(FZP)Lens feature excellent performance in the direction of controlling electromagnetic patterns and are favored by the market for advantages of uncomplicated and inexpensive fabrication.The research concerning FZP has always been one of the most promising research directions at home and abroad.Theoretical development of FZP in the field of traditional media lens has been very mature and mainstream research method for FZP is the combined application with new materials such as metamaterial and semiconductors.For the specific performance of electromagnetic transmission,research works on the combined application of FZP and metamaterial have achieved good results,especially on the direction of high gain and beam steering.Two designs of controlling patterns based on FZP,controllable metamaterial FZP and beam antenna integrated with FZP and circular waveguide,have been shown in this paper.The first design is based on the common circular ring,cross dipoles and I shaped cell.By printing different metallic patterns on opposite side of single-layer FR4 substrate,the composite cell compounded with circular ring and I shaped metallic pattern is chosen for its better performance of electrically induced transparency(EIT).The chosen cell electromagnetic resonant points don‘t change as the angle of oblique incidence of electromagnetic wave changes,and the change of the transmission performance of the metamaterial can be negligible.Based on the equivalent resonant circuit principle,the transmission performance of the metamaterial would be changed by loading capacitance in the chosen unity cell.As the value of loaded capacitance is changed,the 3.5GHz resonant point changes between the transparency and opacity state.Using the variable capacitance diodes of which capacitance value changes within the range of 1.5pF to 6.5pF as the reverse voltage changes,a kind of FZP based on electric controllable metamaterial is designed.After experimental verification,the 3.5GHz resonant point of the metamaterial is on the state of transparency and opacity respectively under the condition of 0V and 7.1V dc bias voltage.Applying the feature in the design of FZP to change the position of transparency and opacity zone,the function has been reached that electromagnetic beam radiated from a standard antenna steers at the angle of 0 degree,10 degree,20 degree and 30 degree.The second design shows integrating circular waveguide with traditional FZP to realize a high directivity beam antenna.Radiation efficiency of the beam antenna is optimized by transition of the circular waveguide feed.At 30 GHz,the beam width is only 4.4 degree,and the directivity reaches 22.5dBi.At 30.5GHz,the beam width is 5.7 degree,and the directivity reaches 21.5dBi.The beam antenna can be extended to realize the circular polarization by transforming the circular waveguide to congruent circular polarizer.