Study On Novel Planar Reflectarrays And Transmitarrays Antennas

In the wireless transmission system,antennas as the main device will directly affect the overall performance of the system.So,the high performance of the antenna design becomes particularly important.Planar reflectarray and transmitarray antennas are the new type of high-gain antenna,and they have many advantages such as simple structure,low cost,no complicated feeding network and flexible beam.The reflectarray and transmitarray antennas can be widely used in long distance wireless communication,electronic countermeasure and radar detection,ect.Therefore,much attention has been paid to develop high performance of reflectarray and transmitarray antennas.In this dissertation,combined with the requirements of the current high-performance antenna design,broadband reflectarray/transmitarray antennas,low-profile transmitarray antenna and dual-polarized transmitarray antenna have been studied.The main contributions of this dissertation are summarized as follows:1.Broadband reflectarray antennas are studied.Firstly,a reflectarray unit cell composed of a cross ring is proposed and designed.To validate the performance of the designed unit cell,a parametric study is carried out and the proposed structure shows an almost linear behavior.Then,a prime-focus reflectarray with this type of unit cell is fabricated and tested.The measured results show that the obtained 1-dB gain bandwidth of the reflectarray can reach as large as 22%.Secondly,a novel broadband single-layer reflectarray element composed of a circular patch and double circular ring is presented.The element in the reflectarray provides a nearly 360° linear phase range and have rebirth capability.The broadband characteristic of this reflectarray is obtained due to the sub-wavelength of the element space and the combination of two resonators of complementary size on a single layer.Then,a prime-focus 225-element microstrip reflectarray with this "phoenix cell" has been designed and implemented.The measured gain is 22 dBi with 1 dBi drop within 29%bandwidth at the center frequency of 10 GHz.2.Broadband transmitarray antennas are studied.Firstly,a four-layer transmitarray operating at 9.5 GHz is designed using a double-petal loop element as the unit cell.The configuration of the double-petal loop elements are used to increase transmission phase variation while maintaining a wide transmission magnitude bandwidth of the unit cell,and a full transmission phase range of 360° is achieved for a transmission magnitude equals to or better than-3 dB.By optimizing the parameter of the unit cell,the four-layer broadband transmitarray antenna is realized.Secondly,a triple-layer wideband transmitarray operating at 12 GHz is designed.The unit cell has three metal layers,which are etched on three dielectric substrates.In order to achieve wideband performance,we design a double square ring element as the intermediate layer.Such a composite structure will produce two different resonances.These two resonant points will approach each other,and the larger transmission response could be realized.Then,a 233-element transmitarray prototype is fabricated and tested.Its measured 1-dB gain bandwidth is 16.8%,and its measured maximum gain is 25.8 dBi at 12.4 GHz,leading to 46.5%aperture efficiency.3.Low-profile dual-linearly-polarized transmitarray antenna is studied.Aiming at requirement of wider spectrum resources,a low-profile dual-linearly-polarized unit cell in X-band is proposed.The unit cell comprises three metallic layers etched on two dielectric slabs without air gap.The middle layer is different from the upper and bottom layers and it will bring a new resonance.By optimizing the parameter of the unit cell,a low-profile with high isolation between dual polarization unit cell is realized.Then,a 341-element transmitarray is designed,with which the linearly polarized field incident from the feed is converted into an outgoing circularly polarized field.The measured results show that the obtained 1-dB gain bandwidth and 3-dB axial ratio(AR)bandwidths of the transmitarray are 4%and 3.5%,respectively.4.Reflectarray/transmitarray and dual-reflectarray antennas are studied.Firstly,the design of the dual-reflectarray antenna is regulated by the design method of the Cassegrain antenna and the phase modulation mechanism of the reflectarray antenna.Secondly,a dual-band array antenna is proposed.The sub-array is a transmitarray and FSS combined structure,which has good transmission characteristic for high frequency and has good reflection characteristic for low frequency.Finally,a dual-reflectarray antenna is proposed,which is based on the square patch structure.The simulation results show that the proposed antenna has high gain radiation performance.