Design And Study On Planar Air-fed Array Antenna

With the rapid development of modern wireless communication technologies and the upgrading of electronic equipment, there has been a growing requirement for antennas with better performance. Planar air-fed array antennas have been drawn more and more attention and become one of the important research topics in antenna area due to the fact that they combine the features of both air-fed antennas and microstrip array antennas, exhibiting advantages of high directivity gain, low profile, simple feeding, design flexibility, ect. Therefore, it is of great significance to research planar air-fed array antennas.This dissertation makes deeply insight into two branches of planar air-fed array antennas-reflectarray antennas and transmitarray antennas. Based on completely studying and summarizing the previous methods, many novel and promising planar air-fed array antennas are proposed and designed. The author’s major contributions can be summarized as follows:1. Broadband circularly polarized reflectarray antenna is designed and studied. A single-layer double split rings element is proposed, which achieves a broad bandwidth by optimizing its geometry parameters. Then, a circularly polarized reflectarray using single-layer double split rings elements and element rotation techniques is designed, realizing 21.4% of 2-dB gain bandwidth and 35.3% of 3-dB axial ratio bandwidth respectively.2. Dual-band circularly polarized reflectarray antennas are designed and studied. Firstly, two single-layer cross dipole elements operating at two different frequencies are proposed and the simulated results show that a small mutual coupling effect between these two proposed elements, then a dual-band circularly polarized reflectarray is designed using proposed elements and element rotation techniques. The results show that the designed transmitarray antenna achieves a 1-dB gain bandwidth of 11.1% and 3-dB axial ratio bandwidth of 20.3% at higher band, and 1-dB gain bandwidth of 12% and 3-dB axial ratio bandwidth of 9.9% at lower band. Secondly, two FSS-backed elements operating at two different frequencies are proposed for designing dual-band circularly polarized reflectarray.For the designed antenna, the mutual coupling effect is obviously reduced by using the feature that different FSS structures present different reflection and transmission performances at different frequencies. Besides, by using element rotation techniques to compensate the phase delay, a 3-dB axial ratio bandwidth of 16.3% and 7.5% are obtained at higher and lower band respectively. Finally, a single-layer dual broadband circularly polarized reflectarray antenna is proposed and designed. For the designed reflectarray antenna, the higher and lower band elements have different grid spacing and use different phase compensation techniques, which result in a good isolation between higher and lower band element. The results indicate that the designed antenna obtain a 1-dB gain bandwidth of 14.1% and 3-dB axial ratio bandwidth of 42% at higher band, and 1-dB gain bandwidth of 15.1% and 3-dB axial ratio bandwidth of 22.9% at lower band.3. Electrically beam scanning reflectarray antennas are designed and studied. Firstly, an ellipse-like split ring element integrating five couple of electronical switches is proposed for designing electrically beam scanning reflectarray antenna. The designed antenna can realize beam steering by flexibly controlling the switches’states of each element in the array. Secondly, a square ring element integrating electronical switches is proposed, and its geometry parameters and switch numbers are optimized. Then, the finally optimized elements are used to design an electrically beam scanning reflectarray antenna. The simulated results show that the designed antenna can achieve beam steering with the scan range of ±40°. Finally, a ring element integrating only three electronical switches is proposed for designing electrically circularly polarized beam scanning reflectarray antenna. By properly controlling the switches’states of each element, the reflection phase can be dynamically varied, leading to the capability of beam scanning. All the results show the designed antenna can achieve beam steering within a certain scan range.4. Low profile and high aperture efficiency transmitarray antennas are designed and studied. Firstly, a double-layer square ring slot element is proposed, of which the transmission phase is adjusted by varying the slot dimensions. Then the geometry parameters of the proposed element are optimized, and the finally optimized element is used for designing a transmitarray antenna. The simulated results show the designed antenna has a 2-dB gain bandwidth of 12%. Secondly, a double-layer three-dimensional (3D) cross dipole element is presented for designing a transmitarray antenna, of which the profile height is only 0.22γ. at the center frequency. Compared with traditional two-dimensional (2D) transmitarray antenna, the designed antenna has a relatively low profile. Besides, a peak aperture efficiency of more than 64% can be achieved. Finally, a 3D cross dipole element with different dimensions in orthogonal directions is proposed for designing CP transmitarray using element rotation technique. The simulated results show the designed antenna obtains a 3-dB axial ratio bandwidth of 15.4% and a peak aperture efficiency of 32%.5. Multiple polarization transmitarray antenna is designed and studied. A triple-layer rectangle ring slot elements is presented, which can independently control the transmission phase at different polarizations by adjusting the slot dimension in orthogonal directions. Then, the proposed element is used for designing multiple polarization transmitarray. By properly rotating the linearly polarized feed antenna with different angles, the designed transmitarray antenna can generate radiation patterns with different polarizations. The measured results show the radiation patterns of the designed antenna have a good consistency at the range of 5.5 GHz to 6.5 GHz.