整合碟形天線與反射陣列天線單元以提升碟形天線之輻射特性

2017-08-012024-05-18https://scholars.lib.ntu.edu.tw/handle/123456789/708951摘要：本計畫發展碟形天線的前瞻技術，尤其針對碟型天線之輻射波形之優化及擴張其特性功能相關的硬體技術。本計畫的動機源自於衛星DTV 通訊及微波點對點連結的核心天線均為碟形天線，更為目前台灣產業所希望發展的核心天線產業，在市場上，由於通訊網路的逐漸壅擠，天線的規格及功能要求愈趨嚴格，傳統僅靠天線的尺寸來產生足夠的效能已不足以因應下一代天線的需求。本技術有助於改善碟型天線的性能，尤其是旁波束的抑制、波束寬的調整及雙頻多波束的優化，產生具備一個額外調整的維度，本技術的核心為發展一周期性的結構作為修正碟型天線的邊界結構及產生雙頻的輻射機制，藉以改善其電磁繞射機制及雙頻碟面優化的特性，更以優化的角度調整。此週期性結構的研究將三個角度來探討，一為產生路徑差來降低邊界感應電流值；二為產生共振型的散射單元，藉由調整此共振型散射單元的相位，讓此新的散射場與原來碟形天線的散射場產生適度的相銷作用，藉以降低旁波束；三為產生非共振型的散射單元，利用與前項相同的機制來抑制旁波束；此類天線單元將會進一步應用於雙頻的天線設計，使得天線的優化可以在雙頻的情境下，各自獨立進行。碟型天線屬於光學型天線，在原型拋物面結構下，其應用頻寬不受限制，然在本技術的應用下將會變成頻帶限制，然本技術應用定位於高頻的通訊應用，其頻寬足以應用於實務上，因此本技術的發展深具產業應用價值。<br> Abstract: The advanced technologies to enhance the performance of reflector antennas are proposed. This work is motivated by the need of antenna applications in satellite DTV and point-to-point microwave links, where the reflector antennas are the core in such applications. The former application is currently one of the core industries in Taiwan for worldwide market while the latter one is also desired to pursue by Taiwan industries. Due the crowded applications, the requirement of antenna specifications is becoming strict, which drives the need to develop the proposed technologies to enhance the radiation performance. The technology development proposed here intends to improve the radiation characteristics of reflector antenna, in which the focus is on the suppression of sidelobe, the control of radiation beamwidth and dual-band pattern synthesis that are most concerned by the above mentioned applications. Especially the technology of edge treatment will be first developed, where instead of using resistive materials structural type of metal materials will be developed in terms of three basic kinds. The first will create short slits/corrugations along the edges to reduce the induced currents along the edge and hence reduce the radiation from edge. The second will develop resonant type scattering metal elements to create diffracted field of different phases, which will suppress the diffractions of the original reflector edges in a negative superposition fashion. On the other hand, the third kind will develop non-resonant type scattering elements to suppress the diffractions. In the implementation, the elements will be distributed in a periodic fashion to create different Floquet modes to control the scattering mechanism. After the elements’ characteristics are validated, they will be used (especially the resonant type elements) in an integration with the reflector antennas to radiate dual-band beams, where multi-beam radiations will be examined. Here the reflector surface is used for the low frequencies while the reflecting elements will form curved reflectarray antennas to radiate the beams at high frequencies. This dual-band design is important for DTV reception at two different bands. It is noted that the implementation of edge treatment and reflectarray will limit the application frequency bandwidth, which is different from the original situation where the performance of parabolic reflector is relatively independent of frequencies. However, our target of applications is in the high frequency band such as in the Ku- and beyond. In this case, the bandwidth of operation is sufficient large. The alter of diffraction mechanism will not significantly impact the bandwidth of operation in the practical applications. Thus the developed technique will be very useful and will be potentially applicable in the coming communication such as in the next generation of mobile communications.整合碟形天線與反射陣列天線單元以提升碟形天線之輻射特性