整合非平衡轉平衡器之新型差動饋入式微帶天線設計

Abstract

在現代的無線通訊系統當中，隨著成本的要求，RF前端之收發器系統正朝著縮小化體積及低成本的方向來發展。而在系統設計當中為了減少總體的電路面積，不同區塊電路的面積必須縮小且彼此之間的距離也會相當接近。此時區塊之間的耦合效應可能無法再被忽視需要仔細的考量以免電路表現受到影響。在無線通訊傳輸當中，天線一直都是相當重要的一個區塊，因此在天線設計中必須注意天線與相鄰電路之間的耦合效應。 這篇論文提出了一種能將差動饋入之微帶天線與BALUN做高度整合之新型結構。首先我們利用差動饋入式微帶天線之兩饋入點中間為虛擬接地之概念將一個以二分之波長共振的差動饋入式天線分為兩個以四分之波長共振的單端短路微帶天線。其短路端以一排接地的via來等效短路面，再將兩個單端短路微帶天線之短路端朝外，輸入端朝內面對面擺放。這樣的架構節省了額外的走線面積且天線部分與饋入網路的差動輸出也很好做整合。如前所述，對天線來說耦合效應在設計中必須審慎考慮，因此我們延伸了短路端的接地via並使其包圍整個天線架構。這樣的via柵欄可省去額外的解耦合架構且可確實的減少天線與電路之間的耦合以避免了天線的表現受到影響。

In modern wireless communication systems, the increasing demands on cost reduction keep pushing the field of transceiver design toward compact and low cost RF-front end solutions. This implies the blocks in the system design must be small and close to each other to reduce the overall required circuit area and one should consider the mutual coupling between blocks to see if it can deteriorate the circuit performance. Antenna, is one of the critical blocks for wireless signal transmission and one should be aware if its coupling toward adjacent elements cannot be ignored. In this paper, a highly-integrated differentially-driven patch antenna with feeding network is proposed. By using the concept of virtual ground at the center between two feeding points of a normal differentially-fed antenna, we split a half-wavelength differentially-fed patch antenna into two shorted-end quarter-wavelength patch antennas shorted by via wall to ground. This inputs arrangement avoids additional layout area for the feed line and the differential feed antenna can be compactly integrated with the feeding network’s differential output. In order to provide better shielding, shorting via wall along both patches are extended to wrap up the whole antenna structure in a nearly closed-wall rectangle. The additional shorting via wall are proved to have better coupling suppression ability that keep our proposed antenna performance from being deteriorated by crosstalk from adjacent circuits.