應用於波束控制系統之毫米波開關與雙平衡式主動混頻器之研究

Abstract

近年來無線通訊對於頻寬與速度的需求大幅增加，促使通訊系統向更高的頻段發展。毫米波頻段具有大頻寬特性，60兆赫茲頻帶為不需執照，在無線通訊收機發前端中，常需要加入切換器切換天線或者接收發，因此開關的損耗會直接影響到系統的NF與PAE，本篇於第二章介紹一個V頻段單刀雙擲開關，首先簡介一下40、65、90奈米互補式金屬氧化物半導體製程對於開關特性影響，單刀雙擲架構上運用電晶體關閉時等效成電容，與串聯傳輸線、並聯電容形成π型匹配網路架構，達到輸入輸出阻抗50-Ω，於61兆赫茲輸入損耗2.3 dB、隔離度15 dB。 本篇於第三章介紹吸收式單刀四擲開關，應用在802.11 ac規格中的波束成型(Beamforming)技術將波束集中至目標體的功能，克服室內環境的牆壁阻隔與雜訊干擾進而擴大Wi-Fi聯網覆蓋範圍與傳輸速率，在滿足開關的隔離度需求同時達到損耗最佳化，並討論巴特勒矩陣相位差對波束成形的影響，於V頻段實現吸收式單刀四擲開關其輸入損耗4.3 dB、隔離度18.2 dB，於Q頻段實現吸收式單刀四擲開關與巴特勒矩陣模擬結果於36至40兆赫茲主波束角度誤差不超過1.6度。 本篇第四章介紹於60兆赫茲之次諧波正交混頻器，其採用放大器的非線性效應於於次諧波項混頻而成，架構使用四顆電晶體組成的雙平衡架構. 有較高的2倍本地震盪訊號對射頻埠的隔離度，需要使用的本地震盪功率較小面積也較小，兩個雙平衡混頻器差動輸出經由功率合成變壓器結合，以縮小面積與較低損耗。 汽車防撞雷達系統使用24GHz作為短通道雷達使用，混頻器在射頻收發機中重要電路元件之一，本篇第五章介紹於24GHz提出藉由交叉耦合對共汲級電流注入吉伯特價架構之降頻混頻器，藉由交叉耦合對共汲級放大器中的寄生電容(Cgs)消除吉伯特架構中轉導級的寄生電容(Cgd)，藉以改善穩定度與線性度，藉由減少通過本地震盪開關的電流以改善轉換增益、線性度與減少閃爍雜訊。

The switch function is extensively employed in RF systems, especially with the development of the multi-mode and multi-band transceivers. The loss of switch degrades the NF and PAE of transceiver. In Chapter 2, the SPDT switch is applied in 40-nm LP CMOS process for 60 GHz, which targets on minimizing insertion loss. The body-floating technology is used to reduce insertion loss, and the architecture consists of equivalent capacitor of turn-off MOS, series transmission line and open stub to form πmatching network. In Chapter 3, the SP4T absorptive switches are applied in 40-nm LP CMOS process for 38 and 60 GHz. By analyzing required value of isolation of absorptive switch for Butler matrix, the absorptive switch is designed for minimizing insertion loss. The proposed topology minimizes chip sizes and insertion loss. Moreover, the absorptive switch with 4×4 Butler matrix in 40-nm LP CMOS process for 38 GHz is realized. In Chapter 4, the 60 GHz IQ sub-harmonic mixer is presented using 40-nm LP CMOS process, which produces sub-harmonic mixing by the non-linearity of transistor. The double-balanced topology pumped by a differential LO signal is adopted, which can obtain the benefit of smaller area and lower LO power. Transformer-based current-type combining is adopted to reduce chip area and loss of matching network. The automotive short-distance radar is permitted to use 24 GHz, the mixer play an important role in transceiver. In Chapter 5, the current bleeding with neutralization is proposed. The 24 GHz down-conversion mixer with this current bleeding is implemented using 0.18-µm CMOS process. The IP1dB of proposed current bleeding is better than 6 dBm IP1dB of traditional PMOS current bleeding. The IM3 of proposed way is lower than 7 dBm IM3 of traditional way in IP1dB of traditional current bleeding.