24 GHz 高轉換增益低雜訊混頻器及毫米波高鏡像抑制比率升降頻混頻器與模組之研究

Abstract

本論文分為三個部分。第一部分(第二章)提出了設計在 24 GHz 的高轉換增益低雜訊的主動降頻混頻器，使用0.18 µm CMOS 製程。此電路利用電流注入技巧以及共振電感的使用，有效地降低雜訊指數以及提升轉換增益。然而，兩次下線的量測結果都不如預期，除錯的過程會在內文中討論，目前尚未找到造成嚴重掉增益的原因。 第二部分(第三章)介紹毫米波鏡像抑制的升降頻模組。利用威爾金森分合波器作為主架構，將左手傳輸線上的電容替換成變容二極體藉以實現可調的相位；將 PIN 型二極體引入 T 型衰減器以實現可調的大小。量測的結果在 2.5 到 5 GHz 可以有 80-100°的相位可調範圍以及 (+2)-(-1.1) dB 的大小可調範圍。整個升降頻模組的鏡像抑制比率在3 到4.5 GHz 有50 dB 的水平，在2.5 和5 GHz 有30 dB 的水平。 最後一部分(第四章)提出了應用於第五代行動通訊系統的高鏡像抑制比率升降頻次諧波混頻器，使用0.15 µm GaAs pHEMT 製程。此電路實現了有很小相位和大小不平衡的 45° LO 分波器，且透過 LO 的級間反射係數的分析，能夠達到高鏡像抑制比率的目的。此外，類集總四分之波長傳輸線的引入，使得端對端的隔離度有很好的表現。藉由第三章的可調式正交分合波器，量測結果在升降頻都有 45 dB 以上的水平。

關鍵字:24 GHz、高增益、低雜訊、電流注入、共振電感、毫米波模組、可調相位、可調大小、第五代行動通訊、高鏡像抑制比率、次諧波升降頻混頻器。

This thesis divided into three parts. In the first part (chapter 2), a 24 GHz high conversion gain and low noise down-conversion active mixer in 0.18 µm CMOS process is presented. The current-bleeding technique and the resonant inductor are adopted to obtain high conversion gain and low noise figure. However, after two tape-outs, the reason for the severe reduction in conversion gain has not been found so far. In the second part (chapter 3), a millimeter-wave up-/down-conversion image rejection module is demonstrated. The capacitors on the left-handed transmission line are replaced with varactors to achieve tunable phase, and the PIN diodes are added to the T-type attenuators to achieve tunable amplitude. The tunable I/Q divider/combiner are based on the Wilkinson power divider. The phase and amplitude tuning at 2.5-5 GHz were measured to be 80-100° and (+2)-(-1.1) dB, respectively. With the great performance of the tunable I/Q divider/combiner, the IRR of the up-/down-conversion image rejection module can reach a 50-dB level at 3-4.5 GHz and a 30-dB level at 2.5 and 5 GHz. In the last part (chapter 4), a 24-32 GHz high image rejection ratio up-/down-conversion subharmonic mixer in 0.15 µm GaAs pHEMT process is proposed. This circuit realizes a 45° LO power divider with small phase and amplitude imbalances. By analyzing the LO inter-stage reflection coefficient, it is able to achieve the desired high image rejection ratio. Besides, good port-to-port isolation is made possible by the implementation of quasi-lumped λLO/4 short/open stubs. With the tunable I/Q divider/combiner in measurement, the IRR in precise phase and amplitude tuning can reach over 45 dB for up-/down-conversion.

Index Terms – 24 GHz, high conversion gain (CG), low noise figure (NF), current-bleeding, resonant inductor, millimeter-wave module, tunable phase, tunable amplitude, fifth-generation (5G), high image rejection ratio (IRR), up-/down-conversion subharmonic mixer.