三位元寬頻移相器

Abstract

本論文提出三位元寬頻數位移相器，並使用共平面波導(Coplanar Waveguide ,CPW)的結構，中心頻率為10 GHz，涵蓋範圍為3.3 ~ 16.5 GHz，高達5倍頻。45°與90°移相器是利用反射型移相器，180°移相器則是採用Balun的方式實現。 本研究設計之3 dB耦合器係應用在45°與90°移相器，並配合PIN二極體切換產生相位差，而3 dB耦合器是由三節耦合器串接以達到-3 dB耦合量與寬頻功能。 利用Balun將CPW訊號轉換成平衡訊號CPS，配合四顆二極體(PIN或 Schottky)當成串接開關並選擇CPS訊號路徑，路徑彼此的相位會相差180°。最後再將三者串接，以CPW結構製作在介電系數9.8，板厚15mil的氧化鋁基板。

In this thesis, a 3-bit broadband phase shifter is designed, which uses CPW(Coplanar Waveguide) with the center frequency of 10 GHz, and it is covered from 3.3 to 16.5 GHz, exhibiting a wide bandwidth of almost 5 to 1 bandwidth. The phase shifters use reflection type for 45° and 90° phase shifters, and Balun (balanced to unbalanced) for 180° phase shifter. The 3 dB coupler is applied for 45° and 90° phase shifter, and it cooperates with PIN diode to generate phase difference. To achieve -3 dB coupling and broad bandwidth, 3-section coupler design is needed. For 180° phase shifter, the broadband Balun is utilized to change CPW signal to balanced CPS signal. The 4 diodes (PIN or Schottky) serve as a series switch to select signal path in the CPS, the direct path and twisted path has inherent phase difference of 180°. Finally, three circuits of phase shifters will be cascaded and fabricated on a 15mil Al2O3 substrate with CPW.