偏移式相鎖迴路輸出雜波之系統化分析

Abstract

本論文提出一個可以正確解釋偏移式相鎖迴路產生輸出雜波的機制。藉由對輸入訊號與干擾訊之關係做嚴謹分析，我們導出一可系統性預測輸出雜波位置的正確公式。由此分析，本文證明了在偏移式相鎖迴路實際的運作中其輸出雜波乃是由壓控振盪器之漏波、本地振盪器之漏波以及影像訊號之干擾所造成，而非以往所認定的雜波是由迴路中混頻器之非線性交互調變輸出雜波所造成。本文所推導的結果對電路的設計以及輸入訊號頻率之規劃提供很好的方針。此外，文中所導出的公式也可以很清楚地描繪出當輸入訊號是調變訊號時，其雜波的分布情形。本文亦提出一個模型校正程序來估算產生雜波之干擾源強度。最後，文中所導出的所有公式皆可由實驗所得的眾多數具獲得完全的驗證。

This work presents a mechanism that explains exactly the cause of spurs at the output of offset-PLL (OPLL) transmitters. By a rigorous analysis of the relationship between the signals and disturbances in OPLL, accurate formulas are obtained which elucidate systematically the intermodulation nature of the output spur spectrum. From the analysis, it is shown that in practical situations the OPLL spurs are due to the disturbances from the VCO leakage, the LO leakage and the image signal, rather than other spurious products of the offset mixer in the loop as previously explained. The formulas give insight into OPLL circuit design and frequencies accommodation, and also clearly depict the output spur distribution in the more realistic situation when the input is modulated. A calibration procedure is also proposed for the estimation of the disturbance hard to be probed from the outside world. Finally, the formulas are verified by some elaborate experiments with extensive numerical results.