Title: 一新型電荷幫浦鎖相迴路
A New Charge-Pump Phase-Locked Loop
Authors: 劉祖勳
Liu, Tsu-Hsun
鄭木火
Cheng Mu-Huo
電控工程研究所
Keywords: 鎖相迴路;電荷幫浦鎖相迴路;拉進時間;phase-locked loop;charge-pump PLL;pull-in time
Issue Date: 1996
Abstract: 鎖相迴路是要控制一振盪器,使其輸出訊號的振盪頻率與相位能夠穩定
且快速地追隨著輸入振盪訊號的變化。因此如何來加快鎖相迴路拉進(
pull-in)及鎖定(lock-in)的速度,是設計鎖相迴路的一個重要課題。在
電荷幫浦型鎖相迴路中,系統頻寬與反應的速度成正比,很明顯的,要減
少拉進時間,就必須加大系統的頻寬。但系統頻寬的大小與雜訊頻寬的大
小成正比。一個常見的解決方法,就是當系統在拉進狀態時,改變系統參
數,用以增大系統頻寬,以得到較快的反應速度;而進入鎖定範圍後,便
以較小的頻寬作為系統的參數,以避免過大的雜訊進入。有許多不同的方
法來達到這個目的,但這些方法都可能會造成電壓控制振盪器(VCO)輸入
電壓的擺動過大,以致於造成 VCO 和電荷幫浦的過載。在本文我們提出
一個新的電荷幫浦型鎖相迴路,可以將 VCO 之輸入電壓擺動固定,因而
不致造成 VCO 及電荷幫浦的過載,來變化系統參數加快拉進的速度。我
們也附上此電路以實際電路完成的實現方法,並且以李帕諾夫穩定度(
Lyaponuv stability)的方法證明此一新的鎖相迴路一定會穩定。最後以
電腦模擬驗證此新的方法確實能加快鎖相迴路的拉進速度。
A phase-locked loop (PLL) is used to control a voltage control
oscillator (VCO) such that the frequency and phase of VCO output
will follow the input signal quickly and stably. Hence it is
important to reduce the pull-in and lock-in time in designing a
PLL. In a charge-pump PLL, the bandwidth is proportional to the
speed of system response. Obviously, we could increase the
system bandwidth to reduce the pull-in time. However, as the
system bandwidth increases, the noise bandwidth increases,
resulting in large frequency and phase errors of the PLL system.
A commonly used method to solve this problem is to increase the
system bandwidth for fast response during pull-in state, and to
decrease the system bandwidth for small noise bandwidth during
lock-in state. This approach can be realized in many ways, but
they may make large swing voltage of VCO input, resulting in VCO
and charge-pump overload. In this thesis, a new charge-pump PLL
is proposed. The proposed charge-pump PLL can reduce the pull-in
time and has constant swing voltage of VCO input such that the
VCO and charge-pump overload can be avoided. One realization of
this new charge-pump PLL is also included. We also use the
Lyaponuv stability method to prove the stability of the proposed
charge-pump PLL. Finally, computer simulations are used to
verify the performance of this new charge-pump PLL.
URI: http://140.113.39.130/cdrfb3/record/nctu/#NT850327022
http://hdl.handle.net/11536/61676
Appears in Collections:Thesis