Browse Prior Art Database

Phase Locked Loop with Frequency Monitor

IP.com Disclosure Number: IPCOM000113810D
Original Publication Date: 1994-Oct-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Kobayashi, Y: AUTHOR

Abstract

Disclosed is a circuit in which a highly stable Phase Locked Loop (PLL) has a wide capture range.

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Phase Locked

Loop

with Frequency Monitor

      Disclosed is a circuit in which a highly stable Phase Locked
Loop (PLL) has a wide capture range.

      A frequency monitor helps to enhance the capture range of a
PLL.  A frequency synthesizer system consists of a Voltage Controlled
Oscillator (VCO) and a PLL .

      A characteristics of PLL is that a highly accurate system is
apt to have a narrow operating range, whereas a PLL that works in a
wide operating range is apt to loose stability or accuracy.  This
frequency monitor is attached to a highly accurate PLL, and brings
the oscillation frequency of the VCO into the capture range of the
PLL when the PLL fail to control the VCO.

      This frequency monitor works exclusively with the PLL.  When
the oscillation frequency is in the capture range of the PLL, the PLL
has control of the VCO, and the frequency monitor has control of the
VCO.  when the oscillation frequency of the VCO is outside the
capture range of the PLL.