Browse Prior Art Database

Synchronization of Tuned Inductor Capacitor Oscillators by Direct Injection

IP.com Disclosure Number: IPCOM000118971D
Original Publication Date: 1997-Oct-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Ghoshal, US: AUTHOR

Abstract

Disclosed is a circuit for synchronizing tuned Inductor Capacitor (LC) oscillators to lower frequency clock signals by direct injection of currents in the LC resonator loop. Tuned oscillators using LC resonator loops have been used in a variety of high frequency applications and have recently been incorporated in many RF chips*. They can also be used for generating high-frequency clocks for digital microprocessors and in data communication applications such as stable clock recovery circuits. These digital applications require the tuned occillator to be synchronized to an external ultra-stable lower frequency oscillator. This in turn requires that the center frequency of the tuned oscillator be a precise multiple of the center frequency of the external lower frequency clock.

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Synchronization of Tuned Inductor Capacitor Oscillators by Direct
Injection

      Disclosed is a circuit for synchronizing tuned Inductor
Capacitor (LC) oscillators to lower frequency clock signals by direct
injection of currents in the LC resonator loop.  Tuned oscillators
using LC resonator loops have been used in a variety of high
frequency applications and have recently been incorporated in many RF
chips*.  They can also be used for generating high-frequency clocks
for digital microprocessors and in data communication applications
such as stable clock recovery circuits.  These digital applications
require the tuned occillator to be synchronized to an external
ultra-stable lower frequency oscillator.  This in turn requires that
the center frequency of the tuned oscillator be a precise multiple of
the center frequency of the external lower frequency clock.  Although
coarse tuning ("targeting") of the center frequency of the oscillator
is possible by fuses and focussed-ion-beam trimming, the fine tuning
of the center frequency of the LC oscillator needs active analog
circuits.  Analog circuits can inject additional thermal noise and
noise due to poor rejection of power supply disturbances.

      The circuit in the Figure shows an effective method to
synchronize a tuned LC oscillator by a simple one-stage current-mode
circuit.  The inductances L and capacitance C form the core LC
resonator.  The resonator along with the cross-coupled NMOS
transistors M3 and...