Browse Prior Art Database

FREQUENCY MODULATION OF REFERENCE OSCILLATOR

IP.com Disclosure Number: IPCOM000006058D
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2001-Nov-29
Document File: 2 page(s) / 83K

Publishing Venue

Motorola

Related People

Tal Mor: AUTHOR [+2]

Abstract

Many phase locked loop oscillators employ a 'Wo Port FM modulation technique. This method consists of applying modulation to both VCO and the reference oscillator.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 50% of the total text.

Page 1 of 2

0 M

MOTOROLA INC. Technical Developments Volume 12 April 1991

FREQUENCY MODULATION OF

REFERENCE OSCILLATOR

by Tal Mor and Michael Rernik

   Many phase locked loop oscillators employ a 'Wo Port FM modulation technique. This method consists of applying modulation to both VCO and the reference oscillator.

  The reference oscillator is usually a TCXO and should be frequency modulated in order for the Two Port modulation to be possible. This is generally available with stability in the order of 5 ppm. More stable oscillators in the order of 1 ppm are usually not modulated. Modulated TCXOs of the 1 ppm stability are very expensive.

  This problem has been addressed by several PLL chip manufacturers by allowing Phase Modulation of the divided reference signal before applying it to the phase detector. The phase modulation can be transformed into frequency modulation by integrating the modulating signal. This method was used in Motorola BBR chip set, and in the direct divide synthesizer developed for the low band MaxTrac.

  Use of those specific chips, however, vastly reduces design flexibility, especially for existing designs needing enhancement of frequency stability. Moreover, most of those chips require specific addi- tional components (BBR) or are otherwise limited in application. (Frequency range, available prescalers etc.)

  The proposed technique uses the Phase Modulation technique employed in some PLL chips, and applies it to a non modulated TCXO.

  The TCXO signal is applied to programmable dividers to divide the frebuency down to a conveni...