Browse Prior Art Database

Synchronization Circuit

IP.com Disclosure Number: IPCOM000093841D
Original Publication Date: 1966-Mar-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Freeman, DG: AUTHOR

Abstract

A pulse position modulated (PPM) signal, with a modulation index of 50-percent is shown. Since information pulses can be present only during one half of the repetition period, the amount of noise and false pulses entering the receiver is diminished by blanking out all signals which occur during the other half of the period. The circuit centers a time gate around the zero modulation point of each PPM pulse. The threshold detector indicates the presence of a pulse which is used as the input to a phase locked loop, PLL. The PLL simulates the nominal clock and, through the pulse conditioner, controls the analog gate. The pulse conditioner opens the analog gate. Such opening is for a long enough duration before and after the center of the repetition period to accommodate the arrival of the pulse.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 1

Synchronization Circuit

A pulse position modulated (PPM) signal, with a modulation index of 50- percent is shown. Since information pulses can be present only during one half of the repetition period, the amount of noise and false pulses entering the receiver is diminished by blanking out all signals which occur during the other half of the period. The circuit centers a time gate around the zero modulation point of each PPM pulse. The threshold detector indicates the presence of a pulse which is used as the input to a phase locked loop, PLL. The PLL simulates the nominal clock and, through the pulse conditioner, controls the analog gate. The pulse conditioner opens the analog gate. Such opening is for a long enough duration before and after the center of the repetition period to accommodate the arrival of the pulse. The accommodation for a given percent of modulation or deviation is established by the system. The time constant of the PLL is large enough to ensure that the loop tracks only slow variations in the clock frequency and not the superimposed PPM. The loop essentially averages out the fast PPM variations, tracking only the mean pulse rates. Rec-P.

1