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Error Correction in Pulse Position Modulation

IP.com Disclosure Number: IPCOM000093933D
Original Publication Date: 1966-Apr-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 3 page(s) / 38K

Publishing Venue

IBM

Related People

Kengla, CA: AUTHOR

Abstract

In pulse-position modulation, data is encoded by the position of the pulse in a time frame. The apparatus corrects two types of errors, first, where the time frame has no pulses and, second, where the time frame has more than one pulse.

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Error Correction in Pulse Position Modulation

In pulse-position modulation, data is encoded by the position of the pulse in a time frame. The apparatus corrects two types of errors, first, where the time frame has no pulses and, second, where the time frame has more than one pulse.

The apparatus can be divided into three major sections as to function. Section 10 performs the function of inserting a pulse in a time frame if the time lapse between pulses exceeds the length of a time frame. Sections 12 and 14 operate in parallel on alternate time frames. The function of each section 12 or 14 is to select for output the last pulse occurring in a time frame. And's 16 and 18 gate alternate frames to sections 12 and 14, respectively. The alternate gating is controlled by clock signal T and its complement in which the length of a pulse in the clock signal is the length of a time frame. The outputs of sections 12 and 14 are recombined in Or 20.

Section 10 operates in the following manner. An input pulse triggers ramp generator 22 and is passed by Or 24 to either section 12 or 14. Single-shot 26 is responsive to the ramp signal from generator 22 to generate an output pulse when the ramp voltage exceeds a given level. This given level is reached by the ramp signal if generator 22 is not reset by a new input pulse within the length of a time frame since the last input pulse. Thus if input pulses are separated by more than the length of one time frame, single-shot 26 is activated to insert a pulse. This inserted pulse is passed by Or 24 to sections 12 or 14 and is also fed back to reset generator 22 as a normal input pulse does. Thus the duration between pulses never exceeds the length of a time frame.

Sections 12 and 14 operate identically on alternate time frames. Only the operation of section 12 is described. The first pulse in...