CMI DECODING SYSTEM

• Main Authors: HASEGAWA MAKOTO, KUSAMA TAKEO
• Format: Patent
• Language: English
• Published: 25.06.1993
• Subjects: BASIC ELECTRONIC CIRCUITRY; CODE CONVERSION IN GENERAL; CODING; DECODING; ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHICCOMMUNICATION

PURPOSE:To always attain correct decoding independently of input polarity of a CMI(coded mark inversion) code by discriminating a same polarity detection output when a noninverting (inverting) frequency division output is at '1'. CONSTITUTION:A phase locked loop circuit 2 generates a pulse whose period is a half of a repeating period of a data code and phase-locked to a change point detected by a change point detection section 1. Then the pulse is subject to 1/2 frequency division as a clock input to obtain noninverting and inverting frequency division outputs whose period is equal to a repeating period of a data code, the input clocks are eliminated by one clock to change the relation of the phase of the CMI code in the frequency division output by 180 deg.. On the other hand, the system is provided with noninverting and inverting logic circuits 8, 9 setting its output to '1' when the same polarity is consecutive in the CMI code over a half of the repeating period of the code, the detection output is ANDed with each of noninverting and inverting frequency division outputs, and the phase of the frequency division output is controlled so that the frequency of occurrence of '1s' of the noninverting AND output is more than that of the inverting AND output.