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Abstract

A method is described of coding baseband signals for processing or transmission through channels which require noise improvement but have insufficient available bandwidth to support wide-band FM or conventional PCM signals. The method, referred to as hybrid-pulse coding, is a variant of multilevel PCM in which the least significant digit is made continuously variable in amplitude, thus avoiding quantizing noise.

A theoretical feasibility study has been made of the application of hybrid-pulse coding to the transmission of 625-line 5.5 MHz video signals over poor RF circuits. The report describes the selection of system parameters and makes a theoretical appraisal of the noise improvement of HPCM systems. The performance of the system is compared with that offered by narrow-band FM transmission; further coding developments and some modulation schemes are also discussed.

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