Browse Prior Art Database

Dual Mode Encoder

IP.com Disclosure Number: IPCOM000092374D
Original Publication Date: 1967-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Jones, GD: AUTHOR [+2]

Abstract

This system is for coding two analog signals A and B on the same digital pulse stream. The system is particularly useful for recording a pair of analog speech signals nonsynchronously on a magnetic or optical media. Thus the number of record-read stations is reduced by one half.

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Dual Mode Encoder

This system is for coding two analog signals A and B on the same digital pulse stream. The system is particularly useful for recording a pair of analog speech signals nonsynchronously on a magnetic or optical media. Thus the number of record-read stations is reduced by one half.

The modulation technique employs a pulse-frequency modulator in conjunction with a duty cycle modulator. This is in such a manner that the density of the resulting digital signal is a function of one analog input signal while the frequency of the leading edges of the digital pulses is proportional to the second analog signal. Since the pulse frequency and the duty cycle can be varied independently of each other, the two analog signals do not interact adversely. Signal reconstruction is accomplished by passing the digital signal through a low-pass filter to derive the duty cycle encoded analog signal and by the use of any standard method of measuring the pulse train frequency to recover the frequency encoded input.

Analog input signal A is passed through a band-limiting filter and applied as the control input to a voltage variable frequency sawtooth waveform generator. The latter's deviation about a center frequency is proportional to the amplitude and polarity of the analog input signal A. The value of the center frequency and the range of deviation are determine by the frequency spectrum of the analog signal and the quality of the modulation required.

The output of the...