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Synthesis of Delta Modulation Representation of Sinusoids

IP.com Disclosure Number: IPCOM000076806D
Original Publication Date: 1972-Apr-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Audretsch, LM: AUTHOR [+2]

Abstract

Delta modulation encoded signal representations of various sinusoids are used in telephone communication systems, for instance as "busy signals", "dial tones", etc. These signals are usually derived by straightforward conversion of corresponding analog signals taken from oscillators. Synthesis of such signals by techniques described below would, in many instances, effect circuit economies in areas of cost, packaging and power consumption.

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Synthesis of Delta Modulation Representation of Sinusoids

Delta modulation encoded signal representations of various sinusoids are used in telephone communication systems, for instance as "busy signals", "dial tones", etc. These signals are usually derived by straightforward conversion of corresponding analog signals taken from oscillators. Synthesis of such signals by techniques described below would, in many instances, effect circuit economies in areas of cost, packaging and power consumption.

Delta modulation conceptually may be viewed as sequences of binary signal units of known timing, each unit derived by sampling the instantaneous polarity of the difference between the corresponding analog function and its cumulative time integral. Interestingly, for most sinusoids, the delta modulation representation for a single cycle of the function would consist of several connected subsequences or packets of alternating binary 1 and 0 (or -1) signal units. The packets vary in length according to the amplitude and frequency of the associated analog function. For many sinusoids, assuming a nominal amplitude level, the code representation for a cycle when graphically plotted is found to have extensive half-cycle and quarter-cycle symmetry of various forms (i.e., mirror-image symmetry, complementary symmetry, repetition, etc.). Also, there are many frequencies which will have a high degree of commonality in length (although not distribution) of packets of alternating binary signal. For example, one frequency exhibiting this condition with a sampling rate of 64 K bits/sec and nominal amplitude of 3.5 volts is 890 cycles/sec.

Half-cycle symmetry in the delta modulated bit pattern would be: 101101101011010101010101001010010010 0 degrees to 180 degrees Segment 1 010010010100101010101010110101101101 180 degrees to 360 degrees Segment 2

Segment 1 is complement of Segment 2.

Quarter-cycle symmetry in the delta modulated bit pattern would be: 1011011010110...