Browse Prior Art Database

Proper Visual Rendering of Coarse Digital Data by a Slow Digital Plotter

IP.com Disclosure Number: IPCOM000052467D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 3 page(s) / 44K

Publishing Venue

IBM

Related People

Mizzi, JV: AUTHOR

Abstract

This article relates generally to the plotting of digital data and, mor particularly, to the plotting of analog signals which have been converted to digital signals. Still more particularly, the article relates to an approach which provides distortion-free, smooth data rendering of an analog signal using multiples of the original sampling rate.

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Proper Visual Rendering of Coarse Digital Data by a Slow Digital Plotter

This article relates generally to the plotting of digital data and, mor particularly, to the plotting of analog signals which have been converted to digital signals. Still more particularly, the article relates to an approach which provides distortion-free, smooth data rendering of an analog signal using multiples of the original sampling rate.

Fig. 1 shows a known technique for plotting analog signals such as ECG signals from digital data using a relatively slow digital plotter. In the prior-art arrangement, an analog-to-digital converter 1 operating at a sampling rate of 250 samples per second provides an output which is stored in digital form in an appropriate storage medium 2. In a variable fetch rate on demand mode from a digital plotter 3, a linear interpolation s used to derive an intermediate point between each of the stored data points to provide a higher resolution of analog data plotting by simulating a data sampling rate of 500 samples per second from data which is derived and stored at 250 samples per second.

In many instances, linear interpolation (carried out under program control) introduces only a negligible amount of distortion. However, in other applications where the discrepancy between the digital system requirements regarding sampling rates and the rates required for "smooth" digital plotting are greater, the distortion introduced by filling in several points between "real" data points by linear interpolation would not be negligible. A straightforward solution to the above-described problem would be to use a higher sampling rate but at the expense of much larger data storage.

Fig. 2 shows an approach which eliminates the linear interpolation function and utilizes digital-to-analog and analog-to-digital converters operating at different sampling rates to provide constant time-base plotting at the same resolution as that provided in the arrangement of Fig. 1.

In Fig. 2, data is provided from a...