Browse Prior Art Database

Real Time Cascadable Digital Differentiator

IP.com Disclosure Number: IPCOM000121574D
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Millas, RJ: AUTHOR [+3]

Abstract

This article describes a real-time cascadable digital differentiator (RTCDD) which utilizes a cascadable method of producing Nth-order derivatives of digital signals.

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Real Time Cascadable Digital Differentiator

      This article describes a real-time cascadable digital
differentiator (RTCDD) which utilizes a cascadable method of
producing Nth-order derivatives of digital signals.

      The computation of digital signals to derive an Nth-order
derivative in real time is significant in the field of
instrumentation.

      Fig. 1 shows a functional block diagram of a RTCDD. The
sampling rate is provided by clock signal (CLK).  The bus marked as
INPUT X contains real-time values.  These values are used to obtain
the OUTPUT dX/dt.  If scaling is desired, SCALE ENABLE is set active
and a scale factor is provided through the bus marked as SCALAR.

      Cascading of RTCDDs allows the designer to generate an
Nth-order derivative.  For example, if a second-order derivative is
desired, two RTCDDs cascaded together provide an output of d2X/dt2
for a given input X, as shown in Fig. 2.

      Fig. 3 shows an internal functional diagram of a RTCDD. The
sample register latches the value on the INPUT X bus according to the
sampling clock CLK.  The difference between the latched value and the
current value on the INPUT X bus is computed by the subtractor, which
is in effect dX/dt, where dt is assumed a unit value determined by
the sampling frequency.  Therefore, since dt is always a constant, it
can be entered as a scalar of 1/dt through the scalar bus.  If a
scaling is indeed desired, the SCALE ENABLE line is set to 1, which...