System operates in the nonreturn-to-zero mode, maintaining the increased bit density capability of this mode but with much higher noise immunity than conventional schemes offer. This integrator performs a mathematical integrating function on inputs from 100 Hz through 100 MHz

Lutz, E. B.

English

NASA Technical Reports Server

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December 1968
	
Brief 68-10547 
NASA TECH BRIEF 
NASA Teèh Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Operational Integrator 
Output Voltage Input Current
3 Input Current 
Stress Pulse	 23::
'f 
In Delay Medium
L1+j	
:'80 P^ 
Output Voltage
Y_
3300	 2K 
-3w	
5 
In the usual technique for storing digital informa-
tion of an aperiodic nature, the information is applied 
to a delay medium and later retrieved in identical for-
mat. In many such techniques, transients (noise 
pulses) can interfere with input pulse sequence in a 
manner that destroys the integrity of the original 
information. Such unpredictable limiting conditions 
reduce accuracy of the retrieval of information pre-
sented to the delay line. In the past, designers chose 
to attenuate the problem by return-to-zero clocked 
pulse techniques. 
The system described here operates in the nonre-
turn-to-zero mode, maintaining the increased bit den-
sity capability of this mode but with much higher 
noise immunity than conventional schemes offer. The 
complete system (shown in the upper figure) has a 
driver circuit converting input voltage pulses into cur-
rent pulses of specific magnitude. These are fed into 
the delay line portion of the system. 
Typical waveforms within ultrasonic delay lines, 
such as magnetorestrictive lines, glass lines or others, 
are shown in the lower left figure. This represents an 
idealized timing diagram where an input current step 
is applied to the launch coil, causing a mechanical 
stress pulse in the delay medium to propagate through 
the line at a certain velocity. It is to be noted that 
this stress pulse is proportional to the derivative of 
the input current step. The response of the output 
pickup coil to the stress pulse is a voltage waveform 
which is proportional to the second derivative of the 
input current step. 
This output waveform is now (again referring to the 
upper figure) amplified several hundred times and fed 
to an operational integrator in order to present the 
(continued overleal) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19680000503 2020-03-12T06:29:32+00:00Z
detector with a signal free of the limiting uncertain-
ties (transient noise effects) discussed previously. The 
result is a more reliable and predictable system since 
sporadic noise transients of appreciable amplitude are 
largely attenuated. Additionally, a simpler detection 
technique can be used by feeding the positive pulses 
to the "set" side and the negative pulses to the "reset" 
side of a bistable device. In the present system, the 
signal is detected by a Schmitt trigger. 
The operational integrator, which is the innovation 
in this system, is illustrated in the lower right figure 
and features a "dead space" generator at both input 
and output for the purpose of removing baseline noise. 
The baseline noise at the input is primarily caused by 
the delay line itself, while the output baseline noise is 
caused by dissymmetry of the input signal. This results 
in undesirable baseline offset and requires excessive 
filtering of the +5v supply in order to maintain purity 
of the integration process. Removal of baseline noise 
through the use of "dead space" generators relaxes 
this requirement.
Notes: 
In tests, power supply variations in excess of ±10% 
resulted in no deterioration in performance. 
The integrator described performs a mathematical 
integrating function on inputs from 100 Hz 
through 100 MHz. 
Documentation for the innovation is available 
from:
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Price $3.00 
Reference: B68-10547 
Patent status: 
This invention is owned by NASA and a patent 
application has been filed. Royalty-free, nonexclusive 
licenses for its commercial use will be granted by 
NASA. Inquiries concerning license rights should be

made to NASA, Code GP, Washington, D.C. 20546. 
Source: Erno B. Lutz

Jet Propulsion Laboratory
(N P0-10230) 
Brief 68-10547	 Category 01


Operational integrator

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