Pulse stretching circuit can linearly stretch pulses as narrow as 50 nanoseconds and block incoming pulses following accepted input pulse until processing has been completed. It also removes baseline distortion by being completely direct coupled and provides monitor output which measures true number of input events that exceed predetermined threshold

Lindsey, R. S., Jr.

English

A pulse stretcher for narrow pulses is presented. The stretcher is composed of an analog section for processing each arriving analog pulse and a digital section with logic for providing command signals to the gates and switches in the analog section

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Pulse stretcher for narrow pulses

October 1973	 B73-10365 
NASA TECH BRIEF
	 4i 
•	 Lyndon B. Johnson Space Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Pulse Stretcher for Narrow Pulses 
The problem: 
Present pulse height analyzers are not capable of 
processing pulses that are much narrower than 1 micro-
second. For this they usually require a pulse stretching 
circuit which will extend these pulses to an acceptable 
width before they are fed into the analyzer input. 
Unfortunately, existing pulse stretching circuits have 
several drawbacks when used with narrow pulse widths. 
First, their output is nonlinear for narrow input pulses. 
This nonlinearity affects analysis of spectra for even low 
event rates. Second, they offer insufficient protection 
against pulse pile-up because of low rejecting analog 
gates located in the input circuitry. Third, they exhibit 
baseline distortion because of capacitive coupling of the 
unipolar or nonsymetrical bipolar input signals. Fourth, 
they provide insufficient means of detecting the true 
number of input events for deadtime corrections.
The solution: 
A pulse stretching circuit was developed which can 
linearly stretch pulses as narrow as 50 nanoseconds and 
block incoming pulses following an accepted input 
pulse until processing has been completed. It also 
removes baseline distortion by being completely direct 
coupled and provides a monitor output which measures 
the true number of input events that exceed a pre-
determined threshold. 
How it's done: 
The pulse stretcher (see figure) is comprised of two 
sections: an analog or linear section, and a digital or a 
decision-making section. The analog section delays the 
incoming pulse with the delay network to allow the 
digital section to decide upon the disposition of the 
pulse event. 
0.
1 n&ogSecuon 
Pulse Delay	 Input Peak Output Outpu to 
Train Input	 Conditioner Network	 Gate Holding Gate Pulse-Height Circuit Analyzer 
L---
--
it&Section --
-- 1 
Level
Positiv I Detector	 , 
Total
-i-- Event s Signal Conditioner Gate Timer	 I Monitor I	 . I Negative I	 Level I Detector L_ 1 
External External 
Inhibit Timing 
Pulse Stretcher Control
(continued overleaf) 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned rights. 
https://ntrs.nasa.gov/search.jsp?R=19730000365 2020-03-17T07:05:35+00:00Z
If the decision is to process this event, the input gate 
connected to the output of the delay network is opened 
and the pulse peak is detected and held for a selectable 
time interval by the peak-holding circuit. The holding 
circuit changes the narrow bipolar pulses to unipolar 
pulses which can be handled without distortion by the 
pulse height analyzer. The duration of the unipolar 
signal is determined by a dump command signal from 
the digital section. 
Meanwhile, the digital section through logic com-
mands prevents the succeeding pulses from changing the 
detected peak amplitude during the hold cycle. The 
undelayed analog pulse is fed to the digital section 
through two level detectors feeding a signal conditioner. 
The conditioned signal is fed to a gate with timing 
externally controlled. When the gate is opened, its out-
put starts the timer which provides the dump signal for 
the holding circuit in the analog section to produce an 
output pulse having an amplitude directly proportional 
to the pulse peak height, but whose pulse shape is 
compatible with ordinary pulse height analyzers. The 
output signal has a positive polarity, and its baseline is 
at zero volts. The digital section control line to the input 
gate also inhibits any other input signals from being 
processed during a predetermined time interval. 
The digital section then resets the analog section to 
process a new event and opens the analog input gate, 
provided a new pulse has not yet been received. If a new 
pulse is present, its processing is specifically inhibited, 
since its peak might have already passed and processing 
would result in an incorrect observation. The digital 
section guarantees the processing of one and only one
analog pulse at a time by keeping the two analog gates 
closed, except when: 
1. The incoming analog pulse has sufficient amplitude 
to trigger the negative level detector; 
2. A minimum period of time has elapsed since the 
processing of a preceding pulse; and 
3. A high level input signal is provided at the external 
timing control input or this input is left open. 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
Johnson Space Center 
Code JM7 
Houston, Texas 77058 
Reference: TSP73-10365 
Patent status: 
This invention is owned by NASA, and a patent 
application has been filed. Inquiries concerning non-
exclusive or exclusive license for its commercial de-
velopment should be addressed to: 
Patent Counsel 
Johnson Space Center 
Code AM 
Houston, Texas 77058 
Source: R. S. Lindsey, Jr., of
Lockheed Electronics Company
under contract to
Johnson Space Center 
(MSC-14130)
I 
. 
B73-10365	 Category 02


Pulse stretcher for narrow pulses

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