Investigation established analytic expressions for the design of pulse modulators with modulating signal control of the reset level of flux in a nonlinear magnetic core. Expressions derived are applicable to both pulse-width and pulse-rate modulator designs

Veillette, L. J.

English

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March 1969	 Brief 69-10070 
NASA TECH BRIEF 
NASA Tech 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. 
Analysis of Magnetically-Controlled Processes 
in Pulse-Modulation Systems 
S
An investigation has been made to establish simple 
analytic expressions applicable to the design of a class 
of pulse mOdulators in which the modulating signal 
controls the reset level of flux in a nonlinear magnetic 
core. Analysis was carried out in the reset-coordinate 
plane Br, T r by defining two constraints on the reset 
process; one imposed by the magnetic core itself, and 
the other which includes the circuitry external to the 
core. Expressions derived for modulator response, 
modulation sensitivity, and limit-cycle stability were 
applied to both pulse-width and pulse-rate modulator 
designs. 
Basic character of modulator behavior was shown 
to depend on the relative magnitudes and algebraic 
signs of the circuit derivative dBr/dTr and the core 
derivative dB,/dlr. Modulator response was found 
to be oscillatory for designs in which (dBr/dTr)/(dBr/ 
dTr) < 0, and is monotonic for (dBr/dTr•)/(dBr/dTr) 
>0. Modulator stability depends only on the magni-
tude of (dB r /dTr) /(dB, /dTr ).Discontinuities in the 
fundamental mode of operation or transitions to a 
subharmonic mode were shown to result from the 
onset of instability. The region of stable operation is 
extended and the modulator response made very fast 
for a design using constant reset time. 
Results of the investigation show that modulator 
performance parameters can vary over a wide range in 
the region of normal operation, with a significant de-
terioration in response occurring as the threshold of 
instability is approached. Pulse-width modulator de-
signs with both finite and infinite circuit derivatives
were analyzed for operation under constant-voltage 
reset conditions. Essentially optimum modulator per; 
formance was obtained for operation under fixed-
reset-time conditions (infinite circuit derivative). The 
results of the generalized analysis were also applied 
to a pulse-rate modulator operating under constant-
current reset conditions. Both an analytical descrip-
tion of the magnetic core reset function and a graphic 
representation of an experimentally-derived character-
istic were used in the analyses, thus illustrating the 
flexibility of the generalized approach. 
Notes: 
I. Performance parameters of each of the above mod-
ulator circuits were measured and compared with 
the theoretical and calculated values. In each case 
good agreement was obtained and the results of the 
generalized analysis thereby substantiated. 
2. Documentation for the innovation is available 
from:
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Price $3.00 
Reference: TSP69- 10070 
Patent status: 
No patent action is contemplated by NASA. 
Source: Leo J. Veillette 
(GSC- 10241) 
Category 01 
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=19690000070 2020-03-16T17:53:35+00:00Z


Analysis of magnetically-controlled processes in pulse-modulation systems

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