Electronic circuit drives sine function generator using square wave and sawtooth sweep generators. The circuit replaces electromechanical driver and increases accuracy

Bogart, T., Jr.

English

NASA Technical Reports Server

February 1966	 Brief 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U. S. space 
program and to encourage their commercial application. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Circuit Operates as Sine Function Generator 
4s Manual Control 
I Square 
Wave I ___________ Filter	 uij Phase  Shifter Control 
Synchronism 
Control
V1 I	 Sweep
__1 Voltage Impulse I	 Generator ___________ I	 Comparator ___________ i Generator
0 Input
Gate	 Ilh	 Hold I	 Sample	 I—.8o=Ksir((P+O) 
The problem: To provide an electrical signal whose 
magnitude is proportional to the trigonometric sine 
of a given angle 0, plus or minus a fixed phase angle 
, when 0 is linearly proportional to the magnitude of 
an input electrical signal. Prior methods have used 
rotating electromechanical components whose dy-
namic accuracy is limited by the slow response time 
of servo controls. 
The solution: A circuit that samples the magnitude 
of a sine wave at a point in its period determined by 
the magnitude of the input signal. 
How it's done: The output of a square wave genera-
tor is filtered in order to recover the fundamental, which 
is a sine wave of the same frequency as the square 
wave. Simultaneously, the square wave is used to 
synchronize a sawtooth sweep generator. The syn-
chronized sweep signal is one input to a voltage com-
parator that also receives a voltage which is linearly
proportional to 0. At a point in time when the value of 
0 is equal to the magnitude of the sweep voltage, the 
output of the voltage comparator drives the impulse 
generator, which in turn opens an electronic gate for a 
short interval. The sine wave obtained from the filter 
is phase shifted through a predetermined angle q by 
the phase shifter and this signal is passed through the 
gate when the impulse generator signal is applied. 
Thus an impulse whose magnitude is proportional to 
sin (0 + 0) is applied to the sample hold. This sample 
is the output voltage, eo=K sin (0 + ), which is 
maintained until the next sample is taken. The syn-
chronism control determines the frequency of sampling. 
which is designed for the anticipated maximum rate of 
change of the input 0, and may be as great as the 
fundamental frequency of the square wave. The greater 
the sampling rate, the more accurately the output will 
represent K sin (0 + ) as 0 varies with time. 
(continued overleaf) 
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=19660000038 2020-03-11T17:33:44+00:00Z
Notes: 
I. The advantages of this innovation are summarized 
as follows: 
a. There are no moving parts, and consequently no 
mechanical wear, no backlash, and no dynamic 
lags as a result of friction and inertia. 
b. A considerable savings is realized in size, weight, 
and reliability over the corresponding character-
istics of a mechanical system. 
c. The static accuracy is not limited by the resolu-
tion (number of turns) of a nonlinear potenti-
ometer. 
d. The accuracy does not depend on the length of 
the interval over which it is desired to generate 
the function.
2. Inquiries concerning this innovation may be di-
rected to: 
Technology Utilization Officer 
Manned Spacecraft Center 
P.O. Box 1537 
Houston, Texas, 77001 
Reference: B66-10038 
Patent status: NASA encourages commercial use 
of this innovation. No patent action is contemplated 
by NASA.
Source: Theodore Bogart, Jr. of

North American Aviation, Inc.

under contract to

Manned Spacecraft Center

(M SC-255)
C 
S. 
Brief 66-10038	 Category 01


Circuit operates as sine function generator

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