System determines the direction of arrival of an electromagnetic wave with the direction information in a readily usable form. It presents a relatively small physical structure and does not require mechanical positioning

Beste, J. M.

Graf, E. R.

English

NASA Technical Reports Server

April 1970	 Brief 70-10112 
NASA TECH BRIEF
Z90 
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 Clearinghouse for Federal Scientific and Technical 
Information, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Analysis and Optimization of an Omnidirectional

Direction- Finding System 
is
The purpose of any radio direction-finding system 
is to obtain information from which the direction 
of arrival of an electromagnetic wave may be deter-
mined. Conventional systems for accomplishing this 
include null-seeking antennas having directional 
characteristics that are altered mechanically or elec-
trically, highly directional antennas that can localize 
a region in space, and antennas composed of elements 
that use time- and space-phase displacement. These 
direction finders exhibit one or more of the following 
disadvantages: (1) they require mechanical position-
ing; (2) they present relatively large physical struc-
tures; and (3) the direction information is redundant 
or is not in a readily usable form. A direction-finding 
system which has been investigated analytically and 
experimentally does not have any of these disadvan-
tages. 
The direction of arrival of an electromagnetic wave 
above a plane earth may be uniquely described in 
terms of any of several space-coordinate systems. 
In particular, the knowledge of the direction cosines 
with respect to two perpendicular axes, both of which 
lie in the horizontal plane, is necessary and sufficient 
to describe completely this direction of arrival. Infor- 
mation in the explicit form of direction cosines (or 
direction cosine analogs) is highly desirable in many 
applications. By means of simple analog circuitry, 
the information may be converted into that relating 
to other coordinate systems. 
Although direction cosines appear as phase factors 
on the terminal voltages in linear arrays, there is
difficulty in actually determining these direction 
cosines by phase measurement, because of the un-
avoidable mutual impedances among the elements 
making up the array. By choosing an array with the 
proper spatial symmetry, and by the use of signal-
processing equipment, the un1esirable mutual im-
pedance effects may be eliminated from the system. 
Essentially omnidirectional antenna elements are 
required to observe the hemisphere above a plane 
earth. 
Certain components and characteristics of a theo-
retical system were analyzed and optimized, and the 
results were used to devise an experimental system 
capable of providing accurate direction information. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: TSP70-101 12 
Patent status: 
No patent action is contemplated by NASA. 
Source: E. R. Graf and J. M. Beste of 
Auburn University 
under contract to 
Marshall Space Flight Center 
(MFS- 14346) 
Category 02 
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 ownedrights.
https://ntrs.nasa.gov/search.jsp?R=19700000108 2020-03-17T00:26:47+00:00Z


Analysis and optimization of an omnidirectional direction-finding system

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server