Measurement of great circle patterns requires rotation in azimuth with discrete rotation in elevation. This technique eliminates a set of slip-rings and rotary joints and permits the use of larger models since only continuous azimuth rotation is required

Lipin, R.

Rainwater, L.

English

NASA Technical Reports Server

December 1969
	
Brief 69-10677 
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. 
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Measurement Technique for the Determination of Antenna Directivity 
The problem: 
The directivity of an antenna—the ratio of radiation 
intensity in a given direction to average radiation in-
tensity—is conventionally measured by integrating 
conical antenna patterns. In order to generate conical 
patterns, rotation in elevation with discrete rotation in 
azimuth is required. The instrumentation required to 
produce the rotation in elevation with discrete rotation 
in azimuth is necessarily composed of complex slip-
rings and rotary joints; use of large, heavier models is 
also limited. 
The solution-: 
The measurement of great circle patterns requires 
rotation in azimuth with discrete rotation in elevation. 
This technique eliminates a set of slip-rings and rotary 
joints, and permits the use of larger models since only 
continuous azimuth rotation is required. 
How it's done: 
A spherical coordinate system describes the rotation 
of the model antenna. Measurements establish the 
angles for maximum radiation intensity and permit 
plotting the radiation as a function of 0 angles at 
discrete 0 angles. A.yerage radiation intensity is found 
by double integration of the radiation intensity func-
tion over the entire sphere. While this method is 
convenient, a special technique is required to inte-
grate measurements while they are being plotted. 
The radiation function is electronically multiplied by 
the sine of 0 by coupling the detected signal into a 
sine potentiometer which is mechanically linked to a 
polar recorder turntable; the product is fed to an 
electronic integrator. The integration process is sim-
plified by multiplying the radiation function by the 
sine of 0. rather than the first integral by the sine of 0. 
Note: 
No additional documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B69-10677 
Patent status: 
No patent action is contemplated by NASA. 
Source: L. Rainwater and R. Lipin of 
Sperry Rand Corporation 
under contract to 
Marshall Space Flight Center 
(M FS- 12799) 
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.
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Measurement technique for the determination of antenna directivity

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