Variable power divider keeps microwave transmitter at full power. This preserves the bandwidth and modulation characteristics and proportions any amount of the full power from the normal antenna into a dissipative load

Kolbly, R. B.

English

NASA Technical Reports Server

August 1969	 Brief 69-10290 
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. 
High-Power Microwave Power Divider Concept 
Circular- Polarized 
TEll Mode At This Posit
Quarter-Wave	 Orthomode 
Plot	 nsducer 
Input Poit 2 
Mode Change Circular Rotar 
Tel 	 (Rect) To Joints Tell Linear Polarized 
Tell (Circular Guide) (At This Point Angle 
Figure 1 Of Polarization Is Variable.) 
(A) )B) (C) 
Ht 
Input Mode Change	 Input To 
(TE1O) TEll)	 Transducer
Figure 2 
The problem:	 circular; two quarter wave rotatable plates which 
Operation of a microwave transmitter occasionally 	 change circular polarization to rotatable linear polari-
requires a considerable reduction in power output in	 zation; an orthomode transducer distributing power 
typical situations as: close range testing, or simulating	 to two output ports. The ratio of distribution is deter-
flight conditions by continuously reducing the power 	 mined by the angle between the two quarter wave 
to the XMTR antenna; common practice is to reduce plates. 
the drive to the last power stage, hence, degrading the 
performance. Bandwidth and modulation character- How it's done: 
istics are appreciably affected. 	 The high power microwave power divider is shown 
The solution:	 in Figure I. The power into the mode change section 
This innovation is a concept of a variable power 	 from the TE 10 mode in the rectangular waveguide to 
divider for the output of a microwave transmitter. By 	 the TE 11 mode in the circular waveguide is con-
use of this device, a microwave transmitter may re- 	 verted to TE 11 circular polarization by the first 
main at full power, hence, preserving the bandwidth	 quarter wave plate. By rotating the second quarter 
and modulation characteristics, and proportion any 	 wave plate with respect to the first, rotatable linear 
amount of the full power from the normal antenna into	 polarization is obtained at the output of the second 
a dissipative load.	 quarter wave plate which is connected to the fixed 
The divider consists of four elements: a transducer 	 (relative to input) orthomode transducer. The power 
which changes the polarization from rectangular to 	 into each port is a function of the polarization angle of 
(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=19690000289 2020-03-16T18:12:05+00:00Z
the incident wave and is controlled by the rotary setting 
of the second quarter wave plate. 
Let us define 0 degrees as the direction of polariza-
tion at the input port as shown in Figure 2A. The 
mode is changed to the TE 11 circular polarization in 
the mode change section and the first quarter wave 
plate. This is shown in Figure 2B. The circular polari-
zation is changed to rotatable linear polarization by 
means of the second quarter wave plate and is rotat-
able through 360 degrees. This input to the orthomode 
transducer is shown in Figure 2C. The amount of 
power distributed to load I or load 2 depends upon 
the angle 0 setting of the second quarter wave plate. 
The power into load 1 (P2) is: 
P2 = P i,put Cos 2 0 
The power into load 1 (P1) is: 
P1 = Pinput Sin 2 0 
Therefore, the attenuation from input to Port 2 is: 
A(db) = 10 log Cos 2 0 or A(db) = 20 log Cos 0
Attenuation is a function only of the rotation angle 
and could be remotely read and controlled. 
Note: 
1. This development is in conceptual stage only, and 
as of date of publication of this Tech Brief, neither 
a model nor prototype has been constructed. 
2. No further documentation is available. 
Patent status: 
This invention is owned by NASA, and a patent 
application has been filed. Royalty-free, non-exclusive
licenses for its commercial use will be granted by
NASA. Inquiries concerning license rights should be

made to NASA, Code GP, Washington, D.C. 20546. 
Source: R. B. Koibly of

Cal Tech /JPL
under contract to

NASA Pasadena Office
(NPO-1103 1)
. 
. 
Brief 69-10290	 Category 01


High-power microwave power divider concept

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