Two types of filters, leaky-wall and open-guide, are combined into single component. Combination gives 10 db or greater additional attenuation to fourth and higher harmonics, at expense of increasing loss of fundamental frequency by perhaps 0.05 to 0.08 db. Filter is applicable to all high power microwave transmitters, but is especially desirable for satellite transmitters

Allen, C. C.

Geia, A. J.

Jankowski, H.

English

NASA Technical Reports Server

December 1973	 B73-10313 
• 
NASA TECH BRIEF 
Lewis Research Center *	
_4V 
NASA Tech Briefs announcenow 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 National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Extended Range Harmonic Filter 
.
The Problem: 
Recent developments in the communications satellite 
field have indicated a strong trend toward operation at 
higher frequencies, particularly in the 12 GHz region. 
Requirements for high power operation in this region 
range from a few hundred watts to possibly several 
kilowatts as manifested in advanced traveling wave tube 
and klystron developments in the 200 to 2000 watt range 
at 12 GHz. 
A critical subsystem in a high power satellite trans-
mitter is the waveguide assembly. One of the components 
of the waveguide assembly is the harmonic filter which is 
required to introduce high attenuation at the second 
through the fifth harmonics with a minimum of loss to 
the fundamental frequency. The conventional leaky-wall 
type filter has a low loss, but its attenuation is inadequate 
at the fourth and fifth harmonics. 
The Solution: 
An extended range harmonic filter combines two types 
of filters, leaky-wall and open-guide, into a single com-
ponent. 
How It's Done: 
The extended range filter is based on the leaky-wall 
filter which uses slots cut in the walls to couple harmonics 
out of the main waveguide. A section of open-guide 
harmonic filter is inserted into the leaky-wall filter, adding 
only a small loss at the fundamental frequency, but 
increasing the attenuation of the fourth and fifth har-
monics. The combined filter configuration is shown in 
Figure 1. 
Figure 2 indicates the general appearance of the input 
and output sections of the filter, with slots tapering from 
very small at the end of the filter, to about half the 
broadwall dimension at the center of the filter. Slots in all 
four walls couple out the harmonic energy with a 
minimum of loss to the fundamental. A few slots at-the 
ends are impedance matching transition slots; the center 
slots of each section are tuned to the second harmonic 
and are effective also at the third harmonic.
Leaky Wall 5pen Guidej Leaky Wall
Figure 1. Combination Type Harmonic Filter 
Figure 2. Leaky Wall End Sections 
4 
Figure 3. Open Guide Center Section 
To obtain at least 20 dB attenuation above the third 
harmonic, an open-guide type of filter with higher 
attenuation of the fourth and fifth harmonics is inserted 
between the input and output sections of the conven-
tional leaky-wall type. The open-guide filter type is shown 
in Figure 3. 
The combination gives 10 dB or greater additional 
attenuation to the fourth and higher harmonics, at the 
expense of increasing the loss of the fundamental fre-
quency by perhaps 0.05 to 0.08 dB. Thus the principal 
advantage is the added reduction of harmonic radiation 
(continued overleaf) 
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from a microwave transmitter, preventing potential inter-
ferences with other devices, in return for a small power 
loss of 1-2%. By combining the two types of filters and 
keeping the open-guide section short, the overall loss was 
kept reasonably low and the high-harmonic attenuation 
was achieved. 
Notes: 
1. This new filter is applicable to all high power micro-
wave transmitters, but is especially desirable for 
satellite transmitters. 
2. A filter of this design has been built and tested for use 
at 8 GHz. Its performance at 12 GHz is being 
investigated. 
3. Further information is available in the following 
report: 
NASA CR-120927 (N73-26152), High Power 
Microwave Components for Space Communications 
Satellites 
Copies may be obtained at cost from: 
Aerospace Research Applications Center 
Indiana University 
400 East Seventh Street 
Bloomington, Indiana 47401 
Telephone: 812-337-7833 
Reference: B73-10313 
4. Specific technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B73-10313 
Patent Status: 
NASA has decided not to apply for a patent. 
Source: H. Jankowski, A.J. Geia,
and C.C. Allen
General Electric Co. 
under contract to
Lewis Research-Center
(LEW-1 2064)
E 
. 
is 
B73-10313	 Category 02


Extended range harmonic filter

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