E-band thermistor mount and a technique for adjusting a temperature compensating thermistor to provide an electrically balanced bridge are used for measuring RF power in the mm-wavelength. The mount is relatively insensitive to temperature effects that cause measurement errors in single ended circuits

Mullen, D. L.

Oltmans, D. A.

Stelzried, C. T.

English

NASA Technical Reports Server

May 1968	 Brief 68-10152 
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. 
MM-Wave Power Meter Mount 
Clamp
Upper Slide 
Thermistor Mount	 I 
"	 Thermistor Mount 
Lower Slide 
Silicone Grease 
Waveguide Window 
The problem: 
In power measurement applications in the mm-
wavelength region, commercially available mounts are 
not useful for precision measurements above a fre-
quency of 40 GHz. Power measurements above this 
frequency can be performed by using a waveguide 
transition section to match an available R-band 
mount to the E-band flange but only with resultant 
poor sensitivity and narrow band performance. The 
E-band thermistor mounts that are commercially 
available consist of only one power detection thermis-
tor and are too strongly affected by changes in mount 
temperature to make accurate measurements. In 
addition, these mounts are not electrically compatible 
with modern commercial power meters. 
The solution: 
An E-band thermistor mount for measuring RF 
power in the mm-wavelength (usually 3 mm) and a 
technique for adjusting a temperature compensating
thermistor to provide an electrically balanced bridge. 
The mount is relatively insensitive to temperature 
effects that cause measurement errors in single ended 
circuits. 
How it's done: 
Two single commercially available thermistor 
mounts are thermally bonded together and wired 
electrically to adapt to a commercial power meter. 
A stainless steel waveguide section with waveguide 
window prevents convection currents,thus thermally 
isolating the power detection (left) thermistor mount. 
One thermistor is mounted in each slide, a tempera-
ture compensating thermistor in the upper slide and 
a power detection thermistor in the lower. The slides 
move laterally and are moved and set for maximum 
output on the power meter. The two thermistors form 
the input bridge circuit, with the detection thermistor 
resistance related to the magnitude of the power enter-
ing the waveguide.
(Contunucd ocrIeaf) 
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=19680000152 2020-03-12T05:28:05+00:00Z
A novel technique is used to provide a thermal path 
or heat leak to the temperature compensating thermis-
tor required to balance the bridge. The upper slide 
is masked leaving a slit in front of the thermistor 
leads. A fine paint spray is then drawn through by a 
low vacuum applied to the opposite side and coats the 
longer thermistor lead to form the thermal path to 
the slide. The thermistor is alternately monitored 
under the microscope and with the power meter, 
between spray coats, until the bridge is within the 
normal operating range. 
Notes 
I. Used in conjunction with a commercially available 
insertion loss test set, this mount extended its 
frequency range to 100 GHz.
2. Inquiries concerning this invention may be di-
rected to:
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: B68-10152 
Patent status: 
This invention is owned by NASA, and a patent 
application has been tiled. Royalty-free, nonexclusive 
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: Charles T. Stelzried, 
Donald L. Mullen, and Donald A. Oltmans 
of Jet Propulsion Laboratory 
(N P0-10348) 
Brief 68-10152	 Category 01


Mm-wave power meter mount

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