An improved test method accurately measures the insertion loss of RF components while avoiding amplifier drift. Currents are balanced across a bridge transformer with shorted probes and then with each component to be tested. Differences in adjustments indicate the loss

Finnie, C. J.

Schuster, D.

English

NASA Technical Reports Server

June 1964
NASA TECH BRIEF
Brief 64-10080 
This NASA Tech Brief is issued by the Technology Utilization Division to acquaint industry 
with the technical content of an innovation derived from the NASA space program. 
Improved Insertion-Loss Tester 
g
^e, ivity (Null) Meter 
Amplifier 
r..ThBridge Transformer 
Bias
Lild Ratio Transformer
	
h 
, 
J,_ Shie d - 
Bias 
"Input Bolometer
Phase Shifter 
Output Bolometer 
I Generator I	 Component 
to be Tested 
Directional Coupler 
The problem: Accurate measurement of the inser-
tion loss of rf components while avoiding the effects 
of amplifier drift. 
The solution: Balancing currents across a bridge 
transformer with shorted probes and then with the 
component to be tested in the circuit. Adjustments 
are made to obtain a null on a sensitivity meter in each 
case and the difference in adjustment is interpreted to 
give the component's insertion loss. 
How it's done: The rf output of the input bolom-
eter is applied to the ratio transformer that is tapped 
to the primary of a bridge transformer. The secondary 
of the bridge transformer drives an amplifier
Directional Coupler 
connected to a null meter. The output of the bridge 
transformer primary is fed to an output bolometer 
through a phase shifter. To test the insertion loss of 
a component, the directional couplers are connected 
(shorted) and the tap on the ratio transformer 
adjusted to obtain a null on the meter. The tap 
position for meter null is recorded. The couplers 
are now disconnected and, with the test component 
inserted, the tap on the ratio transformer is again 
adjusted to obtain a null on the meter. Once an almost 
complete balance is obtained, the phase shifter is ad-
justed until an actual null is obtained. This tap 
position for meter null is recorded. The difference 
between the two recorded tap positions is converted by 
(continued overleat) 
This document was prepared under the sponsorship of the National	 this document, or that the use of any information, apparatus, method, 
Aeronautics and Space Administration. Neither the United States Govern .	 or process disclosed in this document may not infringe privately-owned 
•	 ment, nor NASA, nor any person acting on behalf of NASA: A. Makes 	 rights; or B. Assumes any liabilities with respect to the use of, or for 
any warranty or representation, express or implied, with respect to the 	 damages resulting from the use of, any information, apparatus, method, 
accuracy, completeness, or usefulness of the information contained in 	 or process disclosed in this document.
https://ntrs.nasa.gov/search.jsp?R=19640000026 2020-03-11T17:06:28+00:00Z
a table or chart to give the rf insertion loss of the 
component tested. 
To prevent transients from affecting bridge trans-
former current, an electrostatic shield is placed 
around the transformer primary and maintained at the 
potential of the primary by means of the poten-
tiometer. 
Note: 
For further information about this invention 
inquiries may be directed to: 
Technology Utilization Officer 
Jet Propulsion Laboratory 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: B64-10080
Patent status: NASA encourages the immediate 
commercial use of this invention. It is owned by 
NASA and a patent application has been filed. When 
patented, royalty-free nonexclusive licenses for its 
commercial use will be available. Inquiries concerning 
license rights should be made to NASA Headquarters, 
Washington, D.C. 20546. 
Source: C. J. Finnie and D. Schuster 
(JPL-358) 
Brief 64-10080


Improved insertion-loss tester

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