Determination of phase stability of a high frequency signal using a computer is accomplished by a circuit using two auxiliary oscillators, multipliers and low-pass filters in cross correlation with the oscillator producing the signal of interest

Nichols, G. B.

English

NASA Technical Reports Server

C11 -7,241 
July 1964	 Brief 63-10555 
NASA TECH BRIEF	
_& 
This NASA Tech Brief is issued by the Technology Utilization Division to acquaint 
industry with the technical content of an innovation derived from the space program. 
Computer Determines High-Frequency Phase Stability 
Oscillator
I Low-Pass 
Multiplier I	 Filter 
Oscillator
I  
Multiplier	 Low-Pass I	 Filter
-I 
:Analog-to-Digital	 Storage i C.
Converter	 Device 7rD,L ----- 1j 
Analog-to-Digital	 Storage 
Converter	 Device i 
L -----
Oscillator
3 
The problem: Determining phase stability of a 	 How it's done: Two oscillators (1) and (3) are used, 
high-frequency (30 Mc) signal using a computer. In 	 having characteristics (center frequency, input/output 
narrowband, phase-locked receivers, optimum band- 	 impedance, etc.) similar to those of the oscillator 
pass design requires a knowledge of the signal source 	 (2) producing the signal of interest. The output signal 
phase stability in order to provide the best signal- 	 from (2) is independently multiplied by the output 
to-noise ratio possible. Present computers are not	 signal from each of the auxiliary oscillators (1) and 
useful at high frequencies and a reliable reference 	 (3) in separate multipliers. The ouput signals from the 
source of known phase stability, in the same frequency 	 multipliers, containing the sum and difference fre-
region, is normally unavailable. 	 quencies of (1) and (2) and of (2) and (3), lose their 
The solution: A discriminator-type circuit that
	 higher frequency components to the low-pass filters. 
uses two auxiliary oscillators, multipliers, and low- 	 The remaining signal is digitized in the analog-to-
pass filters, in cross correlation with the oscillator
	 digital converters and fed either to a storage device, 
producing the signal of interest. The products are	 such as a tape recorder or card punch, or directly 
converted to digital data and may be stored or fed
	 to the computer. The computer is programed to 
A; *1 t,- sk
	
comnute the cross-correlation function of the two JI1' I.L1J flJ LII ¼#tuqJuL..1.	 r
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States Govern-
ment, nor NASA, nor any person acting on behalf of NASA: A. Makes 
any warranty or representation, express or implied, with respect to the 
accuracy, completeness, or usefulness of the information contained in
this document, or that the use of any information, apparatus, method, 
or process disclosed in this document may not infringe privately-owned 
rights; or B. Assumes any liabilities with respect to the use of, or for 
damages resulting from the use of, any information, apparatus, method, 
or process disclosed in this document.
https://ntrs.nasa.gov/search.jsp?R=19630000105 2020-03-11T16:48:33+00:00Z
derived signals and determine its frequency distribu-
tion by taking its Laplace transform. This frequency 
distribution of the cross-correlation function is 
equivalent to the spectral power distribution of the 
signal of interest and from it the equivalent phase 
instability of the oscillator under investigation is 
derived. 
Notes: 
1. This technique may be used as a very accurate 
substitute for a high-grade reference oscillator.
2. For further information about this innovation 
inquiries may be directed to: 
Technology Utilization Officer 
Goddard Space Flight Center 
Greenbelt, Maryland 20771 
Reference: B63-10555 
Patent status: NASA encourages the immediate 
commercial use of this innovation. Inquiries about 
obtaining rights for its commercial use may be made 
to NASA Headquarters, Washington, D.C. 20546. 
Source: Grady B. Nichols 
(GSFC-1 13) 
Brief 63-10555


Computer determines high-frequency phase stability

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