Real-time Fourier analysis is provided by "bucket brigade' charge-transfer shift register. Device is small, inexpensive integrated circuit which does analog-to-digital-to-analog conversion, data processing, and time delay

Sutton, J. F.

English

NASA Technical Reports Server

Gate
tntergrate	 VCO Frequency 
and	 •I	 Period 
Hold	 I	 T,-T•I8 
Reconstructed 
Waveform 
May 1975	 B75-10070 
•
	
NASA TECH BRIEF 
Goddard Space Flight Center 	
A 
NASA Tech Briefs announce new 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. 
Fourier Waveform Analyzer 
The problem: 
Complex signal waveforms are analyzed by finding 
their Fourier components. In one method, a swept 
narrow band filter is used. In another method, an 
analog-to-digital conversion is performed followed by 
a digital computer numerical analysis. Both of these 
methods are costly and time consuming. 
Signal Input
The solution: 
In a new technique, real-time Fourier analysis is 
provided by a so-called "bucket brigade" charge-
transfer shift register. This device is a small, 
inexpensive integrated circuit which does analog-to-
digital-to-analog conversion, data processing, and 
time delay. 
Input Waveform	 Sum-Difference	 Period	 T•t) 
Fourier Analysis	 Basic Frequency • I. t,(t) 
.
	 Network
	
Amplitude-Control Voltages 
X I-- I Fourier Amplitude Controls ------
I
Zero
Crossing 
Detector Sum 
Pulse 
Generator (vCo)
41• 
Bias 
Control
—2 Adlust F" A 
I	 I 
I	 —2 
Second Channel I 
torC.dd I

Harmonics I 
l	 I
—2 I	 I 
I	 I 
Fourier Waveform Analyzer Scheme
(continued overleaf) 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19750000070 2020-03-19T20:04:45+00:00Z
4-
. 
How it's done: 
The operation of the Fourier analyzer is as follows 
(see figure): During the signal input, one quasi-
sinusoid of a complex waveform is stored in the shift 
register. The voltage outputs from the "buckets" are 
summed and processed in the Fourier analysis 
network to generate dc voltages proportional to the 
Fourier coefficients. These voltages control analog 
multipliers which serve as gain controls. The gain 
controls govern the amplitudes of sinusoidal signals 
having harmonic frequency relationships. The sinus-
oidal signals are generated using standard analog 
techniques (zero cross-detection, integrate and hold, 
voltage control oscillation (VCO), frequency division, 
and the like). As each new quasi-sinusoid of the 
incoming complex wave is stored in the register, the 
frequencies and amplitudes of the derived Fourier 
components are updated. The individual components 
are then combined in a summing amplifier to 
reconstruct the original wave. 
The analyzer produces dc voltages proportional to 
the Fourier coefficients as well as a reconstructed
waveform for comparison with the original. By 
adjusting a bias (gain) on the VCO, the waveform can 
also be reproduced with a time base different from 
that of the input waveform. This results in the 
frequency shifts of each frequency component in the 
complex wave by some constant ratio. 
Note: 
No further documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Goddard Space Flight Center 
Code 704.1 
Greenbelt, Maryland 20771 
Reference: B75-10070 
Patent status: 
NASA has decided not to apply for a patent. 
Source: John F. Sutton

Goddard Space Flight Center

(GSC-11747) 
Categories: 02 (Electronics Systems) 	 n
01 (Electronics - Components and 
B75-10070
	 Circuitry)


Fourier waveform analyzer

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