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FBN Software proudly presents FFTUTIL. FFTUTIL is an analysis tool
to be used in conjunction with COMPFFT. The utility consists of 2
programs GENINPUT.BAS and PROC.BAS. The programs generate input data
for spectral analysis by COMPFFT. I am providing you with the source
code for these programs so you can modify them to suit your own
applications.

GENINPUT.BAS generates a waveform which can be used by COMPFFT and
PROC.BAS to look at the response of a system to impulses, pulses,
triangular waveforms, Cosine waveforms, or any generalized input you
would care to generate. The opening menu of GENINPUT.BAS is shown
below :

********************************************************************************

---- PROGRAM GENERATES A SPECTRAL FORCING FUNCTION ----

DATA CAN ALSO BE GENERATED BY MANUAL INPUT OR BY EQUATION

by FBN Software

SELECT FROM MENU :

(I)MPULSE FORCING FUNCTION
(S)TEP FORCING FUNCTION
(T)RIANGLE FORCING FUNCTION
(P)ULSE FORCING FUNCTION
(C)OSINE FORCING FUNCTION
(F)ILE TO DISC
(H)ARD COPY (PRINT/DISPLAY)
(D)ATA INPUT (MANUAL/EQUATION)
(E)XIT PROGRAM

*******************************************************************************


INPUT SELECTION : ?

The Impulse, Step, Pulse, and Cosine forcing functions all produce a
complex frequency domain response. If you which to view the numerical
data generated by the program you can do so by using the (H)ard copy
option. This option provides you with a numerical listing of the
response of the chosen forcing function. You can use COMPFFT to view a
graphical response of the function and to convert the function from the
frequency domain to the time domain (and vice versa). You also have the
capability to input your own forcing function manually or you can
represent your function with Basic statements at program line 12000.
Your forcing function can be described in the time domain or in the
frequency domain. If you describe a frequency domain response set V$
= "F" if you input your data via an equation. V$ chooses the header
"Frequency" for display/printout if set to an "F".

You can save the functions you have generated to disk with the
(F)ile option for use by PROC.BAS and COMPFFT. Use an SPC extension on
the file if it contains spectral (frequency) data. COMPFFT uses the SPC
extension to identify a spectral input file.

PROC.BAS allows you to process one or more sets of spectral data so
you can generate the response of a system to impulse, step, cosine, and
other various forcing functions. The opening menu of PROC.BAS is shown
below so that you can see the functions that are performed by the
program.

********************************************************************************

---- WAVEFORM PROCESSOR ---- SELECT FROM MENU ----

by FBN Software


(L)OAD A REGISTER (S)TORE Y REGISTER
(P)RINT A REGISTER (M)ULTIPLY X INTO Y REGISTER
(A)DD X INTO Y REGISTER (D)ELAY OR SCALE X
(I)NTERCHANGE X AND Y (Z)ERO PHASE
(C)ONJUGATE (N)OISE BANDWIDTH
(E)XIT


********************************************************************************

Input your Selection?

In order to use the program you must first input data to a register.
There are 2 input register (data) arrays X and Y. You can perform
mathematical operations on the data in X and Y ( Add, Multiply),
conjugate the data, interchange X and Y, delay and scale the value of
the data in the X register, make a register have zero phase, and compute
the noise bandwidth of a spectral input signal. After you are finished
manipulating the data you can save the results for display and analysis
by COMPFFT. You can also obtain a numerical display and printout of the
data with the (P) option.

This program can used to produce the impulse, step, pulse, cosine,
(or any arbitrary waveform you have generated) response of a filter or
system function that can be defined spectrally. Multiplication of two
frequency functions is equivalent to convolution in the time domain. You
can even use the program to add to waveforms together (time domain) use
COMPFFT to produce a spectral output file and then use PROC.BAS to
multiply the input spectrum by a system (or filter) spectral response,
and output the result to COMPFFT to see what the time domain response of
the system looks like. As you can see, these programs offer you a very
powerful set of analysis tools.


The programs included on this disk are :

FFTUTIL.DOC - This program
PROC.BAS - Waveform Processor
GENINPUT.BAS - Waveform Generator

FFTUTIL was written using QB 4.0. It should work on GWBASIC or IBM
BASICA by deleting the statements that use the following format :
Z$ : Z$ = UCASE$(Z$) which is used to convert inputs to Upper Case. You
can then use the CAPS LOCK key on your computer to supply upper case
only responses to input queries or you can try a line like this :
If ASC(Z$) > 96 THEN Z$ = CHR$(ASC(Z$)-32). Warning this only works on
single character strings and will not properly identify lower case or
mixed set file extensions.


Problems & Freeware Pitch : I offer this program to the general public as
"Freeware". By this I mean you can make copies of the ARC file and give
them to your friends. Just be sure to include all files (Including
FFTUTIL.DOC) in FFTUTIL.ARC. If you have problems and want support, I'll
provide it to you for a negotiable fee (depending on the difficulty of the
problem). If you find a program bug or operational error please notify me
and I'll see if I can fix it.

Who am I and why am I doing this :

Who ?

William L. Gill
12713 Brunswick Lane
Bowie,Md. 20715

My qualifications : I am an Electrical Engineer with 27 years of
experience. My specialty is Signal Processing. I am a former
applications engineer for Westinghouse Integrated Circuits. I have
approximately 15 years of part time teaching experience (Application of
Digital Integrated Circuits, and the Application of Linear Integrated
Circuits). So I have a strong background in circuit analysis and
performance.

Why am I doing this ? I don't really expect to make money from
these programs. It is an engineering program and should therefore have a
limited appeal. I think it provides a tool that some of you will want
to try. I think the total package of CHEBFILT, BESSEL, COMPFFT, and
FFTUTIL are possibly the start of a future shareware business. Only time
and your responses will tell.