<< Chapter < Page
  Digital signal processing - dsp     Page 18 / 24
Chapter >> Page >
  • Because it uses an FFT algorithm, Dsp030 is much less flexible than Dsp028 , particularly with respect to data length and selection of the frequencies of interest.
  • Because it uses an FFT algorithm, Dsp030 is much faster than Dsp028 , particularly when used to perform spectral analysis on long data lengths.

A complete listing of Dsp030 is provided in Listing 22 .

Description of the program named dsp030

This program uses an FFT algorithm to compute and display the magnitude of the spectral content for up to five sinusoids having different frequencies andamplitudes. (See the program named Dsp028 for a program that does not use an FFT algorithm.)

The input parameters

The program gets input parameters from a file named Dsp030.txt . If that file doesn't exist in the current directory, the program uses a set ofdefault parameters.

Each parameter value must be stored as characters on a separate line in the file named Dsp030.txt . The required input parameters are shown in Figure 16 . (Contrast this with the required input parameters for Dsp028 shown in Figure 12 .)

Figure 16. Required input parameters for Dsp030.
Data length as type int (must be a power of 2) Number of spectra as type int. Max value is 5.List of sinusoid frequency values as type double. List of sinusoid amplitude values as type double.

Note that in contrast with Figure 12 , the required input parameters for Dsp030 do not include the sample number representing zero time, the lower frequency bound for computation of the spectra, and the upperfrequency bound for computation of the spectra.

(The computational frequency range cannot be specified for the FFT algorithm. It always computes the spectra from zero to one unit less thanthe sampling frequency.)

Restrictions on the data length

Note also that the data length must always be a power of two. Otherwise, the FFT algorithm will fail to run properly.

(This restriction is an important contributor to the speed achieved by the FFT algorithm.)

The sinusoidal frequency values

As with Dsp028 , the number of values in each of the lists must match the value for the number of spectra.

All frequency values are specified as a double representing a fractional part of the sampling frequency.

Figure 17 shows the parameters used to produce the spectral analysis plots shown later in Figure 18 .

(Note that the data length is a power of two as required by the FFT.)

Figure 17. Example input parameters.
256 50.1 0.20.3 0.50.005 9090 9090 90

The plotting program

The plotting program that is used to plot the output data from this program requires that the program implement GraphIntfc01 . For example, the plotting program named Graph03 can be used to plot the data produced by this program. This requires that you enter the following at thecommand line prompt after everything is compiled:

java Graph03 Dsp030

The plotting program named Graph06 can also be used to plot the data produced by this program, requiring that you enter the following at thecommand line prompt:

java Graph06 Dsp030

The transform method

A static method named transform belonging to the class named ForwardRealToComplexFFT01 is used to perform the actual spectral analysis. The method named transform implements an FFT algorithm. As mentioned above, the FFT algorithm requires that the data lengthbe a power of two. This method will be discussed very briefly later.

Questions & Answers

what is math number
Tric Reply
x-2y+3z=-3 2x-y+z=7 -x+3y-z=6
Sidiki Reply
Need help solving this problem (2/7)^-2
Simone Reply
x+2y-z=7
Sidiki
what is the coefficient of -4×
Mehri Reply
-1
Shedrak
the operation * is x * y =x + y/ 1+(x × y) show if the operation is commutative if x × y is not equal to -1
Alfred Reply
An investment account was opened with an initial deposit of $9,600 and earns 7.4% interest, compounded continuously. How much will the account be worth after 15 years?
Kala Reply
lim x to infinity e^1-e^-1/log(1+x)
given eccentricity and a point find the equiation
Moses Reply
12, 17, 22.... 25th term
Alexandra Reply
12, 17, 22.... 25th term
Akash
College algebra is really hard?
Shirleen Reply
Absolutely, for me. My problems with math started in First grade...involving a nun Sister Anastasia, bad vision, talking & getting expelled from Catholic school. When it comes to math I just can't focus and all I can hear is our family silverware banging and clanging on the pink Formica table.
Carole
I'm 13 and I understand it great
AJ
I am 1 year old but I can do it! 1+1=2 proof very hard for me though.
Atone
hi
Adu
Not really they are just easy concepts which can be understood if you have great basics. I am 14 I understood them easily.
Vedant
hi vedant can u help me with some assignments
Solomon
find the 15th term of the geometric sequince whose first is 18 and last term of 387
Jerwin Reply
I know this work
salma
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
virgelyn Reply
hmm well what is the answer
Abhi
If f(x) = x-2 then, f(3) when 5f(x+1) 5((3-2)+1) 5(1+1) 5(2) 10
Augustine
how do they get the third part x = (32)5/4
kinnecy Reply
make 5/4 into a mixed number, make that a decimal, and then multiply 32 by the decimal 5/4 turns out to be
AJ
how
Sheref
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
hmm
Abhi
is it a question of log
Abhi
🤔.
Abhi
I rally confuse this number And equations too I need exactly help
salma
But this is not salma it's Faiza live in lousvile Ky I garbage this so I am going collage with JCTC that the of the collage thank you my friends
salma
Commplementary angles
Idrissa Reply
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
hii
Uday
hi
salma
hi
Ayuba
Hello
opoku
hi
Ali
greetings from Iran
Ali
salut. from Algeria
Bach
hi
Nharnhar
A soccer field is a rectangle 130 meters wide and 110 meters long. The coach asks players to run from one corner to the other corner diagonally across. What is that distance, to the nearest tenths place.
Kimberly Reply
Jeannette has $5 and $10 bills in her wallet. The number of fives is three more than six times the number of tens. Let t represent the number of tens. Write an expression for the number of fives.
August Reply
What is the expressiin for seven less than four times the number of nickels
Leonardo Reply
How do i figure this problem out.
how do you translate this in Algebraic Expressions
linda Reply
why surface tension is zero at critical temperature
Shanjida
I think if critical temperature denote high temperature then a liquid stats boils that time the water stats to evaporate so some moles of h2o to up and due to high temp the bonding break they have low density so it can be a reason
s.
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!





Source:  OpenStax, Digital signal processing - dsp. OpenStax CNX. Jan 06, 2016 Download for free at https://legacy.cnx.org/content/col11642/1.38
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Digital signal processing - dsp' conversation and receive update notifications?

Ask