# 4.4 Java1485-spectrum analysis using java, forward and inverse  (Page 9/14)

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(The real and complex parts of the frequency spectrum were computed at 256 frequencies between zero and the sampling frequency.)

There were 256 values plotted horizontally in each separate plot. Once again, to make it easier to view the plots on the rightmost end, I plotted the valueson a grid that is 270 units wide. This leaves some blank space on the rightmost end to contain the numbers, thus preventing the numbers from being mixed in withthe plotted values. The last actual data value coincides with the rightmost tick mark on each plot.

## Perform an inverse fourier transform

After modifying the complex spectrum as described above, the program performs an inverse Fourier transform on the modified complex spectrum to produce thefiltered impulse.

## The filtered impulse

The filtered impulse is shown as the bottom plot in Figure 4 . As you can see, the pulse is smeared out in time relative to the input pulse in the top plot.This is the typical result of reducing the bandwidth of a pulse.

(This particular modification of the complex spectrum resulted in a filtered pulse that has the waveform of a SIN(X)/X function. A differentmodification of the complex spectrum would have resulted in a filtered pulse with a different waveform.

This example also illustrates one of the miracles of digital signal processing. Energy appears in the output before it occurs in the input.Obviously that is not possible in the real world of analog systems, but many things are possible in the digital world that are not possible in the realworld.)

## Beginning of the class for Dsp037

Listing 8 shows the beginning of the class definition for the program named Dsp037.

Listing 8. Beginning of the class for Dsp037.
```class Dsp037 implements GraphIntfc01{ final double pi = Math.PI;int len = 256; double[]timeDataIn = new double[len];double[] realSpect = new double[len]; double[]imagSpect = new double[len];double[] angle = new double[len];//unused double[]magnitude = new double[len];double[] timeOut = new double[len];```

Listing 8 simply declares and initializes some variables that will be used later.

## Beginning of the constructor

The constructor begins in Listing 9 .

Listing 9. Beginning of the constructor.
```public Dsp037(){//constructor timeDataIn[32]= 90;```

Listing 9 creates the raw pulse data shown in the topmost plot in Figure 4 .

When the array object referred to by timeDataIn is created, the values of all array elements are set to zero by default. Listing 9 modifies one of the elements to have a value of 90. This results in a single impulse atan index of 32.

## Compute the Fourier transform

Continuing with the constructor, the code in Listing 10 uses an FFT algorithm in the method named transform (discussed earlier) to compute the Fourier transform of the impulse.

Listing 10. Compute the Fourier transform.
```//Compute FFT of the time data and save it in // the output arrays.ForwardRealToComplexFFT01.transform( timeDataIn,realSpect, imagSpect,angle, magnitude);```

how do they get the third part x = (32)5/4
can someone help me with some logarithmic and exponential equations.
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
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
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
Commplementary angles
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
hii
Uday
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
a perfect square v²+2v+_
kkk nice
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
rolling four fair dice and getting an even number an all four dice
Kristine 2*2*2=8
Differences Between Laspeyres and Paasche Indices
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
is it 3×y ?
J, combine like terms 7x-4y
how do you translate this in Algebraic Expressions
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
what's the easiest and fastest way to the synthesize AgNP?
China
Cied
types of nano material
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
what is nano technology
what is system testing?
preparation of nanomaterial
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
what is system testing
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
how did you get the value of 2000N.What calculations are needed to arrive at it
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