# 4.6 Java1490-2d fourier transforms using java, part 1  (Page 8/15)

 Page 8 / 15

Thus, changing the separation between the elements has a significant impact on the wavenumber response of the array.

## Separate the elements even more

Finally, consider the pair of images on the right where the elements are even further apart. This array response has even more peaks and valleys than theother two.

## A wavenumber filter

The sum of the outputs from an array of sensor elements represents a form of wavenumber filter (much as the correct combination of resistors, capacitors, and inductors represents a frequency filter) . If we need to pass signals having one wavenumber and to suppress signals having a different wavenumber, we may be ableto adjust the separation between the elements so as to put a peak on the desirable wavenumber and to put a null point on the undesirable wavenumbers.

## A two-element array is fairly limiting

Of course, with only two elements, we don't have very many degrees of freedom to work with. We could exercise more control over our wavenumber filter if wehad more elements. We could do even better if we had the ability to give each element a different weight (including a negative weight) when the signals from all the elements are added together. Finally, we could do even better still ifwe had the ability to insert a programmable time delay (phase shift) into the output from each of the elements before adding them together.

(The use of programmable time delays falls in the category of a space series that is complex rather than being purely real. Thus, that topic isbeyond the scope of this module.)

## Let's apply some weights

Now let's modify our scenario and see what we can learn in the process. We are going to increase the size of the array from two to three elements. We arealso going to assume that we can apply amplification, sign reversal, or both to the element output signals before adding those signals together. The results areshown in Figure 3 . We will compare the results in Figure 3 with the results discussed earlier in Figure 2 , so this may be a good time for you to open another copy of this module in a separate browser window if you haven't alreadydone so.

Figure 3. A three-element array with weighted sensors.

## The leftmost pair of images

The leftmost pair of images in Figure 3 is similar to the leftmost pair of images in Figure 2 , except that we added a third element in Figure 3 .

All three elements in Figure 3 are weighted equally prior to summation. The separation between the left and center elements is the same as in Figure 2 . The separation between the center and right elements is the same as the separationbetween the left and center elements.

## The wavenumber response

The most noticeable thing about the wavenumber response for this three-element array is that the central peak is narrower than the central peak for thetwo-element array at the left of Figure 2 . In addition, the trough between the central peak and the peaks at the ends is deeper, broader, and probably flatter (although the degree of flatness is hard to determine from this plotting format) .

#### Questions & Answers

are nano particles real
Missy Reply
yeah
Joseph
Hello, if I study Physics teacher in bachelor, can I study Nanotechnology in master?
Lale Reply
no can't
Lohitha
where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
has a lot of application modern world
Kamaluddeen
yes
narayan
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
Bhagvanji
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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Source:  OpenStax, Digital signal processing - dsp. OpenStax CNX. Jan 06, 2016 Download for free at https://legacy.cnx.org/content/col11642/1.38
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