Digital Signal Processing Reference
In-Depth Information
Frequency
(Hertz)
10
2
10
3
10
4
10
5
10
6
10
7
10
8
10
9
10
10
10
11
10
12
10
13
10
14
10
15
ELF F LF
LF
MF
HF
VHF
UHF
SHF HF
Power & telephone
Rotating generators
Musi cal instruments
Voice Microphone
Radio
Radios & televi si ons
Electronic tubes
Integrated ci rcuits
Microwave
Radar
Microwave antennas
Magnetrons
Infrared
Laser
Guided missiles
Rangefinders
Visible
Light
Twisted Pair
Optical
fiber
Coaxial Cable
Terrestrial
and satellite
Transm issi on
FM Radio
and TV
AM Radio
10
3
10
0
10
6
10
5
10
4
10
2
10
1
10
-1
10
-2
10
-3
10
-4
10
-5
10
-6
Wavelength
in space
(meter)
ELF= Extremely low frequency
VF= Voice frequency
VLF= Very low frequency
LF= Low frequency
MF= Medium frequency
HF= High frequency
VHF= Very high frequency
UHF= Ultrahigh frequency
SHF= Super high frequency
EHF= Extremely high frequency
Fig. 3.6
Complete spectrum of electromagnetic radiation
3.5 Dispersion in Optics
In a prism, different colors are refracted at different angles as a result of material
dispersion (a wavelength-dependent refractive index) actually it splits the white
light forming a rainbow. Dispersion is defined in optics as the phenomenon in
which a wave's phase velocity depends on its frequency. The media having such a
property are express as dispersive media.
A rainbow is the most renowned example of dispersion in which spatial separa-
tion of white light is caused by dispersion, splitting the white light into compo-
nents of varying wavelengths (different colors). However, dispersion also has an
effect in many other conditions: for example, it degrades signals as the distance
increases, causing pulses to spread in optical fibers also, a termination between
dispersion and nonlinear effects cause formation of soliton waves.
Dispersion is mostly taken into consideration for light waves, but it may occur for
any kind of wave that can pass through geometry, inhomogeneous in nature such as
sound waves, or any other wave interacting with a medium. Dispersion is at times said
to be the chromatic dispersion because it highlights its wavelength-dependent nature.
There are generally two types of dispersion:
1. Material dispersion.
2. Waveguide dispersion.
Material dispersion is caused by the frequency-dependent response of a material to
waves. For example, material dispersion that leads to chromatic aberration, which
is undesirable in a lens or the separation of colors in a prism.
Search WWH ::
Custom Search