The document discusses different types of noise that affect communication systems, including thermal noise, shot noise, flicker noise, excess resistor noise, and popcorn noise. It provides details on thermal noise generation and its relation to temperature and resistance. The analysis section examines thermal noise in resistors in series and parallel and defines signal-to-noise ratio and noise factor. Additive white Gaussian noise is described as noise that is additive, has a constant spectral density (white), and has a Gaussian amplitude distribution.
Classification of signals and systems as well as their properties are given in the PPT .Examples related to types of signals and systems are also given .
Classification of signals and systems as well as their properties are given in the PPT .Examples related to types of signals and systems are also given .
It is a digital representation of an analog signal that takes samples of the amplitude of the analog signal at regular intervals. The sampled analog data is changed to, and then represented by, binary data.
This presentation will explain about the need for modulation in communication system. We made this presentation as our group assignment in Analog and Digital Communication System course in MIIT.
Base band transmission
*Wave form representation of binary digits
*PCM, DPCM, DM, ADM systems
*Detection of signals in Gaussian noise
*Matched filter - Application of matched filter
*Error probability performance of binary signaling
*Multilevel base band transmission
*Inter symbol interference
*Eye pattern
*Companding
*A law and μ law
*Correlation receiver
Sampling is a basic and fundamental step towards converting an analog signal into digital signal. Types of sampling with its merits and demerits with applications are discussed. Aperture effect observed in case of flat top sampling can be compensated using equalizer filter.
It is a digital representation of an analog signal that takes samples of the amplitude of the analog signal at regular intervals. The sampled analog data is changed to, and then represented by, binary data.
This presentation will explain about the need for modulation in communication system. We made this presentation as our group assignment in Analog and Digital Communication System course in MIIT.
Base band transmission
*Wave form representation of binary digits
*PCM, DPCM, DM, ADM systems
*Detection of signals in Gaussian noise
*Matched filter - Application of matched filter
*Error probability performance of binary signaling
*Multilevel base band transmission
*Inter symbol interference
*Eye pattern
*Companding
*A law and μ law
*Correlation receiver
Sampling is a basic and fundamental step towards converting an analog signal into digital signal. Types of sampling with its merits and demerits with applications are discussed. Aperture effect observed in case of flat top sampling can be compensated using equalizer filter.
The signal is the meaningful information that you’re actually trying to detect. The noise is the random, unwanted variation or fluctuation that interferes with the signal. To get a sense of this, imagine trying to tune into a radio station. Ok, you don’t use radio anymore, so imagine your dad can’t call you to get help setting up his Spotify, so is trying to tune into a radio station. He turns the dial but it’s just picking up white noise and, after a few frustrating minutes, he manages to pick up a signal and tune into a station.
The same is true in statistics — there is something you’re trying to actually measure (say, how many Americans want to leave for Canada), but the data could be noisy (by including everyone who just makes a trip over the border to buy affordable medication). Noisy data are data from which it is hard to determine the true effect.Examples of signal vs noise
If I speak German, for most people, there will be no signal, just noise, although Claus can detect the actual signal.
How accurate are the polls in predicting the election? If the data are noisy (for example, because it’s a small sample size, has low external validity, or small effect size), the poll numbers won’t correlate well with a change in the chance of a different President.
Does money make you happier? The signal (correlation between income and happiness) would be noisy because of confounders — you’d expect people who earn more to be happier because they are in positions of higher social status, they have better working conditions, being happier could cause people to be rich etc. Turns out there is some signal amongst the noise though.
different types of internal and external noises, s/n ratio, s/n ratio of a tandem connection, noise factor, amplifier input noise, noise factor of amplifiers in cascade (friss's formula).
Optical Fiber Communication Part 3 Optical Digital ReceiverMadhumita Tamhane
Current generated by photodetector is very weak and is adversely effected by random noises associated with photo detection process. When amplified, this signal further gets corrupted by amplifiers. Noise considerations are thus important in designing optical receivers.
Most meaningful criteria for measuring performance of a digital communication system is average error probability, and in analog system, it is peak signal to rms noise ratio. ...
2. contents:
Introduction of noise
Types of noise
1) Thermal Noise
2).Shot Noise
3).Low Frequency or Flicker Noise
4).Excess Resister Noise
5).Burst or Popcorn Noise
• Analysis of Noise in Communication Systems
• Thermal Noise
• Noise Voltage Spectral Density
• Resistors in Series
• Resistors in Parallel
• Signal - to – Noise
• Noise Factor –
• System Noise Figure
•Additive White Gaussian Noise
3. Introduction of Noise
Noise is a general term which is used to describe an unwanted
signal which affects a wanted signal. These unwanted signals arise
from a variety of sources which may be considered in one of two
main categories:-
•Interference, usually from a human source (man made)
•Naturally occurring random noise
Interference
Interference arises for example, from other communication
systems (cross talk), 50 Hz supplies (hum) and harmonics,
switched mode power supplies, thyristor circuits, ignition (car
spark plugs) motors … etc.
4. Natural Noise
Naturally occuring external noise sources include atmosphere
disturbance (e.g. electric storms, lighting, ionospheric effect etc),
so called ‘Sky Noise’ or Cosmic noise which includes noise from
galaxy, solar noise and ‘hot spot’ due to oxygen and water vapour
resonance in the earth’s atmosphere.
5. Thermal Noise (Johnson Noise)
This type of noise is generated by all resistances (e.g. a resistor,
semiconductor, the resistance of a resonant circuit, i.e. the real part
of the impedance, cable etc).
Experimental results (by Johnson) and theoretical
studies (by Nyquist) give the mean square noise
voltage as
_ 2
V k TBR volt
4 ( ) 2
Where k = Boltzmann’s constant = 1.38 x 10-23 Joules per K
T = absolute temperature
B = bandwidth noise measured in (Hz)
R = resistance (ohms)
6. Thermal Noise (Johnson Noise ) (Cont’d)
The law relating noise power, N, to the temperature and
bandwidth is
N = k TB watts
Thermal noise is often referred to as ‘white noise’ because it has a
uniform ‘spectral density’.
7. Shot Noise
• Shot noise was originally used to describe noise due to random
fluctuations in electron emission from cathodes in vacuum tubes (called
shot noise by analogy with lead shot).
• Shot noise also occurs in semiconductors due to the liberation of charge
carriers.
• For pn junctions the mean square shot noise current is
Where
2 2 I 2 I 2 I q B (amps) n DC o e
is the direct current as the pn junction (amps)
is the reverse saturation current (amps)
is the electron charge = 1.6 x 10-19 coulombs
B is the effective noise bandwidth (Hz)
• Shot noise is found to have a uniform spectral density as for thermal
noise
8. Low Frequency or Flicker Noeis
Active devices, integrated circuit, diodes, transistors etc also
exhibits a low frequency noise, which is frequency dependent (i.e.
non uniform) known as flicker noise or ‘one – over – f’ noise.
Excess Resistor Noise
Thermal noise in resistors does not vary with frequency, as
previously noted, by many resistors also generates as additional
frequency dependent noise referred to as excess noise.
Burst Noise or Popcorn Noise
Some semiconductors also produce burst or popcorn noise with a
spectral density which is proportional to 2
1
f
9. Analysis of Noise In Communication Systems
Thermal Noise (Johnson noise)
This thermal noise may be represented by an equivalent circuit
as shown below
A) System BW = B Hz
N= Constant B (watts) = KB
B) System BW
N= Constant 2B (watts) =
K2B
S
KB
S
For A,
N
S
K B
S
N
2
For B,
4 ( ) 2
____
2 V k TBR volt
(mean square value , power)
then VRMS
i.e. Vn is the RMS noise voltage
n 2 kTBR V
10. 10
Analysis of Noise In Communication Systems (Cont’d)
Resistors in Series
Assume that R1 at
temperature T1 and R2 at
temperature T2, then
2
2
___
2
1
____ ___
2
n n n V V V
1 1
____
2
1 V 4kT BR n
2 2
____
2
2 V 4kT B R n
4 ( ) 1 1 2 2
____
2 V k B T R T R n
4 ( ) 1 2
____
2 V kT B R R n
i.e. The resistor in series at same temperature behave as a
single resistor
11. Analysis of Noise In Communication Systems (Cont’d)
R R
1 2
11
Resistance in Parallel
2
R
V Vo n
1 1 R R
1 2
R
1
V Vo n
2 2 R R
1 2
2
2
___
2
1
____ ___
2
n o o V V V
____
4
kB
2
n V
2
2 2
1 1 1
2
2 2
1 2
1 2
R R
R T R R T R
R R
kBR R T R T R
1 2 1 1 2 2
2
1 2
_____
2 4 ( )
R R
Vn
R R
1 2
1 2
_____
2 4
R R
V kTB n
12. 12
Signal to Noise
The signal to noise ratio is given by
SignalPower
Noise Power
S
N
The signal to noise in dB is expressed by
S
N
S
N
dB 10 10 log
dB dBm dBm S N
S
N
for S and N measured in mW.
Noise Factor- Noise Figure
Consider the network shown below,
13. 13
Noise Factor- Noise Figure (Cont’d)
• The amount of noise added by the network is embodied in the
Noise Factor F, which is defined by
Noise factor F =
IN
OUT
N
S
N
S
• F equals to 1 for noiseless network and in general F > 1. The
noise figure in the noise factor quoted in dB
i.e. Noise Figure F dB = 10 log10 F F ≥ 0 dB
• The noise figure / factor is the measure of how much a network
degrades the (S/N)IN, the lower the value of F, the better the
network.
14. 14
Additive White Gaussian Noise
Additive
Noise is usually additive in that it adds to the information bearing signal. A model of the
received signal with additive noise is shown below
White
White noise = p f o = Constant
Gaussian
We generally assume that noise voltage amplitudes have a Gaussian or Normal distribution.
15. References:
1 Principles Of Communication (6th
Edition)by Sanjay Sharma S. K.
Kataria & Sons, 2009
2 Electronic communication system
by george kennedy & Bernad
davis,4th edition,2009
3 communication systems-1 by J.S
Chitode revised edition 2007- 2008
4 communication & signal
processing by Herbert Taub &
Donald L.Shiling McGraw-Hill 1986
5 communication theory by T G
Thomas S Chandra Sekhar 2005
edition