Noise maybe defined as unwanted form of energy which tend to interfere with proper reception and reproduction of the transmitted signals.

1. NOISE
DIKSHA PRAKASH
BTech-ECE
140020204002
DIKSHA PRAKASH

2. What is NOISE?
• In electrical terms, noise maybe defined
as unwanted form of energy which tend to
interfere with proper reception and
reproduction of the transmitted signals.
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3. Various Daily-life Examples:
• In radio receivers, noise may produce hiss
type of a sound in the output of the
loudspeaker.
• In TV receivers, noise may produce
‘snow’.
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4. FIGURE : Snow produced in TV channels due to noise
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5. Classification of Noise
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6. • ATMOSPHERIC NOISE/ STATIC NOISE
Produced by lightening discharges in thunderstorm and other
natural electrical disturbances.
• EXTRA TERRESTRIAL NOISE/ SOLAR NOISE
SOLAR NOISE
Sun, being at very high temperature, radiates electrical energy in
the form of noise. It happens at the peak of eleven year cycle.
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7. COSMIC NOISE
Noise received from distant stars, our galaxy and various other
galaxies.
• INDUSTRIAL NOISE
Man-made noise due to sources like automobiles, aircraft ignition,
electric motors etc.
• SHOT NOISE
Arises in active devices due to random behaviour of charge carriers.
“ Fluctuating/shot noise current”
• PARTITION NOISE
Noise generated when current has to divide between two or more
paths in a circuit.
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8. • FLICKER NOISE/ LOW FREQUENCY NOISE/ PINK NOISE
Flow of current at low frequencies produces this particular type of
noise.
• TRANSIT TIME NOISE/ HIGH FREQUENCY NOISE
Increase in conductance with increase in frequency causes this type
of noise.
• THERMAL NOISE/ JHONSON NOISE
The noise produced in resistor with increase in absolute temperature.
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9. Signal to Noise Ratio
Signal to noise ratio is defined as ratio of
signal to noise power at the same point in
the system.
• A ratio higher than 1:1 (greater than 0 dB)
indicates more signal than noise.
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10. Mathematical Interpretation
• The reciprocal of the coefficient of
variation, i.e., the ratio
of mean to standard deviation of a signal
or measurement
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11. Application (contd.)
• This definition holds true for the situation
where the values are non negative. Thus,
it is used in image processing.
• The ’Rose criterion’ (named after Albert
Rose) states that an SNR of at least 5 is
needed to be able to distinguish image
features at 100% certainty.
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12. FIGURE: High SNR vs. Low SNR
(REFERENCE: www.jeffgeerling.com )
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13. Learning SNR with MATLAB
rng default
Tpulse = 20e-3;
Fs = 10e3;
t = -1:1/Fs:1;
x = rectpuls(t,Tpulse);
y = 0.00001*randn(size(x));
s = x + y;
pulseSNR = snr(x,s-x)
OUTPUT:
pulseSNR =
80.0818
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14. NOISE FIGURE
Indicates how much the signal to noise
ratio deteriorates as a signal passes
through a circuit or series of circuits.
The noise figure for an ideal receiver is 1 whereas
that for a practical receiver can be expressed as an
actual ratio or in decibels (dBs).
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15. REFERENCES
• www.electronicdesign.com
• www.en.wikibooks.org
• www.gatebooks.blogspot.in
• www.wikipedia.com
• www.jntubook.com
• www.inmathworks.com
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16. THANK YOU!
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