SIGNAL AND NOISE

Question 1

any unwated form of evnergy that inteferes with transmitted signals

Answer 1

NOISE

Question 2

deviation of received signal from its expected form cause by the imperfect response of a system

Answer 2

DISTORTION

Question 3

contamination caused by interaction with other signals from other sources.

Answer 3

INTERFERENCE

Question 4

two types of interference

Answer 4

constructive and destructive interference

Question 5

a noise that is only present when the signal is also present

Answer 5

CORRELATED NOISE

Question 6

2 main catergories of noIse

Answer 6

CORRELATED NOISE

UNCORRELATED NOISE

Question 7

UNWANTED MULTIPLES OF A SINGLE FREQUENCY CREATED WHEN AMPLIFIED IN A NON LINEAR DEVICE

Answer 7

HARMONIC DISTORTION

Question 8

UNWANTED CROSS-PRODUCT FREQUENCY CREATED WHEN SIGNALS ARE MIXED IN A NON LINEAR DEVICE

Answer 8

INTERMODULATION DEVICE

Question 9

TYPE OF NOISE WHERE IT IS PRESENT REGARDLESS OF SIGNAL

Answer 9

UNCORRELATED NOISE

Question 10

2 TYPES OF UNCORRELATED NOISE

Answer 10

EXTERNAL AND INTERNAL NOISE

Question 11

2 KINDS OF EXTERNAL NOISE

Answer 11

EXTRATERRESTRIAL NOISE

TERRESTRIAL NOISE

Question 12

2 EXAMPLES OF EXTRATERRESTRIAL NOISE

Answer 12

SOLAR NOISE (SOLAR FLARES/ SUN SPOT CYCLE/ RADIATION)
& 
COSMIC NOISE ( NOISE FROM OTHER CELESTIAL BODIES)

Question 13

2 EXAMPLES OF TERRESTRIAL NOISE

Answer 13

ATMOSPHERIC NOISE (LIGHTNING DISCHARGES AND OTHER ELECTRIC DISTURBANCES. LESS SEVERE ABOVE 30MHZ

INDUSTRIAL NOISE (A.K.A MAN MADE NOISE)

Question 14

TYPES OF INTERNAL NOISE

Answer 14

THERMAL NOISE (RAPID AND RANDOM MOVEMENTS OF ELECTRONS)

SEMICONDUCTOR NOISE

MISCELLANEOUS NOISE

Question 15

FOUR OTHER TERMS FORM THERMAL NOISE

Answer 15

WHITE NOSE
BROWNIAN NOISE
JOHNSON NOISE
GAUSSIAN NOISE

Question 16

WHAT IS THE MAIN CONTRIBUTOR TO INTERNAL NOISE

Answer 16

RESISTORS

Question 17

formulas for NOISE POWER & VOLTAGE NOISE FOR RESISTORS

Answer 17

Pn=kTB , Vn=√4kTRB

botzmann constant= k = 1.38x10^-23 (m^2 Kg s^-2 K^-1)
ambient temp= T = 290K
Bandwidth = B = (hertz) hz
Resistance= R = (ohms)

Question 18

2 ELECTRONIC DEVICES/PARTS THAT CONTRIBUTE TO THERMAL NOISE

Answer 18

RESISTORS &

RC NETWORKS

Question 19

RC NETORKS NOISE FORMULAE

-capacitor and inductor doesn’t generate noise, they only shape noise as they are frequency dependent devices

Answer 19

VOLTAGE NOISE= Vn = √(kT/C)

BANDWIDTH= B = 1/(4RC)

Capacitance= C

Question 20

3 TYPES OF SEMICONDUCTOR NOISES (internal)

Answer 20

SHOT NOISE

BURST NOISE

avalance noise

Question 21

KIND OF NOISE THAT IS DEPENDENT ON THE CURRENT FLOW INSTEAD OF THE TEMPERATURE
(also give the formula )

Answer 21

SHOT NOISE= i(n)= √[2Bi(dc)q]
B= hz
i(dc)= direct current (A)
q= charge of an electron 1.609x10^-19 Coulombs (C)

Question 22

IS A LOW FREQUENCY NOISE WHICH APPEARS AS A SERIES OF BURST OF TWO OR MORE LEVELS. (CAN BE OBSERVED IN BJT’S)

Answer 22

BURST NOISE

Question 23

this noise is created when avalance breakdown occurs, it can be used for noise generators

Answer 23

avalance noise

Question 24

kinds of miscellaneous noises

Answer 24

transit time noise

flicker noise

Question 25

this noise is similar to shot noise but occurs when the transit time for electrons is comaparable to the signal’s period.

Answer 25

transit time noise

Question 26

this noise if proportional to emiter current and junction temperature, inversely proportional to frequency (negligible above 500Hz)

Answer 26

flickers noisez

Question 27

flicker noise is also called as?

Answer 27

1/f noise
pink noise

since it it inversely proportional to the frequency.

Question 28

measure of signal’s power content vs ffrequency

Answer 28

POWER SPECTRAL DENSITY

Question 29

POWER SPECTRAL DENSITY (Sp)

pormyula

Answer 29

Sp = kT

Sp (unit= w/hz , v^2/hz, A^2/hz)

(boltmann contant =k)
= 1.38x10^-23 m^2 Kg s^-2 K^-1

(T= ambient temp)= 290K

Question 30

noise voltage across a resistor.

Answer 30

Pn = kTB
Vn^2/R = kTB
(Vn/2)^2 / R = kTB

Question 31

total noise voltage (series)

Answer 31

Vn = √(4kTRB) ----
Vn(total) =  √(4kT(R1+R2 )B)----

Question 32

total noise current (parallel)

Answer 32

G=1/R  = conductance
In(total) =  √(4kT(G1+G2 )B)

Question 33

(equivalent noise ratio)

of cascading devices

Answer 33

Req =(equialent noise ratio)= R1 + R2/G1 + R3/G1G2 + ….

Question 34

RELATIVE MEASURE OF THE DESIRED SIGNAL POWER TO THE UNDESIRED POWER

Answer 34

(SNR)
SIGNAL TO NOISE RATIO
SNR = Ps / Pn = Vs^2/ Vn^2

SNR(db) = 20 log Vs/Vn = 10log Ps/Pn

• • higher SNR the better
• • usually by decibels

Question 35

MINIMUM SNR NOISE FOR: (in db)

TELEPHONE SERVICE:
TRANSMISSION (VIDEO)=
TRANSMISSION (DATA)=

Answer 35

TELEPHONE SERVICE: 30db
TRANSMISSION (VIDEO)= 45db
TRANSMISSION (DATA)= 15db

Question 36

specufues how noisy a device is….

Answer 36

NOISE FACTOR (NF)
NF= SNR(in)/ SNR(out) =

Question 37

ideal NOISE FACTOR = ?

Answer 37

NF= SNRi/ SNRo = (Si/Ni)/(GSi/GNi) =1

1

Question 38

a device with noise

Answer 38

NF= SNRi/ SNRo = (Si/Ni)/(GSi/GNi + Na)

then resulting NF is > 1 (not ideal)

Question 39

NOISE FACTOR, how to express in db?

Answer 39

NF(db) = 10log [(Si/Ni / So/No]

Question 40

total noise factor of cascading amplifiers

Answer 40

NFeq = NF1 + (NF2 -1)/G1 + (NF3-1)/G1G2