Frequency modulation (FM) varies the frequency of the carrier signal based on the message signal. There are two main types:
1. Narrowband FM varies the carrier frequency by a small amount (modulation index β ≤ 0.3), resulting in just the carrier and two significant sidebands.
2. Wideband FM uses a larger frequency deviation (β > 0.3), producing more than two sidebands.
The FM spectrum consists of the carrier frequency fc and an infinite number of sideband frequencies at fc ± nfm, where the amplitudes are determined by Bessel functions and the modulation index β.
Details: https://electronicsembeddedworld.blogspot.com/2018/06/performance-management-mcq.html
FM demodulation involves changing the frequency variations in a signal into amplitude variations at baseband, e.g. audio. There are several techniques and circuits that can be used each with its own advantages and disadvantages.
In any radio that is designed to receive frequency modulated signals there is some form of FM demodulator or detector. This circuit takes in frequency modulated RF signals and takes the modulation from the signal to output only the modulation that had been applied at the transmitter.
There are several types of FM detector / demodulator that can be used. Some types were more popular in the days when radios were made from discrete devices, but nowadays the PLL based detector and quadrature / coincidence detectors are the most widely used as they lend themselves to being incorporated into integrated circuits very easily...
the modulation of a wave by varying its amplitude, used especially as a means of broadcasting an audio signal by combining it with a radio carrier wave.
Details: https://electronicsembeddedworld.blogspot.com/2018/06/performance-management-mcq.html
FM demodulation involves changing the frequency variations in a signal into amplitude variations at baseband, e.g. audio. There are several techniques and circuits that can be used each with its own advantages and disadvantages.
In any radio that is designed to receive frequency modulated signals there is some form of FM demodulator or detector. This circuit takes in frequency modulated RF signals and takes the modulation from the signal to output only the modulation that had been applied at the transmitter.
There are several types of FM detector / demodulator that can be used. Some types were more popular in the days when radios were made from discrete devices, but nowadays the PLL based detector and quadrature / coincidence detectors are the most widely used as they lend themselves to being incorporated into integrated circuits very easily...
the modulation of a wave by varying its amplitude, used especially as a means of broadcasting an audio signal by combining it with a radio carrier wave.
Frequency-Shift Keying, also known as FSK is a type of digital frequency modulation. It is also often called as binary frequency shift keying or BFSK
Similar to analog FM, it is a constant-amplitude angle modulation.
This presentation will discuss the concepts behind FSK
Sampling is a Simple method to convert analog signal into discrete Signal by using any one of its three methods
if the sampling frequency is twice or greater than twice then sampled signal can be convert back into analog signal easily......
Introduction to Angle Modulation, Types of Angle Modulation, Frequency Modulation and Phase Modulation Introduction, Generation of FM, Detection of FM, Frequency stereo Multiplexing, Applications, Difference between FM and PM.
Salient Features:
The magnitude response is nearly constant(equal to 1) at lower frequencies
There are no ripples in passband and stop band
The maximum gain occurs at Ω=0 and it is H(Ω)=1
The magnitude response is monotonically decreasing
As the order of the filter ‘N’ increases, the response of the filter is more close to the ideal response
Frequency-Shift Keying, also known as FSK is a type of digital frequency modulation. It is also often called as binary frequency shift keying or BFSK
Similar to analog FM, it is a constant-amplitude angle modulation.
This presentation will discuss the concepts behind FSK
Sampling is a Simple method to convert analog signal into discrete Signal by using any one of its three methods
if the sampling frequency is twice or greater than twice then sampled signal can be convert back into analog signal easily......
Introduction to Angle Modulation, Types of Angle Modulation, Frequency Modulation and Phase Modulation Introduction, Generation of FM, Detection of FM, Frequency stereo Multiplexing, Applications, Difference between FM and PM.
Salient Features:
The magnitude response is nearly constant(equal to 1) at lower frequencies
There are no ripples in passband and stop band
The maximum gain occurs at Ω=0 and it is H(Ω)=1
The magnitude response is monotonically decreasing
As the order of the filter ‘N’ increases, the response of the filter is more close to the ideal response
Slide 1
Frequency Modulation (FM)
Slide 2
FM Signal Definition (cont.)
Slide 3
Discrete-Time FM Modulator
Slide 4
Single Tone FM Modulation
Slide 5
Single Tone FM (cont.)
Slide 6
Narrow Band FM
Slide 7
Bandwidth of an FM Signal
Slide 8
Demod. by a Frequency Discriminator
Slide 9
FM Discriminator (cont.)
Slide 10
Discriminator Using Pre-Envelope
Slide 11
Discriminator Using Pre-Envelope (cont.)
Slide 12
Discriminator Using Complex Envelope
Slide 13 Phase-Locked Loop Demodulator
Slide 14
PLL Analysis
Slide 15
PLL Analysis (cont. 1)
Slide 16
PLL Analysis (cont. 2)
Slide 17
Linearized Model for PLL
Slide 18
Proof PLL is a Demod for FM
Slide 19
Comments on PLL Performance
Slide 20
FM PLL vs. Costas Loop Bandwidth
Slide 21
Laboratory Experiments for FM
Slide 21
Experiment 8.1 Spectrum of an FM
Signal
Slide 22
Experiment 8.1 FM Spectrum (cont. 1)
Slide 23
Experiment 8.1 FM Spectrum (cont. 1)
Slide 24
Experiment 8.1 FM Spectrum (cont. 3)
Slide 24
Experiment 8.2 Demodulation by a Discriminator
Slide 25
Experiment 8.2 Discriminator (cont. 1)
Slide 26
Experiment 8.2 Discriminator (cont. 2)
Slide 27
Experiment 8.3 Demodulation by a PLL
Slide 28
Experiment 8.3 PLL (cont.)
. Types of Modulation(Analog)
Phase-Frequency Relationships
FM and PM basics
Frequency deviation
MODULATION INDEX
Classification of FM
Narrow Band FM (NBFM)
generating a narrowband FM signal.
Wide Band FM (WBFM).
Carson’s Rule
Generation of WBFM
Average Power
FM BANDWIDTH
Comparing Frequency Modulation to Phase Modulation
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
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Role of Ethnopharmacology in drug evaluation,
Reverse Pharmacology.
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Students, digital devices and success - Andreas Schleicher - 27 May 2024..pptxEduSkills OECD
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2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
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1. Angle Modulation – Frequency
Modulation
Consider again the general carrier vc ( t ) = Vc cos( ωc t + φc )
( ωc t + φc ) represents the angle of the carrier.
There are two ways of varying the angle of the carrier.
• By varying the frequency, ωc – Frequency Modulation.
• By varying the phase, φc – Phase Modulation
1
2. Frequency Modulation
In FM, the message signal m(t) controls the frequency fc of the carrier. Consider the
carrier
vc ( t ) = Vc cos( ωc t )
then for FM we may write:
FM signal v s ( t ) = Vc cos( 2π ( f c + frequency deviation ) t ) ,where the frequency deviation
will depend on m(t).
Given that the carrier frequency will change we may write for an instantaneous
carrier signal
Vc cos( ωi t ) = Vc cos( 2πf i t ) = Vc cos( φi )
where φi is the instantaneous angle = ωi t = 2πf i t and fi is the instantaneous
frequency. 2
3. Frequency Modulation
dφi 1 dφi
Since φi = 2πf i t then = 2πf i or fi =
dt 2π dt
i.e. frequency is proportional to the rate of change of angle.
If fc is the unmodulated carrier and fm is the modulating frequency, then we may
deduce that
1 dφi
f i = f c + Δf c cos( ωm t ) =
2π dt
∆fc is the peak deviation of the carrier.
1 dφi
Hence, we have = f c + Δf c cos( ωm t ) ,i.e. dφi = 2πf c + 2πΔf c cos( ωm t )
2π dt dt
3
4. Frequency Modulation
After integration i.e. ∫ (ωc + 2πΔf c cos( ωm t ) ) dt
2πΔf c sin ( ωm t )
φi = ωc t +
ωm
Δf c
φi = ωc t + sin ( ωm t )
fm
Hence for the FM signal, v s ( t ) = Vc cos( φi )
Δf c
v s ( t ) = Vc cos ωc t +
sin ( ωm t )
fm 4
5. Frequency Modulation
Δf c
The ratio is called the Modulation Index denoted by β i.e.
fm
Peak frequency deviation
β=
modulating frequency
Note – FM, as implicit in the above equation for vs(t), is a non-linear process – i.e.
the principle of superposition does not apply. The FM signal for a message m(t) as a
band of signals is very complex. Hence, m(t) is usually considered as a 'single tone
modulating signal' of the form
m( t ) = Vm cos( ωm t )
5
6. Frequency Modulation
Δf
The equation v s ( t ) = Vc cos ωc t + c sin ( ωm t ) may be expressed as Bessel
fm
series (Bessel functions)
∞
v s ( t ) = Vc ∑ J ( β ) cos( ω
n c + nωm ) t
n= −∞
where Jn(β) are Bessel functions of the first kind. Expanding the equation for a few
terms we have:
v s (t ) = Vc J 0 ( β ) cos(ω c )t + Vc J 1 ( β ) cos(ω c + ω m )t + Vc J −1 ( β ) cos(ω c − ω m )t
Amp fc Amp fc + fm Amp fc − fm
+ Vc J 2 ( β ) cos(ω c + 2ω m )t + Vc J − 2 ( β ) cos(ω c − 2ω m )t +
Amp fc +2 fm Amp fc −2 f m
6
7. FM Signal Spectrum.
The amplitudes drawn are completely arbitrary, since we have not found any value for
Jn(β) – this sketch is only to illustrate the spectrum.
7
8. FM Signal Waveforms.
If we plot fOUT as a function of VIN:
In general, m(t) will be a ‘band of signals’, i.e. it will contain amplitude and frequency
variations. Both amplitude and frequency change in m(t) at the input are translated to
(just) frequency changes in the FM output signal, i.e. the amplitude of the output FM
signal is constant.
Amplitude changes at the input are translated to deviation from the carrier at the
output. The larger the amplitude, the greater the deviation. 16
9. FM Signal Waveforms.
Frequency changes at the input are translated to rate of change of frequency at the
output.An attempt to illustrate this is shown below:
17
10. Significant Sidebands – Spectrum.
As shown, the bandwidth of the spectrum containing significant
components is 6fm, for β = 1.
23
11. Carson’s Rule for FM Bandwidth.
An approximation for the bandwidth of an FM signal is given by
BW = 2(Maximum frequency deviation + highest modulated
frequency)
Bandwidth = 2(∆f c + f m ) Carson’s Rule
25
12. Narrowband and Wideband FM
Narrowband FM NBFM
From the graph/table of Bessel functions it may be seen that for small β, (β ≤ 0.3)
there is only the carrier and 2 significant sidebands, i.e. BW = 2fm.
FM with β ≤ 0.3 is referred to as narrowband FM (NBFM) (Note, the bandwidth is
the same as DSBAM).
Wideband FM WBFM
For β > 0.3 there are more than 2 significant sidebands. As β increases the number of
sidebands increases. This is referred to as wideband FM (WBFM).
26
13. Comments FM
• The FM spectrum contains a carrier component and an infinite number of sidebands
at frequencies fc ± nfm (n = 0, 1, 2, …)
∞
FM signal, v s (t ) = Vc ∑J
n = −∞
n ( β ) cos(ω c + nω m )t
• In FM we refer to sideband pairs not upper and lower sidebands. Carrier or other
components may not be suppressed in FM.
• The relative amplitudes of components in FM depend on the values Jn(β), where
α Vm
β= thus the component at the carrier frequency depends on m(t), as do all the
fm
other components and none may be suppressed.
28