Lecture 1 · Web viewLecture-3 FM Generation and Demodulation 3.0 Introduction. 3.1 Indirect FM...

Dr. M. Venu Gopala Rao, Professor, Dept. of ECE, KL University

Angle / Exponential ModulationLecture-3 FM Generation and Demodulation

3.0 Introduction.

3.1 Indirect FM Generation.

3.2 Direct FM Generation / Parameter Variation Methods.

3.2.1 Reactance Modulator

3.2.2 Varactor Diode Modulator

3.2.3 Limitations of direct methods of FM generation

3.3 FM Demodulators

Direct type FM detector:

3.3.1 Single ended slope detector

3.3.2 Balanced slope detector

3.3.3 Foster-Seeley / Phase discriminator

3.3.4 Ratio detector

3.3.5 Zero crossing detector

Indirect type FM detector

3.3.6 PLL based FM detector

3.4 Performance Comparison of FM Demodulators.

3.5 FM versus PM

3.6 Angle Modulation versus Amplitude Modulation.

3.6.1: Advantages of Angle Modulation

3.6.2: Disadvantages of Angle Modulation

3.7 References.

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Lecture-3 FM Generation and Demodulation

3.0 Introduction: There are two basic methods for generating FM waves namely ‘Indirect FM’

and ‘Direct FM’. In the indirect method (or Armstrong modulator) of producing FM is first used

to produce a narrowband FM wave, and frequency multiplication is next used to increase the

frequency deviation to the desired level. On the other hand, in the direct method of producing

FM, the carrier frequency is directly varied in accordance with the amplitude of modulating

(message) signal. The indirect method is preferred choice for frequency modulation, when the

stability of carrier frequency is of major concern as in commercial broadcasting.

3.1 Indirect (Armstrong) Method of FM Generation: The

indirect method of FM generation consists of two steps as

shown in Fig 1. A narrow band FM generation followed by Fig 1. Block diagram of indirect FM

a frequency multiplier is used to increase the frequency deviation to the desired level.

Step1 Generation of NBFM: The block diagram

of narrowband FM generation using phase

modulator is shown in Fig 2. The NMFM differs

from an ideal FM wave in two respects.

(i) The envelop contains a residual AM and therefore varies with time. Fig 2. Block diagram of generation of NBFM

(ii) For sinusoidal modulating wave, the phase of the FM wave contains harmonic distortion in the form of 3rd and higher harmonics of .

However by restricting , the residual AM and harmonic distortion are negligible levels.The NBFM generation is given by

(1)

where is the first carrier frequency and is modulation sensitivity for NBFM. Then the

instantaneous frequency and , where W is the bandwidth of

message signal.

Step2: Frequency Multiplication: Basically the

frequency multiplier consists of a non-linear device Fig. 3 Block diagram of Frequency Multiplier

(diode or transistor) followed by a band pass filter (BPF) as shown in Fig.3.

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Memoryless Non-linear operation: The non-linear device is assumed to be memory-less means

that there is no energy storage. The memoryless non-linear device is represented by input and

output relation

(2)

where , ,…, are constant coefficients.

By substituting eq (1) in eq(2), then contains dc component and n frequency modulated

waves with carrier frequencies, , 2 , . . . , n and frequency deviation , 2 , …, n .

The value of is determined by the frequency sensitivity of NBFM and maximum

amplitude of the .

Band Pass Filter (BPF): The band pass filter is designed with two aims:

(i) To pass the FM wave centered at the new (desired) carrier frequency and new

(desired) frequency deviation .(ii) To suppress the all other

spectra.

WBFM Generation: The complete block

schematic diagram of WBFM generation is

illustrated in Fig 4. Then the out of the

band pass filter (BPF) is a wideband FM signal represented by Fig 4. block schematic diagram of WBFM generation

(3)

where is new carrier frequency and new modulation sensitivity . Then the

instantaneous frequency and , where W is

the bandwidth of message signal.

Example of Indirect FM:

Fig 5 shows the simplified block diagram of a typical FM transmitter (based on indirect method) used to transmit audio signals containing frequencies in the range 100 Hz to 15 KHz. The NBPM

is supplied with a carrier wave of frequency MHz by a crystal controlled oscillator. The

desired FM wave at the transmitter output has a carrier frequency MHz and frequency

deviation KHz.

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Fig 5 Block diagram of FM for example

In order to limit the harmonic distortion produced by the NBPM, we restrict the modulation

index to be 0.2 rad (i.e., rad).

Since , and for Hz, the frequency deviation Hz.

To produce frequency deviation KHz, A frequency multiplication is

required. However, using straight frequency multiplication equal to the value would produce a much higher carrier frequency at the transmitter output than the desired value of 100 MHz. To generate FM wave having both the desired frequency deviation and carrier frequency, it is need to use two stage frequency multiplier with an intermediate stage of frequency translation, as illustrated in Fig 5.

Let and denote the respective frequency multiplication ratio so that .

The carrier frequency at the first frequency multiplier output is translated downward in

frequency to by mixing it with a sinusoidal wave of frequency MHz, which

is supplied by a second crystal controlled oscillator. However, the carrier frequency at the input

of the second frequency multiplier is equal to .

Equating these two frequencies, we get .

With MHz, MHz, and MHz, we obtain and . Using

these frequency multiplication ratios, we get the set of values indicated below.

ParameterAt the Phase Modulator

output

At the first frequency

multiplier output

At the mixer output

At the second frequency

multiplier outputCarrier frequency 0.1 MHz 7.5 MHz 2.0 MHz 100 MHzFrequency deviation 20 Hz 1.5 KHz 1.5 KHz 75 KHz

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3.2 Direct Method of FM Generation / Parameter Variation Methods: In the direct method

of FM generation, the instantaneous frequency of

the carrier wave varied directly in accordance

with the message signal by means of a device

known as voltage controlled oscillator (VCO).

Fig 6 shows a schematic diagram for a simple direct Fig 6 Simple direct FM generator

FM generator. The tank circuit ( and ) is the frequency determining section for a standard

LC oscillator. The capacitor microphone is a transducer that converts acoustical energy to

mechanical energy, which is used to vary the distance between the plates of and,

consequently change in its capacitance. Thus the oscillator output frequency is changed directly

by the modulating signal, and the magnitude of the frequency change is proportional to the

amplitude of the modulating signal voltage. Reactance modulator and varactor diode method of

FM generations are discussed here.

3.2.1 Reactance Modulator: In direct FM generation, the

instantaneous frequency of the carrier is changed directly in

proportion with the message signal. For this, a device Fig 7 Illustration of Reactance Modulator

called voltage control oscillator (VCO) is used. A VCO can be implemented by using a

sinusoidal oscillator with a tuned circuit having a high quality factor. The frequency of this

oscillator is changed by incremented variation in the reactive components involved in the tuned

circuit. If L or C of a tuned circuit of an oscillator is changed in accordance with amplitude of

modulated signal then FM can be obtained across the tuned circuit as shown in Fig.7. A two or

three terminal device placed across the tuned

circuit. The reactance of the device is varied

proportional to modulating signal voltage. This

will vary the frequency of the oscillator to produce

FM. The device used is FET, transistor or varactor

diode. Fig 8 shows a simple reactance modulator

using FET as the active device. The circuit Fig 8 A simple reactance modulator using FET

configuration is called reactance modulator because the FET looks like a variable reactance load

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to the tank circuit. The modulating signal varies the reactance of FET which causes a

corresponding change in the resonant frequency of the tank circuit.

Circuit Operation:

The gate voltage , Then the drain current .

where is the transconductance of FET and is the capacitive reactance.

Then the impedance between drain and ground is .

Assuming that , the impedance .

Here is equivalent to a variable capacitance. The impedance is inversely

proportional to R, the modulating frequency ( ), and the transconductance .

When the modulating signal is applied, the gate to source voltage varied accordingly, causing

proportional change in . As a result the frequency of oscillator tank circuit is a function of the

amplitude of the modulating signal and the rate at which it changes is equal to .

3.2.2 Varactor Diode Method for FM Generation: The varactor diode is a semiconductor

diode whose junction capacitance changes with dc bias voltage .The capacitance of a varactor is

inversely proportional to the reversed biased voltage amplitude. The most common frequency

modulators use a varactor to vary the frequency of an LC

circuit or crystal in accordance with the modulating

signal. This varactor diode is connected in shunt with the

tuned circuit of the carrier oscillator as shown in Fig 9.

An example of direct FM is shown in Fig 9 which Fig 9. Varactor diode based for FM generation

uses a BJT Hartley oscillator along with a varactor diode. The varactor diode is reverse biased,

and its capacitance is dependent on the reverse voltage applied across it. This capacitance is

shown by the capacitor C(t) in Fig.9. The Frequency of oscillations of the Hartley oscillator

shown in the Fig 9 is given by

(4)

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where is the total capacitance , where again is the fixed tuning

capacitance (in the absence of modulation) and is the varactor diode capacitance, and

are the two inductances in the frequency determining network.

Assume that for a modulating signal m(t) , the capacitance is expressed as

(5)

where is the variable capacitor’s sensitivity to voltage change.

From eq (4) and (5), we get (6)

where is unmodulated frequency of oscillations (7)

Provided that the maximum change in capacitance produced by the modulating wave is small compared with the unmodulated capacitance , then we formulate

(8)

Then the instantaneous frequency of the oscillator where

where is the resultant frequency sensitivity of the modulator, where again called as the frequency sensitivity of the modulator.

Frequency Stabilized FM Modulator: An FM

transmitter using the direct method as described here

has the disadvantage that the carrier frequency is not

obtained from a highly stable oscillator. Fig 10. Frequency stabilized FM modulator A

method to provide a stabilized oscillator based FM generation is shown in Fig 10. The output of

the FM generator is applied to a mixer together with the output of a crystal-controlled oscillator,

and the difference frequency term is extracted. The mixer output is next applied to a frequency

discriminator is a device whose output voltage has an instantaneous amplitude that is

proportional to the instantaneous frequency of FM wave applied to its input. When the FM

transmitter has exactly the correct carrier frequency, the low pass filter output is zero. However

deviations of the transmitter from its assigned value will cause the frequency discriminator-filter

combination to develop a dc output voltage with a polarity determined by the sense of the

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transmitter frequency drift. This dc voltage after suitable amplification is applied to the VCO in

such a way that as to modify the frequency of the oscillator in a direction that tends to restore the

carrier frequency to its required value.

3.2.3 Limitations of direct methods of FM generation: The direct methods of FM generation

suffer from the following limitations:

In the direct methods of FM generation, it is difficult to obtain a high order of stability in

carrier frequency. This is because the modulating signal directly controls the tank circuit

which is generating the carrier. The crystal oscillator can be used for carrier frequency

stability, but frequency deviation is limited.

The non linearity produces a frequency variation due to harmonics of the modulating signal hence there are distortions in the output FM signal.

3.3 FM DEMODULATORS: Frequency demodulation is the process that enables one to extract

the original modulating signal (baseband signal) from the frequency modulated wave. This can

be achieved by a system which has a transfer characteristic just inverse of voltage controlled

oscillator (VCO). In other words a frequency demodulator produces an output voltage whose

instantaneous frequency of input FM signal. The overall transfer function for an FM demodulator

is nonlinear but when operated over its linear range is , where is transfer

function.

The output from an FM demodulator is expressed as

where = demodulated output signal (Volts)

= demodulator transfer function (Volts per Hertz)

= difference between the input frequency and the center frequency of the demodulator (Hertz).Several circuits are used for demodulating FM signals. Basically there are two types of FM

demodulators, frequency discriminators and PLL based demodulator. The slope detector,

Balanced slope detector, Foster-Seeley discriminator, and Ratio detector are tuned circuit

frequency discriminators.

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3.3.1: Slope Detector: Fig 11 shows the schematic diagram of a single ended slope detector

which is a simplest form of frequency discriminator. The single ended

slope detector circuit consists of a tuned circuit tuned to a Fig 11. Simple Slope Detector

frequency slightly below the carrier frequency and followed by an envelope detector.

Tuned Circuit: The tuned circuit transfer function is shown in Fig 12. As the instantaneous

frequency , of the incoming FM wave swings above or below

, the amplitude ratio of tuned circuit converts the frequency

variation to an amplitude variation (FM to AM conversion) as

shown in Fig 13(b). The resulting signal is basically a hybrid

FM-AM modulated wave. Fig 12.Tuned circuit Transfer function

Envelope Detector: This hybrid FM-AM modulated

wave is applied to a peak / envelope detector with

load of suitable time constant. The circuit is in fact to that

of an AM detector. The envelope detector produces the

demodulated signal (baseband signal) as shown in Fig

13(c).

Advantages: The only advantage of the basic slope

detector circuit is its simplicity.

Limitations:

(i). The range of linear slope of tuned circuit is quite

small.

(ii) The detector also responds to spurious amplitude

variations of the input FM.

These drawbacks are overcome by using balanced

slope detector. Fig 13. FM Slope Detector and waveforms

3.3.2: Balanced Slope Detector: Fig 14

shows the circuit diagram of the balanced

slope detector. The circuit shows that the

balanced slope detector consists of two slope

detector circuits. The input transformer has a

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center tapped secondary. Hence the input voltages to the slope detectors are 1800 out of phase. Fig 14. Balanced Slope detector

There are three tuned circuits. Out of them, primary tank is tuned to carrier frequency . The

upper tuned circuit of secondary is tuned to above by i.e., its resonant frequency

. Similarly the lower tuned circuit of secondary is tuned below by , i.e., .

and are the filters used to bypass the RF ripple. and are the output voltages

of the two slope detectors. The final output

voltage is obtained by taking .

Working Operation of the Circuit: It can be

understand the circuit operation by dividing the

input frequency into three ranges as follows:

(i) : When the input frequency is

instantaneously equal to , the induced

voltage in the winding of secondary is

exactly equal to that induced in the

winding . Thus the input voltages to both Fig 15. Characteristics of balanced slope detector

diodes are equal and the net out voltage is zero.

(ii) : In this range of input frequency, the induced voltage in the winding

is higher than that induced in . Therefore the input to is higher than . Hence the

positive output is higher than that of . The resultant output voltage is positive. As

the input frequency increases towards , the positive output voltage increases as

shown in Fig 15.

If the output frequency goes outside the range of to , the output voltage will fall

due to the reduction in tuned circuit response.

Advantages: (i) This circuit is more efficient than simple slope detector.

(ii) It has better linearity than the simple slope detector.

Limitations: (i) Even though linearity is good, it is not good enough.

(ii) This circuit is difficult to tune since the three tuned circuits are to be tuned at

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different frequencies, , and .

(iii) Amplitude limiting is not provided.

3.3.3 Foster-Seeley Discriminator (Phase Discriminator): A Foster-Seeley discriminator is a

tuned circuit frequency discriminator whose operation is very similar to that of the balanced

slope detector as shown in Fig 16. The capacitance values , and are chosen such that

they are short circuits for the center frequency (carrier frequency ). Therefore the input voltage

of FM is fed directly (in phase) across ( ). At the resonant frequency, the secondary

current is in phase with the secondary voltage , and 1800 out of phase with . and

are 1800 out of phase with each other and in quadrature or 900 out of phase with . The

voltage across is the vector sum of and . Similarly, The voltage across is the

vector sum of and . The corresponding vector diagrams are shown in Fig 17.

Principle of Operation: Even though the primary and secondary tuned circuits are tuned to the

same center frequency, the voltages applied to the two diodes and are not constant. They

are very depending on the frequency of the input signal. This is due to change in phase shift

between the primary and secondary windings depending on the input frequency.

The results are described as below:

(i) For input frequency , the individual output voltages of the two diodes will be

equal and opposite. Then the resultant output voltage is zero. That is .

The corresponding phasor diagram shown in Fig 17(a).

(ii) For , the phase shift between the primary and secondary windings is such that the

output of is higher than . That is , and total output voltage is

positive. The corresponding phasor diagram is shown in Fig 17(b).

(iii) For , the phase shift between the primary and secondary windings is such that

output of is higher than that output of making the output voltage is negative.

The corresponding phasor diagram is shown in Fig 17(c).

A Foster-Seeley discriminator is tuned by injecting a frequency equal to the center frequency and

tuning for 0 volts out. Fig 18 shows a typical voltage-versus-frequency response curve for a

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Foster-Seeley discriminator. For obvious reasons, it is often called an S-curve. It can be seen that

the output voltage-versus-frequency deviation curve is more linear than of a slope detector, and

because there is only one tank circuit, it is easier to tune.

For a distortionless demodulation, the frequency deviation should be restricted to the linear

portion of the secondary tuned circuit frequency response curve. As with the slope detector, a

Foster-Seeley discriminator responds to amplitude as well as frequency variations and therefore

must be preceded by a separate limiter circuit.

Fig 16. Foster-Seeley discriminator (Phase discriminator)

Phase Diagrams: The phasor diagrams at different input frequencies are shown below.

Fig 17 Phasor diagrams at different input frequencies (a) , (b) , and (c)

Frequency Response of Phase Discriminator: The frequency response of phase discriminator is

shown in Fig18.

Advantages:

(i) Tuning procedure is simpler than balanced slope

detector, because it contains only two tuned circuits

and both are tuned to the same frequency .

(ii) Better linearity, because the operation of the circuit is Fig 18 The discriminator response

dependent more on the primary to secondary phase relationship which is very much linear.

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Limitations: It does not provide amplitude limiting. So in the presence of noise or any other

spurious amplitude variations, the demodulator output respond to them and produce errors.

3.3.4 Ratio Detector: Ratio detector is another frequency demodulator circuit is illustrated in

Fig.19. The ratio detector has one major advantage over slope detector and Foster-Seeley

discriminator is that, the ratio detector is relatively immune to amplitude variations in its input

signal. As with the Foster-Seeley discriminator, the ratio detector has single tuned circuit in the

transformer secondary. The circuit diagram is similar to the Foster-Seeley discriminator with

minor modifications as described below.

(i) The direction of diode is reversed.

(ii) A large capacitance is included in the circuit.

(iii) The output is taken different locations.

Fig 19 Ratio detector (a) Circuit diagram (b) frequency response curve

Operation: After several cycles of input signal, shunt capacitance charges to approximately

to the peak voltage across the secondary winding. The reactance of is low, and simply

provides a dc path for diode current. Therefore the time constant and is sufficiently long so

that rapid changes in the amplitude of input signal due to thermal noise or other interfering

signals are shorted to ground and have no effect on the average voltage across . Consequently

and charge and discharge proportional to frequency changes in the input signal and are

relatively immune to amplitude variations.

Also the output voltage from ratio detector is taken with respect to ground, and for the

diode polarities shown in Fig.19, the average output voltage is positive. At resonance the output

voltage is divided equally between and , and redistributed as the input frequency is divided

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above and below resonance. Therefore changes in are due to the changing ratio of voltage

across and , while the total voltage is clamped by .

Fig 19(b) shows the output frequency response curve for the ratio detector shown in Fig 19

(a). It can be seen that at resonance, is not equal to zero, but retain the one half of the

voltage across the secondary. Because a ratio detector is relatively immune to amplitude

variations, it is often selected over discriminator. However a discriminator produces a more

linear output voltage-versus-frequency response curve.

Advantages:

(i) Easy to align.

(ii) Good linearity due to linear phase relationship between primary and secondary.

(iii) Amplitude limiting is provided inherently. Hence additional limiter is not required.

3.3.5 Zero Crossing Detector: The zero crossing detector operator on the principle that the

instantaneous frequency of an FM wave approximately given by

where is the time difference between the adjacent zero crossover points of the FM wave as

shown in Fig. Let us consider a time duration T as shown in figure. The time T is chosen such

that it satisfies the following two conditions:

(i) The interval T is small compared to the reciprocal of the message band width ‘W’.

(ii) The interval T is large compared to the reciprocal of the carrier frequency of the FM

wave .

Condition 1 means that the message signal m(t) is essentially constant inside the interval T.

Condition 2 ensures that a reasonable number of

zero crossings of the FM wave occurs inside the

interval T. Fig 20 illustrates these two conditions.

Let denote the number of zero crossings inside

the interval T. We may then express the time

between adjacent zero crossings as Fig 20 FM wave illustrating interval T

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Hence . Since by definition, the instantaneous

frequency is linearly related to the message signal Fig 21. Block diagram of zero crossing detector

m(t), the message signal can be recovered from a knowledge of . Fig 21 is the block diagram

of a simplified form of the zero-crossing detector based on this principle. The limiter produces a

square-wave version of the input FM wave. The pulse generator produces short pulses at the

positive going as well as negative going edges of the limiter output. Finally, the integrator

performs the averaging over interval T, thereby reproducing the original message signal m(t) at

its output.

3.4 Performance Comparison of FM Demodulators

S.No. Parameter of Comparison

Balanced Slope detector

Foster-Seeley (Phase)

discriminatorRatio Detector

(i) Alignment/tuningCritical as three circuits are to be tuned at different frequencies

Not Critical Not Critical

(ii) Output characteristics depends on

Primary and secondary frequency relationship

Primary and secondary phase

relation.

Primary and secondary phase

relation.

(iii) Linearity of output characteristics Poor Very good Good

(iv ) Amplitude limiting Not providing inherently Not Provided inherently Provided

(v) Amplifications Not used in practiceFM radio,

satellite station receiver etc.

TV receiver sound section,

narrow band FM receivers.

3.5 FM versus PM: From a purely theoretical point of view, the difference between FM and PM

is quite simple. The modulation index for FM is defined differently than for PM. With PM, the

modulation index is directly proportional to the amplitude of the modulating signal and

independent of its frequency. With FM, the modulation index is directly proportional to the

amplitude of the modulating signal and inversely proportional to its frequency.

Considering FM as a form of phase modulation, the larger the frequency deviation, the

larger the phase deviation. Therefore, the latter depends, at least to a certain extent, on the

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amplitude of the modulating signal, just as with PM. With PM, the modulation index is

proportional to the amplitude of the modulating signal voltage only, where as with FM, the

modulation index is also inversely proportional to the modulating signal frequency. If FM

transmissions are received on a PM receiver, the bass frequencies would have considerably more

phase deviation than a PM modulator would have given them. Because the output voltage from a

PM demodulator is proportional to the phase deviation, the signal appears excessively bass

boosted. In more practical situation, PM demodulated by an FM receiver produces an

information signal in which the higher frequency modulating signals are boosted.

3.6 Angle Modulation versus Amplitude Modulation: Various advantages and disadvantages

of FM over AM are illustrated as below.

3.6.1: Advantages of Angle Modulation: Angle modulation has several inherent advantages

over amplitude modulation.

(a) Noise Immunity: Probably the most significant advantages of angle modulation

transmission (FM and PM) over amplitude modulation transmission is noise immunity.

Most noise results in unwanted amplitude variations in the modulated wave (i.e., AM

noise). FM and PM reveivers include limiters that remove most of the AM noise from

the received signal before the final demodulation process occurs- a process that cannot

be used with AM receivers because the information is also contained in amplitude

varations, and removing the noise would also remove the information.

(b) Noise performance and Signal-to-Noise Improvement: With the use of limiters, FM

and PM demodulators can actually reduce the noise level and improve the signal-to-

noise ratio during the demodulation process. This is called FM thresholding. With AM,

the noise has contaminated the signal, it cannot be removed.

(c) Capture effect: With the FM and PM, a phenomenon is known as capture effect allows

a receiver to differentiate between two signals received with the same frequency.

Providing one signal at least twice as high in amplitude as the other, the receiver will

capture the stronger signal and eliminate the weaker signal. With the AM, two or more

signals are received with same frequency; both will be demodulated and produce audio

signals. One may be larger in amplitude than the other, but both can be heard.

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(d) Power Utilization and efficiency: With AM transmission, most of the transmitted

power is contained in the carrier while the information is contained in the much lower

sidebands. With angle modulation, the total power remains constant regardless of the

modulation is present. With AM, the carrier power remains constant with modulation,

and the sideband power simply adds to the carrier power. With angle modulation, power

is taken from the carrier with modulation and redistributed in the sidebands; thus angle

modulation puts most of power in the information.

3.6.2 Disadvantages of Angle Modulation: Angle modulation also has several inherent

disadvantages over amplitude modulation.

(a) Bandwidth: High quality angle modulation produces many side frequencies, thus

necessitating a much wider bandwidth than is necessary for AM transmission.

Narrowband FM utilizes a low modulation index and, consequently, produces only one

set of sidebands. Those sidebands, however, contain an even more disproportionate

percentage of the total power than a comparable AM system. For high quality

transmission, FM and PM require much more bandwidth than AM. Each station in the

commercial AM radio band is assigned 10 kHz of bandwidth, whereas in the

commercial FM broadcast band. 200 kHz is assigned each station.

(b) Circuit Complexity and Cost: PM and FM modulators, demodulators, transmitters

and receivers are more complex to design and build than their AM counterparts. At one

time, more complex meant more expensive. Today, however, with the advent of

inexpensive, large scale integration ICs, the cost of manufacturing FM and PM circuits

is comparable to their AM counterparts.

3.7 References:

1. H Taub & D. Schilling, Gautam Sahe, ”Principles of Communication Systems, TMH, 2007,

3rd Edition.

2. Simon Haykin ,”Principles of Communication Systems “,John Wiley, 2nd Ed.

3. John G. Proakis, Masond, Salehi ,”Fundamentals of Communication Systems “,PEA, 2006.

4. B.P. Lathi and Zhi Ding, “Modern Digital and Analog Communication Systems”,

International, 4th Edition, Oxford University Press, 2010.

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5. George Kennedy, “ Electronic Communication Systems”, 3rd edition, Tata McGraw-Hill

Edition.

6. Wayne Tomasi, ‘Electronic Communication Systems- fundamentals through advanced’,

5th edition, Pearson Education Inc, 2011.

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Lecture 1 · Web viewLecture-3 FM Generation and Demodulation 3.0 Introduction. 3.1 Indirect FM...

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Transcript of Lecture 1 · Web viewLecture-3 FM Generation and Demodulation 3.0 Introduction. 3.1 Indirect FM...