Showing posts with label FM. Show all posts
Showing posts with label FM. Show all posts

## What is Carson's Rule?

Carson's formula is used to calculate the bandwidth (BW) of a single tone wideband FM.
According to carson's rule, the FM bandwidth is given as, twice the sum of frequency deviation and the highest modulating frequency.
But it should be noted here that this rule is just an approximation.

Watch the Complete Video Here

So Carson's rule can be written mathematically as-

BW = 2(∆w + wm)

But mf = ∆w/wm

Therefore

BW = 2(mfwmwm)

= 2wm (mf + 1)

Now we have two special cases for the carson's rule -

1 - If ∆w << wm and

2- ∆w >> wm

Case 1- If ∆w << wm

Since mf = ∆w/wm

If ∆w << wm

=> mf << 1

=> It is the case for narrowband FM

Since the bandwidth by the carson's rule is given
as-

BW = 2(∆w + wm)

BW = 2(mfwmwm)

= 2wm (mf + 1)

Therefore for m<< 1

BW = 2wm

Note here that this is equivalent to Amplitude Modulation (AM)

Case 2- ∆w >> wm

Since mf = ∆w/wm

Therefore if ∆w >> wm

=> m>> 1   as is the case for wideband FM
Then, since by Carson's rule

BW = 2wm (mf + 1)

Therefore for mf  >> 1

BW = 2wmmf

But wmmf = ∆w

Therefore

BW = 2∆w

Note- For large values of m this BW relationship can be considered accurate for all practical purposes.

FREQUENCY SPECTRUM OF AMPLITUDE MODULATION (WAVEFORMS AND EQUATIONS DERIVATION)

AMPLITUDE MODULATION (TIME DOMAIN EQUATIONS AND WAVEFORMS)

STEP INDEX OPTICAL FIBER (MULTIMODE AND SINGLE MODE STEP INDEX FIBERS)

PULSE MODULATION TECHNIQUES (PAM, PWM, PPM, PCM)

OPTICAL FIBER: STRUCTURE AND WORKING PRINCIPLE

PULSE AMPLITUDE MODULATION (PAM)

COMPARISON OF PAM, PWM, PPM MODULATION TECHNIQUES

PULSE WIDTH MODULATION (PWM)

CONTINUOUS TIME AND DISCRETE TIME SIGNALS (C.T. AND D.T. SIGNALS)

NEED AND BENEFITS OF MODULATION

PULSE POSITION MODULATION (PPM)

OPTICAL FIBERS IN COMMUNICATION: COVERS ALL IMPORTANT POINTS

OPTICAL FIBER SOURCES (DESIRABLE PROPERTIES)

SAMPLING THEOREM AND RECONSTRUCTION (SAMPLING AND QUANTIZATION)

SUPERPOSITION THEOREM (BASICS, SOLVED PROBLEMS, APPLICATIONS AND LIMITATIONS)

Digital Modulation Techniques (ASK, FSK, PSK, BPSK)/ Amplitude, Frequency and Phase Shift Keying

Conventional AM Vs DSB-SC Vs SSB-SC Vs VSB (Comparison of AM Systems)

What are Microwaves and their Applications (Uses) in various fields

Basic Structure of Bipolar Junction Transistor (BJT) - BJT Transistor - Working and Properties

Polar Plots of Transfer Functions in Control Systems (How to Draw Nyquist Plot Examples)

Generation of Binary Phase Shift Keying (BPSK Generation) - Block Diagram of Binary Phase Shift Keying (BPSK)

Low Level and High Level Modulation Block Diagram (AM Transmitter Block Diagram)

Block Diagram of CRO (Cathode Ray Oscilloscope), Components of CRO and CRT with Structure and Working

Slope Overload Distortion and Granular (Idle Noise), Quantization Noise in Delta Modulation

Frequency Translation/Frequency Mixing/Frequency Conversion/Heterodyning (Basic Concepts and Need)

Quadrature Phase Shift Keying Modulation (QPSK) Basics, Waveform and Benefits

Pulse Code Modulation (PCM) Vs Differential Pulse Code Modulation (DPCM)

## 1 Sept 2018

### Types of Modulation (Classification of Modulation)

Here we will discuss what is modulation and different types of modulation.
So let's first see the definition of modulation and it's classification -

## Definition of Modulation

Modulation is a process by which some characteristic (amplitude/frequency or phase) of a high frequency carrier wave is varied in accordance with the instantaneous value of the message signal (modulating signal).

Now we will see the classification of modulation-

## Types of Modulation

 Types of Modulation

Modulation can be classified broadly into two types -
*Continuous wave modulation
*Pulse modulation

## Continuous Wave Modulation

In this type of modulation the carrier wave is continuous. Continuous wave modulation is a technique of modulation where some parameter (amplitude, frequency or phase) of a sinusoidal carrier is varied in accordance with the instantaneous value of the modulating signal.

In the pulse modulation the carrier wave is in the form of pulses. In Pulse modulation some parameter (amplitude, width or position) of the pulsed carrier wave is varied as per the instantaneous value of the modulating signal.

The continuous wave modulation can again be classified into two types-
*Amplitude Modulation (AM)
*Angle Modulation

Amplitude Modulation

 Message Signal and the Carrier Wave

 Amplitude Modulated Wave (AM Signal)

In amplitude modulation the amplitude of the carrier wave is varied according to the instantaneous value of the modulating (message) signal. Therefore the information is present in the amplitude variations of the carrier wave.

Angle Modulation
It may be defined as the process in which the total phase angle of a carrier wave is varied in accordance with the instantaneous value of the modulating signal.

The Angle modulation is again of two types-
*Frequency Modulation (FM)
*Phase Modulation (PM)

Frequency Modulation

 Frequency Modulation (FM)

In frequency modulation, the frequency of the carrier wave is varied in accordance with the instantaneous value of the modulating signal.

Phase modulation

 Phase Modulation (PM)

In Phase modulation, the phase of the carrier wave is varied according to the instantaneous value of the modulating signal (message signal).

Now let's discuss the pulse modulation

Pulse Modulation
In Pulse modulation some parameter (amplitude, width or position) of the pulsed carrier wave is varied as per the instantaneous value of the modulating signal.

Pulse modulation is of 3 types
*Pulse Amplitude Modulation (PAM)
*Pulse Width Modulation (PWM)/Pulse Duration Modulation (PDM)
*Pulse Position Modulation (PPM)

Pulse Amplitude Modulation

 Pulse Amplitude Modulation (PAM)

In pulse amplitude modulation, the amplitude of the pulsed carrier wave is varied according to the modulating signal value.

Pulse Width Modulation

 Pulse Width Modulation (PWM)/Pulse Duration Modulation (PDM)

In this type of modulation, the width of the pulsed carrier is varied as per the value of the modulating signal

Pulse Position Modulation

 Pulse Position Modulation (PPM)

In Pulse position modulation, the position of the pulsed carrier is varied as per the value of the modulating signal.

# What is Frequency Modulation (FM)

In case of Frequency Modulation (FM) the frequency of the carrier wave varies according to the instantaneous value of the modulating (message) signal.

# Why FM is better than AM

Following reasons make the Frequency Modulation (FM) better than Amplitude Modulation (AM)

1.FM broadcasts operate in upper VHF (Very High Frequency) and UHF (Ultra High Frequency) ranges, while MF (Medium Frequency) and HF (High Frequency) ranges are used by AM broadcasts. This is a big advantage for FM, since in VHF and UHF frequency ranges there is less noise interference.

# AM vs FM Video (Comparison of AM and FM) Video

2.FM receivers are more immune to noise in comparison to AM receivers. since FM receivers may be fitted with amplitude limiters. These amplitude limiters can remove the amplitude variations caused by the noise.