# What is Sampling and Why Sampling is Required?

A continuous time signal at the transmitting end is converted into discrete time signal, it is done as it is easier to process digital signals in comparison to analog signals.

Sampling and Quantization of Signal Videos

# What is Quantization of Signal

If we want to convert analog signals into digital signals then first of all continuous time signal is converted into discrete time signal with the help of sampling process and after this process, this sampled signal is converted into digital signal by the process of quantization.

# Sampling Theorem

A continuous time signal can be completely represented in its samples and then can be recovered back, is the sampling frequency is greater than or equal to the twice of the maximum frequency present in the signal.
i.e. fs>=2fm
Here fs is sampling frequency
fm is maximum frequency present in the signal.
It is essential to take sufficient number of samples to completely represent a signal by its samples and also to reconstruct the signal back to its original form from its samples.

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)

# What is Superposition Theorem (Definition)

In an active linear network containing several sources (including dependent sources), the overall response (branch current or voltage) in any branch in the network is equal to the algebraic sum of the responses of individual source considered separately, with all other sources made inoperative, it means replacing them with their internal resistances or impedances.

# Superposition Theorem (Basics, Applications and Limitations) Video

## How to Make a Source (Voltage or Current Source) Inoperative?

To make a source inoperative, it is first short-circuited leaving behind it's internal resistance or impedance, if it is a voltage source.
But if it is a current source then it is open circuited leaving behind its internal resistance or impedance.

# Applications of Superposition Theorem

1.The superposition theorem is applicable for any linear circuit having time varying or time invariant circuits.

2.It is also very useful in the analysis of circuits. The superposition theorem can be very useful when the circuit has large number of sources (current or voltage sources), to find the value of current or voltage in any branch of the circuit.

Watch the large collection of Video Lectures on Engineering Here-

# A Good Optical Fibre Source Should have the Following Characteristics:

Here you will learn how to choose best optical fiber source like LASER or LED that has the best desirable qualities and is most efficient.

1.Light source should be highly directional to make the launching of light into an optical fiber easy.

2.It should emit light at wavelengths where the optical fiber has low losses and low dispersion. The detectors should also be efficient at these wavelengths.

# Optical Fiber Sources (Desirable Properties) - LASER and LED Video

3.It is also required that the optical source must couple enough optical power to overcome losses in fibre in the connectors. Not only this, after these losses enough power should be left to drive the detector.

4.The optical source should be linear to minimize the distortion and noise.

# 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.

#AMPLITUDE MODULATION (TIME DOMAIN EQUATIONS AND WAVEFORMS)

3.In FM, it is possible to further reduce noise by increasing frequency deviation. This is not possible in case of AM, since in AM, we can not exceed 100℅ modulation without Severe distortions.

4.Standard Frequency allocations provide a guard band between commercial FM stations. This leads to less interference between adjacent channels in FM in comparison to AM.

5.In case of FM, all the transmitted power is useful but in AM, most of the power is present in carrier, that does not contain any information.

# Advantages of Pulse Code Modulation (PCM)

1.Very high noise immunity

2.In pulse code modulation repeaters are used between the transmitter and receiver. Repeaters are used to regenerate the received PCM signal. Use of repeaters is possible due to digital nature of the signal.

3.Effect of noise is further reduced due to the use of repeaters.