Team Leader-Nikhil Tiwari Team Member-Rashmita Kumari Mohapatra PULSE MODULATION OER This work is licensed under the Creative Commons Attribution-ShareAlike 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-sa/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA. Team Leader-Nikhil Tiwari Team Member-Rashmita Kumari Mohapatra

Target Audience Third Year Engineering Students(EXTC)

Learning Objectives Purpose – This chapter includes generation and detection of PAM, PWM, PPM, This chapter includes principle, generation and detection of Delta modulation, adaptive delta modulation Scope – 1. Academic Aspects-Working principle of generation and detection of PAM, PWM, PPM, Working principle, generation and detection of Delta modulation, adaptive delta modulation 2. Technology Aspect-Block diagrams of generation and detection of PAM, PWM, PPM, Block diagrams of generation and detection of Delta modulation, adaptive delta modulation 3. Application Aspect- Use of generation and detection of PAM, PWM, PPM,Use of Delta modulation, adaptive delta modulation. Student Evaluation – 1. Theory questions from working principle of pulse modulation generation and detection of Delta modulation, adaptive delta modulation,multiplexing 2.Short notes on Delta modulation, adaptive delta modulation 3.Viva questions on Delta modulation, adaptive delta modulation ,Multiplexing

Helpful Tool used for Documentation Wordpress used Ms Powerpoint Camstudio Cast-o-matic

Design Decisions 1. Content Decisions 2. Pedagogic Decisions 3. Technology Decisions

Content Decisions SAMPLING T.D.M. PULSE MODULATION P.A.M. P.T.M.

Out-of-class Activity Learning Objective(s) of Out-of-Class Activity At the end of watching the videos student should be able to Able to Understand the Pulse Modulation(PAM,PWM,PPM)(Understand Level) Explain the working principle of PAM,PWM,PPM (Understand Level) Simplify the generation and detection of Pulse Modulation(Apply Level) Key Concept(s) to be covered Defination of Pulse Modulation Generation & Detection of PAM,PWM,PPM Advantages and disadvantages

Video Link for out class activity First check in National Repositories You Tube Video(https://www.youtube.com/watch?v=uvJJlY4yW1w) NPTEL Youtube Channel (https://www.youtube.com/user/nptelhrd) https://www.youtube.com/watch?v=TM47sEXeaj8 https://www.youtube.com/watch?v=OE_05sAxvJ8 Second Look in International Repositories OER Commons (http://www.oercommons.org/courses/pam-transmitter-and-receiver-implementing-coherent-detection/view)

Out-of-class Activity Design - Main Video Source URL https://www.youtube.com/watch?v=uvJJlY4yW1w License of Video © 2017 YouTube, LLC Mapping Concept to Video Source CONCEPT VIDEO SEGMENT DURATION (in min) PAM,PWM,PPM Start Time00.00 – End Time17.44 17.44M TOTAL DURATION 17.44

Out-of-class Activity Design Aligning Assessment with Learning Objective Learning Objective Assessment Strategy Expected duration (in min) Additional Instructions (if any) Q1.Explain working principle of PAM --Block diagram --Working principle --Waveforms These things should be there 10 mins Watch V1 and then answer Q1 Neat and clean circuit diagrams & waveforms required to draw

Out-of-class Activity Design Aligning Assessment with Learning Objective Learning Objective Assessment Strategy Expected duration (in min) Additional Instructions (if any) Q.Explain working principle of PWM,PPM --Block diagram --Working principle --Waveforms These things should be there 10 mins Watch V2 and then answer Qustion Neat and clean circuit diagrams & waveforms required to draw

Assesment of out-class activity 5 marks for submitting assignment on time Attendace of each lecture is given if out class activity is complete by the student.

In-class Activity Design Active Learning activity(ies) that you plan to do Real world problem solving using. Think-Pair-Share Concept clarification using. Peer Instruction

Questions Q 1: Drawback of using PAM method is a. Bandwidth is very large as compared to modulating signal b. Varying amplitude of carrier varies the peak power required for transmission c. Due to varying amplitude of carrier, it is difficult to remove noise at receiver d. All of the above

Q 2: In pulse amplitude modulation, a Q 2: In pulse amplitude modulation, a. Amplitude of the pulse train is varied b. Width of the pulse train is varied c. Frequency of the pulse train is varied d. None of the above

Q3. In different types of Pulse Width Modulation, a Q3. In different types of Pulse Width Modulation, a. Leading edge of the pulse is kept constant b. Tail edge of the pulse is kept constant c. Centre of the pulse is kept constant d. All of the above Q4. In Pulse Position Modulation, the drawbacks are a. Synchronization is required between transmitter and receiver b. Large bandwidth is required as compared to PAM c. None of the above d. Both a and b

Technology Decisions Tool to be used-You tube video link,Ms Powerpoint

Pre requisite To study Applied Mathematics-III Signals and systems

Best Practices with Lesson Activity Here are some of the best practices on using this Lesson Activity in classroom: Provide this activity at least 1 week in advance. Provide minor incentive (marks) for completion of the activity. Ensure that there is a tangible output at the end of out-of-class activity to ensure learners are interested It would be good if the screencasts and resources were separately available in a “Resources” folder in wordpress site

Evaluating Effectiveness of OER 1.At the student level 2. At the consumer level

Effectiveness at the student level Effectiveness at the student level involves metrics related to student access of the resource and student learning. The ppt lesson report can be used to evaluate this effectiveness, with the report showing the total number of students who accessed the reports (along with time) and their marks (based on their answers to MCQs). Additionally there is an option for teacher to grade essays and these marks also will be calculated if needed.

Effectiveness at consumer level OER Consumers are typically teachers who want their students to learn Linking a survey on three main constructs – Ease of Use, Concept Coverage and Concept Complexity, can help in identifying the effectiveness of this OER at consumer level. This has to be done as a follow-up activity

Implementing Survey

Introduction to Pulse Modulation

SAMPLING Process of converting a continuous time signal to an equivalent discrete time signal. Continuous time signal x(t) is applied at input of multiplexer. Other input of multiplexer is train of impulse. At the output of multiplexer we get the sampled version of x(t)

SAMPLING cont. One important property of sampling is that the signal can be fully represented by their sampled value at some discrete time instant. If the sampled values are known the signal can be reconstructed or recovered as original signal. The time interval can be used by other signals if a suitable transmission is produced. The concept of use of time interval by several signal is known as T.D.M. (Time Division Multiplexing) The sampling occurs at regular intervals of time Ts seconds apart. Thus sampling frequency fs may be represented as fs =1/Ts

SAMPLING cont. Sampling theorem is defined for 2 signals Low pass signal A band limiting signal which has no frequency component above a frequency fm Hz can be uniquely described by taking its sample at uniform intervals less than equals to 1/2fm sec apart. So that the sampling rate = 1/2fm seconds. A band limiting signal which has no frequency component above a frequency fm Hz can be uniquely recovered from the knowledge of the sample taken at a rate of 2fm per sec. so that the sampling frequency is greater than equal to 2fm . Band pass signal Band width is smaller compare with the highest frequency components and its possible to use sampling rate i.e. less than the twice the highest frequency component present in the signal. Frequency interval fc-fm<=fc<=fc+fm Minimum sampling frequency = 2(fc+fm)/m where m is integer

TIME DIVISION MULTIPLEXING Sampling theorem makes it possible to transmit the complete information of the continuous signal by transmitting more samples of f(t) at regular intervals. This is done on time sharing basis. The transmission of sample engage the channel for only part of time. All the signals to be transmitted are inter laced in transmitter. It is switched from channel to channel I sequence to the sampling circuits by the pulse generated by the timing circuit. At the receiver, the samples of each signal are separated. Its sampling pulse is in synchronism. The output of the sampling circuit is thus a signal which consist of samples of all signals interlaced

DIFFERENCE PAM Amplitude of pulse is proportional to amplitude of modulating signal. Band width of transmitting channel depends on width of pulse. Instantaneous power of transmitter varies. Noise interference is high. Complex system. Similar to A.M. PWM Width of pulse is proportional to amplitude of modulating signal. Band width of transmitting channel depends on rise time of the pulse. Instantaneous power of transmitter varies. Noise interference is minimum. Simple to implement. Similar to F.M. PPM Relative position of pulse is proportional to amplitude of modulating signal. Band width of transmitting channel depends on rise time of the pulse. Instantaneous power remains constant. Noise interference is minimum. Simple to implement. Similar to P.M.

PULSE AMPLITUDE MODULATION (PAM) PAM can be defined as a process in which the amplitude of regular spaced rectangular pulse vary in direct proportion to the instantaneous sample values of continuous signal. Its is quite similar to Amplitude Modulation. The difference is that here a Pulse Train acts as carrier rather than high freq. sinusoidal wave There are mainly 2 types of PAM signals PAM with Natural Sampling Pam with Flat Top

PAM with Natural Sampling Width of pulse do not have flat top. The top of pulse varies in accordance with the shape of modulating signal. With the Natural Sampling, a signal sampled at NQUIST rate may be reconstructed exactly by passing through LOW PASS FILTER with cut off frequency fm . where fm is the highest frequency component If N signals are to be multiplied, the max sampled duration is T=Ts/N

Flat Top PAM The top of pulses of this PAM is flat. Noise interference at the top of transmitted pulse can be easily removed. Due to this it is widely used. Better than Natural PAM Because in case of Natural PAM, the varying top signal is when received at receiver, it becomes quite difficult to determine shape of top of pulse due to noise (which is always present). Thus errors are introduced in the receiving signals due to wich we prefer a flat top PAM.

Flat Top PAM cont. Sampled and hold circuit consist of 2 flat switches and a capacitor. The sampling switch is closed for a short duration by a short pulse applied to gate G1 of transistor. During this period the capacitor is charged up to a voltage equal to the instantaneous value of input signal x(t) When the sampling switch is opened the capacitor hold the charge. The discharge switch is then closed by a pulse applied to the gate G2 pf the other transistor. Due to this capacitor discharge to zero volts. Hence the output sampled and hold circuit consist of Flat Top Samples. Fig. shows sampled and hold circuit to Produce FLAT TOP sampled P.A.M.

PULSE TIME MODULATION(PTM) There are two types of Pulse Time Modulation Pulse Width Modulation (PWM) Pulse Phase Modulation (PPM) In both PWM and PPM some time parameters of the pulse is modulated. In PWM the width of pulse is varied. In PPM position of the pulse is varied. Amplitude of pulses remain constant for both PWM and PPM

DEMODULATION of P.W.M. The transistor T1 acts as an inverter. During the time interval when the signal is high, the input of transistor T2 is low. Thus during this interval T2 is in cut-off stage. Thus capacitor C is charged through RC combination. During the time interval when the signal is low, the input of transistor is high. Thus it get saturated during thus time. The capacitor gets discharge very rapidly through transistor T2. Hence the waveform at the collector transistor T2 is more or less a saw-tooth waveform whose envelop is modulating signal. When this is passed through 2nd order Op-amp low pass filter, desired demodulated signal is obtained.

DEMODULATION of P.P.M. This circuit makes use of the fact that the gaps between the pulses of PPM signal contains information regarding the Modulating signal. During the gap between pulses The transistor is in cut-off. The capacitor gets charged through RC combination. During the pulse duration The transistor is in saturation. Capacitor is discharged through transistor. Thus the collector voltage becomes low. Hence the waveform at the collector is approximately a saw-tooth waveform whose envelop is Modulating signal. When this is passed through 2nd order low pass filter, the desired demodulated output is obtained.

Consolidated Log of Team Work Activity Team Member Amount of Time Additional Logs if any Discussion Team Leader 1hr Team Member 1 Tool Exploration Plan uploaded in Wordpress Plan uploaded in blog wordpress OER Creation OER Documentation Individual Reflection (Diary Logging) Review Comments in Blog OER Evaluation Edits made in wordpress

Works Cited https://rashmita2017.wordpress.com

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