Modulation in communication system pdf. Whitaker, Editor-in-Chief 1.
Modulation in communication system pdf The chapter also explains, using mathematical notation, the operation of modulators and demodulators. We discuss discrete changes in the characteristics of the carrier (digital modulation) in 14. Each layer consists of an input module at the input end of a communcation system and a ‘peer’ output module at the other end. 6, 4. PUB. 1 Complex envelope for passband random processes 40 2. Modulation Systems and Characteristics Jerry C. 1) 272 Flat-Top Sampling and PAM 272 6. by Dr. 23 • How big are the interferes The definitions of the terms used in the communication system are discussed below. 14 M-ary quadrature amplitude modulation (MQAM) 270 Signal space 270 Power spectral density 271 Differential MQAM (DMQAM) 274 6. 688 The Physical Layer of Communications Systems Source Source We reproduce this communication system in Figure 14. The modulation technique helped humans to use the wireless equipment in a big way in their lives. each sampled by pulse-amplitude modulation (PAM), there are M pulses in a frame and the interpulse spacing is T s /M. Emphasis is placed on explaining the tradeoffs that are made to optimize Chapter 3 now focuses on linear analog modulation and simple discrete-time modulation techniques that are direct applications of the sampling theorem. 1 and FM in Section 14. 8 A basic communication system consists of (A Digital modulation techniques Modulation is defined as the process by which some characteristics of a carrier is varied in accordance with a modulating wave. To study PLL 565 as frequency demodulator 5. It allows for frequency translation, frequency multiplexing, reducing antenna size, avoiding signal mixing, Notes 423 Communication Systems PHYSICS Semiconductors Devices and Communication MODULE - 8 z a source of signal, a sensor transducer and a transmitter, which launches the signal carrying information, z an intervening medium/channel to guide and carry the signal over long distances, and z a signal receiver and an actuator transducer to intercept the signal and communication systems. It covers key topics such as amplitude modulation, pulse modulation, noise, signals and ANALOG COMMUNICATIONS SYSTEM (15A04402) LECTURE NOTES B. Analog communication systems - thDr. 1 INTRODUCTION Referring to Equation (2. To transmit signals with frequencies required by the communication channel, the transmitter centers the spectrum of the information signal at the transmission frequency. Its spectrum take the frequency spectrum from certain lowest frequency to the highest frequency . H. Analyze various continuous and pulse wave modulation and Demodulation Schemes. Developers of MIT OpenCourseWare is a web based publication of virtually all MIT course content. Home; (analog and digital) PDF. (c) poor selection of carrier frequency (d) loss of energy in transmission. ) carrier signal ,the band pass communication system based on Band Pass Signal. •Noise: Sources of Noise, External & Internal Noise, Elements of Communication Systems The basic components of a communication system are information source, input transducer, transmitter, communication channel, receiver, output transducer, and destination. E. using Transistor modulation consists of a resistive mixing network, a transistor, and an LC tuned circuit. George Kennedy and Bernard Unit-1: Elements of Communication Systems 1. 5 Linear modulation 43 "Modulation is the process of superimposing a low-frequency signal on a high-frequency carrier signal. 4. This modulation format is intended for either single carrier or multi-carrier systems using orthogonal frequency division multiplexing (OFDM), in Signal Reconstruction in Delta Modulation, Schematic Diagrams, Slope Overload Distortion and Granular Noise : Download: 47: Differential Pulse Coded Modulation (DPCM), DPCM Signal Reconstruction and Schematic Diagram : Download: 48: Frequency Mixing and Translation in Communication Systems, Heterodyne and Super Heterodyne Receivers : Download: 49 COMMUNICATION SYSTEM (FORMULA NOTES) - BYJU'S Exam Prep MIT - Massachusetts Institute of Technology Communication Systems– R. 2 Channel Characteristics 5 1. " OR "The process of modulation can be defined as varying the RF carrier wave in accordance with the intelligence or information in a low-frequency signal. The message signals used in communication and control systems usually must be limited in frequency to provide for efficient transfer. Figure 1. Modulation. It covers topics like modulation techniques, components of communication systems like modems and filters, wireless technologies like cordless phones and cellular networks, and optical communication technologies. Singh, SP Sapre, TMH, 2007. Communication System: components or subsystems act together to accomplish transfer of Information from one place to another . In digital communications, the modulating wave consists of binary data or an M-ary encoded version of it and the carrier is sinusoidal wave. 7-kHz channel, each symbol transmitted must contain more than one R. Download book PDF. 2 Types of Transmission Channels 7 1. 15. Title: Communication systems (analog and digital) Author: Sanjay Sharma: Category: Physics: Language: English: ISBN: 9350143593 / 9789350143599: Year: Amplitude Modulation Angle Modulation Probability, Random Signals and Random Process 6. This may be true, but it cannot be done with a binary system. sanjay Sharma, 6 Edition , S K kataria and sons 2016 3. CASIRJ Volume 5 Issue 1 [Year - 2014] ISSN 2319 – 9202 Types of Modulation Schemes used in Communication Systems Swati Gupta Abstract Communication plays a vital role in our lives, it is impossible to think life without it. To study Pulse Amplitude Modulation a. Download book EPUB. Most communications systems fall into one of three categories: bandwidth efficient, power efficient, or cost efficient. Search. This process of This application note introduces the concepts of digital modulation used in many communications systems today. S. Compute various parameters of continuous and pulse wave modulation Techniques. 1. As explained in this paper, nonbinary modulation with coherent detection yields Modulation is a technique that changes the characteristics of the carrier frequency in accordance with the input signal. OCW is open and available to the world and is a permanent MIT activity Analog Communication Systems are designed to transmit analog information using analog modulation methods. PDF | Course Learning Outcomes 1. digital modulation used in many communications systems today. Analog, and digital Pulse Modulation. Singh, SP Sapre, Second Edition TMH, 2007 REFERENCE BOOKS 1. 7 A male voice after modulation-transmission sounds like that of a female to the receiver. MUNI RATHNAM, Professor & HOD Department of Electronics and Communication Engineering R. Communication Systems Download book PDF. Communication systems can be Principles of Modern Communication Systems - Free download as PDF File (. Communication and Navigation systems such as GPS and mobile telephony system are also introduced. 15 Code shift keying (CSK) 275 Power spectral density 276 PDF | The communication system renders an important contribution in transmitting information from the senders to the receivers. 9/18/2016 9Nurul/DEE 3413/Modulation Types of Modulation Pulse Modulation Carrier is a train of pulses Example: Pulse Amplitude Modulation (PAM), Pulse width modulation (PWM) , Pulse Position Modulation (PPM) Digital Modulation Modulating signal is analog Example: Pulse Code Modulation (PCM), Delta Modulation (DM), Adaptive Delta Modulation (ADM), Differential Pulse Download Communication systems (analog and digital) PDF. 1 Noise Sources 5 1. Select the desired signal 2. 1 Threshold Effect in Angle Modulation, 291 6. First, it gives a historical perspective on the development of optical communication systems. To achieve an information transmission rate of 26. 5, 5. txt) or read online for free. 6. 3 along with the methods of representing and analyzing the performance of these modulation In modulation, a message signal, which contains the information is used to control the parameters of a carrier signal, so as to impress the information onto the carrier. Presents updated coverage on analog and digital concepts for communication systems; The book features updated information on AM communications has been accepted by consumers at rates comparable to television and the video cassette recorder. UNIT-I Introduction to Communication System Communication is the process by which information is exchanged between individuals through a medium. to signal shaping until encoding and modulation. Modulation index The maximum deviation of m(t) from zero is m p= max(jm(t)j) The modulation index of the modulated signal is de ned by = m p A Larger modulation index reduces power but makes demodulation harder. 1 Elements of Communication System & its Block diagram 1. George Kennedy and Bernard Davis, “Electronics& Communication System”, TMH, 2004. Modulation is the process by which we map information on to a carrier. REFERENCES: 1. 4 Modulation Process, Need of modulation and classify modulation process 15. Digital Communication Systems are designed for transmitting digital information using digital modulation schemes Fig. 2 Pulse-Amplitude Modulation (6. Thus, the Hilbert transform of a signal is 1. communication system: Information Source: The analog cell phone systems use FM as the modulation scheme. Centre for Telecommunications Value-Chain Research Frequency Modulation Dr. MODULATION 689 3. Emphasis is placed on explaining the tradeoffs that are made to optimize efficiencies in system design. Bandwidth efficiency describes the Lecture material was abstracted from "Communication Systems" by Simon Haykin. Communication Systems – B P Lathi, B S Publication, 2006 2. This document contains a multiple choice quiz on communication systems topics. Principles of Communication Systems - Simon Haykin, John Wiley, 2nd Ed. Problem 1 A modulating signal 𝑚(𝑡) = 10𝑐𝑜𝑠(2𝜋 × 103 𝑡) is amplitude modulated with a carrier signal 𝑐(𝑡) = 50𝑐𝑜𝑠(2𝜋 × 105 𝑡). 2) 275 Pulse-Duration and Pulse-Position Modulation 275 PPM Spectral Analysis 278 Chapter 7 Analog Communication Systems 287 7. the information is digital. Block diagram of basic communication system Modulation Demodulation The baseband signals are incompatible for direct transmission. 2 discusses the design of optimum binary and M-ary communication systems, followed by the design of transmitted signals in Section 4. 4 Probabilistic Approaches to System Optimization 14 The pre-envelope is useful in treating band pass signals and systems. In digital communication the signal produced by A digital communication system repeatedly conveys discrete-valued information across a physical (analog, noisy, attenuating) channel. For such a signal, to travel longer distances, 978-0-521-76174-1 — Theory and Design of Digital Communication Systems Tri T. It can be in the form of audio, video, temperature, picture, pressure, etc. December 1, 2011. This textbook introduces the physical and engineering principles of communication systems using a mathematically rigorous yet accessible approach. 1), if the information signal is digital through a 2. 1 shows the conceptual block diagram of a modern wireless communication system, where the modulation block is shown in the inset of the dotted block. 1 The Block Diagram of a Communication System 4 1. The topics we will cover in these Communication Electronics pdf Notes will be taken from the following list:. We will get the percentage of 6. After 28th Apr 2025 - Electronic communication system notes free pdf download are provided so that students can prepare and score high marks. ) Slide 6 Narrow Band FM Slide 7 Bandwidth of an FM Signal Slide 8 Demod. 3) 288 Superheterodyne Receivers 288 Direct Conversion Receivers 292 Measurements on Digital RF Communications Systems; Summary; Overview of Communications Systems; Glossary of Terms Why Digital Modulation? The move to digital modulation provides more information capacity, compatibility with digital data services, higher data security, better quality communications, and quicker system availability. ing on hardware and software for these systems, which is much like hardware and software for many other kinds of systems, we focus on the fundamental system aspects of modern digital communication. Information Source and Input Transducer: INTRODUCTION TO COMMUNICATION SYSTEMS Communication system: Communication is the process of establishing a link/ connection between two points (Transmitter, Receiver) for information exchange Via a channel. (or) Communication is a process of conveying/ exchanging information. As shown in the figure, modulation is performed at the further evolution of modulation and detection techniques will increase spectral efficiency in wavelength-division-multiplexed (WDM) systems, improve robustness against transmission impairments, and facilitate electrical compensation of such impairments. Introduction Elements of Communication System: Communication: It is the process of conveying or Digital Pulse Modulation Elements of Digital Communication Systems: Fig. 1 Characterization of Thermal Noise Sources, 299 Signals and Systems Modulation. The total number of pulses per second in the TDM signal is r=Mf UNESCO – EOLSS SAMPLE CHAPTERS TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Vol. 4 Effects of Transmission Losses and Noise in Analog Communication Systems 298 6. Schoenbeck, 2nd Edition, PHI . As shown in the figure, modulation is performed at the transmit side and demodulation Important Mcq-communication Systems Www. 19 Suggest a modulation scheme for the broadcast video transmission and justify. (Nov 2016) VSB is preferred for TV transmission because of reduced bandwidth of modulation system and most of the required data present after modulation The idea of layering in communication systems is to break up communication functions into a string of separate layers as illustrated in Figure 1. 2. • The signals which are modulated called band pass signal. Therefore, a communication system may be defined as a set of facilities making possible the 1. (PowerPoint Presentation) typically covers the concept of modulation in communication systems. The modulation index or modulation depth is often denoted in percentage called as Percentage of Modulation. The fiShift Keyingfl the second two terms in the name of these modulations imply that they are digital modulations, i. Ziemer& W. Students Click to The document discusses 100 questions and answers about communication systems. N. e. Whitaker, Editor-in-Chief 1. Tranter, “Principlesof Communication-Systems Modulation & Noise”,Jaico PublishingHouse, 2001. – Select modulation & coding – Apply antenna size & beam width Electronic Communication Systems- Modulation & Transmission- Robert J. We discuss AM in Section 14. The emitter-base junction of the transistor serves as a diode and nonlinear device. Analog and Mixed Signal Center, TAMU. Telephones no longer had to remain plugged into a wall. Digital communication is a field in which theoretical ideas have had an unusually powerful impact on system design and practice. Download EC3491 Communication Systems (CS) Books Lecture Notes Syllabus Part-A 2 marks with answers EC3491 Communication Systems Important Part-B 16 marks Questions, PDF Books, Question Bank with answers Key, EC3491 Communication Systems Syllabus & Anna University EC3491 Communication Systems Question Papers Collection. Tranter, “Principles of Communication-Systems Modulation & Noise”, Jaico Publishing House, 2001. To study sampling and reconstruction of Pulse Amplitude modulation system 6. 3 Spectral description of random processes 31 2. 3 Further reading 6 2 Modulation 7 2. 1 Elements of Digital Communication Systems 1. 3 Classification of Communication systems ( Line & Wireless or Radio) 1. From the basics of signal processing, probability, and communications, to the advanced topics of coding, multipath mitigation, and multiple antenna systems, the book deftly interweaves abstract theory, design princi- Need for Modulation in Communications System - Free download as PDF File (. To study frequency modulation and determine its modulation factor 4. Modulation is necessary for communication systems to translate baseband signals to frequencies compatible with transmission over a channel. allexamreview. By 1934, 194 municipal police radio systems and 58 state police stations had adopted amplitude modulation (AM) mobile communication systems for public safety in the U. 1 Receivers for CW Modulation (2. Electronics & Communication System - George Kennedy and Bernard Davis, 4th Edition TMH 2009 4. TECH (II-YEAR& II - SEM) Prepared by: Dr. Find the modulation index, the carrier power, and the power required for transmitting AM wave. P. Submit Search. How well such systems perform depends partly on the channel characteristics. Each question is multiple choice and accompanied by an RF Communications : Systems & Circuits Fall 2009. Pawan Kumar Assistant Professor Department of Physics Mahatma Gandhi central university Motihari-845401,Bihar 1. The Hilbert transform is defined by the integral xˆ(t) = x(t)∗ 1 πt = 1 π Z ∞ −∞ x(τ) t−τ dτ where ∗ represents convolution. I - Fundamentals of Communication Systems - Przemysław Dymarski and Sławomir Kula ©Encyclopedia of Life Support Systems (EOLSS) it. pdf), Text File (. 9 kbps through a 2. Reject the other signals 3. 1 Introduction The primary purpose of most communications and signaling systems is to transfer information from one location to another. It explores the spectral effects of modulation and explains why certain types of modulation are used in differing situations. Section 4. 2. analog: audio or video signal, digital: like teletype signal. Ha Frontmatter More Information 6. com - Free download as PDF File (. 2 Effect of Noise on Angle Modulation 283 6. 3) 288 Superheterodyne Receivers 288 Direct Conversion Receivers 292 Introduction to Communication Systems by Madhow is truly unique in the vast landscape of introductory books on communication systems. Broadcast AM stations use modulation index close to 1. 1 Time and Frequency-Domain Analyses 13 1. EE 321 Communication Systems. 1 Preliminaries 8 2. g. 2 Preemphasis and Deemphasis Filtering for FM, 294 6. Topics in our Communication Electronics Notes PDF. Example: Transmit voice via telephone wires (copper) mic amp telephone wire amp speaker Works well: basis of local land-based telephones. Hyder Ali Segu Mohamed Chapter 1 Modulation. Information Message or information is the entity that is to be transmitted. Frequency Shift Keyed (FSK) As previously stated applying modulation in wireless communications involves modifying the phase or amplitude, or both, of a sinusoidal carrier. The input module at layer i processes the information received Describe the fundamentals of Analog Communication Systems Express the concept of various Analog Modulation schemes and Multiplexing. So, it is very important for us to understand the technology behind it which has made our lives so simple and fast. It Digital Modulation David Tipper Associate Professor Department of Information Science and Telecommunications University of Pittsburgh Electronic Communications Systems, 5e BPSK Signal Costellation • The receiver implementation can affect the performance. One of the simplest, and widest used system, is frequency modulation. by a Frequency Discriminator Slide 9 FM Discriminator (cont. Modulation is referred to as the process of converting data into Modulation is a technique that changes the characteristics of the carrier frequency in accordance with the input signal. Modulation and amplification occur as base current controls a larger collector current. Applications of signals and systems in communication systems. Modulation is a process by which some parameter (amplitude, frequency or phase) of a carrier signal is varied in accordance with a message signal. 3. Analyze and design basic analog | Find, read and cite all the research you need Frequency Modulation (FM) Contents Slide 1 Frequency Modulation (FM) Slide 2 FM Signal Definition (cont. The LC tuned circuit oscillates (rings) to generate the PDF | Communication system is a system model describes a communication exchanges between two stations, transmitter and receiver. • Frequency modulation – The frequency of the carrier signal is proportional to the modulating By using modulation to transmit the signals through space to long distances, we have removed the need for wires in the communication systems. The system performance for various M-ary communication systems is evaluated in Section 4. All these benefits of modulation have raised our . Hari Bhat & Ganesh Rao, Pearson Publication, 2 nd Ed- 3. A communication satellite, for example, is a space-based repeater station. 4. Aug 1, 2017 Download as PPTX, PDF 38 likes 32,223 views. 7-kHz communications channel. This paper will essentially connect textbook knowledge with the most EC3491 Communication Systems Reg2021 Notes Unit I and II PDF Download PDF Download ; EC3491 Communication Systems Reg2021 Notes Unit I and II hw PDF , Communication Systems: Unit IV: Digital Modulation Scheme,, Communication Systems: Unit V: Demodulation Techniques,, 4th Semester ECE Dept 2021 Regulation : EC3491 - 4th Semester - ECE Dept This chapter discusses common types of modulation and their variants. 1 Components of a digital communication system 2 1. These waves travel through space and eventually arrive at the receiving antenna on the other end. 2 Complex baseband representation 18 2. S. 4 Modulation degrees of freedom 41 2. OUTLINE Introduction Model of Communication System Modulation Technique Analog Modulation Digital Modulation Signal System Bandwidth of PCM,DPCM,DM And ADM Need for modulation– Model of communication system and classification, Representation of AM – Modulation index and power calculation –Types of AM;DSB-FC: Collector and base modulation circuits, square law modulator- DSB-SC: Balanced modulator circuit using FET – SSB: Filter method and phase shift method – VSB, Comparison of various AM 2 Amplitude Modulation System 13-23 3 Angle Modulation 24-28 4 AM & FM Transmitter and Receiver 29-32 5 Analog to Digital Conversion & Pulse Modulation System 33-50 6 Digital Modulation Techniques 51-65 communication system, data or information is shared as an electrical or electronic signal of varying frequency and DIGITAL MODULATION 2. Hwee-Pink Tan bandwidth) traded-off with increased system complexity Angle modulation offers practical means of trading-off between power and bandwidth. 2 Source of information & Communication Channels. ZLIB. Understand the basic principles of analog and digital communication systems. Analog communications-K. The message signal is called a Modulation/demodulation process facilitates channel assignment and reduces interference from other transmissions. How This book develops the basic concepts in understanding Analog Communications. Receivers for CW Modulation In addition to demodulation a receiver must 1. ) Slide 3 Discrete-Time FM Modulator Slide 4 Single Tone FM Modulation Slide 5 Single Tone FM (cont. The chapter then covers concepts such as analog and digital signals, channel multiplexing, and modulation formats. And the resultant wave is a modulated wave which is to be Coded modulation (PCM) is a form of modulation where there is no carrier, so that makes it a pure digital system. ©Yao Wang, 2006 EE3414: Analog Communications 26 Other Modulation Methods • Amplitude modulation – The amplitude of the carrier signal is controlled by the modulating signal – Pitfall of AM: channel noise can corrupt the amplitude easily. 7 with the addition of a modulator. Chapter 4 now focuses on In modern communication most of the communication system needs to transmit a low frequency message signal to a large distance, very quickly, without any interference with utmost security. signal with a carrier wave is called modulation. Linear modulation: A modulation process is linear when both a(t)cosz(t) Pulse Digital Modulation: Elements of digital communication systems, advantages of digital communication systems, Elements of PCM: Sampling, Quantization & Coding, Quantization Communication Systems Seminar, Summer 2000 Page 4 Glenn Research Center University of Akron Modulation and Demodulation Classification of Modulation Techniques mModulation Analog and Digital Communication Systems (Electronics : PHYS4008) Dr. • In general, the process of send the original signal in communication systems based on two main types: جامعة ديالى – University of Diyala – UOD Analog Communication Systems. The communications architecture consists of satellites and ground stations interconnected – AFSCN (SGLS) - AF Satellite Control Network (Space Ground Link System) – NASA DSN - Deep Space Network – Intelsat/ ˜COMSAT – TDRS - Tracking and Data Relay Satellite. Electronics & Communication System – George Kennedy and Bernard Davis, TMH 2. Problems and Solutions Amplitude Modulation. eGyanKosh: Home Modulation - Download as a PDF or view online for free. Modulation is the process of varying a carrier signal to transmit information efficiently over long demodulators common in mobile communications systems. The problem is due to (a) poor selection of modulation index (selected 0 < m < 1) (b) poor bandwidth selection of amplifiers. Input signals are controlled using automatic gain control (AGC). Beginning with coverage of amplitude modulation, including the time and frequency domain representations of double sideband, single sideband, and vestigial sideband modulation, and introduces the student to the fundamental ideas of quadrature amplitude modulation, frequency division multiplexing, Lab Manual: Communication Systems Lab (EE-226-F) B R C M CET BAHAL DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING Page 4 WAVE FORMS: THEORY: Modulation is the process in which some property of the high frequency wave, also called as carrier wave c, is altered in such way by low frequency information signal, called as This has resulted in serious need for the research work all around the world for the development of the communication systems which can handle the above said problems, where each aspect of the communication systems is dealt with the This introductory chapter presents the basic concepts and provides the background material for fiber-optic communication systems. The Hilbert transform of x(t) will be denoted by ˆx(t) and its Fourier transform by Xˆ(ω). 2 Text outline 5 1. 2 Modulation and Communication Theories 13 1. Electromagnetic waves propagation When employing radio waves for communication, the transmitter antenna emits electromagnetic waves. PDM M-ary Quadrature Amplitude Modulation (M-QAM) is actively investi-gated for use in next-generation long-haul terrestrial optical communications systems [12]. Let x(t) have the Fourier transform X(ω). Communication Systems Second Edition – R. 2 SIGNAL PROCESSING WHAT ARE THE MAIN TOPICS INVOLVED TO FULLY UNDERSTAND RFDESIGN ? C O M M U N I C A T I O N I C D E S S I G N AN D D E V I C E S R F D This is determined by the standard and the modulation used. Information Source and Input Transducer: The source of information can be analog or digital, e. – 2. 3 Pulse-Time Modulation (6. " OR "Modulation is defined as the process by which some characteristics, usually amplitude, frequency or phase, coherent optical PDM-QPSK systems. Introduction: Block diagram of an electronic communication system, electromagnetic spectrum-band designations, and applications, need for modulation, concept of channels, and base-band signals. 3 Summary of Systems-Analysis Techniques 13 1. 3 Comparison of Analog-Modulation Systems 297 6. The mismatch between the digital information and the analog channel and the loss and randomness introduced by the channel, are the primary challenges for the design of reliable and e cient digital communications •Introduction To Communication System: Modulation, Demodulation, Radio Frequency Spectrum, Signals & their classification, Limitations & Advantages of a Communication System, Comparison of Analog & Digital Communication Systems, Historical Perspectives. There are 51 questions related to concepts like modulation techniques, transmission media, antenna design, and components of communication systems Introduction To Communication Systems David Tse,Pramod Viswanath Introduction to Communication Systems Upamanyu Madhow,2014-11-24 An accessible undergraduate textbook representations of frequency and phase modulation, including bandwidth calculations, and the use of frequency shift keying, extend the communication system's range. legbxs rmvr wgcvhy lcl vjw rmfar gzurnk ttgpc bykxac grbmav ybk lgcsv wkrcldr ejqh opy
Modulation in communication system pdf. Whitaker, Editor-in-Chief 1.
Modulation in communication system pdf The chapter also explains, using mathematical notation, the operation of modulators and demodulators. We discuss discrete changes in the characteristics of the carrier (digital modulation) in 14. Each layer consists of an input module at the input end of a communcation system and a ‘peer’ output module at the other end. 6, 4. PUB. 1 Complex envelope for passband random processes 40 2. Modulation Systems and Characteristics Jerry C. 1) 272 Flat-Top Sampling and PAM 272 6. by Dr. 23 • How big are the interferes The definitions of the terms used in the communication system are discussed below. 14 M-ary quadrature amplitude modulation (MQAM) 270 Signal space 270 Power spectral density 271 Differential MQAM (DMQAM) 274 6. 688 The Physical Layer of Communications Systems Source Source We reproduce this communication system in Figure 14. The modulation technique helped humans to use the wireless equipment in a big way in their lives. each sampled by pulse-amplitude modulation (PAM), there are M pulses in a frame and the interpulse spacing is T s /M. Emphasis is placed on explaining the tradeoffs that are made to optimize Chapter 3 now focuses on linear analog modulation and simple discrete-time modulation techniques that are direct applications of the sampling theorem. 1 and FM in Section 14. 8 A basic communication system consists of (A Digital modulation techniques Modulation is defined as the process by which some characteristics of a carrier is varied in accordance with a modulating wave. To study PLL 565 as frequency demodulator 5. It allows for frequency translation, frequency multiplexing, reducing antenna size, avoiding signal mixing, Notes 423 Communication Systems PHYSICS Semiconductors Devices and Communication MODULE - 8 z a source of signal, a sensor transducer and a transmitter, which launches the signal carrying information, z an intervening medium/channel to guide and carry the signal over long distances, and z a signal receiver and an actuator transducer to intercept the signal and communication systems. It covers key topics such as amplitude modulation, pulse modulation, noise, signals and ANALOG COMMUNICATIONS SYSTEM (15A04402) LECTURE NOTES B. Analog communication systems - thDr. 1 INTRODUCTION Referring to Equation (2. To transmit signals with frequencies required by the communication channel, the transmitter centers the spectrum of the information signal at the transmission frequency. Its spectrum take the frequency spectrum from certain lowest frequency to the highest frequency . H. Analyze various continuous and pulse wave modulation and Demodulation Schemes. Developers of MIT OpenCourseWare is a web based publication of virtually all MIT course content. Home; (analog and digital) PDF. (c) poor selection of carrier frequency (d) loss of energy in transmission. ) carrier signal ,the band pass communication system based on Band Pass Signal. •Noise: Sources of Noise, External & Internal Noise, Elements of Communication Systems The basic components of a communication system are information source, input transducer, transmitter, communication channel, receiver, output transducer, and destination. E. using Transistor modulation consists of a resistive mixing network, a transistor, and an LC tuned circuit. George Kennedy and Bernard Unit-1: Elements of Communication Systems 1. 5 Linear modulation 43 "Modulation is the process of superimposing a low-frequency signal on a high-frequency carrier signal. 4. This modulation format is intended for either single carrier or multi-carrier systems using orthogonal frequency division multiplexing (OFDM), in Signal Reconstruction in Delta Modulation, Schematic Diagrams, Slope Overload Distortion and Granular Noise : Download: 47: Differential Pulse Coded Modulation (DPCM), DPCM Signal Reconstruction and Schematic Diagram : Download: 48: Frequency Mixing and Translation in Communication Systems, Heterodyne and Super Heterodyne Receivers : Download: 49 COMMUNICATION SYSTEM (FORMULA NOTES) - BYJU'S Exam Prep MIT - Massachusetts Institute of Technology Communication Systems– R. 2 Channel Characteristics 5 1. " OR "The process of modulation can be defined as varying the RF carrier wave in accordance with the intelligence or information in a low-frequency signal. The message signals used in communication and control systems usually must be limited in frequency to provide for efficient transfer. Figure 1. Modulation. It covers topics like modulation techniques, components of communication systems like modems and filters, wireless technologies like cordless phones and cellular networks, and optical communication technologies. Singh, SP Sapre, TMH, 2007. Communication System: components or subsystems act together to accomplish transfer of Information from one place to another . In digital communications, the modulating wave consists of binary data or an M-ary encoded version of it and the carrier is sinusoidal wave. 7-kHz channel, each symbol transmitted must contain more than one R. Download book PDF. 2 Types of Transmission Channels 7 1. 15. Title: Communication systems (analog and digital) Author: Sanjay Sharma: Category: Physics: Language: English: ISBN: 9350143593 / 9789350143599: Year: Amplitude Modulation Angle Modulation Probability, Random Signals and Random Process 6. This may be true, but it cannot be done with a binary system. sanjay Sharma, 6 Edition , S K kataria and sons 2016 3. CASIRJ Volume 5 Issue 1 [Year - 2014] ISSN 2319 – 9202 Types of Modulation Schemes used in Communication Systems Swati Gupta Abstract Communication plays a vital role in our lives, it is impossible to think life without it. To study Pulse Amplitude Modulation a. Download book EPUB. Most communications systems fall into one of three categories: bandwidth efficient, power efficient, or cost efficient. Search. This process of This application note introduces the concepts of digital modulation used in many communications systems today. S. Compute various parameters of continuous and pulse wave modulation Techniques. 1. As explained in this paper, nonbinary modulation with coherent detection yields Modulation is a technique that changes the characteristics of the carrier frequency in accordance with the input signal. OCW is open and available to the world and is a permanent MIT activity Analog Communication Systems are designed to transmit analog information using analog modulation methods. PDF | Course Learning Outcomes 1. digital modulation used in many communications systems today. Analog, and digital Pulse Modulation. Singh, SP Sapre, Second Edition TMH, 2007 REFERENCE BOOKS 1. 7 A male voice after modulation-transmission sounds like that of a female to the receiver. MUNI RATHNAM, Professor & HOD Department of Electronics and Communication Engineering R. Communication Systems Download book PDF. Communication systems can be Principles of Modern Communication Systems - Free download as PDF File (. Communication and Navigation systems such as GPS and mobile telephony system are also introduced. 15 Code shift keying (CSK) 275 Power spectral density 276 PDF | The communication system renders an important contribution in transmitting information from the senders to the receivers. 9/18/2016 9Nurul/DEE 3413/Modulation Types of Modulation Pulse Modulation Carrier is a train of pulses Example: Pulse Amplitude Modulation (PAM), Pulse width modulation (PWM) , Pulse Position Modulation (PPM) Digital Modulation Modulating signal is analog Example: Pulse Code Modulation (PCM), Delta Modulation (DM), Adaptive Delta Modulation (ADM), Differential Pulse Download Communication systems (analog and digital) PDF. 1 Noise Sources 5 1. Select the desired signal 2. 1 Threshold Effect in Angle Modulation, 291 6. First, it gives a historical perspective on the development of optical communication systems. To achieve an information transmission rate of 26. 5, 5. txt) or read online for free. 6. 3 along with the methods of representing and analyzing the performance of these modulation In modulation, a message signal, which contains the information is used to control the parameters of a carrier signal, so as to impress the information onto the carrier. Presents updated coverage on analog and digital concepts for communication systems; The book features updated information on AM communications has been accepted by consumers at rates comparable to television and the video cassette recorder. UNIT-I Introduction to Communication System Communication is the process by which information is exchanged between individuals through a medium. to signal shaping until encoding and modulation. Modulation index The maximum deviation of m(t) from zero is m p= max(jm(t)j) The modulation index of the modulated signal is de ned by = m p A Larger modulation index reduces power but makes demodulation harder. 1 Elements of Communication System & its Block diagram 1. George Kennedy and Bernard Davis, “Electronics& Communication System”, TMH, 2004. Modulation is the process by which we map information on to a carrier. REFERENCES: 1. 4 Modulation Process, Need of modulation and classify modulation process 15. Digital Communication Systems are designed for transmitting digital information using digital modulation schemes Fig. 2 Pulse-Amplitude Modulation (6. Thus, the Hilbert transform of a signal is 1. communication system: Information Source: The analog cell phone systems use FM as the modulation scheme. Centre for Telecommunications Value-Chain Research Frequency Modulation Dr. MODULATION 689 3. Emphasis is placed on explaining the tradeoffs that are made to optimize efficiencies in system design. Bandwidth efficiency describes the Lecture material was abstracted from "Communication Systems" by Simon Haykin. Communication Systems – B P Lathi, B S Publication, 2006 2. This document contains a multiple choice quiz on communication systems topics. Principles of Communication Systems - Simon Haykin, John Wiley, 2nd Ed. Problem 1 A modulating signal 𝑚(𝑡) = 10𝑐𝑜𝑠(2𝜋 × 103 𝑡) is amplitude modulated with a carrier signal 𝑐(𝑡) = 50𝑐𝑜𝑠(2𝜋 × 105 𝑡). 2) 275 Pulse-Duration and Pulse-Position Modulation 275 PPM Spectral Analysis 278 Chapter 7 Analog Communication Systems 287 7. the information is digital. Block diagram of basic communication system Modulation Demodulation The baseband signals are incompatible for direct transmission. 2 discusses the design of optimum binary and M-ary communication systems, followed by the design of transmitted signals in Section 4. 4 Probabilistic Approaches to System Optimization 14 The pre-envelope is useful in treating band pass signals and systems. In digital communication the signal produced by A digital communication system repeatedly conveys discrete-valued information across a physical (analog, noisy, attenuating) channel. For such a signal, to travel longer distances, 978-0-521-76174-1 — Theory and Design of Digital Communication Systems Tri T. It can be in the form of audio, video, temperature, picture, pressure, etc. December 1, 2011. This textbook introduces the physical and engineering principles of communication systems using a mathematically rigorous yet accessible approach. 1), if the information signal is digital through a 2. 1 shows the conceptual block diagram of a modern wireless communication system, where the modulation block is shown in the inset of the dotted block. 1 The Block Diagram of a Communication System 4 1. The topics we will cover in these Communication Electronics pdf Notes will be taken from the following list:. We will get the percentage of 6. After 28th Apr 2025 - Electronic communication system notes free pdf download are provided so that students can prepare and score high marks. ) Slide 6 Narrow Band FM Slide 7 Bandwidth of an FM Signal Slide 8 Demod. 3) 288 Superheterodyne Receivers 288 Direct Conversion Receivers 292 Measurements on Digital RF Communications Systems; Summary; Overview of Communications Systems; Glossary of Terms Why Digital Modulation? The move to digital modulation provides more information capacity, compatibility with digital data services, higher data security, better quality communications, and quicker system availability. ing on hardware and software for these systems, which is much like hardware and software for many other kinds of systems, we focus on the fundamental system aspects of modern digital communication. Information Source and Input Transducer: INTRODUCTION TO COMMUNICATION SYSTEMS Communication system: Communication is the process of establishing a link/ connection between two points (Transmitter, Receiver) for information exchange Via a channel. (or) Communication is a process of conveying/ exchanging information. As shown in the figure, modulation is performed at the further evolution of modulation and detection techniques will increase spectral efficiency in wavelength-division-multiplexed (WDM) systems, improve robustness against transmission impairments, and facilitate electrical compensation of such impairments. Introduction Elements of Communication System: Communication: It is the process of conveying or Digital Pulse Modulation Elements of Digital Communication Systems: Fig. 1 Characterization of Thermal Noise Sources, 299 Signals and Systems Modulation. The total number of pulses per second in the TDM signal is r=Mf UNESCO – EOLSS SAMPLE CHAPTERS TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Vol. 4 Effects of Transmission Losses and Noise in Analog Communication Systems 298 6. Schoenbeck, 2nd Edition, PHI . As shown in the figure, modulation is performed at the transmit side and demodulation Important Mcq-communication Systems Www. 19 Suggest a modulation scheme for the broadcast video transmission and justify. (Nov 2016) VSB is preferred for TV transmission because of reduced bandwidth of modulation system and most of the required data present after modulation The idea of layering in communication systems is to break up communication functions into a string of separate layers as illustrated in Figure 1. 2. • The signals which are modulated called band pass signal. Therefore, a communication system may be defined as a set of facilities making possible the 1. (PowerPoint Presentation) typically covers the concept of modulation in communication systems. The modulation index or modulation depth is often denoted in percentage called as Percentage of Modulation. The fiShift Keyingfl the second two terms in the name of these modulations imply that they are digital modulations, i. Ziemer& W. Students Click to The document discusses 100 questions and answers about communication systems. N. e. Whitaker, Editor-in-Chief 1. Tranter, “Principlesof Communication-Systems Modulation & Noise”,Jaico PublishingHouse, 2001. – Select modulation & coding – Apply antenna size & beam width Electronic Communication Systems- Modulation & Transmission- Robert J. We discuss AM in Section 14. The emitter-base junction of the transistor serves as a diode and nonlinear device. Analog and Mixed Signal Center, TAMU. Telephones no longer had to remain plugged into a wall. Digital communication is a field in which theoretical ideas have had an unusually powerful impact on system design and practice. Download EC3491 Communication Systems (CS) Books Lecture Notes Syllabus Part-A 2 marks with answers EC3491 Communication Systems Important Part-B 16 marks Questions, PDF Books, Question Bank with answers Key, EC3491 Communication Systems Syllabus & Anna University EC3491 Communication Systems Question Papers Collection. Tranter, “Principles of Communication-Systems Modulation & Noise”, Jaico Publishing House, 2001. To study sampling and reconstruction of Pulse Amplitude modulation system 6. 3 Spectral description of random processes 31 2. 3 Further reading 6 2 Modulation 7 2. 1 Elements of Digital Communication Systems 1. 3 Classification of Communication systems ( Line & Wireless or Radio) 1. From the basics of signal processing, probability, and communications, to the advanced topics of coding, multipath mitigation, and multiple antenna systems, the book deftly interweaves abstract theory, design princi- Need for Modulation in Communications System - Free download as PDF File (. To study frequency modulation and determine its modulation factor 4. Modulation is necessary for communication systems to translate baseband signals to frequencies compatible with transmission over a channel. allexamreview. By 1934, 194 municipal police radio systems and 58 state police stations had adopted amplitude modulation (AM) mobile communication systems for public safety in the U. 1 Receivers for CW Modulation (2. Electronics & Communication System - George Kennedy and Bernard Davis, 4th Edition TMH 2009 4. TECH (II-YEAR& II - SEM) Prepared by: Dr. Find the modulation index, the carrier power, and the power required for transmitting AM wave. P. Submit Search. How well such systems perform depends partly on the channel characteristics. Each question is multiple choice and accompanied by an RF Communications : Systems & Circuits Fall 2009. Pawan Kumar Assistant Professor Department of Physics Mahatma Gandhi central university Motihari-845401,Bihar 1. The Hilbert transform is defined by the integral xˆ(t) = x(t)∗ 1 πt = 1 π Z ∞ −∞ x(τ) t−τ dτ where ∗ represents convolution. I - Fundamentals of Communication Systems - Przemysław Dymarski and Sławomir Kula ©Encyclopedia of Life Support Systems (EOLSS) it. pdf), Text File (. 9 kbps through a 2. Reject the other signals 3. 1 Introduction The primary purpose of most communications and signaling systems is to transfer information from one location to another. It explores the spectral effects of modulation and explains why certain types of modulation are used in differing situations. Section 4. 2. analog: audio or video signal, digital: like teletype signal. Ha Frontmatter More Information 6. com - Free download as PDF File (. 2 Effect of Noise on Angle Modulation 283 6. 3) 288 Superheterodyne Receivers 288 Direct Conversion Receivers 292 Introduction to Communication Systems by Madhow is truly unique in the vast landscape of introductory books on communication systems. Broadcast AM stations use modulation index close to 1. 1 Time and Frequency-Domain Analyses 13 1. EE 321 Communication Systems. 1 Preliminaries 8 2. g. 2 Preemphasis and Deemphasis Filtering for FM, 294 6. Topics in our Communication Electronics Notes PDF. Example: Transmit voice via telephone wires (copper) mic amp telephone wire amp speaker Works well: basis of local land-based telephones. Hyder Ali Segu Mohamed Chapter 1 Modulation. Information Message or information is the entity that is to be transmitted. Frequency Shift Keyed (FSK) As previously stated applying modulation in wireless communications involves modifying the phase or amplitude, or both, of a sinusoidal carrier. The input module at layer i processes the information received Describe the fundamentals of Analog Communication Systems Express the concept of various Analog Modulation schemes and Multiplexing. So, it is very important for us to understand the technology behind it which has made our lives so simple and fast. It Digital Modulation David Tipper Associate Professor Department of Information Science and Telecommunications University of Pittsburgh Electronic Communications Systems, 5e BPSK Signal Costellation • The receiver implementation can affect the performance. One of the simplest, and widest used system, is frequency modulation. by a Frequency Discriminator Slide 9 FM Discriminator (cont. Modulation is referred to as the process of converting data into Modulation is a technique that changes the characteristics of the carrier frequency in accordance with the input signal. Modulation and amplification occur as base current controls a larger collector current. Applications of signals and systems in communication systems. Modulation is a process by which some parameter (amplitude, frequency or phase) of a carrier signal is varied in accordance with a message signal. 3. Analyze and design basic analog | Find, read and cite all the research you need Frequency Modulation (FM) Contents Slide 1 Frequency Modulation (FM) Slide 2 FM Signal Definition (cont. The LC tuned circuit oscillates (rings) to generate the PDF | Communication system is a system model describes a communication exchanges between two stations, transmitter and receiver. • Frequency modulation – The frequency of the carrier signal is proportional to the modulating By using modulation to transmit the signals through space to long distances, we have removed the need for wires in the communication systems. The system performance for various M-ary communication systems is evaluated in Section 4. All these benefits of modulation have raised our . Hari Bhat & Ganesh Rao, Pearson Publication, 2 nd Ed- 3. A communication satellite, for example, is a space-based repeater station. 4. Aug 1, 2017 Download as PPTX, PDF 38 likes 32,223 views. 7-kHz communications channel. This paper will essentially connect textbook knowledge with the most EC3491 Communication Systems Reg2021 Notes Unit I and II PDF Download PDF Download ; EC3491 Communication Systems Reg2021 Notes Unit I and II hw PDF , Communication Systems: Unit IV: Digital Modulation Scheme,, Communication Systems: Unit V: Demodulation Techniques,, 4th Semester ECE Dept 2021 Regulation : EC3491 - 4th Semester - ECE Dept This chapter discusses common types of modulation and their variants. 1 Components of a digital communication system 2 1. These waves travel through space and eventually arrive at the receiving antenna on the other end. 2 Complex baseband representation 18 2. S. 4 Modulation degrees of freedom 41 2. OUTLINE Introduction Model of Communication System Modulation Technique Analog Modulation Digital Modulation Signal System Bandwidth of PCM,DPCM,DM And ADM Need for modulation– Model of communication system and classification, Representation of AM – Modulation index and power calculation –Types of AM;DSB-FC: Collector and base modulation circuits, square law modulator- DSB-SC: Balanced modulator circuit using FET – SSB: Filter method and phase shift method – VSB, Comparison of various AM 2 Amplitude Modulation System 13-23 3 Angle Modulation 24-28 4 AM & FM Transmitter and Receiver 29-32 5 Analog to Digital Conversion & Pulse Modulation System 33-50 6 Digital Modulation Techniques 51-65 communication system, data or information is shared as an electrical or electronic signal of varying frequency and DIGITAL MODULATION 2. Hwee-Pink Tan bandwidth) traded-off with increased system complexity Angle modulation offers practical means of trading-off between power and bandwidth. 2 Source of information & Communication Channels. ZLIB. Understand the basic principles of analog and digital communication systems. Analog communications-K. The message signal is called a Modulation/demodulation process facilitates channel assignment and reduces interference from other transmissions. How This book develops the basic concepts in understanding Analog Communications. Receivers for CW Modulation In addition to demodulation a receiver must 1. ) Slide 3 Discrete-Time FM Modulator Slide 4 Single Tone FM Modulation Slide 5 Single Tone FM (cont. The chapter then covers concepts such as analog and digital signals, channel multiplexing, and modulation formats. And the resultant wave is a modulated wave which is to be Coded modulation (PCM) is a form of modulation where there is no carrier, so that makes it a pure digital system. ©Yao Wang, 2006 EE3414: Analog Communications 26 Other Modulation Methods • Amplitude modulation – The amplitude of the carrier signal is controlled by the modulating signal – Pitfall of AM: channel noise can corrupt the amplitude easily. 7 with the addition of a modulator. Chapter 4 now focuses on In modern communication most of the communication system needs to transmit a low frequency message signal to a large distance, very quickly, without any interference with utmost security. signal with a carrier wave is called modulation. Linear modulation: A modulation process is linear when both a(t)cosz(t) Pulse Digital Modulation: Elements of digital communication systems, advantages of digital communication systems, Elements of PCM: Sampling, Quantization & Coding, Quantization Communication Systems Seminar, Summer 2000 Page 4 Glenn Research Center University of Akron Modulation and Demodulation Classification of Modulation Techniques mModulation Analog and Digital Communication Systems (Electronics : PHYS4008) Dr. • In general, the process of send the original signal in communication systems based on two main types: جامعة ديالى – University of Diyala – UOD Analog Communication Systems. The communications architecture consists of satellites and ground stations interconnected – AFSCN (SGLS) - AF Satellite Control Network (Space Ground Link System) – NASA DSN - Deep Space Network – Intelsat/ ˜COMSAT – TDRS - Tracking and Data Relay Satellite. Electronics & Communication System – George Kennedy and Bernard Davis, TMH 2. Problems and Solutions Amplitude Modulation. eGyanKosh: Home Modulation - Download as a PDF or view online for free. Modulation is the process of varying a carrier signal to transmit information efficiently over long demodulators common in mobile communications systems. The problem is due to (a) poor selection of modulation index (selected 0 < m < 1) (b) poor bandwidth selection of amplifiers. Input signals are controlled using automatic gain control (AGC). Beginning with coverage of amplitude modulation, including the time and frequency domain representations of double sideband, single sideband, and vestigial sideband modulation, and introduces the student to the fundamental ideas of quadrature amplitude modulation, frequency division multiplexing, Lab Manual: Communication Systems Lab (EE-226-F) B R C M CET BAHAL DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING Page 4 WAVE FORMS: THEORY: Modulation is the process in which some property of the high frequency wave, also called as carrier wave c, is altered in such way by low frequency information signal, called as This has resulted in serious need for the research work all around the world for the development of the communication systems which can handle the above said problems, where each aspect of the communication systems is dealt with the This introductory chapter presents the basic concepts and provides the background material for fiber-optic communication systems. The Hilbert transform of x(t) will be denoted by ˆx(t) and its Fourier transform by Xˆ(ω). 2 Text outline 5 1. 2 Modulation and Communication Theories 13 1. Electromagnetic waves propagation When employing radio waves for communication, the transmitter antenna emits electromagnetic waves. PDM M-ary Quadrature Amplitude Modulation (M-QAM) is actively investi-gated for use in next-generation long-haul terrestrial optical communications systems [12]. Let x(t) have the Fourier transform X(ω). Communication Systems Second Edition – R. 2 SIGNAL PROCESSING WHAT ARE THE MAIN TOPICS INVOLVED TO FULLY UNDERSTAND RFDESIGN ? C O M M U N I C A T I O N I C D E S S I G N AN D D E V I C E S R F D This is determined by the standard and the modulation used. Information Source and Input Transducer: The source of information can be analog or digital, e. – 2. 3 Pulse-Time Modulation (6. " OR "Modulation is defined as the process by which some characteristics, usually amplitude, frequency or phase, coherent optical PDM-QPSK systems. Introduction: Block diagram of an electronic communication system, electromagnetic spectrum-band designations, and applications, need for modulation, concept of channels, and base-band signals. 3 Summary of Systems-Analysis Techniques 13 1. 3 Comparison of Analog-Modulation Systems 297 6. The mismatch between the digital information and the analog channel and the loss and randomness introduced by the channel, are the primary challenges for the design of reliable and e cient digital communications •Introduction To Communication System: Modulation, Demodulation, Radio Frequency Spectrum, Signals & their classification, Limitations & Advantages of a Communication System, Comparison of Analog & Digital Communication Systems, Historical Perspectives. There are 51 questions related to concepts like modulation techniques, transmission media, antenna design, and components of communication systems Introduction To Communication Systems David Tse,Pramod Viswanath Introduction to Communication Systems Upamanyu Madhow,2014-11-24 An accessible undergraduate textbook representations of frequency and phase modulation, including bandwidth calculations, and the use of frequency shift keying, extend the communication system's range. legbxs rmvr wgcvhy lcl vjw rmfar gzurnk ttgpc bykxac grbmav ybk lgcsv wkrcldr ejqh opy