Dublin Institute of Technology. Kevin Street SCHOOL OF ELECTRONIC & COMMUNICATIONS ENGINEERING. Communication Engineering Notes.

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1 Dublin Institute of Technology Kevin Street SCHOOL OF ELECTRONIC & COMMUNICATIONS ENGINEERING Communication Engineering Notes Paul Tobin i

2 CONTENTS CHAPTER ONE... INTRODUCTION TO A COMMUNICATION SYSTEM... 1 THE COMMUNICATIONS CHANNEL... 2 BANDWIDTH... 2 FOURIER SERIES... 3 PULSE SIGNAL TRANSMISSION... 4 CHANNEL ATTENUATION... 4 FREQUENCY RESPONSE OF A LINEAR TRANSMISSION CHANNEL... 4 THE FOURIER TRANSFORM (FT)... 5 SPECTRUM OF AN IMPULSE FUNCTION... 6 STATIONARY AND NON-STATIONARY SIGNALS... 7 NOISE AND INTERFERENCE... 8 FRIIS' FORMULA... 9 EXAMPLE... 9 IMPULSE RESPONSE IN A BAND-LIMITED CHANNEL SINGLE ROUNDED-OFF PULSE QUESTION SOLUTION QUESTION SOLUTION SINGLE RECTANGULAR PULSE INFORMATION AND ENTROPY: EXTRACTS FROM C SHANNON PAPER AVERAGE INFORMATION H (ENTROPY) EXAMPLE EXAMPLE: CHANNEL CAPACITY NYQUIST SIGNAL CRITERION QUESTION SOLUTION: QUESTION SOLUTION CHAPTER TWO... THE NEED FOR MODULATION MODULATION AMPLITUDE MODULATION MODULATION INDEX POWER IN AN AMPLITUDE MODULATED CARRIER TRANSMISSION EFFICIENCY QUESTION QUESTION AMPLITUDE MODULATORS BALANCED MODULATORS: DOUBLE SIDEBAND SUPPRESSED CARRIER SINGLE SIDEBAND SUPPRESSED CARRIER MODULATION PHASE SHIFT METHOD THE HILBERT TRANSFORM THE 12-CHANNEL FDM SSBSC SYSTEM ii

3 CHAPTER THREE... FREQUENCY MODULATION DERIVATION OF FM EQUATION EXAMPLE: FREQUENCY SPECTRUM OF AN FM SIGNAL EXAMPLE FM RADIO STEREO GENERATION FM SUPERHETERODYNE RECEIVER PREEMPHASIS AND DEEMPHASIS EXAMPLE (PAUL YOUNG) SOLUTION EFFICIENCY AND NOISE ADVANTAGES AND DISADVANTAGES OF FM: PHASE-LOCKED LOOP PLL COMPONENTS CAPTURE AND LOCK RANGE SUMMARY QUESTIONS FREQUENCY MODULATION DERIVATION OF FM EQUATION EXAMPLE: FREQUENCY SPECTRUM EXAMPLE FM PERFORMANCE FM RADIO STEREO GENERATION FM SUPERHETERODYNE RECEIVER PREEMPHASIS AND DEEMPHASIS EXAMPLE (PAUL YOUNG) SOLUTION EFFICIENCY AND NOISE ADVANTAGES AND DISADVANTAGES OF FM: PHASE-LOCKED LOOP PLL COMPONENTS CAPTURE AND LOCK RANGE SUMMARY QUESTIONS CHAPTER FOUR... AM-DSBFC SUPERHETERODYNE RECEIVER THE SUPERHETRODYNE RECEIVER ADVANTAGES OF SUPERHETRODYNING: IMAGE FREQUENCY IN SUPERHETERODYNE RECEIVERS ARITHMETIC SELECTIVITY EXAMPLE: DETECTORS AND MIXERS: DIODE DETECTOR ENVELOPE DETECTOR AUTOMATIC GAIN CONTROL iii

4 COHERENT DETECTOR MIXER DOUBLE SIDEBAND SUPPRESSED CARRIER AM DSBSC SINGLE SIDEBAND AMPLITUDE MODULATION (SSB) SSB GENERATION USING HILBERT TRANSFORM ADVANTAGES OF SSB TECHNIQUE RECEIVER DESIGN: PARALLEL TUNED CIRCUIT UNIVERSAL RESPONSE CURVE FOR A PARALLEL TUNED CIRCUIT THE LOADED Q - FACTOR EXERCISE EXERCISE RF TUNED AMPLIFIER THE TRANSFER CHARACTERISTIC SOURCE BIAS RESISTANCE VALUE THE FET OUTPUT CHARACTERISTIC MAGNIFIED SECTION OF THE OUTPUT CHARACTERISTIC FREQUENCY RESPONSE OF THE RF AMPLIFIER QUESTION AM-DSBFC SUPERHETERODYNE RECEIVER THE SUPERHETRODYNE RECEIVER ADVANTAGES OF SUPERHETRODYNING: IMAGE FREQUENCY IN SUPERHETERODYNE RECEIVERS ARITHMETIC SELECTIVITY EXAMPLE: DETECTORS AND MIXERS: DIODE DETECTOR ENVELOPE DETECTOR AUTOMATIC GAIN CONTROL COHERENT DETECTOR MIXER DOUBLE SIDEBAND SUPPRESSED CARRIER AM DSBSC SINGLE SIDEBAND AMPLITUDE MODULATION (SSB) SSB GENERATION USING HILBERT TRANSFORM ADVANTAGES OF SSB TECHNIQUE RECEIVER DESIGN: PARALLEL TUNED CIRCUIT UNIVERSAL RESPONSE CURVE FOR A PARALLEL TUNED CIRCUIT THE LOADED Q - FACTOR EXERCISE EXERCISE RF TUNED AMPLIFIER THE TRANSFER CHARACTERISTIC SOURCE BIAS RESISTANCE VALUE THE FET OUTPUT CHARACTERISTIC MAGNIFIED SECTION OF THE OUTPUT CHARACTERISTIC FREQUENCY RESPONSE OF THE RF AMPLIFIER QUESTION CHAPTER FIVE... BASEBAND DIGITAL TRANSMISSION THE NEED FOR LINE CODING SYNCHRONIZATION LINE CODING: RETURN TO ZERO (RZ) MANCHESTER CODE DIFFERENTIAL MANCHESTER CODE iv

5 RECEIVER CLOCK SYNCHRONIZATION COMPARISON OF LINE CODES QUESTION FULL DUPLEX AND HALF DUPLEX SYNCHRONIZATION ASYNCHRONOUS TRANSMISSION FRAME SYNCHRONISATION IN ASYNCHRONOUS TRANSMISSION: SYNCHRONOUS TRANSMISSION ASCII AMERICAN STANDARD CODE FOR INFORMATION INTERCHANGE BASEBAND DIGITAL TRANSMISSION THE NEED FOR LINE CODING SYNCHRONIZATION LINE CODING: RETURN TO ZERO (RZ) MANCHESTER CODE DIFFERENTIAL MANCHESTER CODE RECEIVER CLOCK SYNCHRONIZATION COMPARISON OF LINE CODES QUESTION FULL DUPLEX AND HALF DUPLEX SYNCHRONIZATION ASYNCHRONOUS TRANSMISSION FRAME SYNCHRONISATION IN ASYNCHRONOUS TRANSMISSION: SYNCHRONOUS TRANSMISSION ASCII American Standard Code for Information Interchange CHAPTER SIX... DIFFERENTIAL QUADRATURE PHASE SHIFT KEYING (DQPSK) QUADRATURE AMPLITUDE MODULATION (QAM) EXERCISE DTE TO MODEM (DCE) INTERFACE - (EIA-232-E) QUESTION SOLUTION PSK QAM DATA COMMUNICATION AND ERRORS EXAMPLE SOLUTION MODEM PERFORMANCE EYE DIAGRAM CHAPTER SEVEN... A BRIEF HISTORY OF THE IRISH TELEPHONE SYSTEM ADVANTAGES OF DIGITAL COMMUNICATION NETWORKS: DISADVANTAGES THE SAMPLING THEOREM SAMPLE DATA NATURAL SAMPLING EXAMPLE v

6 IMPULSE SAMPLING SAMPLING THEOREM EXAMPLE SOLUTION: EXAMPLE EXAMPLE FLAT TOP SAMPLING OMPANDING UNIFORM QUANTIZER: SNR CALCULATION FOR CPCM EXAMPLE QUESTION EXAMPLE NON-UNIFORM SIGN-EXPONENT- MANTISSA FORMAT SIGNAL CODING MU-LAW VERSUS A-LAW TIME DIVISION MULTIPLEXING OF DIGITIZED SPEECH CHANNELS: ISDN AND VOICE DIGITIZATION WITHIN THE PSTN: DIFFERENTIAL PCM ADAPTIVE DIFFERENTIAL PULSE-CODE MODULATION (ADPCM): DELTA MODULATION IDEAL DELTA MODULATOR ADAPTIVE DELTA MODULATION (PAUL YOUNG P) QUESTION SOLUTION QUESTIONS SOLUTION APPENDIX 1: Syllabus APPENDIX 2: Examination papers and Solutions APPENDIX 3: 565 IC APPENDIX 4: MORE QUESTIONS vi

7 TABLE OF FIGURES CHAPTER ONE FIGURE 1: ELEMENTS OF A TELECOMMUNICATION SYSTEM FIGURE 2: RF SPECTRUM... 2 FIGURE 3: A COMMUNICATIONS CHANNEL... 2 FIGURE 4: FUNDAMENTAL + HARMONICS FIGURE 5: 3-D VIEW... 3 FIGURE 6: IMPULSE FUNCTION... 6 FIGURE 7: SUM OF 4 SINES... 7 FIGURE 8: SPECTRUM OF 4 SINES... 7 FIGURE 9: NON-STATIONARY SIGNAL... 8 FIGURE 10: A) SPECTRUM OF TWO SINES B) LOG OF AMPLITUDE OF SPECTRUM... 8 FIGURE 11: FOURIER TRANSFORM OF A PULSE WAVEFORM FIGURE 12: IMPULSE RESPONSE FIGURE 13: INTER-SYMBOL INTERFERENCE FIGURE 14: RAISED COSINE FILTER FIGURE 15: FREQUENCY RESPONSE OF RAISED-COSINE FILTER FIGURE 16: EFFECT OF COSINE ROLL-OFF EXCESS BANDWIDTH FIGURE 17: SIMULATING ONE PULSE FIGURE 18: CONSTANT τ, T VARIED FIGURE 19: DOUBLE τ VALUE FIGURE 20: AS PULSE GETS NARROWER, THE SINC SHAPE SPREADS OUT FIGURE 21: AS PULSE SPREADS, THE SINC SHAPE GETS NARROWER AND TALLER FIGURE 22: ENTROPY OF BINARY SIGNAL CHAPTER TWO FIGURE 1: 10 HZ MODULATING SIGNAL FIGURE 2: MODULATED 100 HZ CARRIER FIGURE 3: PSD OF AN AM SIGNAL FIGURE 4: DYNAMIC RANGE AND FREQUENCY RANGE OF SPEECH AND MUSIC FIGURE 5: DOUBLE SIDEBAND SUPPRESSED CARRIER FIGURE 6: 180 DEGREE PHASE SHIFT FIGURE 7: FORWARD-BIASED DIODE FIGURE 8: RING MODULATOR FIGURE 9: BALANCED MODULATOR FIGURE 10: PHASE SHIFT TECHNIQUE FOR PRODUCING SSBSC FIGURE 11:!2 - CHANNEL FDM SYSTEM FIGURE 12: TWO-WIRE TO FOUR-WIRE CONVERSION FIGURE 13: HIGHER-ORDER FDM MULTIPLEX SYSTEM FIGURE 14: FDM COAX SYSTEMS CHAPTER THREE FIGURE 1: VCO FIGURE 2: VCO CHARACTERISTIC vii

8 FIGURE 3: FM SIGNAL FIGURE 4: STEREO PRODUCTION FIGURE 5: STEREO SPECTRUM FIGURE 6: FM SUPERHETRODYNE RECEIVER FIGURE 7: PRE-EMPHASIS NETWORK FIGURE 8: PREEMPHASIS FREQUENCY RESPONSE FIGURE 9: PHASE LOCKED LOOP BLOCK DIAGRAM FIGURE 10: TYPE I PHASE DETECTOR FIGURE 11: TYPE II PHASE DETECTOR FIGURE 12: CIRCUIT SCHEMATIC FOR FM-PLL DEMODULATION FIGURE 13: LOCK AND CAPTURE RANGE FIGURE 14: 565 IMPORTANT PARAMETERS CHAPTER FOUR FIGURE 1: SUPERHETRODYNING FIGURE 2: BLOCK DIAGRAM OF A SUPERHETRODYNE RECEIVER FIGURE 3: SUPERHETRODYNE DIAGRAM FIGURE 4: IMAGE FREQUENCIES FIGURE 5: DIODE RECTIFICATION FIGURE 6: DIODE CHARACTERISTIC FIGURE 7: ENVELOPE DETECTOR: CHOICE OF TIME CONSTANT FIGURE 8: DIODE DETECTOR WITH AGC FIGURE 9: DSB RECEIVER FIGURE 10: DOUBLE-BALANCED RING MODULATOR FIGURE 11: DSBSC MODULATOR FOR FM STEREO PRODUCTION FIGURE 12: SPECTRUM OF AN FM STEREO SIGNAL FIGURE 13: STEREO SIGNAL RECEIVER FIGURE 14: SPECTRA IN SSB-SC FIGURE 15: PHASE SHIFT METHOD OF GENERATING SSB FIGURE 16: PARALLEL LCR CIRCUIT FIGURE 17: PARALLEL TUNED CIRCUIT FIGURE 18: EQUIVALENT PARALLEL LCR CIRCUIT FIGURE 19: RF AMPLIFIER FIGURE 20: CIRCUIT FOR OBTAINING THE FET CHARACTERISTICS FIGURE 21: TRANSFER CHARACTERISTIC FIGURE 22: THE TRANSISTOR OUTPUT CHARACTERISTIC FIGURE 23: ENLARGED SECTION OF OUTPUT CHARACTERISTIC FIGURE 24: RF AMPLIFIER FREQUENCY RESPONSE CHAPTER FIVE FIGURE 1: CONVERTER CHANNEL LINE FIGURE 2: LINE CODER FIGURE FIGURE 4: MANCHESTER CODE FIGURE FIGURE 6: NYQUIST SIGNAL FIGURE 7: LINE CODER IMPLEMENTATION FIGURE 8: FIGURE 9: ALTERNATE MARK INVERSION FIGURE viii

9 CHAPTER SIX FIGURE 1: MODULATING A BASEBAND SIGNAL FIGURE 2: PASSBAND TO BANDPASS CONVERTER FIGURE 3: MULTI-LEVEL SIGNAL FIGURE 4: FSK TIME DIAGRAMS FIGURE 5: FREQUENCY SPECTRUM OF FSK SIGNAL FIGURE 6 TIME DIAGRAMS OF BINARY PSK: FIGURE 7: SPECTRUM OF DATA AND BINARY PSK: FIGURE 8: IMPLEMENTING THE ONE-BIT DELAY FIGURE 9: DPSK FIGURE 10: FIGURE 11: DQPSK MODULATOR FIGURE FIGURE 13: QAM TRANSMITTER AND RECEIVER FIGURE 14: 16-QAM FIGURE 15: THE CONSTELLATION CAN BE PARTITIONED INTO DECISION REGIONS FIGURE 16: 128-QAM V 32 BIS MODEM FIGURE 17: 8-PSK FIGURE 18: 8-QAM FIGURE 19: BER RATE PLOT FIGURE 20 : PRODUCTION OF AN EYE PATTERN FIGURE FIGURE 22: ACTUAL EYE DIAGRAM FIGURE 23: EYE DIAGRAM USING THE VERY GOOD( FREE) COMMS TOOLBOX FIGURE 24: MATLAB EYE DIAGRAM FOR AN NRZ SIGNAL CHAPTER SEVEN FIGURE FIGURE 2: OVERALL SYSTEM LAYOUT FIGURE 3: STROWGER SWITCHING FIGURE 4: CROSSBAR SYSTEM FIGURE 5: ALIASING FREQUENCIES FIGURE 6: ALIASING COMPONENTS FIGURE 7: NATURAL SAMPLING FIGURE 8: TIME WAVEFORMS IN NATURAL SAMPLING FIGURE 9: NATURAL AND FLAT-TOPPED SAMPLE FIGURE 10: THE SPECTRUM OF FLAT-TOPPED SPECTRUM FIGURE 11: THE SPECTRUM OF NATURAL SPECTRUM FIGURE 12: FIGURE FIGURE 14: FOURIER SERIES FIGURE 15: FOURIER INTEGRAL FIGURE FIGURE FIGURE 18: SPECTRUM OF AN IMPULSE SAMPLED SIGNAL FIGURE 19: SPECTRAL FOLD-OVER WHEN INPUT BANDWIDTH EXCEEDS F S / FIGURE FIGURE FIGURE 22: CIRCUIT TO EXTEND THE WIDTH OF FLAT TOP SAMPLES FIGURE 23: ANALYTICAL MODEL OF FLAT-TOPPED SAMPLING FIGURE 24: RELATIVE GAIN OF FLAT-TOP SAMPLING VS. PULSE WIDTH FIGURE 25: TIME DIVISION MULTIPLEXING OF PAM SAMPLES FIGURE ix

10 FIGURE 27: FDM AND TDM MULTIPLEXING FIGURE 28: FRAME AND MULTI-FRAME LAYOUT CHAPTER EIGHT FIGURE 1: OUTPUT SIGNAL WITH QUANTIZING ERROR FIGURE 2: LINEAR TRANSFER CHARACTERISTIC FIGURE FIGURE 4: OUTPUT SIGNAL WITH QUANTIZING ERROR FIGURE 5: UNIFORM AND NON-UNIFORM QUANTIZATION FIGURE 6: MU-LAW ANALOGUE COMPANDING FIGURE 7: SEGMENTED U-LAW CHARACTERISTIC FIGURE FIGURE FIGURE 10: FORMAT OF 8-BIT COMPANDED PCM SAMPLE WORD FIGURE 11: A-LAW CHARACTERISTIC FIGURE FIGURE 13: MULTIPLEXING FORMATS FIGURE FIGURE FIGURE 16: DELTA MODULATOR FIGURE 17: SLOPE OVERLOAD FIGURE 18: SLOPE OVERLOAD AND GRANULAR NOISE FIGURE 19: DELTA MODULATOR SIGNALS FIGURE FIGURE 21: INTEGRATING DELTA MODULATOR FIGURE 22: DELTA MODULATOR FIGURE 23: DELTA MODULATOR SIGNALS FOR THE CIRCUIT IN FIG FIGURE 24: DELTA DEMODULATOR x

11 INTRODUCTION This set of notes is not meant to replace the normal textbooks as recommended in the syllabus (See appendix 4). The notes were compiled using previous years students note and Internet resources. Apologies for any plagiarism from these Internet files. The notes will be used in the classroom and augmented where necessary. xi

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