AN RFBAND-WIOTH SWITCH FOR MULTIMEDIA TRANSMISSION by Pierre van Rhyn Submitted in partial fulfilment ofthe requirements for the degree Magister Scientiae in the Faculty ofengineering UNIVERSITY OF PRETORIA October 1999 University of Pretoria
SAMEVATTING 'n RF Bandwydte skakelaar vir multimedia transmissie deur Pierre van Rhyn. Studieleier : Prof. J. J. D. van Schalkwyk Departement: Elektriese en Elektroniese Ingenieurswese Graad: Magister Scientiae Die doel van hierdie navorsingsprojek was om 'n RF bandwydte skakelaar te ontwikkel wat multimedia skakeling en transmissie in 'n tegnologie gebaseerde onderrigstelsel moontlik maak, sonder om staat te maak op persoonlike rekenaartegnologie. Die dissiplines binne tegnologie gebaseerde onderrigstelsels wat kortliks ondersoek word, is die opvoedkundige vereistes soos vasgestel deur didaktiese kundiges, asook kommunikasiestelsels wat modeme multimedia ondersteun. Kenmerke van modeme tegnologie gebaseerde onderrigstelsels word onder die loep geneem binne die Suid-Afrikaanse konteks, sowel as nie-tegniese aspekte, soos toegevoegde waarde verkry van audio, video engemtegreerde rekenaartoepassings. Inforrnele eksperimente word beskryf waartydens 'n RF bandwydte skakelaar toegepas word om die funksionele kenmerke van 'n tegnologiegebaseerde onderrigstelsel te verkry, sonder om staat te maak op persoonlike rekenaartegnologie. Die lewering van 'n infonnele lesing tydens die eksperiment word bespreek, asook waamemings gemaaktydens die eksperiment. Die eksperimente mag. dien as 'n metode om die potensiele toepassing van bandwydte skakelaars vir tegnologiegebaseerde onderrigstelsels te evalueer. Aanbevelings vir toekomstige projekte van hierdie aard kan vervolgens gemaak word. Sleutelterme: RF bandwydte skakelaar, multimedia transmissie, Ruthroff se irnpedansie transformator, transmissielyn transformator, hibride sommeerder, invoegverlies, transmissiekenmerke, analoog videotransmissie, faseverwisselende lyn, tegnologie baseerde opleiding (T.B.O.). III
ABSTRACT An RF bandwidth switch for multimedia transmission by Pierre vanrhyn. Advisor: Prof. J. J. D. van Schalkwyk. Department: Electrical and Electronic EnEineering. Degree: Magister Scientiae. The purpose of this research project was to develop an RF bandwidth switch to make multimedia switching and transmission possible within a technology based training system, without reliance on personal computer technology. The disciplines briefly examined within technology based training systems are educational requirements set by didactic expertise, modem multimedia. as well as communications structures supporting Features of modem technology based training systems are considered within the South African context, as well as non-technical aspects of technology based training systems such as the value added by audio, video, and integrated computer applications. Informal experiments are described wherein an RF bandwidth switch is applied to obtain the functional characteristics of a technology based training system, without reliance on personal computer technology. The delivejy of an informal lecture during the experiment is discussed, as well as observations made during the experiment. The experiments may serve as a method to evaluate the potential application of RF bandwidth switches for technology based training. Recommendations for future projects of this nature may then be made. Key terms : RF bandwidth switch, multimedia transmision, Ruthroff's impedance transformer, transmission line transformer, hybrid combiner, insertion loss, transmission characteristics, analogue video transmission, phase alternating line (p.a.l.), (T.B.T.). technology based training v
This study is dedicated to my wife Elsa for her support and personal sacrifices.
ACKNOWLEDGEMENTS The author wishes to thank the following persons and institutions, without whose support this study would not have been possible: Prof 1. 1. D. van Schalkwyk, for study leadership. Reunert Defence Logistics, results, for assistance with confirmation of measured The South African Weather Bureau, evaluating prototypes in terms of practical performance, for making facilities available and Eagle Electronics TIv!, for funding the project. lx
INDEX CHAPTER 1 INTRODUCTION, PROBLEM STATKMENT AND METHODOLOGY PAGE 1.1 INTRODUCTION...... 1 1.2 PROBLEM STATEMENT...... 2 1.2.1 The application requirement.............. 2 1.2.2 The aim.................................................... 4 1.2.3 The objectives................................. 4 1.2.4 The hypotheses... 5 1.3 REVIEW OF THE RELATED LITERATURE................... 5 1.3.1 Video transmission theory............................ 5 1.3.2 Educational requirements and social issues........................ 6. 1.3.3 Video transmission standards........................................ 6 1. 3.4 Electronic product descriptions and application notes... 7 1.4 METHODOLOGY TO SOLVE THE PROBLEM............... 7 1.4. 1 The data............................................. 7 1.4.2 The sample......................................................... 7 1.4.3 Administration................................................... 7 1.4.4 The delimitations................................. 8 1.4.5 Assumptions........................................... 9 1.4.6 Definition ofterms................................. 9 1.5. PROJECT DOCUMENTATION................ 10 CHAPTER 2 EDUCATIONAL REQUIREMENTS, HUMANIMACHINE INTERACTION AND SOCIAL ISSUES 2.1 EDUCATIONAL REQUIREMENTS...................... 11 2.1.1 Components of an interactive T.B. T. system.................... 11 Xl
2.1.2 Functional requirements of T.B. T. systems............... 12 2.2 HUMANIMACHINE INTERACTION................... 13 2.2.1 Lecture mode..................................................................... 13 2.2.2 Collaboration mode............................................. 13 2.2.3 The value of audio.. "............................................ 14 2.2.4 The value of video.............................................. 14 2.2.5 The value of integrated computer applications........... 14 2.3 SOCIAL ISSUES............. "''''''''........"..........,........... 15 2.3.1 Benefits of the videoconferencing model oft.b.t. systems................ 15 2.3.2 Disadvantages of the videoconferencing model................ 16 2.3.3 Social issues within the South African scenario......................... 16 2.3.4 The Forum prototype................................................ 17 2.3.5 Problems to overcome..................................... 18 2.4 NETWORK TOPOLOGY FOR SYSTEM DEVELOPMENT......... 18 2.4.1 System overview for simplex delivery.................................... 18 2.4.2 System overview for duplex delivery.......................... 19 2.4.3 Functional requirements of the transmission apparatus.............. 20 CHAPTER 3 THE PRIMARY TRANSMISSION FORMAT............................ 21 3.1 Factors considered for the selection..................................... 22 3.1.1 The standardized-free network.................................... 22 3.1.2 Media players........................................................ 22 3.1.3 Communication networks......................................... 23 3.1.4 The Radio Act (Act 3 of 1952)...................................... 23 3.1. 5 Availability of components for development.........................24 3.1.6 Compatibility with associated technology.................................... 24 3.2 SPECIFICATION OF PRIMARY TRANSMISSION FORMAT....... 24 3.2.1 PAL system I frequency/destination... ".............................. 25 3.2.2 PAL channel/frequency planning....................................... 26 X111
CHAPTER 4 PROTOTYPE DEVELOPMENT OF RF BANDWIDTH SWITCH 4.1 SPECIFICATION OF RF BANDWIDTH SWITCH........................... 27 4.1.1 Block diagram ofrf bandwidth switch..................................... 27 4.1.2 Electrical inputs and outputs.................................................... 28 4.1.2.1 Video.......................................................... 28 4.1.2.2 Audio................................................................ 29 4.1.2.3 RF..................................................................... 29 4.1.3 Combiner........................................:....................... 29 4.1.4 Selector................................................................ 30 4.1.5. RF modulator.................................. :.................... 30 4.1.6 Power supply requirements.......................................... 30 4.2 DEVELOPMENT OF THE ELECTRONICS................... 31 4.2.1 Hybrid combiner for RF bandwidth switch................................ 31 4.2.l.1 Insertion loss across a single broadband hybrid..................... 33 4.2.1.2 Insertion loss across cascaded broadband hybrids....................... 36 4.2.1.3 Recurring pattern mismatch............................................ 38 4.2.1.4 Matched 75-ohm cascaded hybrids.......................... 44 4.2.2 Development of the selector electronics................... 45 4.2.2.1 RF section........................................................... 45 4.2.2.2 VIF and SIF circuitry.......................................................... 46 4.2.3 Development of the power supply.............................. 54 4.3 SETUP PROCEDORES............................................ 56 4.3.1 Pre-test setup................................................... 56 4.3.2 VIF adjustment.................................................. 57 4.3.3 Detection transformer adjustment........................................ 58 4.3.4 AFC circuit (1) adjustment...................................................... 59 4.3.5 AFC circuit (2) adjustment............................... 60 4.3.6 RF AGC circuit adjustment........................................... fio 4.3.7 Audio adjustment............................................................ 61 xv
4.4 TEST PROCEDURES : INTERNAL NOISE MEASUREMENT........ 61 4.4.1 Thermal agitation noise.............................................. 62 4.4.2 Noise figure.......................................................... 64 4.4.3 Calculation of noise figure.................................... 66 4.4.4 Measurement of noise figure........................................ 68 4.4.5 Accuracy of the noise measurements............................ 69 4.4.6 Informal transmission testing....................................... 69 CHAPTERS INFORMAL EXPERIMENTS AND DEMONSTRATION................. 71 5.1 Experiment 1: Selection and broadcast function.................... 72 5.2 Experiment 2: Activation function and multiple forward connections....... 74 5.3 Experiment 3: Two feedback connections............................. 76 CHAPTER 6 CONCLUSIONS AND RECOMMENDATIONS FOR FUTURE WORK...... 79 7. REFERENCES................................................. 81 8. ANNEXURES.......................................................... 84 8. 1 A : Broadband transformers...................................... 84 8.2 B : Accuracy of the noise measurements.................................. 104 9. End of document................................................................ 110 XVll
LIST OF FIGURES PAGE FIGURE 1.1: FIGURE 2.1: FIGURE 2.2: FIGURE 2.3: FIGURE 4.1: FIGURE 4.2: FIGURE 4.3: FIGURE 4.4: FIGURE 4.5: FIGURE 4.6: FIGURE 4.7: FIGURE 4.8: FIGURE 4.9: FIGURE 4.10: FIGURE 4.11: FIGURE 4.12: FIGURE 4.13.a: FIGURE 4.13.b: FIGURE 4.13.c: FIGURE 4.13.d: FIGURE 4.14: FIGURE 4.15.a: FIGURE 4.15.b: FIGURE 4.16: FIGURE 4.17: FIGURE 4.18: FIGURE 5.1: FIGURE 5.2: FIGURE 5.3: Geographical distribution of facilities..................... 2 Components of an interactive T.B.T. system................... 11 Simplex (lecture mode) network topology...................... 19 Duplex (collaboration mode) network topology.................. 20 Block diagram ofrf bandwidth switch........................ 28 Cascaded hybrids for RF bandwidth switch.............. 31 Single hybrid combiner: Insertion loss vs. Frequency.................. 33 Cascaded hybrid combiner : Insertion loss vs. Frequency............ 36 Recurring pattem mismatch......................... 38 Matched 50-orun hybrid......................................... 39 Matched 75-orun cascaded hybrid...................... 44 Block diagram ofrf section................................. 45 Block diagram of VIF and SIF circuitry........................ 47 Pre-amplifier........................................................... 48 AFC and AGC circuitry........................... 49 SIP circuit................................................................ 50 Detailed VIF circuit.................................................... 52 Detailed SrF circuit........................................... 53 Detailed pre-set select circuit.................................. 53 Dual rail DC powersupply for bandwidth switch......................... 54 Pre-test set-up.......................................... 56 Wavefonn example......................................... 58 Waveform example.......................................... 58 Resistance noise generator................................................... 63 Block diagram for noise figure calculation......................... 66 Input channel spacing.................................. 70 Experiment 1 set-up..................................... 73 Experiment 2 set-up............................................ 75 Experiment 3 set-up................................................... 77 XIX
LIST OF TABLES PAGE TABLE 3.1: TABLE 3.2: TABLE 4.1: TABLE 4.2: TABLE 4.3: TABLE 4.4; TABLE 4.5: TABLE 4.6: TABLE 4.7: TABLE 4.8: PAL system I frequency/destination......................... 25 PAL channellfrequency plan.............................. 26 Transmission characteristics : Single hybrid.................. 34 Transmission characteristics : Single hybrid......................... 34 Isolation characteristics: Single hybrid................ 35 Transmission characteristics: Cascaded hybrid................... 37 Transmission characteristics: Cascaded hybrid............. 37 Isolation characteristics : Cascaded hybrid...................... 37 Transmission characteristics....................................... 40 Dual rail power supply voltages............................... 55 XXI