User Manual DDS200 Digital Demodulation System 070-9952-00

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Manual OperationIntermodulation:For multichannel cable transmission, much greaterdemands are made on amplifier linearity. Intermodulationbetween adjacent channels is critical, especiallywith higher-order QAM modulation. It is second- andthird-order nonlinearities that are of practical relevance.For example, intermodulation on a DVB channel C Nwith a carrier frequency of N ( N = 1 - 2 ) is obtainedfor the channel configuration shown in Figure 2–58.Amplitude N = 2 – 1C N C 2 C 10 N 2 1 2 + 1Intermodulation of C 1and C 2 in channel C NFurther intermodulationof C 1 and C 2Figure 2–58: Intermodulation due to 2nd-order nonlinearities3rd-ordernonlinearity:A third-order nonlinearity is caused by the cubiccomponent of the amplifier characteristic. For example,intermodulation on a DVB channel C N with a carrierfrequency N is obtained for the channel configuration( N = 2 4 – 3 ) shown in Figure 2–59.DDS200 Digital Demodulation System User Manual 2–77
Manual OperationAmplitude N = 2 4 – 3C N C 4 C 30 N 4 3 2 4 – 3Intermodulation of C 3and C 4 in channel C NFurther intermodulationof C 3 and C 4Figure 2–59: Intermodulation due to 3rd-order nonlinearityIntermodulation between digital channels can be regarded as additive randomnoise, since it has the effect of additive noise. Therefore, special requirementsmust be fulfilled with higher-order QAM modulation.Intermodulation between analog channels tends to be more like an interferor withsome additional noise. Intermodulation cannot be analyzed by means of theconstellation diagram. For the analysis methods described so far, intermodulationis interpreted as noise, possibly with some interference, and covered by the S/N(and C/I) ratio information.Frequency and phase errors, echoes. Possible causes:Reflections in cables (echoes) caused by mismatched cable terminations andreturn loss from the equipment connectedTolerances of the pulse shaping filters resulting in inter-symbol interference(ISI) because the first Nyquist criterion is not fulfilledAmplitude frequency response and group-delay distortion resulting from thelowpass characteristics of cables and amplifiers and from amplitude andphase ripple from channel filtersIn contrast to the errors described previously, the three types of errors listed herecan be compensated well by the test receiver. This is possible using a selfadaptingFIR filter (equalizer) integrated in the instrument. For a compensationof errors by the equalizer, the following main requirements must be fulfilled:The noise ripple must not exceed a certain frequency limit.The amplitude of the ripple must not be too high.2–78 DDS200 Digital Demodulation System User Manual
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®Established 1981Advanced Test Equ
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Copyright Tektronix, Inc. All righ
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Table of ContentsRemote ControlHard
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Table of ContentsIndexLocal control
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Table of ContentsFigure 2-35: ALARM
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Table of ContentsList of TablesTabl
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Table of ContentsxDDS200 Digital De
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General Safety SummaryProvide Prope
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PrefacexivDDS200 Digital Demodulati
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Preparation for UseFront PanelFront
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Preparation for UseTable 1-1: Legen
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Preparation for UseTable 1-2: Legen
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Preparation for UseUnpacking the Un
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Preparation for UsePositioning the
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Preparation for UsePowering OnConne
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Preparation for UseInitial update -
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Preparation for UseInstalling Optio
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Preparation for Use1-18 DDS200 Digi
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Manual OperationSample SettingThis
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Manual OperationFigure 2-3: MODE me
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Manual OperationPress the RECEIVER
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Manual OperationBasic OperationThe
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Manual OperationFigure 2-7: MEASURE
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Manual OperationSoft KeysThe soft k
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Manual OperationNumeric KeypadSelec
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Manual OperationPresetting the Unit
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Manual OperationFigure 2-14: RECALL
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Manual OperationThe display mode do
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Manual OperationFigure 2-18: SETUP:
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Manual OperationThe type of printer
Page 65 and 66: Manual OperationOperation as Demodu
Page 67 and 68: Manual OperationFigure 2-24: INPUT:
Page 69 and 70: Manual OperationFigure 2-26: STO: E
Page 71 and 72: Manual Operation84QAM16QAM32QAM64QA
Page 73 and 74: Manual OperationSPECIAL FUNCTION Me
Page 75 and 76: Manual OperationA wide loop bandwid
Page 77 and 78: Manual OperationALARM MenuThis subs
Page 79 and 80: Manual OperationPressing the ALARM
Page 81 and 82: Manual OperationFigure 2-34: ALARM:
Page 83 and 84: Manual OperationThe alarm register
Page 85 and 86: Manual OperationMEASURE MenuThe DDS
Page 87 and 88: Manual OperationFor further informa
Page 89 and 90: Manual OperationConstellation Diagr
Page 91 and 92: Manual OperationFigure 2-42 shows a
Page 93 and 94: Manual OperationQAM Parameters. Whe
Page 95 and 96: Manual OperationNOTE. For reading o
Page 97 and 98: Manual OperationPreset Values and M
Page 99 and 100: Manual OperationTable 2-4: DDS200 P
Page 101 and 102: Manual OperationExamples of Applica
Page 103 and 104: Manual OperationFigure 2-48: Conste
Page 105 and 106: Manual OperationThe magnitude of th
Page 107 and 108: Manual OperationFigure 2-53: Conste
Page 109 and 110: Manual OperationFrequency of occurr
Page 111 and 112: Manual OperationFrom the standard d
Page 113 and 114: Manual OperationTable 2-5: Theoreti
Page 115: Manual OperationThe term “modulat
Page 119 and 120: Manual OperationBER Measurement wit
Page 121 and 122: Manual Operationare taken into acco
Page 123 and 124: Manual OperationIt should be noted
Page 125 and 126: Manual OperationThe key characteris
Page 127: Manual OperationThe key characteris
Page 130 and 131: Remote Control
Page 132 and 133: Remote ControlIEC/IEEE-Bus Messages
Page 134 and 135: Remote ControlCommon commands. Comm
Page 136 and 137: Remote ControlNumeric suffix:If an
Page 138 and 139: Remote ControlExample: Special n
Page 140 and 141: Remote ControlParameter:In the para
Page 142 and 143: Remote Control*CLS*ESE 0 to 255*ESR
Page 144 and 145: Remote ControlInstrument Model and
Page 146 and 147: Remote ControlOutput UnitThe output
Page 148 and 149: Remote ControlCONDition register. T
Page 150 and 151: Remote ControlOverview of StatusReg
Page 152 and 153: Remote ControlTable 3-2: Definition
Page 154 and 155: Remote ControlTable 3-5: Definition
Page 156: Remote ControlResetting the StatusR
Page 159 and 160: Maintenance and TroubleshootingRepl
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Page 164 and 165: Appendix A: SpecificationsTable A-1
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Appendix A: SpecificationsTable A-2
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Appendix A: SpecificationsA-6 DDS20
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Appendix B: IEC/IEEE-Bus InterfaceS
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Appendix B: IEC/IEEE-Bus InterfaceT
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Appendix C: List of Error MessagesT
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Appendix C: List of Error MessagesD
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Appendix D: List of CommandsSTATus
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Appendix D: List of CommandsSYSTem
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Appendix D: List of CommandsINPut S
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Appendix D: List of CommandsTable D
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Appendix D: List of CommandsREAD Su
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Appendix D: List of CommandsD-20 DD
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Appendix E: Programming ExamplesSen
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Appendix E: Programming ExamplesSer
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Appendix E: Programming Examples
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Appendix F: Remote Control via RS-2
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IndexHHandshake, RS232, F-5Hard key
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IndexSetting device address, 3-2Set
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User Manual DDS200 Digital Demodulation System 070-9952-00

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