User Manual DDS200 Digital Demodulation System 070-9952-00

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Manual OperationBER for 4/16/64/256 QAM1 10 0 4 QAM 16 QAM 64 QAM 256 QAM1 10 –11 10 –21 10 –3Actual C/N1 10 –4EndNoise margin1 10 –51 10 –61 10 –71 10 –81 10 –91 10 –101 10 –111 10 –1246810121416182022 24C/N in dB2628303234363840Figure 2–61: BER as a function of C/N ratioDDS200 Digital Demodulation System User Manual 2–83
Manual OperationIt should be noted that the C/N ratio shown in Figure 2–61 was measured afterthe receive filter (1st Nyquist condition fulfilled). Therefore, when comparingthe curves with curves obtained for a channel, a correction of the C/N values hasto be made. The C/N value of a channel increases at the output of the receiverfilter, since the white noise is decreased to a greater extent than the useful signal,which is filtered in the transmitter. Moreover, both the C/N ratio determined bythe method (described page 2–80) and the C/N ratio of the internal noisegenerator are referred to the bandwidth of the receive channel (for example,8 MHz if the 8-MHz filter is selected).For an exact value, the C/N ratio must be corrected in accordance withFigure 2–62. However, the method described is appropriate for practicalpurposes where the C/N value is to be determined for a real channel, and the testpoint after the receiver Nyquist filter is not accessible.1.51.0C/N rec (r) – C/N C (r)0.50.0–0.5–1.00.00.10.2r0.30.40.5Figure 2–62: Effect of receive filter on C/N valueC/Nrec: C/N after receive filter.C/NC: C/N ahead of receive filter (in channel)Example:With the roll-off factor of 0.15 used for DVB signals and a symbol rate of6.95 Msps, the 8-MHz receive channel is utilized fully. A C/N value of24.0 dB is set with the internal noise generator of the DDS200. This value isincreased by 0.441 dB after the receive filter (see Figure 2–62). Thetheoretical BER for the described receiving conditions can be seen fromFigure 2–61; for C/N = 24.4 dB, a BER of approx. 1.1E-4 is obtained. Forthe described relationship between the noise generator and the BER, all BERvalues are shifted to the left by 0.441 dB.2–84 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
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Manual OperationOperation as Demodu
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Manual OperationFigure 2-24: INPUT:
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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 and 116: Manual OperationThe term “modulat
Page 117 and 118: Manual OperationAmplitude N = 2 4 -
Page 119 and 120: Manual OperationBER Measurement wit
Page 121: Manual Operationare taken into acco
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
Page 161: Maintenance and TroubleshootingTabl
Page 164 and 165: Appendix A: SpecificationsTable A-1
Page 166 and 167: Appendix A: SpecificationsTable A-2
Page 168 and 169: Appendix A: SpecificationsA-6 DDS20
Page 170 and 171: 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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