說明ni官方培訓labview rf10digital modulation

1、Lesson 10Digital ModulationModern Digital Communication SystemsDigital Modulation MethodsDigital Modulation and Coding SchemeDigital Demodulation and MeasurementsVisualizationA. Modern Digital Communication SystemsSource CodingChannel CodingModulationAWG (DUC)Digitizer (DDC)DemodulationChannel Decod

2、ingSource DecodingCommunications ChannelUpconversionDownconversionModulation and DemodulationDigital Modulation ProcessData starts out as bitstreamBit values are mapped to symbols. Ex: 2 bits per symbol valueSymbols modulate carrier to form signalDigital Modulation ReviewMessage signal is discrete (

3、binary or 2n-ary)Actual bit values are mapped to symbolsSymbols used to modulate carrierBasic digital modulation types are analogous to analog modulationAmplitude Shift KeyingAmplitude Modulation (AM)Frequency Shift KeyingFrequency Modulation (FM)Phase Shift KeyingPhase Modulation (PM)Digital Versus

4、 Analog ModulationThe instructor will run a VI that will help visualize the differences and similarities between digital and analog modulationB. Digital Modulation MethodsASKAmplitude Shift KeyingDiscrete Version of AMFSKFrequency Shift KeyingDiscrete Version of FMPSKPhase Shift KeyingDiscrete Versi

5、on of PMQuadrature Amplitude ModulationChange both amplitude and phase of carrier based on symbol value (combination of ASK & PSK)Use MT Modulate QAM to generate QAM baseband dataOther Modulation TypesMinimum Shift Keying (MSK) special case of FSK that uses a half-cycle sinusoidal pulseContinuous Ph

6、ase Modulation (CPM) generalized version of MSK that ensures phase continuity in the waveformPulse Amplitude Modulation (PAM) encodes symbols using pulses of varying amplitudeSupported Digital Modulation MethodsThe Modulation Toolkit supports seven different standard digital modulation methodsAmplit

7、ude Shift Keying (ASK)Frequency Shift Keying (FSK)Phase Shift Keying (PSK)Quadrature Amplitude Modultion (QAM)Minimum Shift Keying (MSK)Continuous Phase Modulation (CPM)Pulse Amplitude Modulation (PAM)Digital Modulation ToolkitFunctions RF Communications Modulation Digital Modulation subpaletteC. Mo

8、dulation and Coding Scheme IdentificationModulation System ParametersData FormattingChannel CodingPulse Shape FilteringSynchronization ParametersContinuous vs. BurstArtificial ImpairmentsModulation System ParametersModulation TypeModulation OrderSymbol Mapping InfoSamples Per SymbolSamples per Symbo

9、lNumber of samples used to generate the waveform representation of each symbol.Data FormattingBit-packingPacket / frame definition and assemblyUpper and lower 8 bits of countUpper and lower 8 bits of CRCHeaderStatic BitsHeader(40)Static(56)Count(16)CRC(16)Channel CodingAdds redundant bits to the dat

10、a stream to increase the receivers immunity to noise and interference01 10 01 01 10 01 101 0 1 1 0 1 010Coded bit streamOriginal bit streamSpreading codeExample of spreading code:Pulse Shape FilteringSymbols are filtered to form waveformBit-streamSymbolsModulated CarrierPulse Shaping Modulated DataT

11、he instructor will demonstrate how pulse shaping makes generation more spectrally efficient.Synchronization ParametersHeader(40)Static(56)Count(16)CRC(16)Upper and lower 8 bits of countUpper and lower 8 bits of CRCHeaderStatic BitsContinuous Data versus BurstExercise 10-1: Generating and ModulatingG

12、enerate a data packet to the Atmel FSK evaluation DUT and validate proper data formatting and modulationExercise 10-1: Generating and ModulatingDiscuss the key components that were added to the code necessary to build a waveform to generate.Modulation ImpairmentsReal-world applications include disto

13、rtions based primarily on the introduction of noise into the system known as impairments.DC offset, phase noise, quadrature skew, or gain imbalance are examples of impairmentsTesting requires that you add artificial distortion in the lab to simulate real world conditions.Impairments with the Modulat

14、ion ToolkitApply IQ ImpairmentsApplies offset, gain and skew impairments to the IQ dataAdd AWGNApplies additive white Gaussian noise to dataAdd Phase NoiseAdd MultitoneApply Fading ProfileModulation Impairments IQ ImpairmentsI/Q Gain ImbalanceDC OffsetQuadrature SkewMT Apply IQ ImpairmentsAdding Imp

15、airments to Baseband DataDemonstrate the ability to add impairments into a QAM signal and visually evaluate the effects.Low Level Modulation ToolsResample Symbol MappingInterleavingEqualizationSample Rate ConsiderationsIt can be necessary to resample your modulated waveform to match valid IQ rates f

16、or your hardware.MT ResampleniRFSG Resample and WriteSymbol MappingSync and Guard bits need to be mapped to actual symbols for Demodulation Vis.Symbol map is generated with other System Parameters.Interleaving and EqualizationInterleaving Vis can perform permutation and block and convolutional inter

17、leaving.Equalization can be performed on ASK, PAM, QAM and PSK modulated waveformsD. Digital Demodulation and MeasurementsCommunications engineers use different tools to evaluate how well the digital data was transmitted and received. Bit error rate (BER), modulation error ratio (MER) and error vect

18、or magnitude (EVM) are common metrics for this job.Process of DemodulationCreate SyncCreate FilterSet SystemCalculate AcquisitionParameters AcquireDemodulateMeasureVisualizationResampleDemodulateProcess of DemodulationCreate SyncCreate FilterSet SystemAcquireDemodulateResampleModulation Measurements

19、 with the Demodulation VIsDemodulation VIs also have built-in measurementsQAM, ASK, PAM, PSK: Frequency Offset, Frequency Drift, Phase Offset FSK: Frequency Offset, Frequency Drift, Deviation Error, FSK Error MSK: Frequency Offset, Frequency Drift Exercise 10-2: Acquisition and DemodulationAcquire a

20、nd properly demodulate a data burst from the Atmel FSK Eval DUT. Analyze measurements and data to ensure proper acquisition and demodulation.Exercise 10-2: Acquisition and DemodulationAcquire and properly demodulate an data burst from the Atmel FSK Eval DUT. Analyze measurements and data to ensure p

21、roper acquisition and demodulation.Modulation Measurements with the Modulation ToolkitCalculate BER After TriggerCalculates bit error rate on user specified bit sequenceMeasure Quadrature ImpairmentsMeasures various IQ impairments such as EVM and MERMeasure Burst TimingReturns information relative to a burst signalMeasure RhoReturns the correlation between measured and ideal complex waveformsE. VisualizationIQ to XY GraphConstellation Eye Diagram Trellis DiagramWhen you add a modulation graph to the front panel, the corresponding VIs