Digital Signal Processing (DSP) Fundamentals

Digital Signal Processing(DSP)FundamentalsSignal Processing2Humans are the most advanced signal processorsspeech and pattern recognition, speech synthesis,We encounter many types of signals in various applicationsElectrical signals: voltage, current, magnetic and electric fields,Mechanical signals: velocity, force, displacement,Acoustic signals: sound, vibration,Other signals: pressure, temperature,Most real-world signals are analogThey are continuous in time and amplitudeConvert to voltage or currents using sensors and transducers Analog circuits process these signals usingResistors, Capacitors, Inductors, Amplifiers,Analog signal processing examplesAudio processing in FM radiosVideo processing in traditional TV sets

Limitations of Analog Signal ProcessingCopyright (C) 2005 Gner Arslan351M Digital Signal Processing (Spring 2005)3Accuracy limitations due to Component tolerancesUndesired nonlinearitiesLimited repeatability due toTolerancesChanges in environmental conditionsTemperatureVibrationSensitivity to electrical noiseLimited dynamic range for voltage and currentsInflexibility to changes Difficulty of implementing certain operationsNonlinear operationsTime-varying operationsDifficulty of storing informationDigital Signal ProcessingRepresent signals by a sequence of numbersSampling or analog-to-digital conversionsPerform processing on these numbers with a digital processorDigital signal processingReconstruct analog signal from processed numbersReconstruction or digital-to-analog conversionCopyright (C) 2005 Gner Arslan351M Digital Signal Processing (Spring 2005)4A/DDSPD/Aanalogsignalanalogsignaldigital signaldigital signalAnalog input analog output Digital recording of musicAnalog input digital outputTouch tone phone dialingDigital input analog outputText to speechDigital input digital outputCompression of a file on computerWhat is DSP?Converting a continuously changing waveform (analog) into a series of discrete levels (digital)

What is DSP?The analog waveform is sliced into equal segments and the waveform amplitude is measured in the middle of each segmentThe collection of measurements make up the digital representation of the waveformWhat is DSP?

DSP is Everywhere!Audiological equipmentHearing aidsOtoacoustic systemsAudiometersAural rehabilitation programsABRs TelecommunicationsCellular phonesVoice over InternetAudioCD, DVD, DAT playersMP3 playersBiomedical monitoring equipmentDigital Television8Pros and Cons of Digital Signal ProcessingCopyright (C) 2005 Gner Arslan351M Digital Signal Processing (Spring 2005)9ProsAccuracy can be controlled by choosing word lengthRepeatableSensitivity to electrical noise is minimalDynamic range can be controlled using floating point numbersFlexibility can be achieved with software implementationsNon-linear and time-varying operations are easier to implement Digital storage is cheapDigital information can be encrypted for securityPrice/performance and reduced time-to-marketConsSampling causes loss of informationA/D and D/A requires mixed-signal hardwareLimited speed of processorsQuantization and round-off errorsAnalog vs DigitalAnaloginfinitely detailedcontinuous in timecontinuous in amplitudeDigitaldiscrete numbersdiscrete in timediscrete in amplitudeChallenge: a digital representation that adequately maps the analog values.10Why digital?FlexibilityProgrammabilityReproducibility and Precision (??)Advanced Signal ProcessingMultichannel compressionPrecise frequency shapingFeedback cancellationNoise reductionDirectional processing11DSP ApplicationsDigital signal analysis/displayDigital recording, processing, and reproductionDigital signal synthesis

12Analog-to-Digital Conversion

AnalogDiscreteDigital13QuantizationThe sampled values are converted into bit representationThe process is called QuantizationThe performance of a quantizer is dependent on the number of bits, also called bit resolution.14