02-02-2013, 12:08 PM
Digital Signal Processing
Digital Signal.pdf (Size: 2.18 MB / Downloads: 67)
Introduction
•Digital Signals:
Sampling, Digitizing, ADC, Multiplexer
•Fourier Transform, FFT
–Aliasing
–Leakage
–Windowing
–Averaging
•Coherence
•Correlation
The Fourier Transform
•The transformation from the time domain to the frequency domain is based on forwardFourier Transform
•and back again to time domain from the frequency domain is based on inverseFourier Transform
Anti-Alias Filter
•In practice, input signal may contain some spurious unknown frequencies that are greater than fs
•A low pass filter (Anti-Alias Filter) after the sampler that filters all f above fmax followed by sampling @ fs>2*fmax, will avoid aliasing
•Minimum Sample Rate requirement is called Nyquist Criterion that is stated as,
Cross Correlation
Measure of similarity between two different non-identical signals is cross correlation functionThe cross correlation can be used to detect the presence of one signal in another signal. If the same signal is buried in both the waveforms, it will be reinforced in the cross correlation function, whereas the noise which is uncorrelated will be reducedPractical Examples: Radar, Active Sonar, Room Acoustics, Transmission Path Delays, in which input stimulus can be measured and used to remove contaminating noise from the response by cross correlationThe frequency transform of the cross correlation function is Cross Power Spectrum