sinusoidal waveform where: vis the instantaneous amplitude of the sine wave v m is the peak...
Post on 21-Dec-2015
218 views
TRANSCRIPT
Sinusoidal waveform
Where:V is the instantaneous amplitude of the sine waveVm is the peak amplitude of the sine wave is the angular frequency (2f)of the sine wavet is the time in second
Sinusoidal waveform (cont.)
Types of signal
a: Static: DC b: Quasistatic c: Periodic: sine,square,.. ,v(t)=v(t+T)
d: Repetitive: quasiperiodic
e: Single event transient signal
f: Repetitive single event
Waveform symmetry
A: Square wave with DC component that causes asymmetry
B: Symmetrical square wave
C: Sawtooth waveform forms mirror image across zero basline
D: Quarter-wave symmetry
A B
C D
Signal samplingMost instrumentation transducers have analog output
At the interface between analog transducers and digital computers the signal must be digitized
So the signal is sampled at regular intervals
Each sample voltage is then converted into an equivalent digital value
The next sample cannot be taken until the conversion of the last sample to digital form is completed
Sampled signals
A: continuous waveform
B: Sampled version of continuous waveform
C: Reconstructed waveform
A
B
C
Sampled signals
A: Sine wave
B: Sampling of sine wave
C: Sampled sine wave
A
B
C
Effect of the sampling rate
1 Sample/sec
12 sample/sec
If fsampling > fsignal o.k. Ideally fsampling ≥ 2 fsignal
If fsampling < fsignal aliasing
Some applications don’t accept fsampling= 2 fsignal
as in ECG signal = 5 fsignal
Reconstruction of Sampled signals
To reconstruct the original signal after sampling pass the sampled waveform through a low-pass filter that blocks fs
Sampling is used to formAM, PM,