pam pulse amplitude modulation professor: dr. miguel alonso jr
DESCRIPTION
Description PAM is a type of pulse modulation A PAM signal consists of samples of the analog signal, in which the amplitude of each pulse is proportional to the analog signal at that point Pulses have a fixed widthTRANSCRIPT
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PAMPulse Amplitude
Modulation
Professor: Dr. Miguel Alonso Jr.
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Outline
Description Bandwidth Requirements Signal Reconstruction Types of PAM LABVolt Module 2: PAM
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Description
PAM is a type of pulse modulation A PAM signal consists of samples of the
analog signal, in which the amplitude of each pulse is proportional to the analog signal at that point
Pulses have a fixed width
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Bandwidth Requirements
Sampling Rate of the PAM pulses should be twice that of the analog signal to be transmitted. Nyquist
But what about the bandwidth of the PAM signal itself?
Bandwidth of the PAM signal is roughly computed as
1KBT
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Where BT is the transmission bandwidth τ is the pulse width K1 is a constant that depends on the spacing
between adjacent pulses, the level of acceptable adjacent pulse crosstalk, the sharpness of the cutoff rate, and other factors
Typical values range from 0.5 to 1
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Example
An analog signal is sampled at a rate of 5kHz. The width of each sample is 40 us. Compute the approximate bandwidth for K1=0.5
and K1 = 1 What is the duty cycle of the sampling pulse? Answer: 12.5kHz and 25kHz
What is the bandwidth requirement for a K1 = 1 and a sampling width of 15us?
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Signal Reconstruction
Reconstruction of the PAM occurs through the use of a low-pass filter
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Types of PAM
Flat-top Natural PAM
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LAB Volt Module
Labvolt Module 2: PAM Exercise 2-1 and 2-2