1. PAMPulse Amplitude Modulation Professor: Dr. Miguel Alonso Jr.

2. Outline • Description • Bandwidth Requirements • Signal Reconstruction • Types of PAM • LABVolt Module 2: PAM

3. 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

4. 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

5. Where BT is the transmission bandwidth • τis the pulse width • K1is 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

6. 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?

7. Signal Reconstruction • Reconstruction of the PAM occurs through the use of a low-pass filter

8. Types of PAM • Flat-top • Natural PAM

9. LAB Volt Module • Labvolt Module 2: PAM • Exercise 2-1 and 2-2