Pulse Amplitude Modulation

Section 6.6

DSB/SC-AM Modulation (Review)

Frequency Shift Property (Review)

Frequency Spectrum of DSB/SC-AM Signal (Review)

Carrier Signal for Amplitude Modulation

Pulse Amplitude Modulation

Frequency Spectra for Pulse Amplitude Modulation

(Determined by fourier series)

Replication is caused by multiplication of m(t) by cos()

Frequency Modulation (Review)

Multiple signals are transmitted simultaneously through the samechannel.

Time-Division Multiplexing

Multiple signals are transmitted in the same channel with the signals separated in time, but not in frequency!

The switches at the receiving end issynchronized to the switches of the multiplexer.

Demodulator for PAM

Telephone System in the US

(Need to low pass filter the circuit)The maximum frequency content cannot exceed 3.2 KHz.Drawback: deterioration in voice quality. Ears can hear up to 20 KHz.

(Sampling rate: 8 KHz)

Pulse Modulation Using Sample and Hold

(model the sample and hold with sampling and filtering behavior)

Impulse Response of a Data Hold Circuit

Frequency Spectra for Flat-Top PAM