Am

Electromagnetic Wave

Wireless Communication Transmitter Carrier Circuits

Information Input (Sound, text, image and etc.)

Signal Processing (Transduction and Amplification )

Message m(t) Modulation

Transmitted Signal s(t)

Cellular Phone Radio Television . . .

Noise n(t) Information Sink (Sound, text, image and etc.)

Transmission Medium

Receiver Signal Processing (Amplification and Transduction )

Received Signal r(t)

Recovered Message Demodulation

Carrier Circuits

http://en.wikipedia.org/wiki/Modulation

Analog Modulation Amplitude modulation  Double-sideband modulation DSB + Double-sideband modulation with unsuppressed carrier (DSBWC)(used on the radio AM band) + Double-sideband suppressed-carrier transmission (DSB-SC) + Double-sideband reduced carrier transmission (DSB-RC)  Single-sideband modulation + Single-sideband modulation (SSB, or SSB-AM), very similar to + single-sideband suppressed carrier modulation (SSB-SC)  Vestigial sideband modulation (VSB, or VSB-AM)  Quadrature amplitude modulation (QAM) Angle modulation  Frequency modulation (FM)  Phase modulation (PM)

http://www.williamson-labs.com/480_am.htm

Amplitude Modulation

Amplitude Modulation

Envelope and Modulation Percentage Transmitted signal:

Envelope:

Percentage of Modulation:

For any message satisfies -1≤ Bm(t) ≤ +1:

Over Modulation:

Envelope and Modulation Percentage Transmitted signal:

Envelope:

Percentage of Modulation:

For a message:

http://www.williamson-labs.com/480_am.htm

Over Modulation

Envelope Detector Envelope:

Example for Square Wave