Amplitude Modulation

By National Instruments Corporation

Modulation is the process of varying a higher frequency carrier wave to transmit information. Though it is theoretically possible to transmit baseband signals (or information) without modulating it, it is far more efficient to send data by modulating it onto a higher frequency "carrier wave." Higher frequency waves require smaller antennas, use the available bandwidth more efficiently, and are flexible enough to carry different types of data. AM radio stations transmit audio signals, which range from 20 Hz to 20 kHz, using carrier waves that range from 500 kHz to 1.7 MHz. If we were to transmit audio signals directly we would need an antenna that is around 10,000 km! Modulation techniques can be broadly divided into analog modulation and digital modulation. Amplitude modulation (AM) is one form of analog modulation.