An amplitude modulated (AM) wave is produced by varying the amplitude of a carrier wave in accordance with the characteristics of the modulating signal (often an audio signal). The process of producing an AM wave involves the following steps:
Carrier Wave Generation: A high-frequency sinusoidal waveform, known as the carrier wave, is generated. This carrier wave typically has a much higher frequency than the modulating signal. For example, in broadcast AM radio, the carrier frequency is in the range of hundreds of kilohertz (kHz).
Modulating Signal: The modulating signal, which carries the desired information (such as audio), is generated. This signal typically has a much lower frequency compared to the carrier wave. For example, in audio broadcasting, the modulating signal represents the sound waveform.
Modulation: The modulating signal is used to modulate the amplitude of the carrier wave. This is usually achieved by multiplying the carrier wave with the modulating signal. The resulting waveform is an amplitude-modulated wave.
Amplitude Variation: The amplitude of the carrier wave is varied in accordance with the instantaneous amplitude of the modulating signal. As the modulating signal varies, the amplitude of the carrier wave follows the same variations.
Spectrum Shifting: The modulated wave consists of the original carrier frequency as well as two additional sidebands: an upper sideband and a lower sideband. These sidebands contain the information from the modulating signal and are located symmetrically around the carrier frequency.
Transmission: The modulated wave is transmitted through a medium, such as air or a transmission line, to carry the modulating signal to the receiver.
At the receiving end, the process is reversed through demodulation, where the original modulating signal is extracted from the received amplitude modulated wave, allowing the reproduction of the original information (e.g., audio) that was modulated onto the carrier wave.