Modulation

Modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal containing information. This process is fundamental in transmitting information across a communication channel, allowing data (like audio or video) to be encoded onto a carrier wave suitable for transmission. The specific property varied depends on the modulation technique used (e.g., amplitude, frequency, phase). Effectively, modulation superimposes the information signal onto the carrier, enabling long-distance transmission or storage.

Modulation meaning with examples

• In radio broadcasting, amplitude modulation (AM) is used to encode audio signals onto radio waves. The amplitude of the carrier wave is varied to represent the sound's loudness. This allows radio signals to travel through the air. Receivers then demodulate, or extract the information and reproduce the audio. Modern FM radio works through frequency modulation, which is more resilient to interference and provides a more robust signal.
• Digital communication systems employ various modulation schemes. Quadrature Amplitude modulation (QAM) is often used for data transmission where both the amplitude and phase of the carrier wave are varied. Each constellation point represents a specific symbol, encoding multiple bits of data. This enables high data rates and efficient spectrum use. Error correction codes are used to further improve the signal reliability.
• Musical instruments, such as synthesizers, make use of modulation to create complex and evolving sounds. Voltage-controlled oscillators (VCOs) can have their frequency or other parameters changed by a modulation signal like an LFO (low frequency oscillator). This adds dynamic richness and variation to the synthesized tones. Tremolo is an example of AM in this context, and vibrato is an example of FM.
• In optical fiber communication, modulation techniques similar to those in radio are employed. The intensity of a light beam (amplitude modulation) or the frequency (frequency modulation) can be altered to transmit data along the fiber. This permits high-speed data transmission over long distances. Demodulation at the receiver is used to decode the information.