Frequency Modulation (FM) is a modulation technique in which the carrier signal’s frequency is varied in proportion to the instantaneous amplitude of the modulating signal. The modulating signal typically represents the information to be transmitted, such as voice or music.
In FM, the carrier signal is a high-frequency sinusoidal waveform, usually in the radio frequency range. The modulating signal, which is typically an audio signal, is used to modulate the frequency of the carrier signal. The resulting waveform is the modulated signal.
The process of frequency modulation involves the following steps:
- Carrier Signal Generation: A high-frequency sinusoidal carrier signal is generated using an oscillator.
- Modulating Signal Generation: The modulating signal, which carries the information to be transmitted, is generated. This signal may come from a microphone, audio player, or any other audio source.
- Frequency Deviation: The amplitude of the modulating signal determines the frequency deviation of the carrier signal. As the amplitude of the modulating signal varies, the instantaneous frequency of the carrier signal changes proportionally.
- Modulation: The modulating signal is used to modulate the frequency of the carrier signal. The carrier signal’s frequency is shifted above and below its nominal frequency based on the instantaneous amplitude of the modulating signal.
- Modulated Signal Transmission: The modulated signal is transmitted through the communication channel, such as a radio transmitter or a wired medium.
- Demodulation: At the receiving end, a demodulator or receiver circuit extracts the original modulating signal from the received modulated signal. This process is known as demodulation.
FM has several characteristics and applications:
- Spectrum: In FM, the modulated signal consists of the carrier signal and an infinite number of sidebands extending from the carrier frequency. The sidebands carry the information being transmitted.
- Bandwidth: FM signals have a larger bandwidth compared to AM signals. The bandwidth depends on the maximum frequency deviation and the highest frequency present in the modulating signal.
- Noise Immunity: FM signals are more resistant to noise and interference compared to AM signals. This makes FM suitable for applications where signal quality is crucial, such as broadcast radio and audio transmission.
- Broadcasting: FM is widely used in radio broadcasting, especially for FM radio. It offers high-fidelity audio transmission and allows for stereo broadcasting.
- Wireless Communication: FM is also used in various wireless communication systems, such as two-way radios, aviation communication, and certain mobile communication standards.
FM modulation provides advantages in terms of signal quality and noise immunity, making it suitable for applications that require high-fidelity audio transmission and robustness against interference.