Frequency Modulation (FM) is a method of transmitting information (such as audio signals) by varying the frequency of the carrier wave in accordance with the modulating signal. In commercial FM radio broadcasting, the audio signal (voice or music) is used to modulate the carrier frequency, and this modulated signal is transmitted over the airwaves to be received by FM radios.
The channel bandwidth refers to the range of frequencies that the FM signal occupies in the radio frequency spectrum. In FM broadcasting, the signal is allocated a specific frequency band, and this band needs to be wide enough to accommodate the modulated signal.
The channel bandwidth is influenced by various factors, including the audio quality, the data rate required for the transmission, and the interference considerations to ensure proper reception. In commercial FM broadcasting, a bandwidth of approximately 150 kHz is chosen as a trade-off between audio quality and spectrum efficiency.
1. Audio Quality: A wider bandwidth allows for higher fidelity audio transmission. The wider the bandwidth, the more accurately the original audio signal can be reconstructed at the receiving end. A 150 kHz bandwidth is considered sufficient to provide good audio quality for commercial FM radio broadcasting.
2. Spectrum Efficiency: On the other hand, allocating too much bandwidth for each FM channel would be inefficient in terms of spectrum usage. It would limit the number of radio stations that could coexist within the available radio frequency spectrum, leading to congestion and reduced choices for listeners.
3. Interference: FM channels are typically spaced apart in the radio frequency spectrum to avoid interference between adjacent channels. Allocating a wider bandwidth for each FM channel would require more significant spacing between channels, further reducing the available spectrum for broadcasting.
For these reasons, a practical compromise is made by selecting a channel bandwidth of around 150 kHz in commercial FM systems. This allows for good audio quality while optimizing spectrum utilization and providing enough spacing between channels to minimize interference.
One of the advantages of base modulation over collector modulation of a transistor class C amplifier is