Wide Band Frequency Modulation

Wideband Frequency Modulation (WBFM) is a type of frequency modulation (FM) that uses a relatively large frequency deviation and a wide bandwidth. WBFM is often used for high-fidelity audio and stereo sound transmission in radio broadcasting.

In WBFM, the frequency deviation is typically much larger than the audio signal frequency, allowing for the transmission of a wider range of audio frequencies with high fidelity. The bandwidth of a WBFM signal is proportional to the frequency deviation, and it can be several times wider than the bandwidth of a narrowband FM signal.

The wide bandwidth of WBFM signals makes them more susceptible to noise and interference compared to narrowband FM signals. However, the high fidelity and low distortion of WBFM signals make them well-suited for broadcasting music and other audio content over long distances.

One common application of WBFM is in FM radio broadcasting, where it is used to transmit high-fidelity audio and stereo sound to listeners. WBFM is also used in some mobile communication systems, such as certain digital cellular systems, where it can provide a higher data rate compared to narrowband FM signals.

Overall, WBFM is a powerful and flexible modulation technique that can transmit a wide range of audio frequencies with high fidelity, making it an important tool for audio broadcasting and other telecommunications applications.

Consider the following block diagram

 

Wideband FM Signals

A narrowband FM signal can be generated easily using the block diagram of the narrowbandbFM modulator that was described in a previous lecture. The narrowband FM modulator generates a narrowband FM signal using simple components such as an integrator (an OpAmp), oscillators, multipliers, and adders. The generated narrowband FM signal can be converted to a wideband FM signal by simply passing it through a non–linear device with power P. Both the
carrier frequency and the frequency deviation f of the narrowband signal are increased by a factor P. Sometimes, the desired increase in the carrier frequency and the desired increase in f are different. In this case, we increase f to the desired value and use a frequency shifter (multiplication by a sinusoid followed by a BPF) to change the carrier frequency to the desired value.