Important Topic of Physics: Frequency Modulation

Frequency modulation, or FM as it’s more generally known, is a term we hear all the time. Frequency modulation is frequently utilised in radio communication and broadcasting nowadays. Have we ever questioned what FM is or what the technology and process behind it is? In this lesson, we’ll try to figure out what frequency modulation is, as well as its mechanism and uses.

What exactly is Frequency Modulation (FM) and how does it function?

Frequency modulation is a method of encoding data on a signal (analogue or digital) by changing the carrier wave frequency in accordance with the frequency of the modulating signal. As we all know, a modulating signal is simply information or a message that must be transmitted after being converted into an electronic signal.

In the same way as amplitude modulation modulates a carrier signal, frequency modulation modulates a carrier signal. In FM, on the other hand, the modulated signal’s amplitude is preserved or remains constant.

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Frequency Modulation: Applications

When it comes to frequency modulation applications, radio transmission is by far the most common. It has a higher signal-to-noise ratio, which helps it perform well in radio transmission. It has a modest level of radio frequency interference as a result of this. This is the primary reason why many radio stations broadcast music over the airwaves using FM.

Radar, telemetry, seismic exploration, EEG, various radio systems, music synthesis, and video transmission tools are all examples of its applications. Frequency modulation outperforms other modulation techniques in radio transmission. Because it has a higher signal-to-noise ratio than equal-power amplitude modulation (AM) signal, it can reject radio frequency interferences significantly better.

Modulators for FM

Direct or indirect frequency-modulated signals can be generated using a variety of techniques.

A voltage-controlled oscillator, often known as a Varactor diode oscillator, consists of the following components: By directly putting the message into the oscillator’s input, a voltage-controlled oscillator can be utilised to provide Direct FM modulation. In the case of the varactor diode, we use it in an oscillator circuit’s tuned circuit.

When the signal needs to be multiplied in frequency and only narrowband FM is desired, a varactor diode can be utilised in a crystal oscillator circuit.

The phase-locked loop is a great way to create frequency modulation signals. However, the loop’s limitations should be carefully examined, and once everything is stable, it provides an option excellent solution.

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Advantages and disadvantages of frequency modulation

There are various advantages and cons to using modulation, as there are with any other type of modulation. Before making any decision or choice about its use, keep the following in mind:

Frequency modulation, or FM, has a number of advantages.

• Frequency modulation has been widely employed for high-quality audio broadcasting, two-way radio communications, and a variety of other applications due to its many advantages.
• Frequency modulation has a number of advantages, one of which being its resistance to signal level changes. The modulation is simply carried as frequency fluctuations. This means that any changes in signal level will have no effect on the audio output, as long as the signal does not dip below the receiver’s capability. As a result, FM is appropriate for mobile radio communication applications such as general two-way radio or portable applications where signal levels are expected to vary significantly.
• Another benefit of FM is that it is resistant to noise and interference. FM is utilised for high-quality broadcast transmissions for this reason.
• Another benefit of frequency modulation is that it is simple to apply modulation at the transmitter’s low power stage. It is possible to use modulation on a low-power transmitter stage, and linear amplification is not required to raise the signal’s power level to its final value.
• With frequency modulated signals, it’s feasible to employ efficient RF amplifiers: In a transmitter, non-linear RF amplifiers can be used to amplify FM signals, which are more efficient than linear ones for signals with amplitude changes.
• Between adjoining stations, there is less geographical interference. There is less power being radiated. For a given transmitter power, well-defined service zones.

FM’s disadvantages include the following:

• Frequency modulation, like all schemes and approaches, has several drawbacks that must be considered when FM is likely to be utilised.
  The spectral efficiency of FM is lower than that of other modulation formats: Frequency shift keying, a type of frequency modulation, has a lower spectral efficiency for data transmission than some phase modulation and quadrature amplitude modulation formats. As a result, PSK and QAM are used in the majority of data transmission systems.
• Frequency modulation has a few small drawbacks, one of which is that the demodulator is a bit more complicated, and thus slightly more expensive, than the very simple diode detectors used in AM. However, because many radio integrated circuits now include a built-in frequency demodulator, this is no longer an issue.
• Other modes have a higher data spectral efficiency, for example: Frequency shift keying, a type of frequency modulation, has a lower spectral efficiency for data transmission than some phase modulation and quadrature amplitude modulation formats. As a result, PSK and QAM are used in the majority of data transmission systems.

Difference between Amplitude Modulation and Frequency Modulation