Home Education Amplitude Modulation vs Frequency Modulation: All You Need To Know

Amplitude Modulation vs Frequency Modulation: All You Need To Know

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In this article, we will explore 2 popular modulations types – Amplitude Modulation and Frequency Modulation. Also, we will look into the amplitude modulation vs frequency modulation comparison.

Amplitude Modulation

Amplitude modulation (AM) is a technique that is commonly used in electronic devices for transmitting data through a radio carrier wave. The final modulation comprises three mechanisms: carrier, lower sideband, upper sideband. Different amalgamations of these workings give birth to different types of AM with various properties for data transfer. We can also add that the modulation depth has a major impact on modulation properties.

Although one of the initial forms of modulation is still in use in today’s world, primarily for long, medium, and shortwave broadcasting. Also, for some aeronautical specific point-to-point communications.

Amplitude Modulation is one of the key features that makes it easy to use. They just require the modulation of the carrier amplitude, but the better thing is that the detector required in the receiving device can be a simple diode-based circuit. This implies that AM radios did not require any kind of complicated demodulators and hence, costing was diminished. This was a key condition for such wide use of radios, especially in the early era of radio technology when integrated circuits did not exist.

Amplitude Modulation Applications

Amplitude modulation is used in a wide variety of solicitations. Although it is not used in the modern world, it still can be found.

  • Broadcast Transmission: Amplitude Modulation is still widely utilized for broadcasting on the long, medium, and short wavebands. AM is simple to demodulate and that implies that radio receivers which are able to demodulate amplitude AM are very cheap and easy to produce.
  • Airband radio: Very high frequency (VHF) transmissions for a lot of airborne applications still use AM. It is used for land-to-air communications.
  • Single sideband: Amplitude Modulation in single sideband form is used even today for high-frequency radio links.
  • Quadrature Amplitude Modulation: AM is majorly used for data transmission in everything from short-range wireless links like Wi-Fi to cellular services and many more. Effectively it is formed by having two carriers out of phase.

What is Amplitude Modulation?

In order to carry a radio signal that can carry audio or other types of information for two-way communication, it is supposed to be modulated or changed in some sort of way. Though, there are different other ways in which a radio frequency can be modulated. The easiest way is to change the amplitude in line with various sounds.

By doing this, the amplitude of the radio signal varies in line along with the immediate value of the intensity of the modulation. This implies that the radio signal has a depiction of the sound wave in it.

In simple words, the basic signal “carries” the sound of modulation, the radio frequency is often known as the carrier.

Amplitude Demodulation

Amplitude Modulation (AM) is an upfront way of modulating a radio signal or carrier. the simplest uses a single diode rectifier.

There are other methods to demodulate Amplitude Modulation signals that use synchronous techniques and provide comparatively lower levels of distortion and improved reception where the selective presence has occurred.

The main reason for AM’s popularity is because of the level of simplicity of the demodulation. It enables the pricing to be super low – a vital point to consider while producing in vast quantities.

Advantages & Disadvantages of Amplitude Modulation, AM

Everything in this world has some advantages and disadvantages which should be considered.

Some of the advantages of Amplitude Modulation are; AM is super easy to implement. AM can be demodulated using a simple diode circuit. AM receiving devices are super cheap because they do not have any specialized components.

Some of the disadvantages are; inefficient in terms of usage. Inefficient in terms which requires a bandwidth equal to twice that of the highest audio frequency. Prone to high levels of noise because most noise is based on amplitude and Amplitude Modulation devices are sensitive to it.

Frequency Modulation

While we change the amplitude of a radio channel, it is a technique to modulate it. It turns out that this is not the only way. The frequency of a particular signal can also be changed by us, to emit frequency modulation (FM). The method of FM is usually used on frequencies higher than 30 Mhz. It is primarily known for its usage of VHF and FM broadcasting.

Not being as straight as amplitude modulation, frequency modulation, has some of its own significant advantages. The ability to provide interference-free reception. Thus, this is one of the reasons why it was chosen for the VHF sound broadcasts. These transmissions have the ability to offer good quality audio, because of which frequency modulation is more popular than previous old transmissions that had the long, medium, and short wavebands.

In addition to the vast usage of frequency modulation for high fidelity audio broadcasts. However, FM can further be used for a few certain varieties of two-way communications. FM holds a widespread usage at very high frequency (VHF) and above

When the audio is modulated onto the radio channel carrier, the new radio frequency signal moves upwards and downwards in the direction of frequency. Important thing is, by what amount the signal moves. The movement of the frequency is known as the deviation and it is usually noted as the number of kHz (kilohertz) deviation.

Frequency demodulation

With any form of modulation, it is compulsory that it successfully modulates it and retrieves the original signal. FM demodulator is to be known by different names such as FM demodulator, FM detector, or FM discriminator.

There are ample FM demodulators, but all the demodulators enable the variations that occur during the frequency which allows the incoming signal to be converted. It converts the signal into amplitude variations on the outgoing signal. These are usually fed into a device that amplifies the audio. So basically, an audio amplifier or even a digital interface some data that is being passed around.

FM Modulators

  • Varactor diode oscillator phase-locked loop 

Frequency modulation advantages and disadvantages

There are a lot of advantages to frequency modulations that are to be noted.

  • Resilience to noise: FM has one major advantage: it is resilient to variations in signal strength. This implies that the signal level variations will have no effect on the audio output, needed that the signal does not drop to a level where the receiving device is not able to cope.
  • Application of modulation is very easy for the transmitter at a low power stage. 
  • Possibility of using efficient RF amplifiers with FM signals. 

Everything has its own pros and cons some of the FM’s cons are listed below;

  • FM has poor spectral efficiency.
  • Requirement of a more complicated demodulator.
  • Higher data spectral efficiency in some other modes.
  • Infinite extension of the sidebands to either side. 
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