Need For Modulation

General Modulation is the process of converting data into radio waves by adding information to an electronic or optical carrier signal. A Carrier signal is one that has a constant waveform- constant height, or amplitude, and frequency.

Working of Modulation

Modulations are often applied to the electromagnetic signals: radio waves, laser / optics and computer networks. It can even be applied to a direct current that can be treated as a degenerated carrier wave with constant amplitude and frequency of 0 Hz – especially by turning it on and off, such as on Morse code telegraphy or digital current loop interface.

 A special case of no Carrier then a response message showing the attached device is no longer connected to the remote system and is called baseband modulation.

Modulation can also be applied to low frequency alternating current like 50-60 Hz as in the power line networking.

Types of Modulation

Frequency Modulation

Frequency Modulation is a modulation in which the frequency of the carrying wave is adjusted according to the instantaneous amplitude of the modulating signal, keeping the phase and the amplitude unchanged. Modifications to the wave frequency were used for the purpose of transmitting data or information over short distances.

Frequency Modulation index is always over 1, requires a maximum bandwidth of 200 kHz, operates at a very high frequency of 88 to 108 Megahertz, has a complex frequency with an infinite number of sidebands, and receives a high quality signal with high sound quality. Frequency and phase modulation are another principle of angle modulation, which are the class of frequency modulation which are used in telecommunication transmission systems.

Amplitude Modulation VS Frequency Modulation

Amplitude Modulation (AM) is a modulation in which the amplitude of a carrying wave is adjusted according to the instantaneous amplitude of the modulating signal, in which phase and frequency are the same. The modification of a wave amplitude happens for the purpose of sending data or information over long distances.

The Amplitude Modulation Index ranges from 0 to 1, requires a minimum bandwidth of 10 kHz, operates at medium frequencies and high frequencies from 535 to 1705 Kilohertz, has a simple circuit with only two sidebands, and receives low-quality signals with unsatisfactory sound level.

In general, FM and AM work in the same way, yet the way their carrier waves are modulated is different. With AM, signal strength varies to combine audio information. With FM, the current frequency at which the current changes direction per second of the carrier signal varies in order to incorporate audio information.

Frequency Modulation in Vibration Analysis

Vibration analysis is the process of measuring and analysing the levels and patterns of vibration signals or frequency of equipment in order to detect abnormal vibration events and assess the lifetime of the machine and its components. 

Vibration analysis is particularly important for rotating machines, where there are errors that can cause abnormal amplitude and frequency fluctuations. The demodulated process can directly detect these modulation frequencies and is used to retrieve information content from a modulated carrier wave.

Uses of Modulation in communication

Many carriers of different frequencies can usually be transmitted over a signal medium, with each carrier being modulated by an independent signal. For example, Wi-Fi uses individual channels to simultaneously transfer data to or from multiple clients.

The carrier signal is used to reduce the wavelength for effective transmission and reception. Because the optimum antenna size is half or a quarter of the wavelength, an audio frequency of  3000 Hz will require a wavelength of 100 km and a 25 kilometre antenna. Instead, using a 100 MHz FM carrier, of wavelength 3 meters, the antenna would only need to be 80 cm long.

Modulation Index of Frequency Modulation

The frequency modulation index describes how the frequency of the signal frequency and message signal affects the frequency of modulated (FM) signal frequency.

Or

Frequency modulation is usually defined as the ratio of highest frequency deviation of the carrier signal to the frequency of the message signal.

That is given by:

Modulation index=fm

 Where, Δf = Maximum frequency deviation of the carrier signal

Advantage of Frequency Modulation

1. All the power transferred to the frequency modulation is useful whereas in the amplitude modulation, most power is in the carrier (which is useless).
2. The nearby station interruption does not occur in the frequency modulation.
3. High signal to noise ratio (S / N). In simple words, it has a smaller amount of sound or noise.

Application of Frequency Modulation

There are some application of Frequency Modulation as:

• FM broadcasting
• Radar
• Magnetic tape recording systems
• Telemetry
• Two-way radio systems
• Music synthesis
• Seismic prospecting
• Video transmission systems

Use of Modulation

Generally the carrier wave used by radio frequency band (RF) transmission does not carry much information on its own. In order to include speech or data, another wave must be placed at the top of the carrier wave. This process is known as superimposition. 

Thus it changes the shape of the carrier wave. The process of doing so is called modulation. To transmit sound, the audio signal must first be converted into an electronic signal, using a transducer. After conversion, it is used to modulate a carrier signal.

Conclusion

Basically in this article we came to know that Modulation. Modulation is the process of encoding information from a source that is suitable for transmission. This is achieved by changing the characteristics of the waves. By placing the message above a high frequency signal known as a carrier wave (or sinusoidal signal), video, voice and other data can be transmitted.

In the modulation process, the parameter of the carrier wave (such as amplitude, frequency or phase) varies according to the modulating signal. This variation acts as a code for data transfer code.