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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.
FM signals can be generated using direct frequency modulation, which are achieved by inserting a message directly into a voltage-controlled oscillator, or by indirect modulation, which is achieved by combining a message signal to produce a phase modulated signal, and used to modulate a crystalline oscillator.
There are various Cases of using Frequency Modulation which include FM radio broadcasting, magnetic tape-recording systems, monitoring new-borns for EEG, radar, seismic prospecting, audio synthesis, telemetry, dual-mode radio systems, and Video-transmission systems.
Frequency Modulation equation
In General the, Frequency Modulation Equation is given by:
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 Communication System
There are two different types of frequency Modulation used in communication: analog frequency modulation and digital frequency modulation.
In analog modulation, a continuously changing sine wave modulates the data signal. Three descriptive features of a carrier wave- frequency, amplitude, and phase are used to create AM, PM, and Phase Modulation. Digital modulation, separated by Frequency Shift Key, Amplitude Shift Key, or Phase Shift Key, work in the same way as analog, however when analog modulation is commonly used for AM, FM, and short-wave broadcasts, whereas digital modulation consist transmission of binary signals (0 and 1).
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.
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:
Where, Δf = Maximum frequency deviation of the carrier signal
Advantage of Frequency Modulation
All the power transferred to the frequency modulation is useful whereas in the amplitude modulation, most power is in the carrier (which is useless).
The nearby station interruption does not occur in the frequency modulation.
High signal to noise ratio (S / N). In simple words, it has a less 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
Conclusion
Basically in this article we came to know that Frequency Modulation is another way to encode a signal to a carrier wave.
The wave amplitude remains unchanged but the carrier frequency is changed. This change is usually prevented, so the frequency changes over a small scale.
Any binary signal can be carried from source to any detector, where it can also be decoded into a string of 1 and 0.
In order to encode an analogue code, the frequency of the carrier must vary smoothly. Do this by addition process – the carrier frequency is added to the signal frequency to provide the converted or modulated frequency. To avoid difficulty, the amplitude of the signal first normalised.
