What is frequency modulation?

Frequency modulation is a method or process of encoding the data of a specific signal (analog or digital) by modulating the carrier wave frequency according to the frequency of the modulated signal. Modulated signals are nothing more than information or data that should be conveyed after being converted into electronic signals.

What is a principal Frequency modulation?

The frequency modulation index is mostly above 1, usually requiring a maximum bandwidth of 200 kHz. Eagle FM operates at a very high-frequency range between 88 to 108 megahertz. There are complex circuits with an infinite number of sidebands that assist in obtaining high-quality audio signals. At the same time, broadcast channels in the VHF phase of the frequency spectrum between 88.5 and 108 MHz typically use high deviation values ±75 kHz. This is known as the side-band Frequency Modulation index (WBFM). Although these signals support high-quality transmission they take up a large amount of bandwidth.

Generally, each wideband FM transmission allows the use of 200 kHz. On the other hand, communication uses very little bandwidth. Alternatively, the Narrow Band Frequency Modulation Index (NBFM) usually uses a 3 kHz deviation. In addition, narrow-band FM is widely used in two-way radio communication systems.

What is modulation?

This process of inputting a signal into a carrier is called modulation. Put another way; the frequency modulated of network operators to encrypt the data we intend to manage. Flexibility is like hiding code in the continuous wave of internet companies. The circuit used to generate AM is called a modulator. It has two inputs, a carrier, and a model signal, and the output is a modified signal. The amplitude modulation includes the carrier product and the switching signal.

There are three types of modulation, namely:

  • Frequency modulation
  • Amplitude modulation
  • Phase modulation

Amplitude modulation

It is a kind of change in which the signal height of the carrier is exchanged according to the message signal, while the phase and frequency always remain unchanged.

The length (i.e., intensity or thickness) of the carrier wave changes to represent the data added to the signal.
Amplitude modulation

Phase modulation

In this type of variable, the signal level of the carrier is adjusted according to the low-frequency signal of the message and hence it is called phase-locked flexibility.

The waveform of the carrier will change with the change of the data frequency. In PM, the frequency does not change, but the phase changes relative to the carrier's frequency.
Phase modulation

Frequency modulation

In this modulate, the frequency of the carrier signal is adjusted according to the message signal while maintaining the phase and amplitude. This is usually called frequency modulation.

The waveform frequency of the carrier changes to reflect the frequency of the data.
Frequency modulation

Method of Frequency modulation

Many methods can be used to produce direct or indirect signals.

Voltage-controlled oscillator or Varactor diode oscillator: A voltage-controlled oscillator can be used to perform Direct FM flexibility by feeding a direct message to the oscillator input. In the case of a varactor diode, we place this device within the adjusted circuit of the oscillator circuit.

Crystal oscillator circuit: The Varactor diode can be used inside a crystal oscillator circuit where the signal needs to be multiplied by volume, and only narrowband FM is available.

Closed section loop: This is an excellent way to produce signals for frequency fluctuations. However, the barriers within the loop should be carefully considered and once everything is stable it provides the best solution.

Type of signal in frequency modulation

The amplitude of the input signal increases, the carrier frequency will increase. when the input signal is too high, the carrier frequency is higher. At this time, if the amplitude of the modulated signal drops, the carrier frequency drops. This means that if the input signal is too low, the carrier frequency is the lowest.

Message signal

The signal that contains the message to be transmitted locally is called the message signal. The message signal is also known as the model signal or baseband signal. The first distance of the transmission signal frequency is called the baseband signal. A message signal or baseband signal enters a process called modulation before it is transmitted to a communication channel. Therefore, the message signal is also known as the model signal.

Carrier signal

A high-power or high-frequency signal that has characteristics such as amplitude, frequency, and phase, but does not contain information, is called a carrier signal. It is also called a carrier. The carrier signal is used to manage the message signal from the sender to the receiver. The carrier signal is sometimes called an empty signal.

Modulate signal

When the message signal is mixed with the carrier signal, a new signal is generated. This new signal is known as a modulated signal. The modulated signal is a combination of a carrier signal and a message signal.

Uses of Frequency modulation

  • Frequency modulation is a commonly use broadcast in FM broadcast. Each radio station has its frequency band and signals from all radio stations are broadcast by a single broadcast line.
  • The frequency modulation is used for the modem in our computer.
  • In the Magnetic Tape recording system, the Frequency Modulation method is used.
  • The Conversion Method is usually applied to the radio acquisition and flexibility system or in RADAR (radio detection and ranging).
  • Frequency variation is also used for multimedia data transmissions such as audio and video transmission. Most of the time the audio is broadcast on FM and sometimes the video is broadcast using the FM method.

Common Mistakes

Remember that, the direct method of producing FM, as the generation of the carrier is directly affected by the model signal, it is not easy to obtain high order stability in the carrier frequencies.

Context and Applications

In each of the expert exams for undergraduate and graduate publications, this topic is huge and is mainly used for:

  • Bachelor of technology in the electrical and electronic department
  • Bachelor of Science in physics
  • Master of Science in physics
  • Amplitude demodulation
  • Amplitude modulation

Practice Problems

Q1. Automatic Level Control (ALC) is used to keep the modulation index close to 100%.

(a) true

(b) false

Correct option: (a)

Explanation: ALC stands for Automatic Level Control. It is a technology used to automatically control the output power. It helps to save the output when there are different input changes.

Q2. Baseband compression produces ________.

a) a small range of frequencies from low to high

b) a small range of different phases

c) a small range of angles

d) a small range of amplitude

Correct option: (a)

Explanation: The signal compression method on the wireless network provides efficient transmission of compressed signal samples through the serial data link in the system. Baseband compression produces a small amplitude range.

Q3. A signal that ________ must have a linear power amplifier.

a) is complex

b) has variable frequency

c) is linear

d) has a variable amplitude         

Correct option: (d)

Explanation: If any signal has a variable amplitude, then its amplifier should be in line. Some may or may not have the same but may have non-linear amplifiers.

Q4. The carrier is suppressed in ________

a) a mixer

b) a frequency multiplier

c) a transducer

d) a balanced modulator

Correct option: (d)

Explanation: The mixer is the mixer of the frequency and frequency of the carrier. The transducer converts the signal from one form to another. The balanced modulator pressures the carrier and leaves only the side belts.

Q5. What is the full form of AFC?

a) Amplitude to frequency conversion

b) Automatic frequency conversion

c) Automatic frequency control

d) Audio frequency control

Correct option: (a)

Explanation: AFC stands for Automatic Frequency Control. This is a method of automatically keeping the resonant circuit tuned to the frequency of the incoming radio signal. It is used in the receiver to tune to the desired frequency.

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