FM Receiver Block Diagram with Explanation | New Topic

In this note, we are going to know about FM Receiver Block Diagram with Explanation PDF. Welcome to Poly Notes Hub, a leading destination for engineering notes for diploma and degree engineering students.

Author Name: Arun Paul.

What is FM Receiver?

A Frequency Modulation (FM) Receiver is an electrical system or device that detects, demodulates, and converts frequency-modulated radio signals into human-readable audio or data signals. It works by catching electromagnetic waves through an antenna, isolating a specific frequency using a tuning circuit, and then retrieving the original information—typically sound—from the modulated carrier wave via a demodulation process. FM receivers are widely used in a variety of communication systems, including commercial radio broadcasting, two-way radios, wireless microphones, and public address systems, since they have better sound quality and noise resistance than amplitude modulation (AM) systems.

Key Features of FM Radio Receiver

• FM receivers produce higher sound quality with less noise and distortion than AM receivers, particularly for music and conversation.
• FM signals aren’t as affected by amplitude noise (such as static and interference), leading in better reception.
• FM receivers have a broader bandwidth (usually ±75 kHz variation), allowing for improved quality and stereo broadcasts.
• Standard IF (10.7 MHz) makes tuning and filtering easier, enhancing selectivity and signal stability.
• FM receivers use fine tuning circuits, either analog or digital (PLL synthesizers), to choose selected stations properly.
• FM receivers, particularly in portable and mobile applications, are engineered to require less power.

FM Receiver Block Diagram with Explanation

Here is the block diagram of FM Receiver with Explanation –

• Antenna: The antenna receives frequency modulated (FM) radio waves from the air. These signals are often quite faint, with frequencies ranging from 88 MHz to 108 MHz. The antenna converts electromagnetic waves into electrical impulses, often in the range of a few microvolts (μV), as 2 μV in the diagram.
• RF Amplifier: The RF (Radio Frequency) amplifier boosts the weak FM signals picked up by the antenna. It ensures that the target signal is strong enough for subsequent processing while minimizing the impact of undesired noise. In this diagram, the RF amplifier’s output is increased to around 200 μV.
• Mixer: The mixer combines the RF amplifier’s output and the signal generated by the local oscillator. The goal is to change the frequency of the received signal to a specified intermediate frequency (IF), which is usually 10.7 MHz in FM receivers. This frequency conversion facilitates signal processing in following phases.
• Local Oscillator: The local oscillator produces a constant frequency signal, which is combined with the incoming RF signal in the mixer. The intermediate frequency (IF) is the difference between the local oscillator frequency and the RF signal frequency, and it is set at 10.7 MHz in this system. This stage is critical to obtaining frequency selectivity and stability.
• IF Amplifier: The Intermediate Frequency (IF) amplifier boosts the 10.7 MHz signal from the mixer. The use of a fixed intermediate frequency enables improved filtering and gain control. This stage guarantees that the signal is strong and clear prior to demodulation.
• Limiter: The limiter reduces amplitude changes in the FM signal that may have been caused by noise or interference. Because FM is based on frequency shifts rather than amplitude, this stage protects signal integrity and enhances noise immunity by clipping any amplitude spikes. The limiter normally outputs around 2 volts.
• FM Detector: The FM detector, sometimes referred to as a discriminator or demodulator, separates the original audio signal from the modulated carrier wave. It translates frequency fluctuations in the FM signal into voltage variations that indicate the audio data that was sent.
• AF Amplifier: The Audio Frequency (AF) amplifier amplifies the weak audio signal recovered by the FM detector to a level sufficient to drive an output device such as a speaker or headphones. This stage guarantees that the listener can hear the audio clearly and at the desired volume.
• Speaker: The speaker converts the amplified audio electrical signal into human-hearable sound waves. This is the FM receiver’s final stage, in which it receives and reproduces a transmitted radio signal.

FM Receiver Applications

Here we have listed some applications of FM Receiver –

• FM receivers are commonly used in commercial and public radio broadcasting to receive high-fidelity audio signals from FM radio stations, particularly in the frequency range of 88-108 MHz.
• FM receivers are standard in vehicle infotainment systems, allowing drivers and passengers to listen to music, get news, and check the weather while driving.
• FM receivers are used in walkie-talkies, police radios, and emergency service radios to provide dependable, short-distance voice communication.
• FM receivers are used to amplify signals from wireless microphones during stage performances, public speaking, and broadcasting.
• FM technology, while not commonly utilized for standard navigation, is used in several auxiliary communication systems in the aviation and maritime industries.