Question

The subsystems in an FM receiver are
A. Mixer
B. RF amplifier
C. Limiter
D. IF amplifier
Choose the correct sequence of subsystems in an FM receiver from the options given below:

• A. A, B, C, D
• B. A, C, B, D
• C. B, A, D, C
• D. C, B, D, A

Hint:

The basic signal path in a superheterodyne receiver is always: RF Amp \(\to\) Mixer/LO \(\to\) IF Amp \(\to\) Demodulator. FM receivers have the additional special stage of a Limiter right before the demodulator to remove AM noise.

Answer 1

The Correct Option is C

Step 1: Review the standard superheterodyne FM receiver's block diagram. The received antenna signal undergoes a specific process to isolate the original message.

RF Amplifier (B): This initial stage, a tuned Radio Frequency amplifier, boosts the weak antenna signal. It also provides preliminary selectivity, rejecting signals distant from the desired frequency, such as the image frequency.
Mixer (A): The amplified RF signal is then mixed with a local oscillator (LO) signal. This frequency conversion process down-converts the RF signal to a fixed, lower Intermediate Frequency (IF).
IF Amplifier (D): The IF signal is amplified through multiple stages. This section provides the majority of the receiver's gain and selectivity.
Limiter (C): Before demodulation, the FM receiver's IF signal passes through a limiter. This circuit eliminates amplitude variations, which are considered noise in FM systems, where information is conveyed through frequency variations. Removing these variations ensures high-quality output.
(Following the limiter are the FM demodulator/discriminator and the audio amplifier.)

Step 2: Establish the correct order.Based on the standard architecture, the correct sequence of the provided blocks is RF amplifier \(\to\) Mixer \(\to\) IF amplifier \(\to\) Limiter, corresponding to B, A, D, C.