In the transmission and receiving of amplitude modulation of a signal, following steps are required. Arrange these in correct sequence.
(A) Modulated signal is fed to an antenna after providing necessary power through power amplifier before transmission
(B) The signal is passed through a rectifier, followed by a envelope detector to receive the message signal
(C) The modulating signal is superimposed on high frequency carrier wave
(D) After receiving antenna the received signal is fed to amplifier and then passed through. If stage where carrier frequency is lowered
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (C), (A), (D), (B)
In an amplitude modulation system the message is first put on a high-frequency carrier and transmitted; at the receiver the carrier is brought down and removed to recover the message.
(C) The modulating signal is superimposed on high frequency carrier wave — the first step, done in the modulator.
(A) Modulated signal is fed to an antenna after providing necessary power through power amplifier before transmission — the power amplifier follows the modulator at the transmitter.
(D) After receiving antenna the received signal is fed to amplifier and then passed through. If stage where carrier frequency is lowered — the first step at the receiver; the IF stage lowers the carrier to an intermediate frequency.
(B) The signal is passed through a rectifier, followed by a envelope detector to receive the message signal — the last step, which recovers the message signal.
So the correct sequence is (C), (A), (D), (B).
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), and it also appears to be out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Summary – “… 5. Low frequencies cannot be transmitted to long distances. Therefore, they are superimposed on a high frequency carrier signal by a process known as modulation.”
Production of Amplitude Modulated Wave – “… The modulator is to be followed by a power amplifier which provides the necessary power and then the modulated signal is fed to an antenna of appropriate size for radiation as shown in Fig. 15.11.”
Detection of Amplitude Modulated Wave – “… The receiving antenna is therefore to be followed by an amplifier and a detector. In addition, to facilitate further processing, the carrier frequency is usually changed to a lower frequency by what is called an intermediate frequency (IF) stage preceding the detection.”
Summary – “… 13. AM detection, which is the process of recovering the modulating signal from an AM waveform, is carried out using a rectifier and an envelope detector.”
