Question

The purpose of a detector at the receiving end is
(A) to amplify signal
(B) to reduce its frequency level
(C) to modulate signal
(D) to demodulate signal

Answer 1

Hint: The detectors are present in electronic circuits known as the demodulators. A radio frequency signal which is coming from the transmitter has to be demodulated to remove the carrier frequency and receive back the original signal of low frequency.

Complete step by step answer:
A transmitter modulates a radio signal and redirects it in the form of an electromagnetic wave. The modulated radio signal consists of a carrier frequency along with its original frequency for it to travel large distances. A detector is a device that extracts information from a modulated radio frequency source. So at the receiving end, the detector is placed. It receives the modulated radio signal and then it removes the carrier frequency which is present in the modulated wave so that we get back the original wave which we had before modulation. So the main purpose of the detector at the receiving end is to demodulate the signal which it receives.

Additional NoteThe process of imposing an input signal over a carrier wave is called modulation. There are mainly three types of modulation, namely frequency modulation, amplitude modulation, and phase modulation. A modem is a device that can do both the modulation and demodulation.
Both the processes of modulation and demodulation aim at transferring information with minimum distortion and loss.

Note An envelope detector is a type of detector that can be used to demodulate a previously modulated signal by removing all high-frequency components of the signal. In a detector, a capacitor and a resistor form a low-pass filter to filter out the carrier frequency.