A radio receiver performs three functions through the antenna; filtering, amplification and demodulation. It starts when the radio wave having a particular frequency passing through the air is captured by the antenna and the bandpass filter allows the specific frequency wave to pass on and restricts other frequency waves.
As the power of radio waves decreases with its square of the distance from the transmitting antenna, the amplification process occurs in which the amplifier circuit uses electric power to increase the amplitude of the signal received. Usually, a transistor is used as an amplifier in modern receivers. Sensitivity is the parameter used to measure the degree of amplification required by the radio signals.
The next process is demodulation, which is the extraction of useful information. It extracts the information carrying modulation signal from the modulated radio frequency carrier wave by the demodulator. Different demodulators are used for amplitude modulated signals and frequency modulated signals. The output of the demodulator is then amplified to increase its power and then converted back with the help of a transducer for the use of humans.