What are analog and digital communications? Draw the basic block diagram of the transmitter and receivers.
Answer: Analog and digital communication
Analog communication is a type of communication in which the transmitted message or information signal is analog in nature. This means that in analog communication the modulating signal i.e. baseband signal is an analog signal. This analog message signal may be obtained from sources such as speech, video shooting, etc.
In digital communication, the message signal to be transmitted is digital in nature. This means that digital communication involves the transmission of information in digital form. The immunity to channel noise and external interference is better than analog communication.
Block diagram of transmitter and receiver :
- Radio transmitter: A radio transmitter consists of several elements that work together to generate radio waves that contain useful information such as audio, video, or digital data.
(i) Power supply: It provides the necessary electrical power to operate the transmitter.
(ii) Oscillator: It creates an alternating current at the frequency on which the transmitter will transmit. The oscillator usually generates a sine wave, which is referred to as a carrier wave.
(iii) Modulator: It adds useful information to the carrier wave. There are two fundamental ways to add this information. The first, called amplitude modulation or AM, makes slight increases or decreases to the amplitude of the carrier wave. The second, called frequency modulation or FM, make slight increases or decreases the frequency of the carrier wave.
(iv) Amplifier: It amplifies the modulated carrier wave to increase its power. The more powerful the amplifier, the more powerful the broadcast.
(v) Antenna: It converts the amplified signal to radio waves.
- Radio receiver: A radio receiver is the opposite of a radio transmitter. It uses an antenna to capture radio waves, processes those waves to extract only those waves that are vibrating at the desired frequency, extracts the audio signals that were added to those waves, amplifies the signals.
- Antenna: It captures the radio waves. Typically, the antenna is simply a length of wire. When this wire is exposed to radio waves, the waves induce a tiny alternating current in the antenna.
- RF amplifier: A sensitive amplifier that amplifies the very weak radio frequency (RF) signal from the antenna so that the tuner can process the signal.
- Tuner: A circuit that can extract signals of a particular frequency from a mix of signals of different frequencies. On its own, the antenna captures radio waves of all frequencies and sends them to the RF amplifier, which dutifully amplifies them all.
- Detector: It separates the audio information from the carrier wave. For AM signals, this can be done with a diode that just rectifies the alternating current signal.
- Audio amplifier: This component’s task is to amplify the weak signal that comes from the detector so that it can be heard. This can be done using a simple transistor amplifier circuit.