Concept of Bandwidth in Communication Systems


In this lecture, we are going to learn about the concept of bandwidth used in a communication system. We will learn the basic definition of bandwidth and then we will learn the concept of the frequency spectrum

Concept of Bandwidth

  • Bandwidth may be defined as the portion of the electromagnetic spectrum occupied by a signal.
  • We may also define the bandwidth as the frequency range over which an information signal is transmitted.
  • Bandwidth is the difference between the udder and lower frequency limits of the signal.
  • We already know different types of passband signals such as voice signals music signals, TV signals, etc. Each of these signals will have its own frequency range. This frequency range of the signal is known as bandwidth.
  • As an example, the range of music signals is 20 Hz to 15 kHz. Therefore, as shown in the figure, the bandwidth is (f2 – f1)
  • Thus, we write BW = f2 – f1 = 15000-20 = 14980 Hz
concept of bandwidth

The bandwidth of Different types of Signals

Sr. NoTypes of SignalRange of Frequency in HzBandwidth in Hz
1.Voice signal (speech) for telephony300 – 34003100
2.Music Signal20 – 2000019980
3.TV signal (picture)0 – 5 MHz5 MHz
4.Digital data300 – 3400
( If it is using the telephone line for its transmission)
Important Point: In fact, the required bandwidth in data transmission depends upon the rate at which the data is being transmitted. The BW increases with an increase in the rate of data transmission.

Concept of Frequency Spectrum

Frequency spectrum may be defined as the representation of a signal in the frequency domain. It can be obtained by using either the Fourier series or the Fourier transform. it consists of the amplitude and phase spectrum of the signal The frequency spectrum indicated the amplitude and phase of various frequency components present in the given signal. the frequency spectrum enables us to analyze and synthesize a signal.

Frequently Asked Questions on Bandwidth and Frequency Spectrum

Answer: In technical terms, bandwidth is a range of frequencies within a given band, particularly used for transmitting a signal. Frequency, on the other hand, is the number of cycles or oscillations that occur in a signal per second. Frequency helps to calculate bandwidth.

Answer: Bandwidth is a range of frequencies within a continuous set of frequencies. It is measured in Hertz. The purpose of a communication system is to transfer information from the transmitter which is located in one place to a receiver which is usually far away from the transmitter.

Answer: The bandwidth of a signal is defined as the difference between the upper and lower frequencies of a signal generated. As seen from the above representation, the Bandwidth (B) of the signal is equal to the difference between the higher or upper frequency (fH) and the lower frequency (fL).

Answer: The radio frequency spectrum is divided into small chunks for a huge number of applications, from AM and FM radio, television, and cellular networks to walkie-talkies, satellite communications, military applications, and even sending and receiving signals into outer space.

Answer: The spectrum of a signal is the range of frequencies contained in the signal. The bandwidth is the difference between the lowest and highest frequency in the spectrum. It is therefore the width of the spectrum and is a measure of the information-carrying capacity of the signal.

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