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
The bandwidth of Different types of Signals
|Types of Signal
|Range of Frequency in Hz
|Bandwidth in Hz
|Voice signal (speech) for telephony
|300 – 3400
|20 – 20000
|TV signal (picture)
|0 – 5 MHz
|300 – 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