Bandwidth of Signals

Signals are pieces of information converted into an electrical form to be transmitted. Essentially, they are single-valued functions of time. This signal can be music, computer data, pictures or voice in a communication system. The different types of signals require different ranges of frequencies. 

The bandwidth of signals is the range of frequency over which a piece of equipment operates or the portion of the spectrum occupied by the signal. Every signal has its unique composition of frequencies. There are several methods of identifying these signals. The bandwidth of signals helps in the process of identifying these unique signals. 

The bandwidth of signals

The bandwidth of signals is the difference between the upper and lower frequencies of a signal generated. It is measured in terms of Hertz (Hz), the unit of frequency.

Let us compare bandwidth to water flowing through a pipe. So, the rate at which water (data) flows through the pipe (the connection) under several conditions is the bandwidth. Bandwidth can be represented by the amount of water that can flow through the pipe. The water which flows at the current time would be the current bandwidth.

A frequency band is the range of frequencies associated with a signal. The bandwidth of the signal is the difference between the highest and the lowest frequencies in this band. It is the property of the signal and has details of the information in the signal used to identify it. The cost of the transmission system increases with the number of bandwidth in a signal being transmitted.

Example:

1. 300 Hz to 3100 Hz of the frequency range is sufficient for speech signals.
2. A bandwidth of 20 kHz is required to transmit music.
3. 4.2 MHz of bandwidth is required to transmit pictures.
4.  20 Hz to 20 kHz is the audible range for humans.

For long-distance communication, smaller frequencies are used because the factor of weakening of the signals over long distances is low. So, the signal is transmitted and it remains unaffected. On the other hand, larger frequencies are used to transmit signals over a shorter distance. Though they are capable of carrying more information, they cannot be transmitted over a longer distance. 

Significance of bandwidth

Several ways make the knowledge of the bandwidth of signals important. The range of frequencies in which the signal has to be used can be identified through the bandwidth of signals. No distortion of the signal occurs in the process. Secondly, the amount of data that is to be transmitted can be identified by the bandwidth of signals.

Measurement of bandwidth of signals

Bandwidth portrays the contrast among upper and lower frequencies in transmission signals like radio signals etc., for preparing signals. It is a critical idea in a few technological fields. The bandwidth of signals is estimated in Hertz (Hz). Depending on the context, the bandwidth of signals is sometimes referred to as passband or base bandwidth. 

The limited frequency scope is required to run a signal processing system efficiently. The reaction of a system is flat within the band of frequencies and it drops off in bits outside of it. The boundary in a system’s frequency response at which the energy moving through a system decreases instead of going through is known as the cut-off frequency. 

The distinction between the upper and lower cut-off frequency is called the passband bandwidth. A baseband bandwidth is the highest system frequency. The bandwidth of signals in Hertz is the focal idea in several fields like hardware, radio, digital communications, the theory of information, etc.

The Bandwidth of Transmission Medium

A transmission medium is a medium through which signals are transmitted. The different types of transmission mediums have different types of bandwidth of signals. Wire, free space, fibre optic cable (750 MHz) and optical fibre (100 GHz.) are commonly used transmission mediums. 

Have a look at the allocation of the range of frequency band to several services in the table below – 

India used dial-up internet between 1900 and early 2000s. Its speed was sluggish. Nowadays we have faster internet as the infrastructure has changed massively. The most commonly used transmission media are wires. It offers a bandwidth of about 750 MHz. Over the air and free space, the transmission ranges from a few hundred kHz to a few GHz. Optical fibre offers a signal bandwidth of more than 100 GHz.

Conclusion

The concept of bandwidth is important to know the range of frequency and the amount of data transmitted at a particular time. While officially it is measured in Hertz, it is generally reported in bits per second (bps). Bandwidth might vary over time depending on the usage and the network connection. Hence we can say that a single measurement of bandwidth of signals can determine very little information about the actual bandwidth usage. Series of measurements prove to be more while determining the averages.