Applications of Filters in Telecommunication Systems

Electronic filters have many applications in the telecommunication and data communications industry. For example, they are used in a multichannel communication system employing a technique known as time-division multiplexing (TDM). In this system, several channels are transmitted through a medium such as optical fiber or through a co-axial cable or waveguide. Multiplexing means combining several signals into one and this is accomplished in TDM by allocating time slots for each channel so that each channel is transmitted at a particular time. If the signals are synchronized correctly there will be no interference between them. At the transmitter end a multiplexer is used to combine the signals, while at the receiver end a demultiplexer is used to separate the original channels.

However, when the channel signals arrive at the receivers they have deteriorated in shape and amplitude. So as to clean them up, they are reconstructed by an integrator which sums up the incoming. Once this has been completed, a filter is used to pass wanted channel frequencies while attenuating the unwanted signals such as noise.

The combined functions of the integrator and filter cause the transmitted channels to be reproduced. In the illustration above, where three channels are involved, each filter will be designed to pass the particular channel and its related information hence a band of frequencies is passed by each filter.

Related: Basics of Radio Frequency (RF) and Wireless Communication Systems

Filters can also be used to pass frequencies below a certain frequency while attenuating all frequencies above it. Similarly, it is possible to construct a filter which passes all frequencies above a certain frequency while attenuating all frequencies below it.

Other filter applications include:

• Noise filtering
• Guard band separation of channels
• Harmonic reduction
• Boosting and cutting certain frequencies in the frequency spectrum
• Bandpass selection