Importance of the Modulation IndexThe modulation index (also defined as the modulation factor) plays an important role in the quadrature amplitude modulation as it measures the extent of any variation of the non-modulated carrier signal. The depth or degree of the modulation is achieved with the help of the modulation index. The various components needed in the quadrature amplitude modulation are product modulator, 90-degree phase shifter, multiplexer, transmitter, receiver, low pass filter, etc. This type of modulation has an important application in the color televisions.
The significance of Communication Channels in Analog and Digital Communication SystemCommunication Channel- The communication channel is needed in any communication system whether analog or digital to pass the signal from transmitter to receiver. It is a physical medium to pass any types of the signal from the source to the destination.
There are mainly two types of the communication channel. They are termed as wirelines channel and wireless channel.
Some of the examples of the wire-lines communication channel are waveguides, optical fibers, copper cables, etc. And, the free space is the medium for wireless communication. Both wire-lines and wireless communication channel have a huge importance in any communication system.
The other three types of the communication channel are the channel with linear time-invariant filter, the channel with linear time-variant filter and channel with additive noise only.
1. Channel with linear time-invariant filter- In this type of communication channel, the linear time the invariant filter is placed at various components of the communication system to limit the bandwidth. In the channel with linear time invariant filter, such types of filter are placed at both input and output of the receiver and transmitter.
By placing such filter in the receiver and transmitter, there is a high chance of avoiding or reducing the interference from other nearby channels. This type of communication channel is best for the complex wireline channels.
2. Channel with linear time variant filter- The communication channel with the linear time a variant filter is best for the wireless channels where the multiple fading occurs. This multiple fading present in the wireless channels increases or decreases the signal level at the receiver point. This problem is totally addressed by introducing the linear time variant filter at the particular communication channel. The channel capacity, bandwidth, and signal-to-noise-ratio are important elements in the channel with linear time variant filter.
3. Channel with additive noise only- The channel with the additive noise only is best for the simple types the of wire-lines communication channel. It is due to the fact that this type of channel is normally operated at the low-frequency bands and the various elements in the particular communication channel is assumed to be constant i.e. no any further element is added nor the present element is removed. The certain amount of noise is only added to the particular signal.