Effects of Predistortion on Linearized Transmitter Design for Videoconferencing Channel
M.E., Department of Electronics & Communication, L.J.Institute of Engineering and Technology, Gujarat, India
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In this paper usingPredistortion technique for reducing distortion in the Videoconferencing channel. QPSK modulation is widely used technique in communication system whenever any data travelling through the channel it gets the AM/AM and AM/PM distortions .Predistortion is the technique in which if we know the channel response then We can create the inverse response of it and applying before the nonlinear PA in the transmitter side combining both response and travelling through the channel we can get good linearity and better performance at the receiver side. Earlier Predistortion is designed by using the Active Circuit and It can be made using passive circuit. For Pulse Shaping requirement Raised Cosine filter which is more suitable and adjustable shaping curve sharpness by changing roll off factor which nullify the effect of ISI .Non-linear Saleh Model is used for reducing AM/AM and AM/PM distortion. For Simulink purpose The channel is Distorted the Eye of it is Closed in the Eye diagram but after applying the Predistortion technique when we see the Eye Diagram of it Open Eye Which introduce the less ISI .