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Unformatted text preview: ECE 561 Digital Communications Systems MATLAB Tutorial #4 In this tutorial we will: Generate Raised Cosine Pulses Generate Duobinary Pulses Create Eye Diagrams Raised Cosine Pulses Construct the Simulink model shown below. The Raised Cosine Transmit Filter is found in the Comm Filter Library of the Communications Blockset. Random Integer Generator: Set the M-ary number to 2 (binary data) and the sample time to 1E-3. This will generate data at a rate of 1Kbps. Unipolar to Bipolar Converter: Set the M-ary number to 2. Raised Cosine Filter: Set the filter type to Normal, the Group delay to 4, the Roll-off factor to 0 (creates a Sinc pulse) the Framing to Maintain input frame size, the Upsampling factor to 50 and the User Specified Filter gain to 1. The upsampling will provide an output with 50 samples per bit so that the output waveform has better resolution. Configuration Parameters: Set the stop time to 10E-3 (10 bits) and perform a discrete, fixed step simulation. Simulate the model. The scope displays will be similar to those shown below. Note that the output of the raised cosine filter has its first peak around 5 ms. This is due to the fact that the group delay was set to 4. The first bit occurs at 1ms. Adding on an additional 4 symbols (or 4ms) of delay means that the initial 1 will appear at 5 ms. The random bit pattern that is generated and shown in the first output display is: 1 0 0 0 1 1 1 1 1 0. Due to the 4 symbol delay, only the first six bits are displayed at the output of the filter. In order to confirm that the samples of the filter output are exactly equal to the input bit pattern values we can superimpose the values on the output curve. This must be done in MATLAB....
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This document was uploaded on 02/27/2010.
- Spring '09