By appropriately modifying the MATLAB program in Appendix A, rework Example so that the filter is a raised cosine filter as described. Plot the direct channel and the quadrature channel signals at the filter output. Also plot the eye diagram. Compare the resulting eye diagrams with those illustrated. Use roll off factors of 0.5 and 0.7.
Example
In this example, several important signals present in a π/2 DPSK system are generated and displayed. The MATLAB program for simulating the system and generating the graphical output is given in Appendix A. Upon entering the program name, c8 pi4demo, at the MATLAB prompt, a menu is presented. From this menu the user may select one of the following seven options (after a plot is generated, hitting the space bar will display the menu so that another selection can be made):
1. Unfiltered π/4 DQPSK signal constellation
2. Unfiltered π4 DQPSK eye diagram
3. Filtered π/4 DQPSK signal constellation
4. Filtered π4 DQPSK eye diagram
5. Unfiltered direct and quadrature signals
6. Filtered direct and quadrature signals
7. Exit program (return MATLAB prompt)