HW4 - ECEN 661 Modulation Theory Homework#4 Assignment Date...

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ECEN 661 - Modulation Theory Homework #4 Assignment Date: 2/13/08 Due Date: 2/20/08 1. (Text 4.34, 4th edition) The information sequence is a sequence of iid random variables, each taking values with equal probabilities. This sequence is to be transmitted at base- band by a biphase coding scheme, described by . where is shown in the figure. (a) Find the PSD of . (b) Assume that it is desirable to have a zero in the PSD at . To this end, we use a pre- coding scheme by introducing , where is some constant, and then transmit the sequence using the same pulse shape. Is it possible to choose to produce a frequency null at ? If yes, what are the appropriate values and the resulting power spectrum? (c) Now assume we want to have zeros at all multiples of . Is it possible to have these zeros with an appropriate choice of in the previous part? If not, then what kind of precod- ing do you suggest to result in the desired nulls? 2. (Text 5.6, 4th edition) Consider the low-pass equivalent (complex valued) signal , , with energy .
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HW4 - ECEN 661 Modulation Theory Homework#4 Assignment Date...

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