ECEN5533     Final Exam    13 December 2007 

1) A Binary PSK signal is transmitted over the link shown. Due to a mis- communication, the phase angle between the Logic 1 and Logic 0 signals is 145 degrees instead of the preferred 180 degrees.

1a) [25] Compute the P(BE) for this system. [Answer: 0.4627]

1b) [15] How much signal power is input to the MFD in this case? [2.754(10-15) watts]

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2) An 80 Kbps binary antipodal phase shifted keyed system has an Eb/No = 5.7, with No calculated based on the system temperature. Suppose this system is being used by the military and is subjected to an enemy Band Limited White Noise jammer. This band-limited white noise jammer has the effect of raising the antenna temperature, and hence the system temperature, by a value of Tjammer. The signal power picked up by the receiving antenna is known to be 1 microwatt.

[35] Compute the amount of jammer noise power that must be picked up by the antenna in order for the P(Bit Error) to be degraded to 0.01. [194.3 nano watts]

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3) You are a staff engineer in the FEC Coding Division of MegaMoron Communications, Inc. You have been tasked to develop a (X,3) linear block code capable of correcting 2 errors.

[20] Determine a generator matrix G (there are many possibilities) for a linear block code that will meet this criterion. [Note: An optimum choice is not an issue here. Just find one that works.]

[20] If your code is used on a system that has a P(Code bit error) = 0.009 at the input to the receiver's FEC decoder, compute the P(data word error). [3.932(10-5)].

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4) A Linear Time Invariant filter has output y(t) = x(t) + 0.5x(t-0.1). If this filter is subjected to band-limited white noise with power spectral density GN(f) = 5.5; |f| < 8 Hertz...

[35] Compute the noise bandwidth of the filter. [3.771 Hertz]

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