ECE 318: Assigned Homework: P 5.7.4

The DSB-LC signal

phi(t) = 3cos(10000*pi*t) + cost(1000*pi*t)cos(10000*pi*t) V

is present with additive white noise whose (two-sided) power spectral density is 1 microW/Hz. This signal-plus-noise is passed through an ideal low-pass filter with a bandwidth of 10kHz. Assume all resistance levels are 1 ohm.

  1. Compute the average S/N ratio at the output of the low-pass filter.
  2. A synchronous detector is used to demodulate the above signal. Compute the average S/N ratio if the output of the detector is filtered to 0 < f lt; 1 kHz
  3. An ideal square-law detector (i.e., the signal-plus-noise is multiplied by itself) is used to demodulate the above signal. Compute the average S/N ratio if the output of the detector is filtered to 0 < f < 1kHz

[eyes get very, very big]

Leave a Reply

Your email address will not be published / Required fields are marked *