1) One of the sidebands of an AM (DSB-LC) broadcast station is measured to have a power of 63 dBm. If the modulation is 100%, what is the total signal power in watts?
2) The input to an ideal (rectangular) lowpass filter is x(t) = 2 sinc(0.0005t). If the low pass filter's cutoff frequency is 5,000 Hz, what is the energy of the output signal?
3) A satellite is to receive signals on a frequency of 28.5 GHz and re-transmit them back to earth on a frequency of 12.5 GHz. Using a mixer:
a) What local oscillator frequency would you use? There are two possibilities. What is the alternate frequency?
b) For the local oscillator you selected, what transmission frequencies could cause interference to the satellite system and how could the interference be avoided? Show a diagram.
Answer to 3a:
Answer to part of 3b:
Interference can be avoided by filtering using a bandpass filter.