Question

A carrier signal with unit amplitude and frequency fc1 = 50 kHz is modulated with a message signal
?1(?)=2cos(2??1?), where f1 = 15 kHz, to produce a DSB-SC signal. This DSB signal must be up-converted to a center frequency fc = 100 kHz.
a. Determine the image frequency of the DSB signal. [2]
b. An Upper-SSB signal with unit amplitude carrier at the image frequency calculated above also exists in the spectrum. The SSB signal is tone modulated with ?2(?)=4cos(2??2?), where f2 = 10 kHz. Write expressions for the magnitude spectra of the DSB and SSB signals. [9]
2
c. Sketch the double-sided magnitude spectrum of the DSB and SSB signals before frequency conversion. Clearly show all the amplitudes and frequencies of interest. [2]
d. Sketch the double-sided magnitude spectrum of the DSB and SSB signals after it is up-converted and passed through a bandpass filter with center frequency fc and bandwidth 40 kHz. [

Answer 1