the input to a frequency translation system has a bandwidth

the input to a frequency translation system has a bandwidth of 19 to 20 Mhz and it is desired to shift the spectrum to the range of 50 to 51 Mhz while reversing the spectral sense. determine the required frequency in Mhz of the LO frequency.

please show with steps.

Solution

The mixer frequency(Fm) have two frequency componenets that iare Fi+FL and Fi-FL, where Fi is in put frequency and FlL is local oscilator frquency

Fm=51 Mhz

Fi=20Mhz

FL=Fm-Fi=51-20 Mhz

so required local osc frequency is 31 mhz