Re: tuneable LO and fixed IF
Therefore,
(1)When BW(RF) = n1 * BW(IF), BW(IF)=n2 * FS(LO step), n1, n2 = 1,2,3,4..., the mixer ouput is just the fixed IF with the fixed BW(IF). And the IF filter is used to choose the signal channel. This case is the simplest!
(2) when FS(LO step)=1/n3 * BW(IF), n3 =2,3,4,5..., how is the LO tuned? The LO is tuned one step after the other step, or the LO should be tuned to the step around the f1(RF)+n*BW(IF)? In this case, How is the fixed IF determined. It is diffcult to choose the right signal channel by IF filter.
(3) what do the Frequency bands I, II, III, IV and V mean?