2 18 solution a suppose that the rf input signal is

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Unformatted text preview: LO = fc + fIF , where fc is the desired carrier frequency: fi = fc + fIF ∓ fIF /3 fi = fc + 2fIF /3 or fi = fc + 4fIF /3. 2-18 Solution a. Suppose that the RF input signal is: sRF (t) = A cos(ωRF t) The signal at point a is sa (t) = sRF (t) cos(ωLO t) = A cos(ωRF t) cos(ωLO t) = 1 2 A{cos[(ωRF + ωLO )t] + cos[(ωLO − ωRF )t]} 1 The signal at point b is sb (t) = sRF (t) sin(ωLO t) = A cos(ωRF t) sin(ωLO t) = 1 2 A{sin[(ωRF + ωLO )t] + sin[(ωLO − ωRF )t]} The signal at point c is sc (t) = 1 A{− cos[(ωRF + ωLO )t] ∓ cos[(ωLO − ωRF )t]} 2 The upper sign applies when ωLO > ωR...
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