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Published byJolie Crosswell Modified over 2 years ago

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FM Demodulation v out kdkd fdfd f in Frequency Discriminator f d, k d v out f in

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Phase Locked Loop VCO f 0, k o, f 0 FM in LPF ~ 5 Hz Phase Error: v PM “Average” Phase Error Phase Demodulation

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Phase Locked Loop VCO f 0, k o, f 0 FM in LPF ~ 15 KHz v FM Frequency Demodulation

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Slope Detection FM IN = f c + f(t) fcfc ff AM Detector v FM

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Balanced Slope Detector FM IN fcfc ff AM Detector v FM fcfc ff AM Detector + _

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k C p L p CcCc LsLs +V1_+V1_ _V2+_V2+ CsCs R DC RFC + V p @ _ R DC + V out = |V A | – |V B | (2) _ VAVA VBVB |V A | V A = V p + V 1 = V p + V s /2 (1a) V B = V p + V 2 = V p – V s /2 (1b) |V B | Foster Seeley Discriminator Analysis V s = V 1 – V 2 V 1 = V s /2 V 2 = -V s /2 VpVp Redraw secondary circuit for Analysis @ High Frequencies Low Frequencies

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Find secondary voltage (V s ) as a function of Primary Voltage (V p ). LsLs CsCs R DC /2 V i = V p k(n s /n p ) R DC /2 +_+_ QuXTQuXT LsLs CsCs +_+_ XT/QsXT/Qs +VS_+VS_ Can neglect for high Q s Cannot neglect, or denominator will go to zero at resonance Simplify Secondary Circuit for RF: +VS_+VS_

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LsLs CsCs +_+_ XL/QsXL/Qs +VS_+VS_ V i = V p k(n s /n p ) (2) V out = |V A | – |V B |

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VpVp V s /2 -V s /2 VAVA VBVB VsVs

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Ratio Detector k C p L p CcCc LsLs CsCs R DC RFC + V p @ _ R DC V out VpVp

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Quadrature/Coincidence Detectors FM IN v out

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