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Problem HH15.2
The figure below shows a basic phase detector.
An analog signal passes through a linear amplifier whose gain is reversed by a square
wave “reference” signal controlling an FET switch. The output signal passes through a
lowpass filter, RC.
Let’s assume we apply a signal E
s
cos(
ω
t +
φ
) to the phase detector with transitions at the
zeros of sin
ω
t, i.e. at t = 0,
π
/
ω
, 2
π
/
ω
etc. Let us further assume that we average the
output, V
out
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Unformatted text preview: , by passing it through a lowpass filter whose time constant is longer than one period: τ = RC >> T = 2 π / ω Then the low pass filter output is E s cos( " t + # )  $ / % E s cos( t + )  / 2 / where the brackets represent averages, and the minus sign comes from the gain reversal over alternate half cycles of V ref . Show that V out = " (2 E s / )sin by doing the integrals and assuming unity gain for the amplifier...
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This note was uploaded on 07/25/2008 for the course PHY 440 taught by Professor Abolins during the Spring '06 term at Michigan State University.
 Spring '06
 ABOLINS
 Electronics

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