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Al
IA4
Al
lA4
YIG-Tuned
Oscillator
(YTO)
Phase
Detector,
Circuit
Description
The
AllA
YTO Phase Detector compares the frequency and phase of the
AllA
Sampler
IF signal to the output of the A10
20/30
Synthesizer Loop. The resultant error signal is
integrated, amplified, and applied to the A21 FM Coil Driver where it is routed to either the
main coil (dc path) or FM coil (ac path) of the
AllA
YTO. This tunes the YTO frequency
the proper amount in the proper direction to maintain phase lock.
70
MHz
LPF
@
The output of the
AllA
Sampler (IF IN) is passed through a 70 MHz LPF to remove any
unwanted frequencies which may have been introduced during the sampling process.
Limiters
@
and
@
and
Divide
by
Twos
@
and
@
Each of the two input signals (IF IN and
20/30
IN) are passed through a limiter to
establish ECL signal levels. Each signal is then divided by two before being applied to the
phase/frequency detector. This lowers the frequency at which the detector must operate.
Phase/Frequency Detector
0
and
1.5
MHz
LPF
@
The two input signals (IF IN and
20/30
IN), after being divided by two, are applied to Phase
Frequency Detector U3. The function of U3 is to output a pulse which is related to the phase
difference of the two input signals. The width of this pulse is directly proportional to the
amount of phase difference. If the IF signal leads the
20/30
signal, a negative pulse appears at
U3 pin 3
(TP3),
the width of which is proportional to the amount of phase difference. If the
20/30
signal leads the IF signal, a negative pulse appears at U3 pin 12 (TP2). In each case,
the other output is an ECL high (approximately -0.6 V). If the inputs are in phase, one of
the detector outputs is an ECL high (approximately -0.6 V)
with narrow negative spikes and
the other just an ECL high. The detector outputs are averaged in the 1.5 MHz LPF before
being applied to the differential amplifier.
Differential
Amplifier
GiJ
The detector outputs are applied to Differential Amplifier Q4. The output of this differential
amplifier is directly related to the phase difference of the IF IN and
20/30
IN signals.
AllA
1