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Theory of
Opera0on
-
4g4[l4g4Ap
Servlce,
Vot.
1
Tune
Amplilier
..
Thg
FET-input
operationat
amptifier
(Ui034)
takes
the
output
of
the
phasefrequency
d€tector,
amplifies
tJre
gqgr
and
supplies
an
appropriate
tune
vottage
to
the
1O0
MHz
voltage
controlled
oscillator.
The
tun€
ampliller,
with
feedback
components
c1031,
c1o3g,
Rl028,
and
Rl029,
determine
the toop
transfer
charac-
teristics.
The
toop
dc
gain
is very
high
which
takes
advantagg
of
the
high
accuracy
of
tire
internal
or
exter-
nal
references.
The
loop
ac
aain
(determined
by
ClOgl)
rolls off
very
quickly
so
any
phase
noise,
on
an
external
reference
signal,
is
not
amplified.
Lock
Detector
U1012 is
used as
a
tune
volts
window
detector.
R1013,
R1012,
and
R1011
set
the
upper
threshotd
at
11
V6s,
and
the
lower
threshold
at
2 Vo".
As long
as
the
tune
volts stays
within
these
limits,
d trigtr
output
tells
the
processor
that
the
3rd Lo
loop
is locked.
A
low
output
from
Ul012, indicates
that
the reference
oscilta_
tor frequency
is
beyond
the
Ord LO's
tune
range.
This
REF
LOCK
status line,
along
with
the othEr
two
proc€s_
sor
interface
lines,
is routed
through
thE
Swe€p
board
for
processor
interrupt generation.
The
processor
r€ads
the
lines
and
displays
their status
on
th€ crt
r€adout.
t
o
O
o
o
a
a
I
a
o
o
I
a
o
o
o
o
t
O
a
o
a
o
o
o
o
o
o
a
,
o
o
o
a
t
o
o
a
t
o
o
o
o
o
7-22