Wavetek 171 - Page 17

quency
is divided
by a multiple
of
10,
as
controlled
by the
FREQ
MULT
range switch,
and fed
to the function
generator
phase
lock loop (figure 4-1
).
A
10k
to 200
kHz
output is used
to
create
the F
N
signal
which
gives
rapid function
generator
response
to frequency
changes.
A one-shot
changes the
signal
to
fixed
width
pulses
whose spacing is
frequency
dependent.
These are
converted
to
a
frequency
dependent voltage
level
at
the
FA/
converter
output.
One pole
of the function
generator/synthesizer
mode
switch
furnishes
the
ground signal CLK
KILL.
CLK
KILL
stops
synthesizer
loop activity when
the instrument
is in
function
generator
mode
or
set on X
1,
a dial-only
range.
Lamps
in-
dicating
mode
are also controlled
by
this
CLK KILL.
TTL
BUFFER
(OPTION)
XTAL
OSC/
5V
-4
PHASE
REG
i
I.OOOOkHz DETECTOR
EXT/I
NT
REF
SELECTION
EXT
REF
IN
1.0000 kHz
1M
-
20 MHz
P- Ik
-20k L
*p
Lu
*
2N
l
^^prescalerF
CLK KILL
8M
-
20 MHz
0.1000-
1.9999
DIGITAL
_
SWITCH
~
N
=
0
-
3
7
•
SYNTHE-
SIZER
10k
-
200 kHz
-r
10
R
FREQUENCY
RANGING
SYNTHESIZER LOOP
FREQUENCY (REF)
FCTN
GEN
IIHL/IUM
1
Wn
SELECTOR
/T\
SYNTHESIZER
Figure
4-5.
Synthesizer
Phase Lock Loop