Wavetek 3000 - Unleveled Light Driver; M172 - Sweep Drive;DAC

,PF
FROM
/Yl9 kv
PIN
O/OOE
ATTENUATO
.q
" S
UNG FVEL EO "
L
AS NT
0 .4l VER
TO L /LINT ON
MJETENP B0 .4k'D
3 .8 .3
"Unleveled" LightDriver
3 .9
M172 - SWEEP DRIVE/DAC
WlOE BANp
AMPG l
FlEQ
401r1 - EREN7 -
1A1
AMP
When the
differential amp in the leveler
circuit is putting out a voltagewhich
would cause the PIN diode attenuator to
be at its high or lowresistance limit,
the levelingcircuit can no longer be
effective . The above voltage levels,
which are applied to the unlevel light
driver, are adequate to turn on a source
of current for the indicator which ap-
pears through the front panel .
This module provides two output voltages .
One is linear from 0 V to -5 V as the
frequency goes from 0 to 39 MHz, re-
peating every 40 MHz ; the othervaries
from +7 V to -8 V as the frequency goes
from 0 to 520 MHz . The second voltage
is shaped to linearize the VCO in the
M9W Sweep Oscillator .
s
(''EFERENCE)
L E VEL
CONTROL
F .QOM /LIFTER BGARO
Figure 3-13
.
M10W - Output
Amplifier
THEORY OF OPERATION
lwCi/Vl TO .Q
OIOGE
-~ O4/~rPUT
MO AASSIYE
STEP ArrrArkA1TOR)
Two digital-to-analog converter ICs,
programmed by the front-panel Lever/
Indicator switches, provide the 0 to 520
MHz voltage . This is shaped in the next
section of the module . A third DAC pro-
vides the repeating 0 - 40 MHz voltage .
Since the state of the 20's line depends
on the 100's line, the 20's line is in-
verted when the 100's line is high .
The analogtuningsignal from the M172
is "shaped"before driving the M9Wwide
oscillator . The shaper is an inverting
DC amplifier which
amplifies
the input
by a
smaller factor for smaller magni=
tude inputs . Shaping this
analog voltage
compensates for the non-linear change
in capacitance of the varactordiodes
in the oscillator circuit .
3-13