Filter
Top Products
a
o
I
o
o
o
o
o
o
t
o
I
a
o
o
o
I
o
a
a
I
o
o
o
o
o
I
o
I
o
o
o
I
a
?
o
O
o
a
o
o
o
I
a
Video
Leveling
. -A^mjnor
slope
in
frequency
response,
caused
by
the
1.86
GHz
low-pass
filter
in
the
front
end,
is
corr€cted
with
band
I
Slope adjustment
R1012.
Wiren
operatng
in
band
1,
contacts
6
and
7 of
U3025
are
closed;
therJ
forq
a
portion
of
the PRESELECTOR
DRTVE
signat
is
applied
to
the
VIDEO
I
output
signal,
providiig
the
ofiset
necessary
to correct
slope
difference.
Theory
of
Operaton
-
4g4AJ4g4Ap
Service,
Vol.
1
From
the
normalizer,
the output
is
applied
through
a
jumper
switch
to
buffer
amptifier
U2OS5B,
which
his a
gain
of
five,
then
to offs€t
amplifier
U2OSsA.
This
amplifier
has
a
gain
of
two, but
its
primary
purpose
is
to
offset
the 0
to +5
V
(normal),
0 to
-5
V-(invert),
buffer
output
to the
levels
required
by
th€ Log
Amplifier
cir-
cuits.
The
range
required
by
the Log
Amplifier
is
O
to
. J-0
V. The
output
voltage
is
a
seriss
of
linear
interpo_
lations
of
th€
voltag€
betwe€n
adjacent
trimming
reiis_
tors
at
the
outprrts
of
the normalizer.
Compensation
adjustment
R1065
sets
corect
interpolation.
Jumper
ptug
p2060
setects
the input
side
of
buffer
amplifi€r
U20558
and
proper
ofiset
vottage
for
U2055A.
This
provides
the
means
to
invert
the
buffer output
dur_
ing
the
instrument
adjustment procedure.
The
adjust-
ment
procedure
is
described
in
that
section
of
this
manual.
As
previously
noted, only
band 4 requires
significant
compensaflon.
Selection
of
band 4 is
indicated
by
data
bit
0
switching
to
a
1
(see
the
Lev€ling
tabte at
tire
top
right
_corner
of Diagram
24).
When
DBO
is
a
1,
pins
b
and
2 ot
switch
U201
5
are
connected,
and
the output
from
offset
amplifier
U205SA
is supplied
out
as
the
VIDEO
I signat.
Minor
compensation
is
required
for
Band
1,
to
correct
a minor
slope caused
by the 1.8
GHz
low-pass
filter
and
2
GHz limiter.
When
pins
6
and
7 of
switch
U3025
are connected,
the
PRESELECTOR
DRTVE
signal
is
ofrset
by
R4023
and
R4011
and
Band
Stope
adjust-
ment
R1
01
2 to
provide
an
attenuated
negative-going
ramp
to the VIDEO
I output
line.
Switch
Ug02S is con-
trolled
by
inverter
04025.
O402S
is activated
by data
bit
6
going
low. As shown
in
the Video
Blanking
table
on
the
schematic
diagram,
DB6 is
1 except
when
Band
1
is selected.
Video
Leveler
Circuits
.
Mdeo
leveling
comp€nsates
for
analyzer
front-end
microwave
circuit
characteristics
that
cause
unflat
response.
ln
band 4
(5.4
GHz
to 1g
GHz).
Since
band 4
is
a
multiplied
band,
any
unflatness
is
ac"entuatecl.
Leveling
is
accomplished
through
programmable
pertur-
bation
of
the
disptay
basetine
[trai
is
opposate
in
direc_
tion
to
the flatness
error.
As
the
signai power
output
decreases,
the
baseline
rises
an
equil
amount
to
com_
pensate,
and
as
power
output
increases,
the
baseline
falls
an
equal
amount.
.The
perturbation
is
produced
by
a normalizer
integrated
-circuit
that
produces
19
evenly
spaced
valu€s
of
the input
voltage,
with
each
valui
corrected
to compensate
for
unflatness.
The
PRESELECTOR
DRTVE
signat
from
the
tst
LO
driver
circuits
is
applied
to a
translation
circuit
that con-
sists
of
two
current
drivers
(U3O45A
and
hatf
of
e303g,
plus
U30458
and
the
other
half
of
e303g).
The
PRESELECTOR
DRIVE
signat
is
direcfly
r€tated
in
amplitude
to
displayed
analyzer
frequency.
The
nominal
+1
0V
to
-10V
gxcursion
voltage
versus
frequency
9urve1
in
maximum
span,
relates
to
the
full
bandwidth.
This
20
V maximurn
excursion
is
scaled
to a
precise
current
(from
1
mA
at
+10
v
to
o
current
at
_10
v)
that
is
applied
to
the
normalizer
lC
to
generate
the
baieline
perturbation.
Actual
signal
scaling
is
done
by current
driver
U3045A/Agmg.
The
outpui
signat
is
apptied
to
the
normalizer
SWp
lN
input,
pin
5 of
U20g9.
The
second
current
driver,
Ug04SB/Og03g,
generates
a
2 mA
reference
current
for
the
normalizer]
Horizontal
Freq
adiustment
Rl069,
in
the input
translation
circuits,
shifts
the 19 evenly
spaced
points
up or
down
in
fre-
quency
to compensate
tor
unflatness.
Normalizer
lC
U2039
operates
as
a shaper
and
con-
tains 19
transistors
that
turn
on
and off
in
sequence
as
the
current
input
to
pin
5
decreases
from
1
rnA
to
0.
Each
collector
is
connected
to
a
potentiometer
that
allows
output
trimming.
potentiometer
R1061
is
active
with
no
current,
and
R1013
is
acfive
at
I
mA.
The
trim_
ming operation
is
described
later.
Video
Filter
Gircuits
Video filtering provides
selection
of onE
of six
bandwidths,
under
microcomputer
control.
As
shown in
the
Vid€o Filter
table
on
Diagram
24,
data its 1
through
4 select
any
of six
bandwidths:
30
kHz,
3 kHz,
300 Hz,
30 Hz,
3
Hz,
and
0.3H2. Either
wide or
nanow-band
filtering
is
selected
at
the front
panel
(Wide
band
is
defined
as
1/30th of
the
selected
resolution
bandwidth
and
narrow
is
defined
as
1/30fth
of
the resolution
bandwidth).
The microcomputer
makes
the
selection,
based on
such
factors
as
sweep
rate and total
disper-
sion.
With
no video
filtering
(all
data bits are
0), the
video system
bandwidth
is
500
kHz.
7-37