HP 435B - Ower Sensor

S ERV IC E S HEE T 2 (Cont'd)
Di od es A 4C R 1, C R 2, VR
1 a nd VR 2 a nd t h ei r assoc i ate d co mp o-
n e n ts a re par t of α s
h
a
pin g
n et
w o rk w h ic h co mp e n sates f o r t h e
non-linear bu t pu t o
f
t
h epo w e r sensor's po w e r se n s i ng d e vi ce . A t
RF inpu ts
n
ea
r
t
h e
m
a ximum po w er inpu t (100 m W f or M od e
l
8481 Α ), t
h
ep
o w
e
r
se
n s in g d ev ice i s s li g h t ly m o re ef fic i e
n
t a nd t
h
e
hybrid amplifier's
ga in i s r e du ce d s l
ig
h t ly to pr o vid e an o v e ra
ll
r es po n se t
h
at
i s lin ea r .
Th e co mbin at
i o n of A 4C5, R 8a nd R 9 i s o n e of t hr ee R C netwo rks
in t h e ac a
mpl ifie rs w hi c h d ete rmin e t h e hi gh fre qu e n c y c u to
ff
(240
Hz) o f t h
e 220
±20 Hz bandp ass . A 4C1, C6 a nd C30 a r e lin e
no i se
fi l te rs .
R ange
Switc h
Th e RAN G
E s wi tc ha nd assoc i ate d co mp o n e n ts on t h e
Α 4
a nd
Α 5
asse mbli
es f o rm two se p a r ate atte nu ato r n etwo rk s a nd α
l o w p ass
filter (t
h
e filter
i
s
s h o wn a nd di sc u sse d on Se rvi ce S
h
eet 3) .
W i t
h
hi
g h e r p owe r RF i n pu ts, r e l at iv e ly high vo
l
tages a
re
co upl e
d to t h e atte nu ato r inpu ts . Th e hi g h er t h ev o l tage
t h
e
m o re
it
i
s atte nu
ate d , t hu s a ll o win g f o r g r eate r se n sit ivi t y
n
ee
d
e
d f o
r
l o w p
o w e r m easure m e n ts whil e pr o vidi ng t h e
n
ee d e
d r eso lu t i on
f
o
r
eac
h r a n ge . Th e v a ri ou s l e ve l s o f atte nu at i o
np
e
rmi t te n
usa-
ble
r an gep os i t i o n s fro m 3
μ
W to 100 mW (full sca
l
e) .
Th e f o ll ow-
in g ta bl e s h o w s t h e individu a l a nd co mbin e
d e ffect o f t h e atte nu -
ato r s on t h e ac s i g na l .
Th e b a ndp ass o f t h e ac ampli fie rs in t h e P o
w
e
r M ete r i s a ppr o xi-
m ate ly 220±20 Hz . Th e l o w er c u to ff fr e que n c y (200 Hz)
i s
fixe
d
by
t h e co
mbi nat i o n o f A 4C7 w i t h A 5 R 1, A5 R 2 a nd A 4 R 19 ; also
A4 R 15
w i t
h
A 5 R 3, A 5 R 4, A 5 R 5 a nd A 4 R 20 .
RAN G E
Switc h
P ositio n
3
μω
10
μ
W
30 μ W
100
μ
W
300 μ W
1 M W
3m W
10 MW
30 m W
100 MW
N etwo rk #1
(A51`11, R2 and
ΜΑ 191
+
1
+
1
+1
+1
1000
1000
+
100 Ό
+ 1000
+
1000
1000
Atte nu at i on
N etwor k #2
(00,1`14,115
a nd A4 R
20)
+1
10
100
-
1000
+
10
100
1000
+
10
100
- 1000
Total
+1
+
101/2
10
10 3 /
2
10
2
. χ .
10
5 /
2
10 3
10
7
/
2
10 4
10 9 /
2