, \
-
, ,
" ,
I Model
8730A
&
H'
Series'
, '
I '
/'
:/
r
'/
y
:",
," ,
, PERMANENT M1JUNTING ""': ''
"I
FO~6-32tapp"d,mounting
holes have been pro-
vided
for
mounting
purposes.
The
location'
of
these ,
holes and
the
I~VeraII
external.:dimensions 'of: )the 1
, PIN,Modulator l,are illustrated in Figure' 2.
,\
' '
.'/~~
'.
,
Also
on
tt,e
PIN
Modu
lator underside
are,
, the
foufco~er
retaining screws and the
PIN
diode retaining screws.
Any
moue-
J'
ment
olr
adjustment
of,
diode retaining
I '
"',
",
screuie
ioill cause permanent damage. "
PRINClfLES
OF
~PERATION
, !
The
PIN,Modulator
is a high-speed, current-con-
trolled 'absorption
type
attenuator. A simplified
,illustration
of
the
modulator
is shown in Figure
3."
Each PIN
unit
includes a low-passfilter, .two high-
pass' filters, a
number
of
PIN diodes" and a
50~ohm
'strip
transmission, line (ridged waveguide' in
the
,',
higher frequency
M,odeI8733,
8734,
and
8735
units).
The
PIN diode is a silicon
junction
diode whose P
and N trace regions are separated by a layer
of
in-
trinsic (I) semiconductor (silicon).
Thus
the
name
PIN diode.'
At
frequencies below
about
100 MHz
the
PIN,
diode rectifies
as,
a
junction
diode. How-
,
ever
at
,frequencies above
100
MHz, 'rectification
,,'
ceases-due
to
stored,charge
in
the
iritrinsicIl)
layer'
and
'the
diode
:;~cts
like a resistor by conducting
,
current
in"
both
directions. 'Thi,s equivalent resis-
tance is inversely proportional,
to
the
amount
of
,
charge
in
the
I' layer. An increase in forward bias
" current,
(current'
'at a negative voltage) increases
.'
, . \
!"
the
stored charge and decreases
the
equivalent re-
sistance
of
the
PIN diodes. When reverse bias is
applied,reverse
current
flows 'until stored charce.is
depleted
at which
time
equivalent resistance be-
comes
a maximum in
the
order
of
'thousands
of
"
\'
ohms.
,)
, ,
, ,
I '
\ '
a. Maximum
temperature:
149°F (+65°C)'.
, ,
, , ,
b. Minimum
temperature:
-40
o'F
(~~(fC).
'c. Humidity Maximum: 95%.
Environment.
Temperature
during storage
or
ship-
ment
should belimited as follows:
, "
Pin
Diodes in Shunt.
To
understand how a PIN
Mo~ulator
works, considerthe following:
the
PIN '
,di()l\~es
are'
mounted
as
shunt
elements between
the
"'UJl1':l'\~;ransmissiollpa~h
and ground.
The
transmis- '
,::sfQ~(\',I!path
hasu-eharacteristicimpedance
of,50ohms.
,
,:,'
\Vhe:n"
the
PIN'dinges are forward-biased,
the
equiv-
c. Wrap
instrumentin
heavy protective
paper"
alent: diode resistance is
about
30
ohms
and
most
to
avoid abrasion. ' , of;
Ifhe
,Hi"
energy':' is absorbed by
the
diodes in-
.stead
of
propagating down
the
50-ohm transmis-
sion p,ath.
'However,
when
the
diodes are 'reverse-
biased
'the
equivalent diode resistance is
in
the
'
\
.','
, .'
~
\'
, .',' " .
order
of
thousandsof
'ohms and
the
microwave,
, "
',',
I,
' "
,"""
\
.,'/:.
' ,
"I.
I,
• ': / " ,
b.
If
the'
original
carton
is
n~t
usable, a
do~ble.:
walled
carton
0(1.4
MPa
(200
lb/sq
inch) bursting'
I,
.'
_ ,\l
"I
,
strength should be used. ' ' '
STOR,AGE
AND
SHI,PMENT
,
,;.
.
INTRODUCYI'PN "
The
He~lett.Pa~kard
'8730 series
of
'PIN, modula-
tors'
are 'variable
RF
attenuators
whose
input
and
output
impedance is nearly
constant
for
all levels
of
attenuation.
The
8730,
PIN Modulators cover
the
coaxial range from 0.8
to
12.4
,GHz
in
four
overlapping
bandsin
addition
to
'X-band
ill
wave-
guide.
Two
models
are, available'
in,
each
band;
an
'~A"
model
'which'provides
at
least
35
dB
of
.at-
tenuation
range" arid
a.
"B'tmodel
which .provides
at
,least
80
dB,~
,Typbal
uses include pulsing" switch-
ing, leveling,
and
amplitude, modulating
of
RF sig- ,
naIs. Table 1 lists
complete
PIN Modulator speci-
fications.
,
Maximum
RF
Power.,
The
maximum.Input rating
(peak
or
CW),',
for
the
PIN Modulators
is'1
watt.
Excessive
RF
power
levels will cause internal
damage.
Maximum Bias
Input.
DC
voltage applied to
the
BIAS
input
must
not
exceed
+20
volts
or
-10
volts. '
Bxcessive
de
voltages
may
cause
internal
damage; ,
Packaging; \To'
protect
the
8730
PIN Modulators
during 'storage
or
shipmentv always use the
best
packaging'
methods
available.
The
following sug-
gested
steps:
can
be used
asa
guide
for
packaging.
\.
"
a.
The
~:i'liginal'
carton,
if
undamaged, can be
'reused. \
' '
" d.Place in carton, surrounded
by
at
least.
four
inches
of
tightly packed shock absorbing''material.
e.
Sealcarton
with
strongtape
.or
metal
bands.
,
,"
",
PRECAUTIONS
,,'
,
Page 2
, I
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