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Model 8730A &
H'
Series'
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, PERMANENT M1JUNTING
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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
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, PIN,Modulator l,are illustrated in Figure' 2. ,\ '
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, Also on tt,e PIN Modu la
tor
underside are,
, the
foufco~er
retaining
screws and the
PIN diode retaining screws.
Any
moue-
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ment
olr adjustment of, diode retaining
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screuie ioill
cause permanent damage. "
PRINClfLES OF
~PERATION
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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
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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
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a. Maximum temperature: 149° F (+65°C)'.
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b. Minimum temperature: -40
o'F
(~~(fC).
'c. Humidity Maximum: 95%.
Environment. Temperature during storage or ship-
ment should
belimited
as follows:
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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-eharacteristic
impedance of,50ohms.
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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
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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 '
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order of thousandsof 'ohms and the
microwave,
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b. If the' original carton is
n~t
usable, a
do~ble.:
walled carton 0(1.4 MPa (200 lb/sq inch) bursting'
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strength should be used. '
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STOR,AGE AND SHI,PMENT
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INTRODUCYI'PN
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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.
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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.
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a. The
~:i'liginal'
carton, if undamaged, can be
'reused.
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d.Place
in
carton,
surrounded by at least. four
inches of tightly packed shock absorbing' 'material.
e. Sealcarton with strongtape .or
metal
bands.
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PRECAUTIONS
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Page 2
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