參數(shù)資料
型號: HSMS-286L
英文描述: Surface Mount RF Schottky Detector Diodes in SOT-363(表貼型射頻肖特基檢測二極管(SOT-363封裝))
中文描述: 表面貼裝RF肖特基二極管檢測器采用SOT - 363(表貼型射頻肖特基檢測二極管(采用SOT - 363封裝))
文件頁數(shù): 6/12頁
文件大?。?/td> 96K
代理商: HSMS-286L
6
R
V
and C
J
are very difficult to
measure. Consider the impedance
of C
J
= 0.12 pF when measured at
1 MHz — it is approximately 1 M
.
For a well designed zero bias
Schottky, R
V
is in the range of 5 to
25 K
, and it shorts out the
junction capacitance. Moving up to
a higher frequency enables the
measurement of the capacitance,
but it then shorts out the video
resistance. The best measurement
technique is to mount the diode in
series in a 50
microstrip test
circuit and measure its insertion
loss at low power levels (around
-20 dBm) using an HP8753C
network analyzer. The resulting
display will appear as shown in
Figure 11.
I
3
-40
FREQUENCY (MHz)
-10
-25
3000
-20
10
1000
100
-35
-30
-15
50
50
0.12 pF
50
50
9 K
Figure 11. Measuring C
J
and R
V
.
At frequencies below 10 MHz, the
video resistance dominates the
loss and can easily be calculated
from it. At frequencies above 300
MHz, the junction capacitance sets
the loss, which plots out as a
straight line when frequency is
plotted on a log scale. Again,
calculation is straightforward.
L
P
and C
P
are best measured on
the HP8753C, with the diode
terminating a 50
line on the
input port. The resulting tabulation
of S
11
can be put into a microwave
linear analysis program having the
five element equivalent circuit
with R
V
, C
J
and R
S
fixed. The
optimizer can then adjust the
values of L
P
and C
P
until the
calculated S
11
matches the
measured values. Note that
extreme care must be taken to de-
embed the parasitics of the 50
test fixture.
Detector Circuits
When DC bias is available,
Schottky diode detector circuits
can be used to create low cost RF
and microwave receivers with a
sensitivity of -55 dBm to
-57dBm.
[1]
Moreover, since
external DC bias sets the video
impedance of such circuits, they
display classic square law
response over a wide range of
input power levels
[2,3]
. These
circuits can take a variety of
forms, but in the most simple case
they appear as shown in Figure 12.
This is the basic detector circuit
used with the HSMS-286X family
of diodes.
Where DC bias is not available, a
zero bias Schottky diode is used to
replace the conventional Schottky
in these circuits, and bias choke L
1
is eliminated. The circuit then is
reduced to a diode, an RF
impedance matching network and
(if required) a DC return choke
and a capacitor. This is the basic
detector circuit used with the
HSMS-285
a
family of diodes.
Output voltage can be virtually
doubled and input impedance
(normally very high) can be halved
through the use of the voltage
doubler circuit
[4]
.
In the design of such detector
circuits, the starting point is the
equivalent circuit of the diode, as
shown in Figure 10. Of interest in
the design of the video portion of
the circuit is the diode’s video
impedance—the other four
elements of the equivalent circuit
disappear at all reasonable video
frequencies. In general, the lower
the diode’s video impedance, the
better the design.
VIDEO
OUT
RF
IN
Z-MATCH
NETWORK
L
1
DC BIAS
VIDEO
OUT
Z-MATCH
NETWORK
L
1
DC BIAS
RF
IN
Figure 12. Basic Detector
Circuits.
The situation is somewhat more
complicated in the design of the
RF impedance matching network,
which includes the package
inductance and capacitance
(which can be tuned out), the
series resistance, the junction
[1]
Hewlett-Packard Application Note 923,
Schottky Barrier Diode Video Detectors.
[2]
Hewlett-Packard Application Note 986,
Square Law and Linear Detection.
[3]
Hewlett-Packard Application Note 956-5,
Dynamic Range Extension of Schottky Detectors.
[4]
Hewlett-Packard Application Note 956-4,
Schottky Diode Voltage Doubler.
相關PDF資料
PDF描述
HSMS-286P Surface Mount RF Schottky Detector Diodes in SOT-363(表貼型射頻肖特基檢測二極管(SOT-363封裝))
HSMS-286R Surface Mount RF Schottky Detector Diodes in SOT-363(表貼型射頻肖特基檢測二極管(SOT-363封裝))
HSMS-8205 Surface Mount Microwave Schottky Mixer Diodes(表貼型微波肖特基混頻二極管(成對分離))
HSMS-8207 Surface Mount Microwave Schottky Mixer Diodes(表貼型微波肖特基混頻二極管(四路振鈴))
HSMS-8101 Surface Mount Microwave Schottky Mixer Diodes(表貼型微波肖特基混頻二極管(單路))
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