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Section
lli
Paragraph 3-21
and source impedance is lower than that of
Model 4436A, two series resistors may beused
between source and attenuator as shown in
Figure 3-6. The resistor value should be half
of the difference between Model 4436A im-
pedance and source impedance. For example,
to match the Model 4436A to a 200 ohms
source requires two series resistances of 200
ohms each.
b.
Except for the condition stated in a.,a resistive
impedance - matching network or a matching
transformer should be used. Impedance match-
ing with matching transformer is shown in Fig-
ure 3-7. The transformer should possess good
balance and frequency characteristics at the
range of frequency to be used and proper input
and output impedances
equal to the source
impedance and the impedance of the Model
4436A. Also, insertion loss of the transformer
Model 4436A
should be small.
Impedance matching
with
matching network is shown in Figure 3-8. Re-
sistors used in the network should be deposited
film or carbon type. Also, better accuracy is
obtained if the network is enclosed in a shield-
ed container and connecting leads are kept
short.
3-21.
NEED FOR OUTPUT MATCH.
To maintain
the rated attenuation accuracy of the Model 4436A,
the impedance of the load must match the output im-
pedance of the Model 4436A. When the load also must
be terminated in its matching impedance, a matching
transformer or a resistive matching network
must
be used. When mismatch does not affect the load,
the required impedance match for the Model 4436A
can under some conditions be obtained by used of two
resistors. Conditions under which resistors can be
used and use
of
matching transformers and match-
ing networks
are discussed in the following para-
graphs.
SOURCE
MODEL
4436A
LOAD
3-4
SOURCE
OUTPUT
IMPEDANCE
~'""~-....1..
Z
SOURCE
OUTPUT
IMPEDANCE
z
600-Z
- 2 -
600 OHMS
IMPEDANCE
~~----------~~~
6000HMS
INPUT
IMPEDANCE
Figure 3-6. Simple Input Matching with Series Resistors.
MODEL
4436A
600 OHMS
IMPEDANCE
LOAD
6000HMS
INPUT
r-~~-----------+-oiMPEDANCE
Figure 3-7. Input Matching with Transformer.
MODEL
4436A
LOAD
600 OHMS
IMPEDANCE
6000HMS
INPUT
~~~----------~~JlMPEDANCE
Figure 3-8. Input Matching with Resistive Network.
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