Advertisement
Model 415E
Section III
Paragraphs 3-33 to 3-36
IF MINIMUM DOES NOT
SHIFT,LOAD EQUALS E0/SWR
Figure 3-8.
Impedance Measurement Rules Summary
3-32. LOAD IMPEDANCE MEASUREMENT.
3-33. GENERAL.
3-34. Slotted line techniques provide information to
allow calculation of a load impedance.
The following-
rules apply to the indications given by the voltage min¬
imum when the load is replaced by a short.
Figure
3-8
summarizes and graphically presents these im¬
pedance measurement rules. When the load is replaced
by a short, then:
a. The shift in the minimum is never more than
±1/4 wavelength.
d. Referring to Figure 3-9
and the following for
mulas, compute the normalized load impedance:
Normalized Zl =
1 - j(swr) Tan X
(swr) - j Tan X
where X =
180° (a Ad)
Ag
/2
b. If the minimum moves toward the load, the load
has a capacitive component.
c. If the minimum moves toward the generator, the
load has an inductive component.
d. If the minimum does not move, the load is com¬
pletely resistive and has a normalized value of 1/swr.
e. If the minimum shifts exactly one-quarter wave¬
length, the load is completely resistive and has a nor¬
malized value equal to the swr.
f.
The minimum will always be at a multiple of a
half wavelength from the load.
3-35. IMPEDANCE MEASUREMENT PROCEDURE.
3-38. The procedure for performing the actual im¬
pedance measurement with a slotted line is as follows:
a. Connect the load under test to the slotted line
section and measure the swr (see Paragraph 3-26 or
3-28). Also note the position of the probe carriage at
the minimum.
b. Replace the load under test with a short.
c. Locate the minimum with the line shorted.
A d
■
Figure 3-9.
Shift of Minimum with Load and Short
02152-2
3-7
Advertisement
