Agilent Technologies E4445A PSA Series, Руководство пользователя, Страница: 35 / 74

Chapter 2 35
Measurement Concepts
Equations and Conversion Table
M
e
a
s
ure
m
en
t Conc
epts
Figure 2-2 Ranges and Relationships
Where: RL is the measured return loss value.
Note that a VSWR of 1 (sometimes referred to as 1:1) means that all of
the transmitted incident power is absorbed at the load and no power is
reflected back. (This assumes a perfect impedance match.) Similarly, an
infinite VSWR is for a perfect open or short, where all of the incident
power is reflected back.
Z
L
= 0 ,
∞
Load
(Z
L
- Device
Impedance)
Incident
Reflected
Z
O
- Transmission
Line Impedence
Z
L
=
Z
O
RL
ρ
SWR
∞
dB 0 dB
∞
1
1 0
ranges.vsd
VSWR
V
max
V
min
------------
1
ρ
+
1
ρ
–
------------
1 10
RL –
20
----------
+
1 10
RL –
20
----------
–
----------------------- = = =