Agilent Technologies ENA Series

Chapter 7 89
Characteristics
SRL Measurement Uncertainty vs System Directivity
Table 7-1 Effect of Directivity on Cable Impedance for Z
DUT
= 74 Ohms
Directivity
(Logarithmic)
Refl. Coef.
(Linear)
Measurement
Uncertainty
ρ
m
Z
m
40 dB ±0.01 ±1.5 ohm −0.0167 72.5
+0.0032 75.5
45 dB ±0.00562 ±0.8 ohm −0.0123 73.2
+0.0011 74.8
48 dB ±0.004 ±0.6 ohm −0.0107 73.4
+0.0027 74.6
Z
m
75
1 p
m
+
1 p
m
–
---------------


=
ρ
m
ρ
DUT
0.01±=
ρ
DUT
Z
DUT
Z
0
–
Z
DUT
Z
0
+
-------------------------
=
ρ
m
0.0067– 0.01 Min–
0.0067– 0.01 Max+



=
ρ
DUT
74 75–
74 75+
------------------
0.0067–==