User`s guide

7-73
Operating Concepts
TRL*/LRM* Calibration (ES Models Only)
Transmission magnitude uncertainty = E
X
+ E
T
S
21
+ E
S
S
11
S
21
+ E
L
S
22
S
21
where:
E
D
= effective directivity
E
R
= effective reflection tracking
E
S
= effective source match
E
L
= effective load match
E
X
= effective crosstalk
E
T
= effective transmission tracking
S
xx
= S-parameters of the device under test
The TRL Calibration Procedure
Requirements for TRL Standards
When building a set of TRL standards for a microstrip or fixture environment, the
requirements for each of these standard types must be satisfied.
Types Requirements
THRU
(Zero length) • No loss. Characteristic impedance (Z
0
) need not be known.
•S
21
= S
12
= 1 ∠0°
•S
11
= S
22
= 0
THRU
(Non-zero
length) • Z
0
of the thru must be the same as the line. (If they are not the same,
the average impedance is used.)
• Attenuation of the thru need not be known.
• If the thru is used to set the reference plane, the insertion phase or
electrical length must be well-known and specified. If a non-zero length
thru is specified to have zero delay, the reference plane is established in
the middle of the thru, resulting in phase errors during measurement of
devices.
REFLECT • Reflection coefficient Γ magnitude is optimally 1.0, but need not be
known.
• Phase of Γ must known and specified to within ± 1/4 wavelength or
± 90°. During computation of the error model, the root choice in the
solution of a quadratic equation is based on the reflection data. An error
in definition would show up as a 180° error in the measured phase.
• Γ must be identical on both ports.