7- 70
Operating Concepts
TRL*/LRM* Calibration (ES Models Only)
for their effects. Although the fixed attenuators improve the raw mismatch of the network analyzer system,
they also degrade the overall measurement dynamic range.
This effective mismatch of the system after calibration has the biggest effect on reflection measurements of
highly reflective devices. Likewise, for well matched devices, the effects of mismatch are negligible. This
can be shown by the following approximation:
Reflection magnitude uncertainty = E
D
+ E
R
S
11
+ E
S
(S
11
)
2
+ E
L
S
21
S
12
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.
Typ es 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 magnitude is optimally 1.0, but need not be known.
•Phase of must known and specified to within 1/4 wavelength or 90. During
To Next Page
Loading...
Need help?
General
