Agilent Technologies 8753ET User Manual page 439

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.
•  must be identical on both ports.
• If the reflect is used to set the reference plane, the phase response must be
well-known and specified.
LINE/MATCH 
(LINE) • Z
0
= 0). The calibration impedance is defined to be the same as Z
known but not the desired value (i.e., not equal to 50 ), the SYSTEMS Z
under the TRL/LRM options menu is used.
• Insertion phase of the line must not be the same as the thru (zero length or non-zero
length). The difference between the thru and line must be between (20 and 160)  n
x 180. Measurement uncertainty will increase significantly when the insertion phase
nears 0 or an integer multiple of 180.
• Optimal line length is 1/4 wavelength or 90 of insertion phase relative to the thru at
the middle of the desired frequency span.
• Usable bandwidth for a single thru/line pair is 8:1 (frequency span:start frequency).
• Multiple thru/line pairs (Z
to the extent transmission lines are available.
• Attenuation of the line need not be known.
• Insertion phase must be known and specified within  1/4 wavelength or  90.
LINE/MATCH 
(MATCH) • Z
0
•  must be identical on both ports.
Fabricating and defining calibration standards for TRL/LRM
When calibrating a network analyzer, the actual calibration standards must have known physical
characteristics. For the reflect standard, these characteristics include the offset in electrical delay (seconds)
and the loss (ohms/second of delay). The characteristic impedance,
calculations in that it is determined by the line standard. The reflection coefficient magnitude should
optimally be 1.0, but need not be known since the same reflection coefficient magnitude must be applied to
both ports.
The thru standard may be a zero-length or known length of transmission line. The value of length must be
converted to electrical delay, just like that done for the reflect standard. The loss term must also be
specified.
The line standard must meet specific frequency related criteria, in conjunction with the length used by the
thru standard. In particular, the insertion phase of the line must not be the same as the thru. The optimal line
length is 1/4 wavelength (90 degrees) relative to a zero length thru at the center frequency of interest, and
between 20 and 160 degrees of phase difference over the frequency range of interest. (Note: these phase
values can be N  180 degrees where N is an integer.) If two lines are used (LRL), the difference in
electrical length of the two lines should meet these optimal conditions. Measurement uncertainty will
of the line establishes the reference impedance of the measurement (i.e. S
0
of the match establishes the reference impedance of the measurement.
TRL*/LRM* Calibration (ES Models Only)
assumed identical) can be used to extend the bandwidth
OFFSET Z0
Operating Concepts
= S
11 22
of the line. If the Z is
0 0
selection
0
, is not used in the
7- 71