Reflection Coefficient; The Trl Calibration Procedure - HP 8753E User Manual

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.
Requirements
THRU (Zero No loss. Characteristic impedance (ZO ) need not be known.
q
q &?I=
THRU
q
(Non-zero average impedance is used.)
Attenuation of the thru need not be known.
q
If the thru is used to set the reference plane, the insertion phase or
q
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
REFLECT Reflection coefficient (I' ) magnitude is optimally 1.0, but need not be
q
known.
Phase of I' must known and specified to within f l/4 wavelength or f 90'.
q
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 delinition
would show up as a 180° error in the measured phase.
q
If the reflect is used to set the reference plane, the phase response must be
q
well-known and specified.
LINE/MATCH
q
(i.e. Sll = &2 = 0). The calibration impedance is defined to be the same as
50 a), the SYSTEMS ZO selection under the TRL/LRM options menu is used.
Insertion phase of the line must not be the same as the thru (zero length
q
or non-zero length). The difference between the thru and line must be
between (20° and 1600) f n x 1800. Measurement uncertainty will increase
significantly when the
Optimal line length is l/4 wavelength or 90" of insertion phase relative to
q
the thru at the middle of the desired frequency span.
Usable bandwidth for a single thru/Iine pair is 8:l (frequency spanstart
q
frequency).
Multiple thru/line pairs (ZO assumed identical) can be used to extend the
q
bandwidth to the extent transmission lines are available.
Attenuation of the line need not be known.
q
Insertion phase must be known and specified within
q
LINE/MATCH
q
q
1 LO0
0
phase nears 0 or an integer multiple of 180".
insertion
Application and Operation Concepts
devices.