Reflection Coefficient - Agilent Technologies 8719D User Manual

REFLECT
Reflection coefficient (I' ) magnitude is optimally 1.0, but need not be
q
known.
Phase of P 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 deRnition
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.
•I ZO of the line establishes the reference impedance of the measurement
LINE/MATCH
(i.e. &I= S22 = 0). The calibration impedance is defined to be the same as
50 Q), the SYSTEMS ZO selection under the TRLLRM 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 (200 and 160°) f n x 18OO. Measurement uncertainty will increase
significantly when the insertion phase nears 0 or an integer multiple of 1800.
•I Optimal line length is l/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/Iine pair is 8:l (frequency spamstart
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 specked within
q
LINE/MATCH
q
q
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,
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.
Application and Operation Concepts