Frequency Drift

Minute changes in frequency accuracy and stability can occur as a result of temperature and aging (on the order of parts per million). If you require greater frequency accuracy, do the following:

w Override the internal crystal with a high-stability external source, frequency standard, or (if your analyzer is equipped with Option lD5) use the internal frequency standard.

Performance Verification

You should periodically check the accuracy of the analyzer measurements, by doing the following:

nperform a measurement verification at least once per year

Refer to the HP 8753E Service Guide for the measurement verification procedure.

Reference Plane and Port Extensions

Use the port extension feature to compensate for the phase shift of an extended measurement reference plane, due to such additions as cables, adapters, and Bxtures, after completing an error-correction procedure (or when there is no active correction).

Using port extensions is similar to using electrical delay. However, using port extensions is the preferred method of compensating for test fixture phase shift. ‘Ihble 5-l explains the difference between port extensions and electrical delay.

 

 

 

 

‘Ihble 5-1.

 

 

 

 

Differences between PORT EXTENSIONS and ELECI’IUCAL DELAY

 

 

i; ,, ._ ; _

; ;

;; /

 

 

 

 

 

 

 

 

 

 

:~~~~~~~~..

 

 

 

 

 

..__.

...................../....

......:::m

 

 

 

Bldn meet

 

The end of a cable becomes the test port plane

Compensates for the electrical length of a

 

 

for all S-parameter

measurements.

cable.

 

 

 

 

 

 

 

Set the cable’s electrical length x 1 for

 

 

 

 

 

transmission.

 

 

 

 

 

 

 

Set the cable’s electrical length x 2 for

 

 

 

 

 

reflection.

 

 

 

 

 

 

 

 

Meamrements

 

All S-parameters.

 

 

Only the currently selected Sparameter.

AlTected

 

 

 

 

 

 

 

EIectrical

 

Intelligently compensates for 1 times or 2

Only compensates for electrical length.

Compeneation

 

times the cable’s electrical delay, depending

 

 

 

 

 

on which S-parameter is computed.

 

 

 

 

 

 

 

 

:

............................i_

_.,

You cm a&v&e apoe extensionbypressing Lcal]~~~ ~~~~~~~~~~~~~~~~~~~~~.

::::.._

::::..:

iii....A.~;

~;....

~.~;;;._ .A

~..~..~~~~ .A

,...:.:.../:.: :,..:.

:..i..,, ......A.. ...........................................~

A.....A...A.... v~.;;;:

_..

Then enter the delay to the reference plane.

Optimizing Measurement Results 6 3

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HP 8753E manual Frequency Drift, Performance Verification, Reference Plane and Port Extensions