Agilent Technologies 4294A Specifications download pdf (Page 70)

4-6-7. Electrical length compensation

In the lower frequency region, using the open/short compensation function can minimize most of

test fixture residuals. In the RF region, however, this is not enough to reduce the effect of the test

fixture residuals. The wavelength of RF frequencies is short and is not negligible compared to phys-

ical transmission line length of the test fixture. So, a phase shift induced error will occur as a result

of the test fixture, and this error cannot be reduced by using open/short compensation. The phase

shift can be compensated if the electrical length of the transmission line is known. As shown in

Figure 4-16, both the electrical length compensation and open/short compensation should be per-

formed after calibrating at the test port.

The electrical length compensation corrects phase error only and ignores propagation loss induced

error. This is only effective when transmission line (test port extension) is short enough to neglect

the propagation loss.

Note: Theoretical explanation for the effects of the electrical length and the compensation is given

in APPENDIX D.

Figure 4-16. Complete calibration and compensation procedure

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Agilent Technologies 4294A Specifications Page 70