HP 8753E manual Load Match Em

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Figure 6-44. Load Match Em

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The measured value, SLIM, consists of signal components that vary as a function of the relationship between Esr and &A as well as ELF and f&2& so the input and output reflection coefficients of the test device must be measured and stored for use in the &IA error-correction computation. Thus, the test setup is calibrated as described above for reflection to establish the directivity, Enr , source match, Esr , and reflection frequency response, Em, terms for reflection measurements on both ports.

Now that a calibrated port is available for reflection measurements, the thru is connected and load match, ELF, is determined by measuring the reflection coefficient of the thru connection.

Transmission signal path frequency response is then measured with the thru COMected. The data is corrected for source and load match effects, then stored as transmission frequency response, Err.

Note It is very important that the exact electrical length of the thru be known. Most calibration kits assume a zero length thru. For some connection types such as Type-N, this implies one male and one female port. If the test system requires a non-zero length thru, for example, one with two male test ports, the exact electrical delay of the thru adapter must be used to modify the built-in calibration kit definition of the thru.

Isolation, EXF, represents the part of the incident signal that appears at the receiver without actuaIly passing through the test device (see Figure 6-45). Isolation is measured with the test set in the transmission configuration and with terminations installed at the points where the test device will be connected. Since isolation can be lower than the noise floor, it is best to

increase averaging by at least a factor of four during the isolation portion of the calibration.
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s	~~~~~~~ softkey under the (GJ menu allows a calibration sequence to
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resume after a change to the averaging factor.

If the leakage fails below the noise floor, it is best to increase averaging before calibration. In this case, ommitting isolation is better than measuring the isolation standards without increasing the averaging factor.

6-66 Application and Operation Concepts