Boonton 4500B Peak Power Meter Manual do Utilizador descarregar pdf (Página 328)

Boonton 4500B RF Peak Power Analyzer

Application Notes

6-18

The value to use for calibration level uncertainty depends upon the sensor calibration technique used. If AutoCal



with FixedCal, the calibrator is only used as a single-level source, and you 

the FixedCal level, (0dBm, for most sensors). This may make FixedCal seem more accurate than AutoCal at some

levels, but this is usually more than offset by the reduction in shaping error afforded by the AutoCal technique.

Calibrator Mismatch Uncertainty. This term is the mismatch error caused by impedance differences between the



CAL

)



SNSR

) at the calibration frequency with the following equation:



CAL



SNSR

× 100 %

The calibrator reflection coefficient is a calibrator specification:

Internal 1 GHz Calibrator Reflection Coe

CAL

): 0.091 (at 1GHz)



SNSR

is frequency dependent, and may be looked up in the sensor datasheet or the

Boonton Electronics Power Sensor Manual.

Source Mismatch Uncertainty. This term is the mismatch error caused by impedance differences between the

                



SRCE



SNSR

) at the measurement frequency with the following equation:

Source 

SRCE



SNSR

× 100 %

The source reflection coefficient is a characteristic of the RF source under test. If only the SWR of the source is

known, its reflection coefficient may be calculated from the source SWR using the following equation:



SRCE

) = (SWR - 1) / (SWR + 1)



SNSR

is frequency dependent, and may be looked up in the sensor datasheet or the

Boonton Electronics Power Sensor Manual. For most measurements, this is the single largest error term, and care

should be used to ensure the best possible match between source and sensor.

Sensor Shaping Error.         -linearity in the

measurement after an AutoCal            



steps and is extended to all levels. Generally, sensor shaping error is close to zero at the autocal points, and

increases in between due to imperfections in the curve-fitting algorithm.

 be

identical at all frequencies. The published shaping error includes terms to account for these deviations. If your

measurement frequency is close to your AutoCal frequency, it is probably acceptable to use a value lower than the

published uncertainty in your calculations.

All peak power sensors use the AutoCal method only. The sensor shaping error for peak sensors is listed on the

Boonton Electronics Power Sensor Manual.

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