HP 83487A, Руководство пользователя, Страница: 75 / 98

5-7
Reference
Measuring High Power Waveforms
Average power measurements are made independent of the amplifier in the
optical receiver and are accurate up to an average input power level of 500
µ
W
or –3.0 dBm (2000
µ
W peak power input).
If overshoot is present, the correct level of attenuation is the difference
between the average power and –10 dBm. For example, a –3 dBm average
power signal would require 7 dB of attenuation (–3 dBm minus –10 dBm =
7 dBm, which requires a 7 dB attenuator). This is based upon the assumption
of a worst case overshoot of 100%. The end result is that the maximum peak
signal at the instrument input must be below 400
µ
W (–4 dBm). Again, this is
peak power and should not be confused with average power. Attenuation is
not required for signals that do not exceed 400
µ
W peak. Table 5-1 on
page 5-8 shows the conversion from average power to peak power when the
overshoot is 100% (the peak power is double the “1” level power), and the
attenuation needed to make measurements for power levels of these magni-
tudes. Note that the current maximum average power allowed by the stan-
dards is –5 dBm.
Average power can be measured directly using the internal power meter of the
HP 83487A, by pressing: blue Shift key, More meas key on the numeric keypad and then
the
Avg Power softkey. Then select the data to be reported in dBm.