MEAS - Analyzer R&S ESCI
1166.6004.12 4.170 E-1
Measurement of Signal Amplitude Statistics
Digital modulated signals are similar to white noise within the transmit channel, but are different in their
amplitude distribution. In order to transmit the modulated signal without distortion all amplitudes of the
signal have to be transmitted linearly, e. g. from the output power amplifier. Most critical are the peak
amplitude values, of course.
Degradation in transmit quality caused by a transmitter two port network is dependent on the amplitude
of the peak values as well as on their probability.
The probability of amplitude values can be measured with the APD function (Amplitude Probability
Distribution). During a selectable measurement time all occurring amplitude values are assigned to an
amplitude range. The number of amplitude values in the specific ranges is counted and the result is
displayed as a histogram. Each bar of the histogram represents the percentage of measured
amplitudes within the specific amplitude range.
ADC
RAM
address
logic
read
write
clock
display
video
voltage
CPU
Fig. 4-16 Simplified block diagram for APD measurement
Fig. 4-17 Display of the amplitude probability distribution
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