Modern communications systems rely on increased signal complexity to
pack more data into each symbol transmitted. These complex signals can
result in data dependent, high peak-to-average power ratios requiring
amplifiers and related components with large dynamic ranges.
Oscilloscopes can help designers of such systems evaluate dynamic range
requirements by providing a method to measure instantaneous power on
very long data records. Measurement parameters can read the average and
peak power levels directly from the instantaneous power waveform. The
following example illustrates the techniques that can be used to measure
Figure 1 shows the in-phase (I) and
quadrature (Q) components of a 16-state quadrature amplitude modulated
(16 QAM) baseband signal in the channel traces 1 and 2, respectively.
The X-Y display shows the state transition diagram for the signal. There
are distinct average power levels corresponding to the three possible
combinations of the I and Q voltage levels of 0.58 and 0.18 V
Figure 1: Trace 1 shows the in-phase (I) component and Trace 2 the
quadrature (Q) component of a 16 QAM signal. The state transitions are
shown in the X-Y diagram.
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