PMX40 RF Power Meter – INSTRUCTION MANUAL
3-10
Figure 3-6. Marker Measurements on CH1 and CH2 Pulses
Pulse mode is only available when using RTP Series power sensors and is the best choice for most pulse
modulated and periodic signals. Pulse mode requires a repeating signal edge that can be used as a
trigger, or an external trigger pulse that is synchronized with the modulation cycle. Pulse mode
performs measurements that are synchronous with the trigger (that is the measurements are timed or
gated) so that the same portion of the waveform is measured on each successive modulation cycle.
Multiple modulation cycles may be averaged together, and measurement intervals may span both
before and after the trigger. Pulse mode is best for the following types of measurements:
•
Moderate signal level (above about -40 dBm except when modulation is off).
•
The signal is periodic.
•
A time snapshot of a single event is needed (minimum single-shot time is 200
nanoseconds).
•
Typical modulation and signal types: LTE, 5G, RADAR, SatCom, TCAS, Bluetooth, Wireless
LAN.
3.5.3
Statistical Mode
Certain modulated signals are completely random and provide no event that can serve as a trigger for
measurements. CDMA or OFDM are common examples. The PMX40 Statistical mode was designed to
provide measurements for these types of signals.
Statistical mode is only available when using peak power sensors with the PMX40. It is the best choice
for analyzing signals with a high crest factor, that are noise-like with random or infrequent peaks, or are
modulated in a random, non-periodic fashion. Statistical mode yields information about the
probability
of occurrence
of various power levels without regard for
when
those power levels occurred. In the
Statistical mode the instrument continuously samples the input signal and processes all of the samples
to build power histograms.
Many digitally modulated spread-spectrum formats use bandwidth coding
techniques or many individual modulated carriers to distribute a source’s digital information over a
wide bandwidth, and temporally spread the data for improved robustness against interference. When
these techniques are used, it is difficult to predict when peak signal levels will occur. Analysis of millions
of data points gathered during a sustained measurement of several seconds or more can yield the
statistical probabilities of each signal level with a high degree of confidence. Statistical mode is best for
the following types of measurements:
