Boonton 4540 Peak Power Meter Quick Start - Manual (Page 30)

4540 Power Meter
Quick Start Guide
PN: 98406000A © Copyright 2008 Boonton Page 30
PULSE MODE
If pulses are rectangular, and the pulse width as well as the duty cycle is known,
Modulated Mode measurements can be sufficient to determine the pulse power. For
example GSM is a TDMA
technology with one timeslot (P
T1
)
out of eight (8) possible ones .
Modulated Mode measurement
would show an average value. This
would allow to calculate the power
of this particular timeslot. P
T1
=
P
avg
* 8. With systems like RADAR,
that use a very large duty cycle,
the calculated measurement
results would be significantly less
accurate. Under such circumstances, simple Modulation Mode measurement is no
longer sufficient. Besides this fact, real pulses are usually not rectangular at all. They
show specific rise behavior, usually
overshoot, the horizontal part of the
signal varies, often significantly, and
the falling edges can behave
differently as well. To prevent
distortion of signals or even damage
of components, it is usually
necessary to analyze such pulses in
great detail. The 4540 is the ideal
instrument for this task, with its
Pulse Mode measurements allowing
to analyze and measuring every
increments of a pulse. The
screenshot shows one active
timeslot of a GSM signal. By moving
the cursors information of every single increment of signal is provided.
Pulse mode requires a repeating signal edge that can be used as at rigger, 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.
Note:
While in the Graph Mode the header in this screenshot shows six different
parameters (MkLvl1, MkMin, MkMax, Width, Freq, and Average). Users can create
their individual headers that provide all the information needed.
P
T1
P
T1
Pulse Width (PW)
Pulse Repetition Interval (PRI)
P
t
Avg. Pwr
P
Avg
Pk Pwr
Pk Pwr = P
Avg
/ Duty Cycle
Duty Cycle = PRI / PW