Boonton 4530 Peak Power Meter User Manual User Manual
Page 152
Chapter 5
Boonton Electronics
Making Measurements
4530 Series RF Power Meter
5-10
Meas Mode:
Pulse
Frequency:
850 MHz (or whatever operating frequency is in use)
Averaging:
4 (use less for faster response time, more for better noise rejection)
TimeSpan:
10 ms (shows the full 6.67ms burst and both edges)
Trig Source:
Sensor 1 (triggers on RF signal)
Trig Slope:
Positive (trigger on leading edge of pulse)
Trig Mode:
Pk-To-Pk (automatically sets based on signal level)
Trig Position:
Left (position trigger point at left edge of screen)
Trig Delay:
-2.0 ms (moves leading edge of pulse 2ms to the right to center pulse in display)
Trig Holdoff:
19.000 ms (delay for almost a full frame, and arm trigger 1ms before next expected edge)
Marker Mode:
Vertical (set markers to measure power at time offsets)
Marker1 Pos:
0.10ms (set Marker 1 at beginning of timeslot’s “active interval”)
Marker2 Pos:
6.50ms (set Marker 2 at end of timeslot’s “active interval”)
Query Cmnd:
FETCh1:ARRay:PULse:POWer?
(returns array inclulding average pwr betwn markers)
Other measurements may include timing information such as burst rate, width, and transition times of the
leading and trailing edges of the burst.
To measure NADC basestation signals reliably, it is necessary to either limit the basestation to transmitting
during only one timeslot, or provide an external trigger pulse that is synchronized with the frame. Otherwise,
it is difficult to guarantee that the power meter will synchronize with the desired portion of the frame (timeslot).
The entire, 6-timeslot frame may be viewed by setting the timespan to 50ms, and power of each timeslot can be
measured by moving marker positions to each timeslot.
An alternative method for measuring average and peak power for the NADC reverse link (handset) is to use
modulated mode. Peak power is measured directly. Overall average power may be accurately measured, and
average power during the burst may be calculated by multiplying the overall average by 3 since the burst is
active during one of every three timeslots. This can be done by setting the measurement offset to 4.77dB.
Note, however, that this will make the peak power and peak-to-average ratio read 4.77dB too high, since the
peak power does not vary with duty cycle. Since the pulse repetition rate is relatively slow, the integration
filter should be set for an integral number of frames, or at some multiple of 40mS. This ensures that the signal
will be averaged over one or more full cycles, and the average reading will be the same no matter where in the
frame the reading is synchronized. The following table shows how to use modulated mode for this measure-
ment.
Meas Mode:
Modulated
Frequency:
850 MHz (or whatever operating frequency is in use)
Filter:
400ms (average power over ten full frames. Any multiple of 40ms is OK.)
Offset:
4.77dB (multiply power by 3.0 to account for the 1/3 duty cycle of the signal)
Query Cmnd:
FETCh1:ARRay:CW:POWer?
(returns array including average and peak power)
5.6.3
Measuring iDEN.
The iDEN (integrated Digital Enhanced Network) signal is a Time Division Multiple
Access (TDMA) multiplexing scheme that uses a repeating sequence of 6 time slots in a frame. The data frame
duration is 90ms, and each time slot is 15ms. Handsets transmit during one of the six timeslots. Base stations
transmit during all timeslots, but often at different levels for each timeslot. The power envelope of the 4-carrier
QAM modulation varies during each timeslot, and it is generally desired to measure the average power and
peak-to-average ratio during the entire 15ms timeslot. This is accomplished by using Pulse Mode, and setting
markers at the desired points in time.