Boonton 4530 Peak Power Meter User Manual User Manual
Page 154
Chapter 5
Boonton Electronics
Making Measurements
4530 Series RF Power Meter
5-12
Meas Mode:
Pulse
Frequency:
2.44 GHz (center frequency of Bluetooth band)
Averaging:
4 (use less for faster response time, more for better noise rejection)
TimeSpan:
0.5 ms (shows the full 366
µs burst)
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:
-0.07 ms (moves leading edge of pulse 70
µs to the right to center pulse in display)
Trig Holdoff:
1.200 ms (delay for almost two time slots, and arm trigger 50
µs before next expected edge)
Marker Mode:
Vertical (set markers to measure power at time offsets)
Marker1 Pos:
5.0
µs (set Marker 1 at beginning of timeslot’s “active interval”)
Marker2 Pos:
360
µs (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.
5.6.5
Measuring CDMA (all types).
The CDMA (Code Division Multiple Access) signal is a spread-spectrum
multiplexing scheme that modulates data at a very high rate by use of a “spreading code” to produce a very
wide spectrum signal that is quite immune to interference. The spreading code is unique for each user, and has
the effect of sending each bit as a predictable series of bits. The receiver is able to correlate the codes of one
device even though a number of other devices may be transmitting simultaneously on the same frequency,
since each user has his own spreading code. This requires that each user’s signal reach the receiver with
approximately the same amplitude, which necessitates very careful control of transmitted power. The modu-
lated signal appears very much like random noise in the time domain, with a fairly high peak-to-average ratio
(sometimes called “crest factor”). There is no periodicity, and it is not very helpful to use a triggered
measurement such as Pulse Mode. It is a simple matter to measure average power and peak-to-average ratio
in Modulated Mode (default settings are usually fine), but this doesn’t tell the whole story. A Statistical
Mode measurement taken over several seconds is a much better choice, and can be used to display the
probability of occurence of all power levels in the sample population.
Meas Mode:
Statistical
Frequency:
0.90 GHz (or whatever operating frequency is in use)
Stat Mode:
1 - CDF
Terminal Count: 10 Msamples
Marker Mode:
Vertical (set markers to measure power at a percent probability)
Marker1 Pos:
0.1% (returns power level exceeded by 0.1% of all samples)
Marker2 Pos:
0.001% (returns power level exceeded by 0.001% of all samples)
Query Cmnd:
FETCh1:ARRay:AMEAsure:POWer?
(returns array of statistical measurements)
Statistical measurements include long term average power, minimum and maximum instantaneous powers,
peak-to-average ratio, power at each marker, percent at each marker, and total number of samples. This
measurement format is valid for all CDMA formats including cdmaOne, cdma2000, and W-CDMA.
The video bandwidth of the 4530 Series power meters with a Boonton 575xx peak power sensors is wide
enough to easily cover these formats. For future wideband formats that may require more than the 6MHz
bandwidth of the 575xx sensors, the 573xx sensors offer a bandwidth of 20MHz when used with the 4530
Series.