Atec Boonton-4400A-4500A - Manual (Page 2)

Time-domain waveform of 8 carriers spaced 700 kHz apart from
1.8 GHz to 1.8049 GHz and phase aligned for highest peak power.
THE MODEL 4400A IS THE
LEADER IN PULSE
MEASUREMENTS
The Model 4400A provides power-
versus-time waveform analysis of repetitive
RF signals. Applications include AM, radar,
TDMA, and GSM, as well as RF amplifier
linearity testing. The time base extends to
10 nanoseconds per division with internal
and external triggering. The logarithmic
power display permits the entire dynamic
range of more than 60 dB to be seen at the
same time.
Convenient scale and centering controls
allow vertical expansion of any portion of
the display. A linear display scale is also
provided covering power levels from
nanowatts to megawatts. Two adjustable
markers can read the power at any point
across the waveform. In addition, the markers
can be used to define a region on the
waveform in which maximum power (peak
hold), minimum power, long-term average
power, and peak-to-average ration are
measured.
This function is especially useful for
characterizing the power level over a portion
of the top of a pulse, such as top-level power.
Two adjustable reference lines can be used
with the markers to identify and measure
particular power levels.
The reference lines also have the ability to
automatically track the following:
· Markers
· Top/Bottom Power
· Distal/Mesial Power
· Distal/Proximal Power
An Automeasure function measures and
calculates 14 common parameters of a pulse
waveform and makes them available at all
times in a both a summary text table and
individually as a user-defined display
parameter. The 14 Automeasure functions
are:
· Peak Power · Pulse Power
· Average Power · Overshoot
· Risetime
· Falltime
· Top Amplitude · Bottom
Amplitude
· Pulse Width · Pulse Period
· Duty Cycle · Offtime
· Delay · Pulse
An Autosetup function is provided to assist
the user in obtaining a useful time-domain
display of the input signal by just pressing a
key. Appropriate vertical scaling, time base,
and trigger settings are determined
automatically. The Model 4400A is made even
more powerful by the addition of a second
measurement channel. Comparisons between
signals are facilitated by a Math channel that
displays the sum or difference of the inputs. The
full-color display provides unambiguous data,
with each trace clearly identified. Two
Reference channels are used to save
waveforms for comparison purposes. The
Reference channels can be displayed with their
own unique colors, just as the input channels,
and compared using the Math channel. For
archival purposes, the Reference waveforms
can be saved on a floppy disk using the built-in
3.5-inch, 1.44-Mbyte floppy drive.
The problem of diode non-linearity for levels
above –30 dBm, which occurs in all
conventional power meters, is eliminated in the
Model 4400A. Each individual sample is
converted to power before averaging. Since the
sampling rate is one megasample per second,
the system completes the analog-to-digital
conversion, interpolates the level in a calibration
table, and stores the result in less than one
microsecond.
To create the calibration tables, a 1-GHz
step calibrator, traceable to NIST, is built-in to
the Model 4400A. This precision source
provides calibrated power levels from +20 dBm
(100 milliwatts) to –40 dBm (100 nanowatts) in
steps as small as 0.1 dB. An Autocalibration
function makes the process completely
automatic. At all other times, the calibrator is
available as a test source with both CW and
pulsed output.
MODEL 4500A ADDS STATISTICAL
MEASUREMENTS CAPABILITY
Many modern communications systems use
modulation methods that result in
pseudorandom or noise-like signals. Examples
of this are CDMA, WCDMA, multi-carrier,
HDTV, and DAB. The
traditional methods of RF
power measurement are
not adequate for these
systems. A CW power
meter can measure the
average power of these
signals provided care is
taken not to overload the
sensor or operate above
the linear power region for
diode sensors. Since the
peak power can be 16 dB
higher than the average
power and these peaks
are often compressed by
amplifiers and other
components of the
communication system,
some method is needed
to measure the peak
power as well as the average power. The
Pulse Measurement mode described above
can measure peak power over relatively short
time intervals as required for time-based
systems. However, CDMA, in particular,
requires the measurement of infrequent power
peaks over long time periods. It is also
necessary to know how often various power
levels occur as a percentage of the total run
time.
This is achieved by calculating a cumulative
distribution function (CDF) from a large
number of power measurements. The Model
4500A can accumulate 500,000 power
readings per second from one channel and
internally create a histogram containing 4,096
discrete power levels of better than 0.02-dB
resolution. Each power level bin is a 31-bit
counter that records the number of
occurrences of the corresponding power level.
This process can be performed for two
channels simultaneously at a rate of 250,000
power readings per second.
The histogram data is displayed as a
cumulative distribution function (CDF) or a
complementary cumulative distribution function
(CCDF) for each channel. CCDF is also
referred to as 1-CDF. A statistical
measurement begins by clearing the histogram
array to zero and resetting the elapsed time
and sample counters. The measurement can
be allowed to continue until one of the count
bins fills to the maximum allowable number of
counts: 2,100,000,000. At the maximum
sampling rate, the running time exceeds one
hour. The advantage of this method is that
even a single occurrence of the highest power
level during the running time will be recorded
and appear on the distribution function display.
BOONTON ELECTRONICS (A Wireless Telecom Group Company)
P.O. Box 465, Parsippany, New Jersey 07054-0465 · Tel: (973) 386-9696 · Fax: (973) 386-9191 · E-mail: [email protected] · Website: www.boonton.com