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PULSED-RF MEASUREMENTS
AND THE
HP 85108 NETWORK ANALVZER
John Barr
Richard Grimmett
Roger McAleenan
Network Measurements Division
1400 Fountaingrove Parkway
Santa Rosa, California 95403
RF & Microwave
Measurement
Symposium
and
Exhibition
rlin- HEWLETT
~~ PACKARD
www.HPARCHIVE.com
ABSTRACT
Traditional vector network analyzers have been limited to testing with continuous wave
stimulus. Previously, it has not been possible to achieve vector error correction and
phase measurement capabilities under pulsed-RF conditions. Now, with new improvements
in I.P. detectors, testsets and system firmware, it is possible for a vector network
analyzer to make these needed measurements.
This paper will first cover the fundamentals of pulsed-RF waveforms. Then, three
pulsed-RF measurement modes and their use with the HP851 OB will be presented. This will
include a discussion of the new detectors, testset and firmware that makes possible these
pulsed-RF measurements. Measurement examples will be used to illustrate typical test results
of the pulsed-RF modes and the enhanced external triggering capabilities.
AUTHORS
John Barr received a BSEE from the Georgia Institute of Technology in 1971, an MSEE in
1974 and an MSEngMngt in 1982 from Stanford University. He joined Hewlett-Packard in
1971 and is presently an R&D Project Manager at Network Measurements Division. John
has been involved with development and design of RF / Microwave Vector Network
Analyzers, such as HP8505 and HP8510A/B.
Richard Grimmett received his BSEE from the University of Idaho in 1984. He joined
Hewlett-Packard in 1984, and is currently an R&D engineer at Network Measurements
Division. Richard has been involved with applications development on Microwave
Synthesizers and Microwave Vector Network Analyzers.
Roger N. McA1eenan received a BS degree in 1973 and an MS degree in 1975 from the
University of Wyoming. He has been with Hewlett Packard since 1981, involved in systems
consulting, sales support, and training. In 1985, he joined the Network Measurements
Division as a marketing engineer and later as manager of an application group.
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The vector network analyzer has
traditionally been limited to measuring a
IPUlSIE[D)-!R\f' M IEASURIEM lE~lS device-under-test (DUT) under a continuous
wave (CW) stimulus. However, there are
A~[D) lHIE HIP ~51(Ql1B many times when a pulsed (non-CW)
stimulus is desired or required. Now, with
recent improvements in the HP851 OD, both
\. amplitude and phase measurements can be
made on a DUT with a pulsed-RF stimulus.
1==
CJ
PAT6617
Pulsed-RF measurements are required in
cases where continuous test power could
destroy the OUT. The DUT may be
Wh~ 1P~~~~d-Rf' damaged because it does not have sufficient
M~a~~Ii"~m~IT'II~~l heatsinking or the heatsink may not yet be
attached, as in the case of an unpackaged
device or a device still on the wafer. Also,
* High Power Devices are destroyed the behavior of DUT during the pulse may
by a CW Test Signal be of some interest. For example, does the
gain drop as the device heats up or does
* Behavior within the pulse critical for
phase change with time as the power
supplies run out of current storage?
system operation
PAT6617a
The purpose of this paper is to address a
number of different pulsed-RF measurement
techniques possible with the HP851 08. First,
some basic pulse concepts will be reviewed.
Then three different pulse techniques will be
I) Pulse Concepts explained: Pulse Duty Cycle, Pulse Profiling
and Swept Frequency Pulse. Finally, the
II) Pulse Duty Cycle Measurement expanded external trigger capabilities will be
discussed.
III) Pulse Profile Measurement
IV) Swept Pulse Testing
V) External Trigger
PAT66178
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First, before describing the new pulse
measurement capabilities, let's review some
basic pulse terminology and concepts.
I) Pulse Concepts
II) Pulse Duty Cycle Measurement
III) Pulse Profile Measurement
IV) Swept Pulse Testing
V) External Trigger
PAT66f7c
In defining any pulsed-RF waveform, there
are a number of parameters.
PW - pulse width - this is the ON time from
50% of the rise edge to the 50% point of
the falling edge.
TIME PRP - Pulse Repetition Period - this is the
time from the start of one pulse to the
start of the next. Note, the Pulse
-
Repetition Frequency (PRF) is I/PRP.
tr - pulse rise time - this is the time it ta kes
for the pulse to go from the 10% ON
<] Pulse Width l> condition to the 90% ON condition.
PW
Duty Cycle= - -
<]Pulse Repetition Period l> PRP Duty Cycle - this is the ratio of pulse time
ON to the total pulse period. It is this
PAT6716
ratio, the PW and DDT characteristics
that determine how much the DUT will
heat up.
When viewed in the frequency domain, such
PULSE TERMS as with a spectrum analyzer, the pulsed-RF
waveform has many spectral lines. There is
~R!EQU!ENCV a Central Spectral Line, at the carrier
Center Spectral Line frequency. Then there are a series of
<}-- additional spectral lines spaced at the PRF
from the center line. The amplitudes and
number of lines depend on the pulse
parameters.
Pulse Repetition Frequency
Total Energy=Sum of the amplitudes of all spectral lines
PAT6725
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The pulsed-RF waveform can be viewed in
either the time domain or the frequency
domain. One fully describes the other, and
IPlUJlSIE TIE !RMS the choice depends which is more convenient
!RlElAl~OINlS!H ~IPS
to observe a particular characteristic.
PRP =
PRF
PAT6734
This functional block diagram will help
explain how the standard HP8510 I.F. chain
will react to a pulsed-RF waveform. The
TEST and REFERENCE signals are first
downconverted to 20 MHz in the testset
with roughly 1.5 MHz of bandwidth. A
o
....... second con version occurs to 100 kHz