HP 85108, System Manual

Page: 37 / 136

3
Operation
Introduction
This c hapter con tains the follo wing information.
A system description
Op erational tests
Pulsed-RF measuremen t examples
Pulsed-RF applications
Pulsed-RF timing information
External pulse mo dulation information
High p o w er measuremen t considerations
System Description
Pulsed-RF stim ulus may b e required in cases where con tinuous application of the test signal
could destroy the device, suc h as when testing o ccurs prior to pac k aging, or where the device
m ust b e tested using a PRF and dut y cycle that accurately represen ts its nal application.
The HP 8510 pulsed-RF net w ork analyzer conguration adds sp ecialized hardw are and an
optimized rm w are feature set to make fully error-corrected S-parameter measuremen ts of
pulsed-RF resp onses. F or the rst time, the com bination of wideband IF and accurate timing
circuits pro vides precise sync hronization with the pulse, allo wing S-parameters to b e measured
at a precisely kno wn, rep eatable time during the pulse. This extends the HP 8510 applications
in to t w o ma jor areas: tests in whic h the stimulus signal to the device is pulsed, and tests of
devices whic h accept a CW input and pro duce a pulsed output.
A simplied blo c k diagram of the system is sho wn in Figure 3-1. One syn thesizer pro vides
the test signal stimulus to the RF input of the test set and the other pro vides the LO signal
to the four frequency con v erters (only t w o are sho wn). The LO source is alwa ys tuned 20
MHz ab o v e the test signal source. The standard in ternal phaselo c k tec hnique is not used;
instead, a common 10 MHz frequency reference is used for b oth of these sources and the
in ternal sample selection and timing logic in the HP 8510. These sources are considered to b e
coheren t, th us generating the correct 20 MHz rst IF and the correct clo c k frequency for the
reference and test sync hronous detectors. This eliminates the need to use the reference signal
for receiv er phaselo c k and allo ws all reference and test signals to b e pulsed, thereb y making
fully error-corrected 2-p ort, pulsed-RF S-parameter measuremen ts p ossible.
Operation 3-1