Manual - 8500A Series Peak Power Meter - Giga-tronics

Series 8500A Peak Power Meters
2.14 Swept Peak Power Measurements
The frequency response and power level characteristics of pulsed signals can be measured under swept
frequency conditions by combining the capabilities of the Giga-tronics PPM with those of the
Giga-tronics Model 8003 Scalar Network Analyzer.
The Analyzer’s normalization memory can be used to subtract out residual test setup responses, thus
allowing direct readout of the frequency response of the device under test. There are a variety of
applications where this ability can be very useful such as:
• Pulsed TWT testing
• Microwave frequency performance of pulsed radar systems
• Return Loss
• VSWR Measurements under Pulsed Conditions
• and others.
Figure 2-17 illustrates a typical setup for measuring swept peak power.
Figure 2-17. Typical Pulsed Swept Measurement System
If a Giga-tronics Scalar Analyzer system is not available, a conventional oscilloscope can be used by first
displaying the PPM’s output, and then marking the system tracking errors on the CRT in grease pencil for
visual correction.
The PPM is normally used in the Peak Mode for this type of testing. Most PPM settings would be the
same as when measuring a single frequency pulsed signal. In order to use the Swept/Pulse system with
any degree of accuracy, the pulse repetition rate must be considerably faster than the speed at which the
RF sweep takes place. This is determined mostly by the setting of the sweep generator’s sweep speed.
The PPM is capable of reading better than 100 pps, and the output level will be at 100 mV/dB. Swept
measurements can also be made simultaneously from channels A and B of the 8502A, but the PPM’s
reading rate will be somewhat slower.
It is very convenient to use the sweep generator’s Frequency Reference signal to continually inform the
PPM as to what the RF frequency is at any given time. (Frequency Reference is synonymous with
V/GHz, VpropF, etc.) Using this feature ensures that, as the sweep generator changes frequency, the PPM
2-42 Manual No. 20790, Rev C, November 1998
Superceded by Revision D, March 2009