Product specifications

20
Synchronizing pulsed-RF stimulus and measurements
In wideband pulse measurements, the appropriate IF bandwidth and the pulse
generators’ width/delay are set in order to acquire the data within pulses.
The following measurements demonstrate the results with inappropriate IF
bandwidth and delay settings, which should be avoided when customizing
pulse measurement setups. The following point-in-pulse measurements
are made using a PNA-X with DSP version 4, 4 to 6 GHz frequency range,
-5 dBm input power, and 2 us pulse width and 20 us PRI (10% duty cycle).
With “Autoselect” mode, 1 MHz IF bandwidth (which takes 1.433 us for the
data acquisition) and 467 ns measurement delay are selected. A narrower
IF bandwidth may be used to reduce noise. If the IF bandwidth becomes too
narrow such as 100 kHz, the data acquisition takes 10.65 us and the majority
of the measurements occur outside of the pulses, resulting in significant
errors in the absolute power measurements (B receiver trace) and noisy ratio
measurements (S21 trace) as shown in Figure 14a. Note that the examples
show S21 measurements with 1 dB/div and the B receiver measurements with
10 dB/div in both Figure 14a and 14b.
Figure 14a. Measurement errors caused by improper IF bandwidth