Product specifications

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Comparing the results
Figure 24 also shows memory traces comparing the input match, gain, input power,
and output power under pulsed conditions with open loop and receiver leveling.
The difference is very small in the input match and gain measurements, but it is
quite large in the absolute power measurements. If you perform only S-parameter
measurements and the DUT is in the linear operation, the open loop leveling is
probably acceptable. However, if you measure absolute power and/or power
dependent performance such as compression and distortion, the pulsed stimulus
power needs to be accurately leveled. With wideband detection, the receivers
always measure during the pulses, thus receiver leveling is recommended.
Receiver leveling with narrowband detection
The PNA-X with DSP version 4 or version 5 must use narrowband detection
method for a pulse width narrower than 267 ns or 100 ns respectively. Fortunately,
the procedure to level the stimulus with narrowband pulse is exactly the same
as the one with wideband pulse – set up pulse measurements, turn off the pulse
modulator for calibration, then turn back on the modulator and use a receiver
to level the pulsed stimulus. In narrowband pulse, the receiver gates must be
placed inside the pulse, otherwise the receivers do not measure pulsed-RF sig-
nals. PNA-X firmware sets the receiver gate width one half of the pulse width by
default. Receiver gates have internal delay from the pulses that drive the pulse
modulator. This may cause the receiver gates to be off the pulse, resulting in
noisy measurements. The delay varies by frequency band and frequency model of
the PNA-X. It is recommended increasing receiver gate delay by the pulse system
timing resolution, 16.7 ns increments with DSP version 4 and 10 ns increments
with DSP version 5, to find an optimum delay at a particular measurement setup.
This example uses a 50 GHz PNA-X with DSP version 4, with a minimum receiver
gate delay of 16.7 ns. Figure 25a through Figure 25c show the S11, S21, input and
output powers of the same amplifier used in the previous example at each step.
The setup is 100 ns pulse width, 50 ns receiver gate width, 10 us pulse period,
16.7 ns receiver gate delay, and -10 dBm source power.
Figure 25a. Uncorrected narrowband pulse measurements