Keysight Technologies CXA N9000B, Manual

Page: 63 / 88

N9069C Noise Figure Measurement Guide 63
Measurement Related Tasks and Concepts
Setting the Signal Analyzer to Make a Measurement
5 Sideband (both for
DUT and system
downconverter)
LSB Lower Sideband – the RF input frequency is < the LO frequency.
For example(downconverter):
USB Upper Sideband – the RF input frequency is > the LO frequency.
For example (downconverter):
DSB Double Sideband – both upper and lower sidebands.
Available when the DUT is a Downconverter,
or System Downconverter is set to on.
When making a Double Side Band (
DSB)
measurement with
RF
Frequency Context,
the frequencies you specify as the RF Start
and Stop frequencies refer to the Lower Side
Band (
LSB)
only.
When making Double Sideband (
DSB
) measurements, it is important that the
IF frequency is much smaller than the LO frequency. This is because the ENR
values in the ENR table can only be applied to one frequency, which is the LO
frequency. The ENR values cannot be applied simultaneously to both the
upper sideband and to the lower sideband. The ENR values are therefore
applied to the midpoint between the upper sideband and the lower sideband,
and this equates to the LO frequency.
Consequently, the higher the IF frequency is in comparison to the LO
frequency, the further apart the upper and lower sidebands will be. The further
these upper and lower sidebands are from the LO frequency, the less accurate
the ENR value be.
It is recommended for greatest accuracy that the IF be no greater than 1% of
the LO frequency when making double sideband measurements. When making
a swept measurement, no frequency in the swept frequency band should
exceed 1% of the LO frequency.
6 LO Freq Mode Fixed The External LO frequency is constant.
Swept The External LO frequency changes between sweep points.
When LO Freq Mode is set to Swept, an
external LO control on a separate signal
source is needed.
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