Keysight B Series - Spectrum Emission Mask (SEM) - (SA Mode Only)

Keysight N9938-90003 User’s Guide 181
SA (Spectrum Analyzer) Mode (Option 233–Mixed Analyzers)
Spectrum Emission Mask (SEM) — (SA Mode Only)
Spectrum Emission Mask (SEM) — (SA Mode Only)
This section explains how to make the spectrum emission mask, (SEM),
measurement. SEM compares the total power level within the defined carrier
bandwidth and offset channels on both sides of the carrier frequency, to levels
allowed by standard. Results of the measurement of each offset segment can
be viewed separately.
Purpose
The Spectrum Emission Mask measurement includes the in-band and
out-of-band spurious emissions. It is the power contained in a specified
frequency bandwidth at certain offsets relative to the total carrier power. It
may also be expressed as a ratio of power spectral densities between the
carrier and the specified offset frequency band.
The spectrum emission mask measurement is a composite measurement of
out-of-channel emissions, combining both in-band and out-of-band
specifications. It provides useful figures-of-merit for the spectral regrowth and
emissions produced by components and circuit blocks.
Measurement Method
The spectrum emission mask measurement measures spurious signal levels in
up to 8 pairs of offset/region frequencies and relates them to the carrier power.
The integration bandwidth method is used to perform a data acquisition. The
reference channel integration bandwidth (Meas BW) is analyzed using the user
defined resolution bandwidth (Res BW), which is much narrower than the
channel bandwidth. The measurement computes an average power of the
channel or offset/region over a specified number of data acquisitions,
automatically compensating for resolution bandwidth and noise bandwidth.
This measurement requires the user to specify the measurement bandwidths of
carrier channel and each of the offset/region frequency pairs up to 12 (A - L).
Each pair may be defined with unique measurement bandwidths. The results
are displayed both as relative power in dBc and as absolute power in dBm.
Summary
Similar to other Radio Channel measurements, SEM sweeps and measures the
total power within a Reference channel. It also optionally performs sweeps of
user defined offset segments both above and below the reference channel. The
peak signals within the offsets are compared against limits, to determine PASS
or FAIL results. Tabular data is presented showing individual offset segment
results, one row for each offset. A final trace is displayed that contains all of
offset segment sweeps and the reference channel sweep is formed and plotted
along with the limits.
The following are displayed:
— Total Power Ref (dBm / Hz) - measures total power over the specified
Integrated BW.