LTE FDD/TDD Signal Analyzer Measurement Guide : LTE Analyzer (Option 883) : LTE Spectrum Emission Mask
 
LTE Spectrum Emission Mask
To select spectral emission mask (SEM) measurement go to main menu and press MEASURE > MEASUREMENT >SEM. The SEM measurements are set up using the SETUP Menu (LTE SEM). The spectrum emission mask (SEM) measurement is a relative measurement method to identify the power level of out-of-band spurious emissions outside of the in-channel bandwidth signal. The SEM measures the power ratio between in-band and adjacent channels. The SEM measurement then identifies the emissions that interfere with other channels. Then, the spurious signal levels of pairs of offset frequencies are identified and related to the carrier power.
The spectral emission mask measurement supports the testing for “Operating Band Unwanted Emissions” described in the 3GPP base station conformance testing document. There is support for LTE masks which are automatically built based on the current carrier frequency/channel and BW values. Masks with the (KR) designation in the title are built according to Korean regulator standards for FR1 signals. The instrument indicates if the signal is within the specified limits by displaying PASS or FAIL. The emission mask information is also displayed in a table format with different frequency ranges and whether the signal PASSED/FAILED in that region. Selecting the SEM measurement does the following:
• Disables all other measurements
• Adds a predefined LTE emission mask
• Sets the span to the mask width
• Sets the detection method to RMS
A spectrum emission mask measurement showing the LTE P<38 dBm mask setting is illustrated in Figure: SEM Measurement.
SEM Measurement
1. The status panel provides quick access to common spectrum analyzer settings. See STATUS PANEL (LTE SEM).
2. SEM Mask
3. Spectrum Emission
4. SEM Mask
5. All SEM measurement parameters are set using the setup menu. See SETUP Menu (LTE SEM).
Spectrum Emission Mask Measurement Basic Setup
1. Select MEASURE > MEASUREMENT > SEM from the right side menu.
2. Select SETUP and select upper or lower mask (LTE P>38 dBm or LTE P<38 dBm).
3. Enter the reference channel bandwidth.
4. Toggle AUTO MAX PWR or set MANUAL MAX POWER.
5. The SEM measurement results are displayed in a table with pass/fail results.
SETUP Menu (LTE SEM)
SETUP Menu (SEM)
 
SELECT MASK
Selects the desired upper or lower emission mask. Choose the desired mask from the list.
IMPORT MASK
Used to import a custom user mask.
EXPORT MASK
Exports an example user mask as a comma separated value file (see Example Custom Signal Emission Mask) or exports the currently selected custom mask.
REF CH BW
Sets the reference channel bandwidth for the measurement.
AUTO MAX PWR
Toggles automatic max power. Some segments in the mask are dependent on the main channel power. Enabling this automatically calculates the reference channel power by measuring the channel power of the center channel bandwidth. When disabled, the reference power must be entered manually below.
MANUAL MAX PWR
Used to manually enter the reference channel power for masks that have limits dependent on main channel power.
PRESET SETUP
Presets all values on the SETUP menu to default values.
Example Custom Signal Emission Mask
To create a custom SEM, use the following steps:
1. Export the existing mask as a csv file by pressing the EXPORT MASK button in the SEM SETUP menu.
2. From the FILES menu, move the exported file to a USB device and then to a computer for editing.
3. If this is the first time exporting the file, the following data should be in the file:
# Example Custom Signal Emission Mask
# Start Frequency, Stop Frequency, RBW, VBW, Is Start Amplitude Relative, Is Stop Amplitude Relative, Start Amplitude, Stop Amplitude
-3.5e6, -2.1e6, 100e6, 100e6, 0, 0, -9.5, -9.5
-2.1e6, -0.7e6, 100e6, 100e6, 0, 0, -9.5, 0.5
0.7e6, 2.1e6, 100e6, 100e6, 0, 0, 0.5, -9.5
2.1e6, 3.5e6, 100e6, 100e6, 0, 0, -9.5, -9.5
4. Change each of the values as desired. Note that the values must be entered in the listed order of the file header.
5. Save the file to a USB device and insert it into the instrument.
6. Select the IMPORT MASK button in the SEM SETUP menu and select the new file from the USB drive. The file name of the imported mask file will be displayed on the EXPORT MASK button.
7. Select the SELECT MASK button and select Custom.
STATUS PANEL (LTE SEM)
Below is the status panel with the corresponding minimized status panel icons that is unique only to spectral emission mask measurement.
Status Panel with Minimized Status Panel Icons (SEM)
 
MIMO ANTENNAS: Toggles the current MIMO antenna setting between AUTO or to select one of the available antennas. When a single antenna is selected, a blue underscore will appear below the antenna icon. The antenna icon is highlighted green when receiving a signal.
SWEEP: Toggles the current sweep setting between continuously or sweep once.
SWEEP ONCE
When sweep is set to single sweep, SWEEP ONCE updates the measurement display. Data continues to be captured in the background.
REF LEVEL
Sets the reference level of the top graticule line in the selected units. If the reference level offset is not zero, OFFSET REF LEVEL is displayed at this location. Refer to Setting Amplitude.
SCALE/DIV
Sets the graticule scale/division for log-based units. This setting does not apply to linear units.
CHANNEL BW
Sets the measurement channel bandwidth. The available bandwidth settings depend on the selected band and bandwidth option installed in the instrument.
CENTER FREQUENCY
Sets the center frequency of the measurement channel.
ATTEN LEVEL
When auto attenuation is off, sets input attenuation.
PRE AMP
Toggles the low-noise front-end preamplifier on or off. Refer to Setting Amplitude.
TRACES
Displays the current status of up to six traces in a quick-view summary. The summary information includes the trace number, type, mode, and detector type. The active trace will show a highlighted background with the mode and detector type restated under the table. Pressing a trace in the summary panel activates the pressed trace and opens the TRACE menu, which allows you to select and set up an individual trace as desired. Refer to Setting Trace Parameters.
FREQ REFERENCE
Indicates the current frequency reference source of Internal, External, or GNSS (GPS) Hi Accuracy (requires GPS). The instrument automatically selects the frequency reference in the following order of priority: external, GNSS (GPS), then the internal time base.