LTE FDD/TDD Signal Analyzer Measurement Guide : LTE Analyzer (Option 883) : LTE Channel Spectrum
 
LTE Channel Spectrum
To select channel spectrum measurement go to main menu and press MEASURE > MEASUREMENT >Channel Spectrum. The channel spectrum measurements are set up using the SETUP Menu (LTE Channel Spectrum). Channel spectrum (occupied bandwidth) is a common measurement performed on radio transmitters. This measurement calculates the bandwidth containing the total integrated power occupied in a given signal bandwidth. There are two different methods of calculation depending upon the technique used to modulate the carrier.
• % Integrated Power Method: The occupied frequency bandwidth is calculated as the bandwidth containing the specified percentage of the transmitted power.
• X dB Method: The occupied frequency bandwidth is defined as the bandwidth between the upper and lower frequency points at which the signal level is a desired number of dB below the peak carrier level.
An occupied bandwidth measurement using the % integrated power is shown in Figure: LTE Channel Spectrum (Occupied Bandwidth) Measurement. The occupied bandwidth here is the bandwidth containing 99% of the total channel power. This is calculated from 0.5 % of the total mean power below the lower frequency limit and 0.5% above its upper frequency limit of the signal. Alternatively, the measurement can be set up to use the X dB method where the occupied bandwidth is determined from the upper and lower bandwidth edges that are X dB down from the total mean power of the signal.
LTE Channel Spectrum (Occupied Bandwidth) Measurement

1. LTE Channel Spectrum Analyzer Status Panel: Each measurement features a unique status panel that displays settings and information relevant to the current measurement and view settings. This panel provides quick access to the measurement frequency and band configuration. See Status Panel (LTE Channel Spectrum).
2. Occupied Bandwidth: Occupied bandwidth is integrated over the shaded region where the dashed green lines indicate the upper and lower frequency thresholds. The analyzer will determine and track the occupied bandwidth of the signal within the current span.
3. SETUP Menu: The occupied bandwidth settings are configured in the SETUP menu. See SETUP Menu (LTE Channel Spectrum).
4. Marker frequency values for OBW center, upper and lower frequencies.
5. OBW Summary: This area shows the occupied bandwidth measurement summary data and pass/fail test results, when enabled:
• The occupied bandwidth value and the test limit are expressed in frequency units with a pass/fail result.
• The total power is integrated over the measured bandwidth and is expressed in dBm.
• The received signal power is expressed in dBm.
• The transmit signal frequency error is expressed in frequency units (Hz).
• Tapping this summary area opens the OBW SETUP menu.
SETUP Menu (LTE Channel Spectrum)
The Occupied Bandwidth SETUP menu is available in MEASURE > MEASUREMENT > Channel Spectrum > SETUP. Once the channel spectrum measurement is selected, the SETUP menu can be quickly accessed by tapping on the summary display area below the spectrum display.
LTE SETUP Menu (Channel Spectrum)
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% OBW POWER
Sets the percentage of the total power that is measured within the occupied bandwidth for the current measurement. The resulting occupied bandwidth and total power values are displayed in the measurements results table.
X dB
Sets the x dB value used for the "x dB bandwidth" measurement. The occupied bandwidth is the frequency range between two points on the signal that are x dB down from the highest signal point within the OBW span.
OBW LIMIT
Enables limit checking at the specified frequency. The limit test results show as a green PASS or a red FAIL in the measurement table.
METHOD
Select the measurement method to be PERCENT (%) or X (dB).
PRESET SETUP
Presets the SETUP menu to default settings.
 
Status Panel (LTE Channel Spectrum)
The status panel illustrated in this section is unique to the current analyzer and to the particular measurement and view that is selected.
Figure: Status Panel (LTE Channel Spectrum Measurement) shows the LTE status panel that covers the LTE Channel Spectrum measurements.
Status Panel (LTE Channel Spectrum Measurement) 
 
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.