About OBW Marker (Markers Properties)

The OBW Occupied bandwidth is closely related to channel power. It indicates how much frequency spectrum is covered by some given percentage (often 99%) of the total power of the modulated signal. marker easily performs generic occupied bandwidth measurements. The OBW measurement determines the band of frequencies that contain a specified percentage of the total power within the measurement span.

The OBW marker sets up the OBW measurement to meet your specific test requirements. The target % Power property specifies how much of the signal power is used to determine the OBW of the signal. The OBW marker readout provides these data results: the occupied bandwidth, the centroid (or mid-point) frequency, and the offset frequency (difference between the specified center frequency and the centroid frequency).

There is also an OBW Summary table that is available for each trace. The OBW Summary table provides a complete set of data results including: the OBW, the OBW Power, the Power Ratio (OBW power/Total power), the Upper Frequency, the Lower Frequency, the Centroid Frequency, and the Offset Frequency.

Measurement Method

The OBW measurement dynamically computes the OBW for each measurement sweep. The OBW is defined as the frequency band in the measurement that contains a specific percentage of the total power in the measured frequency span. The measurement algorithm used for determining the occupied bandwidth uses the following process.

  1. Compute the total power in the measurement span.

  2. Determine the OBW lower frequency: Sum the power beginning from the measurement start frequency while increasing the frequency until the accumulated power is equal to [(100 - % Power)/2] of the total power. This is the OBW lower frequency.

  3. Determine the OBW upper frequency: Sum the power beginning from the measurement stop frequency while decreasing the frequency until the accumulated power is equal to [(100 - % Power)/2] of the total power. This is the OBW upper frequency.

  4. Determine the OBW. Compute the OBW as the upper frequency minus the lower frequency.

  5. Determine the Centroid frequency: Compute the centroid frequency as the (OBW Upper frequency + OBW Lower frequency)/ 2.

See Also

OBW Markers Properties (Markers)

Making an OBW Measurement (Markers)

OBW Summary table trace data (Markers)