Band Power (Bluetooth Spectrum)
The trace shows the measured power in each measurement band — the 1 MHz Megahertz: A unit of frequency equal to one million hertz or cycles per second. grid the conformance procedure sweeps. This is the quantity the emissions limits are applied to.
For LE, the measurement bands are 81 bands of 1 MHz centered at 2401 MHz through 2481 MHz. That grid is not the radio channel grid and does not share its anchor: the Channel Power trace integrates 40 channels of 2 MHz from 2402 MHz. Both traces are plotted against absolute frequency so they can be read against each other and against the Spectrum.
Bands that the acquisition span did not cover are not plotted, and read out as under a marker. On a typical span most of the 81-band LE grid is uncovered, so the plotted trace is usually a short run of bands around the carrier.
Setting Power Calculation to reports each band as a mean power spectral density (dBm deciBels referenced to a milliWatt: dB relative to 1 milliwatt dissipated in the nominal input impedance of the analyzer/Hz) instead of an integrated power (dBm).
Spec Limit Line
The limit line is drawn on this trace, showing the mask the selected Test Purpose applies, positioned relative to the carrier band. Because the mask and this trace share the band grid, the line can be compared band for band with the trace.
The limit line does not itself produce a pass/fail result — a point-by-point test cannot express the specification's exception-band allowance. Per-band verdicts are in the Band Table and the overall verdict is in the Summary.
See Also
