About Bluetooth Spectrum Measurements

The Bluetooth Spectrum measurement performs spectrum-domain Bluetooth transmitter tests. It is part of the Bluetooth extension (89601BLTC), which also includes the Bluetooth Demod measurement; the two measurements share a common Bluetooth Mode configuration (PHY Physical Layer family and rate, packet type, and channel index).

The measurement is organized around a Test Purpose that selects which conformance test is run. Selecting a purpose re-profiles the acquisition and selects the limit tables the results are tested against. In this release the available purpose is LE In-band Emissions, which measures the power the transmitter emits across the 2.4 GHz Gigahertz: A frequency measurement which equals one billion hertz. band and tests it against an absolute mask.

The Two Grids

Two different frequency grids appear in the results, and they are not two views of the same thing:

The radio channel grid is the grid the radio uses. For LE it is 40 channels of 2 MHz Megahertz: A unit of frequency equal to one million hertz or cycles per second., with channel k centered at 2402 + 2k MHz. Per-channel results appear in the Channel Power trace.
The measurement-band grid is the grid the conformance procedure sweeps. For LE it is 81 bands of 1 MHz, centered at 2401 MHz through 2481 MHz. Per-band results appear in the Band Power and Band Table traces.

For LE the two grids do not coincide and do not even share an anchor, and the limits are applied on the measurement-band grid — that is where the mask, the per-band verdicts, and the overall pass/fail result are computed. Every trace is plotted against absolute frequency so the grids can be read against each other. For BR and EDR the procedure steps the radio channels themselves, so there the two grids are the same.

Acquisition

For LE in-band emissions, only channels that are required to be tested are tested.

Averaging is set from the measurement's own Average settings rather than from a control on this dialog box. This measurement enables the Style choice, and offers Off, RMS, RMS Exponential, Continuous Peak Hold, and Peak Hold. Each test purpose defaults the style to RMS, the N-sweep average the conformance tests are specified with; the other styles remain available as manual choices.

Results

Per-channel powers, per-band powers with their limits and margins, the worst offender, and the overall verdict are reported in the Channel Power, Band Table, and Summary traces.

The Bluetooth Spectrum measurement is introduced in this release as a beta feature and currently supports Bluetooth low energy (LE) only.

Reference

LE in-band emissions is specified by the Bluetooth RF Radio Frequency: A generic term for radio-based technologies, operating between the Low Frequency range (30k Hz) and the Extra High Frequency range (300 GHz).-PHY Test Specification, test RFPHY/TRM/BV-03-C (LE 1M) and RFPHY/TRM/BV-08-C (LE 2M), §4.6.2, and by the Bluetooth Core Specification, Vol 6, Part A, §3.2.