Reference

note

The noise floor profile is sent only in TDM mode so far. Sending in DDM mode is not supported yet!

Type: MMW_OUTPUT_MSG_NOISE_PROFILE

Length: (Range FFT size) × (sizeof(uint16_t), or 2 bytes)

Value: Dense array containing one noise-floor value for each range bin. The values have the same unsigned Q8 format as the range profile, but are selected from the maximum positive Doppler bin rather than the zero-Doppler bin.

How the values are produced

The range and noise profiles are derived from the same range–Doppler detection matrix. See How values are produced for the complete processing sequence and Q8 conversion.

Previously for Range profile, range profile selects Doppler bin zero:

$$\operatorname{rangeProfile}[r] = \operatorname{rawValueToOutput}[r,0]$$

The Noise profile instead selects:

$$d_{\mathrm{noise}} = \frac{N_D}{2}-1$$

and transmits:

$$\operatorname{noiseProfile}[r] = \operatorname{rawValueToOutput} \left[r,\frac{N_D}{2}-1\right]$$

$r$ is the range-bin index,

$N_{D}$ is the number of Doppler FFT bins. The selected bin represents the maximum positive Doppler frequency, corresponding to the maximum positive unambiguous radial speed.

In a stationary scene, objects and static clutter are (generally) concentrated near the zero-Doppler bin. The values in the maximum-Doppler bin therefore provide an estimate of the receiver noise floor at each range bin. A fast-moving object or interference occupying this maximal Doppler bin can raise the reported noise profile above the underlying receiver noise floor. Therefore, knowing the noise floor in advance is a useful metric.

Selecting the output

The CLI config command guiMonitor selects the TLV elements that are sent in the output packet. This includes the noise floor profile.