Data Sheet

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9.7 Proper Ultrasonic Signal Detection
This chapter mostly related to HW v4.9 beacons. Super-Beacons, Industrial Super-Beacons have
high-power digital microphones for noise filtering and proper signal detection. Anyway, if you have
problems with signal detection, read this chapter no matter which beacons do you use
These recommendations suitable only for NIA
Marvelmind Indoor Navigation System uses proprietary multi-frequency for ultrasonic signal and
employs additional filtering to combat external noise. This also makes the system rather immune
against the “usual suspects.” However, if the external noise is too strong, its source is too close,
or it’s emitting a strong signal on frequencies close to 19, 25, 31, 37, 45kHz or white noise, the
system functionality can be affected.
When external noise is high, identify the source. Usual sources include:
- Ultrasonic-based volume or movement detection alarm systems
- Other robots using ultrasonic
- Parktronics
- Sources of very strong white or impulse noise (air guns, air press,
cutters, vacuum cleaner, etc.)
- Rotors of drones/copters
The best things to do in this case:
- Identify the beacons that are affected. Usually, they are those that are
the closest to the source of noise. Try to reposition them
- Manually reduce the gain of the affected stationary beacons so that the
signal from the mobile beacon would have a 1000–1800 amplitude. That
would give the best signal-to-noise ratio. Don’t make the gain too high.
The noise will be amplified, but the desired signal will be saturated and
signal-to-noise ratio will be poor
- Input distances between beacons manually. More information – Table of
distances
The gain settings may be very non-linear. There is almost no change at 4000 to 3000. But
around 2500, the gain starts reducing very quickly (1200 – for some HW versions). By setting
the gain manually, it is possible to find the optimal gain to obtain the highest signal to noise
ratio so the system can work even in very challenging external conditions.
When the map is formed, only the mobile beacon is emitting, whereas stationary beacons are
not. Thus, it does not matter how close the mobile beacon is to the source of the noise.
However, it matters how close the stationary beacons are to those sources. Select the
positions of the stationary beacons accordingly - place them further away from the noise
sources.