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#MUZZLE ENERGY CALCULATOR AOA FULL#
#MUZZLE ENERGY CALCULATOR AOA BLUETOOTH#
#MUZZLE ENERGY CALCULATOR AOA MAC#

Here, the signal and noise subspaces are calculated using linear algebra and are orthogonal to each other. Since this algorithm takes uncorrelated noise into account, the generated covariance matrix is diagonal. The main approach of this algorithm is the decomposition of the covariance matrix of the received signal into eigenvalues. Therefore, we decided to use the more accurate MUltiple SIgnal Classification algorithms. The solution to the problem was the choice of the frequency channel at which the angle obtained from the phase difference has the closest value to the real one.ĭespite the resolved issues, the phase difference is stable but quite noisy.

#MUZZLE ENERGY CALCULATOR AOA BLUETOOTH#

It turned out that they correspond to the switching of the frequency channels on which Bluetooth works (37: 2402 MHz, 38: 2426 MHz, 39: 2480 MHz).

And even after solving these problems, we could not understand where the jumps in the phase difference between random data packets come from.

#MUZZLE ENERGY CALCULATOR AOA FULL#

Then we tried to process IQ samples for one data packet arriving at a frequency of about 10 Hz, which was not enough for a full analysis, and we decided to collect more data in 10 seconds (in practice, 1 second is enough).

#MUZZLE ENERGY CALCULATOR AOA MAC#

We just forgot to add parsing by MAC addresses of devices :) The first problem that we encountered was the determination of the angle of arrival from one signal source with the parallel operation of other sources.Problems in calculating the AoA and their solutions In practice, however, many problems arise. The phase difference between the antennas In summary, the angle can be calculated using the following formula. The signal transmitted by the Bluetooth Low Energy device has a frequency of approximately 2440 MHz, which gives a wavelength of 12 cm. The Minew Aoa Locator has a square shape and consists of 12 antenna elements.ĭetermining the AoA by sampling phase and switching antennas In doing so, the receiver takes an IQ sample every microsecond during the reference period and an IQ sample in each sample slot.

When receiving a packet containing the AoA Constant Tone Extension, the receiver switches antennas according to a predefined switching pattern. The Bluetooth core CTE specification says that the CTE packet contains a guard period of 4 µs, a check period of 8 µs, as well as several antenna samples. And by doing this for at least several antennas, the receiver can calculate at what angle the transmitter signal is coming.

Thus, the receiver can sample the IQ components of the signal and determine the phase of the signal. To enable AoA, the Bluetooth Direction Finder feature must add a Constant Tone Extension (CTE) to the data packet. With the introduction of the Bluetooth 5.1 standard, it became possible to determine the direction of an incoming signal by using the angular phase shifts that occur between antennas when they receive RF signals.

AoA angle of arrival belongs to Bluetooth® triangulation based methods. The Angle of Arrival method provides for the use of not only the signal strength (RSSI) but also the angle of its arrival, which allows calculating the exact location of the object within the range of 0.1 - 1 m. In such situations, AoA based positioning, whose realization is possible thanks to the Bluetooth® 5.1 technology, comes for help. Many real-time location systems (RTLS) require high accuracy of results, up to several centimeters.