This disclosure describes systems and methods for optimization of the antenna switching pattern, and more particularly changing the antenna switching pattern to maximize the accuracy of the direction finding algorithm.

BACKGROUND

Angle of Arrival and Angle of Departure algorithms, collectively referred to as AoX algorithms, operate by determining a phase difference between different antenna elements in an antenna array. The antenna array may be a one or two dimensional array. This phase difference can be used to determine the angle from which the signal originated, since the distance between antenna elements is known.

Specifically, assume a one dimensional antenna array where the distance between two adjacent antenna elements is d. The phase difference between when the incoming signal is detected at these two adjacent antennas can be given as cp. This phase difference, φ, divided by 2π, multiplied by the wavelength, A, represents the distance between the two antenna elements, as viewed from the signal source. Knowing this difference in the distance that the incoming signal travelled allows the angle of arrival to be calculated. Specifically, the angle of arrival can be given by the difference in the distance that the incoming signal travelled, divided by d represents the cosine of the incoming signal. In other words, the angle of arrival is defined as the arc cosine of (φλ/2π)/d.

This algorithm, and others, relies on the accuracy of several parameters. Specifically, the distance between adjacent antenna elements must be accurate. This is typically not problematic, as the geometry of the antenna array is well defined. The algorithm also relies on the quality of the incoming signal. Specifically, the quality of the I and Q signals is critical for accurate operation of any direction finding algorithm. In many systems, signals from the various elements of the antenna array are multiplexed and utilize common electronics. These common electronics may include inductive or capacitive elements that cannot be switched instantaneously and therefore have settling delays.

However, many protocols allow only a predetermined amount of time to acquire signals from all of the antenna elements. Therefore, the device performing the direction finding algorithm must acquire the necessary signals from each element of the antenna array in a timely manner, despite the settling delays noted above.

Therefore, it would be beneficial if there were a system and method that minimized the settling delays so that accurate I and Q signals can be obtained and evaluated. In this way, the accuracy of the AoX algorithm can be improved.

SUMMARY

A device and method for improving the accuracy of angle of arrival and departure computations is disclosed. The device and method rely on manipulation of the antenna switching pattern to achieve an improved calculation of arrival angle. In one embodiment, the device calculates an estimate angle of arrival using conventional methods. The device then determines which of a plurality of different antenna switching pattern yields the more accurate results at this estimated angle of arrival. The AoA measurement is then repeated using the preferred antenna switching pattern. In another embodiment, the device captures the amplitude and/or phase of the signal from each antenna element. The device then sorts these antenna elements and defines a preferred antenna switching pattern based on the sort list. The AoA measurement is then performed using the preferred antenna switching pattern. In another embodiment, the device utilizes a neural network which is trained using I and Q signals and provides an indication of the preferred antenna switching pattern.

According to one embodiment, a device to calculate an angle of arrival or an angle of departure is disclosed. The device comprises a wireless network interface, wherein the wireless network interface comprises an antenna array having a plurality of antenna elements and an analog multiplexer, wherein the wireless network interface receives an incoming signal from an antenna element and generates an I signal and a Q signal associated with the antenna element; a processing unit; and a memory device, comprising instructions, which when executed by the processing unit, enable the device to: receive a packet that includes a constant tone extension (CTE), wherein the CTE comprises a tone having a known frequency and wherein the CTE comprises a plurality of switch slots and a plurality of sample slots; sample the CTE during a plurality of the sample slots using a default antenna switching pattern, wherein an antenna switching pattern determines an order in which the analog multiplexer selects each antenna element of the antenna array; use I and Q signals from the plurality of sample slots to calculate an estimated angle of arrival; select a preferred antenna switching pattern based on a predetermined relationship between the estimated angle of arrival and a plurality of antenna switching patterns; sample the CTE during a plurality of the sample slots using the preferred antenna switching pattern; and use I and Q signals from the plurality of sample slots to calculate an angle of arrival. In certain embodiments, the memory device comprises the plurality of antenna switching patterns. In some embodiments, the predetermined relationship associates each estimated angle of arrival with one of the plurality of antenna switching patterns. In certain embodiments, the antenna switching pattern associated with each estimated angle of arrival minimizes an absolute error, wherein the absolute error is defined as an absolute value of a difference between the estimated angle of arrival and an actual angle of arrival. In another embodiment, the predetermined relationship associates ranges of estimated angles of arrival with one of the plurality of antenna switching patterns. In certain embodiments, the angle of arrival calculated using the preferred antenna switching pattern is used to select an updated preferred antenna switching pattern based on the predetermined relationship between the angle of arrival and a plurality of antenna switching patterns; and the instructions enable the device to: sample the CTE during a plurality of the sample slots using the updated preferred antenna switching pattern; and use I and Q signals from the plurality of sample slots to calculate an improved angle of arrival.

According to another embodiment, a method for calculating an angle of arrival or an angle of departure is disclosed. The method comprises using a device having a wireless network interface, wherein the wireless network interface comprises an antenna array having a plurality of antenna elements and an analog multiplexer, wherein the wireless network interface receives an incoming signal from an antenna element and generates an I signal and a Q signal associated with the antenna element, to receive a packet that includes a constant tone extension (CTE), wherein the CTE comprises a tone having a known frequency and wherein the CTE comprises a plurality of switch slots and a plurality of sample slots; sampling the CTE during a plurality of the sample slots using a default antenna switching pattern, wherein an antenna switching pattern determines an order in which the analog multiplexer selects each antenna element of the antenna array; using I and Q signals from the plurality of sample slots to calculate an estimated angle of arrival; selecting a preferred antenna switching pattern based on a predetermined relationship between the estimated angle of arrival and a plurality of antenna switching patterns; sampling the CTE during a plurality of the sample slots using the preferred antenna switching pattern; and using I and Q signals from the plurality of sample slots to calculate an angle of arrival. In certain embodiments, the preferred antenna switching pattern is selected from one of a plurality of antenna switching patterns. In some embodiments, the predetermined relationship associates each estimated angle of arrival with one of the plurality of antenna switching patterns. In certain embodiments, the predetermined relationship associates ranges of estimated angles of arrival with one of the plurality of antenna switching patterns. In some embodiments, the predetermined relationship is created by: disposing a beacon at a fixed location; rotating a test device having an antenna configuration that is identical to the antenna array of the device, wherein the test device is rotated through 360 degrees of azimuth; sampling the CTE from the beacon to calculate a computed angle of arrival for a plurality of azimuth angles; creating an error profile for each of a plurality of antenna switching patterns, wherein the error profile represents a difference between an actual angle of arrival and the computed angle of arrival; and minimizing the absolute error at each azimuth angle based on the error profiles. In certain embodiments, minimizing the absolute error at each azimuth angle is performed by: for each antenna switching pattern, determining the difference between an actual angle of arrival and the computed angle of arrival; selecting the antenna switching pattern having a smallest absolute value of the difference. In certain embodiments, the method further comprises: selecting an updated preferred antenna switching pattern using the angle of arrival calculated using the preferred antenna switching pattern, based on the predetermined relationship between the angle of arrival and a plurality of antenna switching patterns; sampling the CTE during a plurality of the sample slots using the updated preferred antenna switching pattern; and using I and Q signals from the plurality of sample slots to calculate an improved angle of arrival.

According to another embodiment, a software program is disclosed. The software program comprises instructions, which when executed by a processing unit disposed on a device a wireless network interface, wherein the wireless network interface comprises an antenna array having a plurality of antenna elements and an analog multiplexer, wherein the wireless network interface receives an incoming signal from an antenna element and generates an I signal and a Q signal associated with the antenna element, enable the device to: receive a packet that includes a constant tone extension (CTE), wherein the CTE comprises a tone having a known frequency and wherein the CTE comprises a plurality of switch slots and a plurality of sample slots; sample the CTE during a plurality of the sample slots using a default antenna switching pattern, wherein an antenna switching pattern determines an order in which the analog multiplexer selects each antenna element of the antenna array; use I and Q signals from the plurality of sample slots to calculate an estimated angle of arrival; select a preferred antenna switching pattern based on a predetermined relationship between the estimated angle of arrival and a plurality of antenna switching patterns; sample the CTE during a plurality of the sample slots using the preferred antenna switching pattern; and use I and Q signals from the plurality of sample slots to calculate an angle of arrival. In certain embodiments, the software program comprises a plurality of antenna switching patterns. In some embodiments, the predetermined relationship associates each estimated angle of arrival with one of the plurality of antenna switching patterns. In some embodiments, the antenna switching pattern associated with each estimated angle of arrival minimizes an absolute error, wherein the absolute error is defined as an absolute value of a difference between the estimated angle of arrival and an actual angle of arrival. In some embodiments, the software program further comprises instructions that enable the device to: select an updated preferred antenna switching pattern using the angle of arrival calculated using the preferred antenna switching pattern, based on the predetermined relationship between the angle of arrival and a plurality of antenna switching patterns; sample the CTE during a plurality of the sample slots using the updated preferred antenna switching pattern; and use I and Q signals from the plurality of sample slots to calculate an improved angle of arrival.

