CoreHW Bluetooth Direction Finding Solution
Direction finding enhancements (equipped with) Bluetooth 5.1 provide capabilities for high accuracy indoor and outdoor positioning systems. Bluetooth direction finding systems are cost-effective, very low energy consumption, and compact solutions offering unobtrusive hardware implementation in environments where satellite (GNSS) coverage is not sufficient. The technology allows locating objects, equipment, inventory and people accurately within buildings.
In conventional RSSI based proximity sensing systems signal strength is used to estimate distance to the tracked object. Bluetooth 5.1 increases the accuracy of the RSSI systems by providing angle estimates calculated based on signals from antenna arrays. Bluetooth standard supports two methods for bluetooth signal direction finding: Bluetooth Angle of Arrival (AoA) and Bluetooth Angle of Departure (AoD).
CoreHW indoor positioning technology works with Bluetooth® Low Energy (BLE) and brings accurate positioning capabilities to all devices that can scan BLE signals. This technology introduced with Bluetooth 5.1 brings new indoor locationing and business opportunities to any industry.
In the angle of arrival (AoA) method, the device to be tracked transmits a special direction finding signal using a single antenna. The receiving locator device, with multiple antennas or antenna array, calculates the relative signal direction. Then, based on the angle calculation of several locators, each object can be accurately located.
The number of locator/beacon devices in an AoA and AoD system affects position accuracy. Direction data can be achieved with one device but at least two devices are needed to calculate position. However, it is possible to calculate position data also by using one antenna array if height of the tracked devices is known and is taken into account in position calculations.
AoA locators can see phase differences of received signals from transmitting devices. Locator integrated BLE SoC generates IQ samples from the received signals. Signal direction can be calculated inside a locator based on the IQ samples or the IQ samples can be sent to an external processor for angle calculations.
AoD beacons work different than AoA locators. Instead of receiving multiple signals, AoD beacons transmits multiple special signals with phase differences. Signal direction can be calculated in the receiving device based on the IQ data.
AoA locators and AoD beacons are both based on use of multi-element antenna arrays.
CoreHW locator is a Bluetooth AoA locator device intended for indoor positioning system providers. Our locator includes CoreHW AoA antenna array board and CoreHW main board.
The design of antenna arrays is one of the most critical parts of the AoA/AoD systems to get reliable and accurate phase difference data for IQ sampling. Phase differences of the signals are due to the geometry of the antenna array and the relative location of each antenna element. The signals must be measured and transmitted with minimal impact to phase data and therefore the array shall be optimized for phase balances between antenna chains.
Phase differences can be calculated with two antenna elements; however, in real use cases the number of elements is chosen based on application specific requirements to achieve optimal performance for the system.
In AoA and AoD systems, only one element of an antenna array is active at a time. Therefore an reliable high accuracy RF switch is needed for antenna element controls.
CoreHW antenna array board contains 8 dual linear polarized patch antennas and CoreHW CHW1010 SP16T Bluetooth AoA/AoD capable antenna switch for Bluetooth AoA CTE sampling. It is highly capable of tracking tags with arbitrary antenna polarization and available in multiple sizes to support locator designs for different markets.
Antenna elements of antenna arrays are controlled by antenna switches. Typically the switches are integrated to antenna PCBs. Switching time of the used switch needs to be compliant with Bluetooth 5.1 requirements (1µs/2µs). Low current consumption is especially required for battery-powered devices.
Multichannel antenna arrays can be controlled by several regular antenna switches. However, manufacturing costs can be minimized by using low cost multichannel switches. RF efficiency of the system is kept optimal by selecting a switch with highly optimized RF channel isolation. Low phase-mismatch between switch paths minimizes residual error in computed angles of beam direction and subsequently improves estimated location accuracy.
CHW1010 and CHW1020 are a chip product family supporting Bluetooth® Low Energy (BLE) applications. CHW1010 and CHW1020 are the new generation RF Switches designed to transfer the real-time location data with a powerful indoor positioning and outstanding power efficiency.
In AoA systems, tracked tags continuously broadcast their location by transmitting direction finding-enabled packets (CTE). At its simplest, a tag contains an antenna, a BLE SoC and a power source. Antenna design of a tag is one of the most critical hardware components to ensure that CTE packets are transmitted equally to all intended directions. Hardware and firmware design of a BLE SoC shall be optimized to minimize current consumption and maximize battery life.
AoD mobiles are also single antenna devices, but they receive CTE packets from AoD beacons instead of transmitting. The devices are more complex since angle calculation and signal positioning algorithms run on AoD mobiles. In practice, an AoD mobile can be a smart phone or a tablet that supports Bluetooth 5.1 standards.
BLE Indoor Location System is a reliable solution which can be used in different location solutions like:
Here are some of many indoor positioning system applications and purposes the system may serve. This is a quick guide to how this technology can transform your business.
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