Performance Analysis of BLE-5.1 Angle of Arrival Estimation Using Embedded Radiation Patterns on a 3 × 3 Uniform Rectangular Array

The introduction of new Direction finding (DF) features in Bluetooth Low Energy (BLE) 5.1, has brought about new hardware design requirements for locators. These requirements include the ability to support accurate and fast direction-finding algorithms while maintaining compactness. To address these needs, a uniform rectangular antenna array with octagonal patches has been chosen. The single antenna features a Circular Polarized (CP) Bandwidth (BW) of 3.1% for a 6-dB threshold and a CP BW of 1.59% for a 3-dB threshold. Different antenna array configurations have been compared in terms of the inter-element distance of the radiators to find a balance between antenna miniaturization and accuracy. From this analysis, an array antenna prototype (i.e., locator BLE) has been manufactured. In this paper, we analyze the performance of Direction of Arrival (DoA) estimation in BLE by comparing the Conventional Steering Vector (CSV) approach with a new Embedded Radiation Pattern (ERP) approach, which takes into account mutual coupling effects and gain loss due to miniaturization. The Mean Absolute Error (MAE) served as the performance metric to assess the accuracy of the main DoA detection. ERP outperforms CSV, in no-loss and multi-path scenarios. Numerical simulations show that ERP offers higher accuracy (lower MAE over theta and Phi) when the number of snapshots increases. Performance evaluation for MUltiple SIgnal Classification (MUSIC) and Bartlett algorithms highlights that for a SNR >20 dB, the accuracy does not depend on the number of snapshots used and faster computation is achieved for a single snapshot.