Optimizing Switching Pattern to Reduce CFO Effects in Single RF Chain Direction Finding Systems

Single RF chain multi-antenna wireless communication systems are increasingly favored for Direction of Arrival (DoA) estimation due to their low cost, efficiency and simplicity. However, non-simultaneous signal sampling and slight carrier frequency differences, known as carrier frequency offset (CFO), lead to phase errors that degrade DoA accuracy. In this paper, we propose an Antenna Switching Pattern (ASP) design method to minimize CFO-induced phase errors. The CFO errors are represented as phase weights and by calculating the center of gravity from these weights, we derive the candidates for optimal ASP. We performed a comparative analysis with conventional round-robin ASP, evaluating the DoA estimation error. MATLAB simulations using MUSIC algorithm with uniform linear and circular antenna arrays show significantly reduced DoA errors and reveal a CFO upper bound, making the method applicable in scenarios with coarse CFO estimation and correction.