Impedance Variation Detection at MISO Receivers

Techniques have been proposed to estimate unknown antenna impedance due to time-varying near-field loading conditions at multiple-input single-output (MISO) receivers. However, it remains unclear when a change occurs and impedance estimation becomes necessary. In this letter, we address this problem by formulating it as a hypothesis test. Our contributions include deriving a generalized likelihood-ratio test (GLRT) detector to decide if the antenna impedance has changed over two groups of packets. This GLRT formulation leads to a novel optimization problem, but we propose a binary search based algorithm to solve it efficiently. Our derived GLRT detector enjoys a better detection and false alarm trade-off when compared with a well-known, reference detector in simulations. As one result, more transmit diversity significantly improves detection accuracy at a given false alarm rate, especially in slow fading channels.

Automated summary

This paper proposes a method to estimate antenna impedance in MISO receivers and addresses the problem of when impedance estimation is necessary. By formulating the problem as a hypothesis test and deriving a generalized likelihood-ratio test detector, the authors achieved a better trade-off between detection and false alarm compared to a reference detector. The results show that transmit diversity significantly improves detection accuracy, especially in slow fading channels.