Optimized antenna placement improves near-field wireless sensing accuracy
Antenna Placement for Monostatic Near-Field Wireless Sensing
Information Theory
Summary
Positioning antennas correctly is really important for sensing objects nearby using wireless signals. The authors studied how to arrange antennas and set power levels so that the system's worst measurement error is as small as possible. They found exact mathematical formulas for this error and showed that placing antennas symmetrically and focusing transmit antennas at specific points works best. Their designs outperform common antenna setups, meaning the system can locate objects more accurately in the near field.
What this means in practice
- •For wireless communication engineers: Design antenna arrays for near-field devices to reduce positioning errors and improve sensing precision by adopting optimized antenna placement and power schemes.
- •For automotive radar system designers: Improve accuracy of vehicle-mounted near-field sensors by applying closed-form antenna placement strategies that minimize worst-case localization errors.
Authors
Jinjian Liu, Xianxin Song, Xianghao Yu
Abstract
The emergence of movable antenna technology enables flexible antenna placement, allowing transceiver antennas to more effectively exploit spatial degrees of freedom. In this paper, we investigate a monostatic near-field sensing system, aiming to minimize the worst-case squared position error bound (SPEB) over the entire near-field region by jointly optimizing the transmit and receive antenna placements, along with the transmit power allocation. Toward this end, we first derive the closed-form expression of SPEB by calculating the Cramér-Rao bound (CRB) for estimating the target's angle and distance. It is shown that the derived SPEB is governed by the power-weighted moments of the transmit antenna locations and the moments of the receive antenna locations, motivating the development of a moment-based optimization algorithm. Functional analysis of the SPEB's moment structure proves that the optimal antenna distributions can be realized by a centro-symmetric structure, and shows that the worst-case target is located at the array broadside on the Rayleigh boundary. Moreover, by leveraging moment-based analysis and the Richter-Tchakaloff theorem, we derive closed-form antenna distributions with three points supported at the aperture center and two edges. Specifically, the optimal transmit antenna distribution can be exactly realized by activating only three transmit antennas while the optimal receive antenna distribution consists of three clusters. Numerical results show that the proposed closed-form design significantly outperforms conventional antenna placements and power allocation benchmark schemes.