On the Potential of Multi-Mode Antennas for Direction-of-Arrival Estimation

Abstract

A multi-mode antenna (MMA) can be an interesting alternative to a conventional phased antenna array for directionof-arrival (DoA) estimation. By MMA we mean a single physical radiator with multiple ports, which excite different characteristic modes. In contrast to phased arrays, a closed-form mathematical model of the antenna response, like a steering vector, is not straightforward to define for MMAs. Instead one has to rely on calibration measurement or electromagnetic field (EMF) simulation data, which is discrete. To perform DoA estimation, an array interpolation technique (AIT) and wavefield modeling (WM) are suggested as methods with inherent interpolation capabilities, fully taking antenna nonidealities like mutual coupling into account. We present a non-coherent DoA estimator for low-cost receivers and show how coherent DoA estimation and joint DoA and polarization estimation can be performed with MMAs. Utilizing these methods, we assess the DoA estimation performance of an MMA prototype in simulations for both 2D and 3D cases. The results show that WM outperforms AIT for high SNR. The coherent estimation is superior to non-coherent, especially in 3D, because non-coherent suffers from estimation ambiguities. In conclusion, DoA estimation with a single MMA is feasible and accurate.

Multi-Mode Antenna Enabled Direction-of-Arrival Estimation for Swarm Navigation

“…An MMA is a multiport antenna, where each port features distinct radiation characteristics. Thus, an MMA with M ports can be described by their gain pattern g m (φ) and phase pattern Φ m (φ) [18], [27]. For port m and DoA φ we get the antenna response a m (φ) = g m (φ)e jΦm(φ) .…”

“…The antenna response must be square integrable and the U basis functions orthonormal on the manifold φ ∈ [−π, π). An extension to 3D is possible [18], [29], [30], but out of scope for this paper. A suitable basis for 2D is given by the Fourier functions…”

“…Agent orientation is closely linked to the direction-ofarrival (DoA), which is classically observed using antenna arrays [17]. Recently, MMAs have been proposed as a new approach for DoA estimation [18]- [21]. An MMA is based on the theory of characteristic modes [22], [23] and can be defined as a multiport antenna, where different characteristic modes are excited independently.…”

Single-Element Beamforming using Multi-Mode Antenna Patterns

“…Emphasis is on increasing the overall sum-rate of the system. Contrary, in [9], [10] multi-mode antennas are used for angle-of-arrival estimation for the purpose of precise positioning. In the latter contributions, a single multi-mode antenna element is modeled as a uniform linear array (ULA).…”

In-Field Calibration of Antennas or Antenna Arrays Using Wavefield Modeling

“…Multiport antenna systems like phased arrays [1], colocated antennas [2], [3] or multi-mode antennas [4], [5] enable direction-of-arrival (DoA) estimation of radio signals or transmit beamforming. This requires a precise knowledge of the antenna characteristics.…”