Abstract
The use of global navigation satellite system (GNSS) antenna arrays for applications such as interference counter-measure, attitude determination and signal-to-noise ratio (SNR) enhancement is attracting significant attention. However, precise antenna array calibration remains a major challenge. This paper proposes a new method for calibrating a GNSS antenna array using live signals and an inertial measurement unit (IMU). Moreover, a second method that employs the calibration results for the estimation of steering vectors is also proposed. These two methods are applied to the receiver in two modes, namely calibration and operation. In the calibration mode, a two-stage optimization for precise calibration is used; in the first stage, constant uncertainties are estimated while in the second stage, the dependency of each antenna element gain and phase patterns to the received signal direction of arrival (DOA) is considered for refined calibration. In the operation mode, a low-complexity iterative and fast-converging method is applied to estimate the satellite signal steering vectors using the calibration results. This makes the technique suitable for real-time applications employing a precisely calibrated antenna array. The proposed calibration method is applied to GPS signals to verify its applicability and assess its performance. Furthermore, the data set is used to evaluate the proposed iterative method in the receiver operation mode for two different applications, namely attitude determination and SNR enhancement.
Highlights
Global navigation satellite system (GNSS) applications utilizing antenna arrays are starting to gain significant attention due to their lower hardware and computational costs
All of the main uncertainties in the calibration process were modeled and it was shown that they could be separated into two parts; one is constant and the other one consists of directions of arrival (DOA)-dependent parameters
The estimated constant term could provide coarse estimates of satellite steering vectors, for more precise calibration the second stage provided compensation amplitude and phase for each incident signal corresponding to its DOA in a form of a set of look up tables for each antenna element
Summary
Global navigation satellite system (GNSS) applications utilizing antenna arrays are starting to gain significant attention due to their lower hardware and computational costs. Methods not requiring calibration do not employ any information about the array configuration, orientation or direction of the incident signals They do not generally involve the directions of arrival (DOA) of signals in their structure and could be employed as stand-alone methods for anti-jamming and anti-spoofing [5,6]. These methods are not complicated in terms of implementation and complexity, they may degrade receiver performance by accidentally nullifying signals. This initially requires an accurately calibrated array to specify the signal DOA, which is referred to as the steering vector or array manifold vector in the literature
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