Marco Marinho, Halmstad University, Sweden; Per Gustafson, Gutec AB, Sweden; Felix Antreich, Aeronautics Technology Institute, Brazil; Stefano Caizzone, German Aerospace Agency, Germany; Alexey Vinel, Halmstad University, Sweden

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Abstract:

Multi-band or multi-frequency antennas have become essential for many Global Navigation Satellite Systems (GNSS) applications. These antennas allow a receiver to simultaneously receive from multiple bands, which is essential for ionosphere corrections, can help mitigating multipath induced biases, and improve overall system availability. Another advancement that has recently attracted attention in the GNSS community is the usage of antenna arrays at the receiver. These arrays can be used to enhance system performance in multiple ways such as using beamforming to null out interferers or multipath components or enable a receiver to estimate its attitude while relying solely on received GNSS signals. While both multi-band antennas and antenna arrays offer attractive advantages for precise GNSS positioning, merging such systems on a single receiver can be challenging. Antenna arrays have their performance largely dictated by their geometries and the spacing between antenna elements. This spacing is defined with respect to the frequency of the signal that is received at the antenna array. If the spacing is too large the receiver will suffer from inaccuracy introduced by ambiguities that will be present when trying to filter out undesired signals or when trying to estimate the direction of arrival of received signals. If the spacing is too small, the total array directivity will be lower, which will lead to more biased direction of arrival estimations or to beamformers with lobes that are too broad to filter out undesired signals. The relationship between frequency and geometry makes it impossible to create a multi-band antenna array that is optimal for every frequency received, as optimizing one frequency will inevitably lead to performance degradation in the remaining ones. To tackle this issue, a technique known as array interpolation can be employed. Array interpolation consists of creating a mathematical transformation that projects the signal received at a real and imperfect array onto an ideal and abstract receiver. A different array interpolation can be constructed for each individual frequency received at the array. Thus, array interpolation can be a valuable tool for allowing multi-band antenna arrays to achieve high performance over the entire range of frequencies they are designed to receive. This work studies the effects of optimizing antenna array geometries for a given frequency band while applying array interpolation over the array response for the remaining frequency bands. The performance of multiple array interpolation methods is verified, and the tradeoffs between performance and computational complexity is studied.