Full Wideband Calibration for an Array of Spatially Distributed Subarrays

Resilient GNSS reception is a critical requirement for automated and autonomous driving cars. Single-antenna receivers are prone to interference and spoofers and lack the possibility for mitigation. The usage of array antennas instead introduces the advantage to form spatial nulls in the direction of an emitting source. To counteract interferers, blind techniques can be employed for mitigation. In case of spoofers, deterministic approaches are typically desired. However, the analogue frontend channels introduce differential effects to incident signals while they travel from the reception at the antennas to the digitization at the ADCs, such as delay and frequency-dependent amplitude and phase characteristics. The desire for a hidden installation of the array in the area of passenger cars further increases the problem: The only possibility for an array installation is to distribute individual subarrays in the synthetic parts of the car, such as bumpers or side mirrors. This increases the lengths of the cables from antennas to the central processing unit and hence the mismatch after digitization. This paper presents an approach to a full calibration for an array of distributed subarrays, which is able to estimate differential delays and the frequency-dependent transfer characteristic to also incorporate wideband signals such as GPS L5 or Galileo E5a.