Testing a Coherent Software Defined Radio Platform for Detection of Angle of Arrival of RF Signals

Past efforts in characterizing and preventing GPS/GNSS signal multipath propagation and interference have led to the development of commercial-off-the shelf (COTS) advanced receiver platforms capable of making angle-of-arrival (AoA) measurements. This paper investigates the testing of a low-cost, coherent radio platform called the KrakenSDR. The KrakenSDR is an experimental platform which has only recently become available and has a wide range of RF applications. In this work the KrakenSDR receiver functionality is characterized to better understand how it operates. Key components of the KrakenSDR such as the phase calibration, antenna array, and signal processing in a multiple signal classification (MUSIC) algorithm are studied. Laboratory testing with a function generator verified that the KrakenSDR can achieve phase coherence across its five input channels. In the field AoA testing was performed with a continuous wave (CW) RF signal source at 900 MHz. This testing revealed that the KrakenSDR can make AoA measurements to an accuracy within its specified field of resolution and also produces a confidence metric which can be used to check the accuracy of measurements. The KrakenSDR has a frequency range of 24 MHz – 1766 MHz making it capable of working at GNSS frequencies. However, there has not been an opportunity to test the KrakenSDR in the GNSS band yet. The future goal of this research is to extend the KrakenSDR into the GNSS range and further characterize its performance, ideally to be used in a GPS/GNSS interference localization system.