Fast signal acquisition technology for new GPS/Galileo receivers

Parallel acquisition units that drastically improve acquisition performance have been presented in the past for military and indoor applications. These units are usually dedicated to the acquisition of one particular code. Because GNSS receivers of the next generation must be able to acquire multiple signals with various code modulations, Septentrio developed a flexible hardware Fast Acquisition Unit (FAU), which is capable of acquiring any of the new civil signals. The paper begins with an overview of traditional signal acquisition techniques. The acquisition time is proportional to the two dimensions of the satellite acquisition space (frequency dimension and range dimension). The range dimension is directly related to the length (repeatability period) of ranging codes, hence the acquisition time significantly increases for long codes, such as Galileo and GPS L2C. Dedicated hardware acquisition units can drastically reduce this acquisition time. The new FAU is capable of acquiring any of the new civil signals including Galileo and modernized GPS. The uniqueness of this FAU is due to its flexible design, which allows it to support all the planned code modulations, including those from Galileo, GSTB-v2, and modernized GPS. The paper discusses the architecture and features of the new FAU, whereof the design is based on the combination of a matched filter with an FFT to search through the range/frequency space in a highly efficient manner. Performance analysis of the new FAU demonstrates that resulting acquisition times are short enough to ensure compliance with user application requirements.