The Local Area Augmentation System (LAAS) is an augmentation of the Global Positioning System (GPS) to allow for precision approach and landing at airports. Stanford University has, with support from U.S. Federal Aviation Administration (FAA), developed a real time prototype of the LAAS Ground Facility (LGF) known as the Integrity Monitor Testbed (IMT). It is used to evaluate whether the LGF can meet the integrity and continuity requirements that apply to aircraft Category I precision approach (i.e. close to the runway, but non-zero visibility). The first generation IMT system was designed in the mid-1990s. Since that date computational power and, to a somewhat lesser extent, receiver technology has evolved dramatically. The dated processing platform and Radio Frequency (RF) hardware limit further progress. Therefore, a transition to a new and improved system is needed to further continue development and testing for Category I precision approach and to use as a starting point for Category II/III LGF development.
This thesis describes the design goals and motivation behind the second-generation IMT system, known as IMT2. The hardware upgrade involves new L1/L2 antennas, low-loss antenna cables, new L1 and L2-upgradeable GPS receivers, and a new computer platform. Considerable effort was placed on the computer platform as this is the element that has experienced the most advanced since the first prototype. The computer platform was designed to provide additional flexibility, incorporated new GPS hardware, and enhance the development environment. One key element of the upgrade has been the addition of new software to communicate with the receivers. This function, known as Signal-in-Space Receive and Decode 2 (SISRAD2), is now a modular means of integrating different receiver types, providing synchronization of receiver measurement packets, and fits the measurement packets into a single IMT2 data format.
Author: Normark, Per-Ludvig
Source: Luleå University of Technology
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