A wideband airport pseudolite architecture for the Local Area Augmentation System

by Kiran, Sai.

KIRAN, SAI. Ph.D. November 2003. Electrical Engineering A Wideband Airport Pseudolite Architecture for the Local Area Augmentation System (168 pp.) Director of Dissertation: Chris G. Bartone This dissertation documents the design, development, and field and flight testing of a WBAPL for integration into a prototype LAAS. One major area of risk in the LAAS CAT II/III program is the unresolved issue of sufficient system availability. One feasible, low-cost, means of augmenting the GPS constellation for LAAS to enhance availability is by the incorporation of APLs. Critical issues that seek consideration in APL design are a low-cost solution to the near-far problem, effective mitigation of APL multipath at the LGF reception sites, and a solution to the issue of measurement errors as a function of peak received signal power level. This dissertation details the development of a prototype WBAPL within the framework of LAAS requirements, with the intent of resolving the aforementioned issues. The architecture includes a simple and novel method to facilitate rapid direct-WB signal acquisition, and details a cost-effective resolution to the powerbias problem. Results from laboratory tests to verify and characterize the power-induced measurement errors are described in the dissertation. Independent solutions to the powerbias problem at the ground and airborne segments were incorporated into the prototype WBAPL architecture. The solution on the ground involves the employment of RF powercontrol techniques. With the aim of low-cost implementation, the solution adopted for the airborne segment relies on carrier-phase measurements as the aircraft approaches the WBAPL transmission antenna. A time-differenced carrier-phase positioning algorithm that does not require real-time resolution of the unknown carrier-phase integer ambiguities is adopted. This differential CP approach is launched from a carriersmoothed code based solution that is maintained from the beginning of the approach until the phase handover-point. A modification to the WBAPL single difference geometry matrix is incorporated into the TDCP algorithm. The proposed architecture was successfully flight-tested to demonstrate the feasibility of its incorporation into LAAS, the results of which are presented in the dissertation. The performance of the prototype WBAPL-inclusive LAAS is gauged in terms of the accuracy of the differential positioning solution. The integration of the WBAPL into the prototype LAAS provided an additional ranging measurement, and increased system availability. Approved: Chris G. Bartone Assistant Professor of Electrical Engineering