Doctor of Philosophy (PhD), Ohio University, 1998, Electrical Engineering & Computer Science (Engineering and Technology)

The Local Area Augmentation System (LAAS) is being developed to support precision approach and landing operations in and about the local area surrounding an airport. The LAAS Program is currently under development by the Federal Aviation Administration (FAA) with Minimum Aviation System Performance Standards for the LAAS being developed by RTCA, Incorporated. The LAAS uses differential Global Positioning System (DGPS) and includes one or more airport pseudolites (APL) to increase the availability for certain installations. This dissertation addresses the addition of a differentially corrected, ranging APL into a LAAS. Prior to this work, no ranging APL has been integrated into a prototype LAAS and demonstrated in a real-time flight environment showing that an increase in LAAS availability is feasible. The APL requirements resulted in a prototype APL transmitting and receiving subsystem with a coarse-acquisition (C/A) code format that could be operated at any frequency within the L1 ± 10.0 MHz band. To investigate the major APL error the developmental approach was performed in two phases. Phase I implemented an APL operating at a center frequency off-L1 and concentrated on multipath limiting. The Phase II on-L1 APL architecture implemented a unique pulsing, automatic gain control (AGC) and GPS Blanker technique in the common reception path to maximize APL signal tracking and minimize electromagnetic interference to DGPS. To minimize ground multipath for the APL geometry, which is more severe than for GPS, a multipath limiting antenna (MLA) was designed, fabricated, and tested within a 4-month period. The implementation of this MLA concept was a first for APL applications and also contributed to the successful multipath limiting of ground multipath at the DGPS LAAS Ground Station. This effort successfully demonstrated that ground multipath can be limited (with low variance and no long-term bias) for the APL geometry and that suitable precision approach performance can (open full item for complete abstract)

Committee: Frank van Graas (Advisor) Subjects:

Doctor of Philosophy (PhD), Ohio University, 2003, Electrical Engineering & Computer Science (Engineering and Technology)

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 power-bias problem. Results from laboratory tests to verify and characterize the power-induced measurement errors are described in the dissertation. Independent solutions to the power-bias problem at the ground and airborne segments were incorporated into the prototype WBAPL architecture. The solution on the ground involves the employment of RF power-control 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 carrier-smoothed 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-te (open full item for complete abstract)

Committee: Chris Bartone (Advisor) Subjects: