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:

Master of Science (MS), Ohio University, 2001, Electrical Engineering & Computer Science (Engineering and Technology)

The next generation of advanced aircraft landing system will utilize the Global Positioning System (GPS). The availabilityof GPS is augmented by the use of pseudolites "pseudo satellites." Pseudolites transmit a GPS-like signal that can be used as a ranging source in place of or in addition to ranging sources from a satellite. The Local Area Augmentation System (LAAS) is being used to further augment GPS for precision approaches and landings by using a concept known as Differential GPS (DGPS). One major error source in DGPS is due to transmitted signal reflections (multipath) off nearby obstacles. Efficient antenna design can be used to mitigate multipath by severely attenuating signals from negative elevation angles. The research contained in this document was conducted in order to optimize the current wideband airport pseudolite (WBAPL) multipath limiting antenna (MLA) for pseudolite transmission in the LAAS. To that end, three phases of study were conducted. The first stage modeled the ground-to-air link between the WBAPL transmitting MLA and the reception antenna during approaches with an attempt to define optimal WBAPL antenna locations. The second stage was conducted to characterize the basic pattern requirements of the WBAPL transmitting MLA and sought to project a hypothetical coverage volume given a preliminary pseudolite antenna pattern. The third stage was performed to attain some level of validation for the new WBAPL MLA transmitting antenna pattern measured by an external contractor through the independent synthesis of a similar antenna radiation pattern.

Committee: Chris Bartone (Advisor) Subjects: