Topics: Wide Area Augmentation System, Global Positioning System, Radio navigation Pages: 17 (3272 words) Published: October 13, 2013
GPS Landing System
Reference Antenna
Alfred R. Lopez
BAE Systems - Electronics, Intelligence and Support
450 Pulaski Road, Greenlawn, NY 11740 USA
Tel: +1 (631) 262-8021; Fax: +1 (631) 262-8053; E-mail:

The GPS landing system (GLS) is a reality today, and will undoubtedly become the workhorse system in the future. GPS aircraft navigation is currently utilized for aircraft en-route, terminal, and initial-approach navigation. It is expected that in 2009, a Category I GPS landing system will start its initial phase of a worldwide deployment. The ARL-1900 antenna was designed specifically to satisfy the stringent requirements for the Category I, II, and III GPS landing system reference-receiver stations.

A difficult problem for a Category I, II, and III GPS landing systems is the mitigation of ground-reflected multipath effects. The antenna must provide coverage of the upper hemisphere while suppressing ground-reflected multipath. In addition, the antenna must operate at the L1, L2, and L5 GPS frequencies, have right-hand circular polarization, and ideally have constant carrier and code (group) delay throughout the coverage region. Over a period of 15 years, BAE Systems has developed the ARL-1900 antenna, a unique antenna with near-ideal performance that satisfies the stringent requirements for a Category I, II, and III GPS landing systems. This paper reviewsthe requirements for a GPS landing system reference antenna, presents the design principles for the ARL-1900 antenna, describes its implementation, and presents performance data. Keywords: Antenna arrays; Global Positioning System; GPS reference antenna; delay effects; GPS antenna group delay; GPS antenna carrier delay; wideband GPS antenna

1. Introduction


he instrument landing system (ILS) was introduced in 1941. It was selected by the ICAO (International Civil Aviation
Organization) in 1946 as the international all-weather landing aid [1]. It is currently the primary worldwide aircraft landing system. It uses a localizer antenna to provide horizontal guidance with respect to the runway's centerline, and a glide-slope antenna to provide vertical guidance with respect to the runway's glide path. Distance-to-runway-threshold guidance is provided by marker beacon antennas and/or a DME (distance measuring equipment) antenna.

azimuth approach path, an elevation antenna provides vertical guidance with respect to the elevation approach path, and a distance-measuring-equipment antenna provides guidance with respect to the distance from the runway's threshold. However, the antenna technology is much different. A microwave landing system incorporates electronically scanned azimuth and elevation antennas operating at a much higher frequency, which provides significant performance advantages over an instrument landing system.

The microwave landing system (MLS) was originally
intended to replace the instrument landing system. The widespread deployment initially envisioned by its designers in the 1970s and 1980s never became a reality. GPS-based landing systems (GLS), notably WAAS (wide-area augmentation system), provide the same level of positional accuracy and substantially larger coverage, with no equipment needed at the airport. The dramatically lower cost and performance advantages of a wide-area-augmentation-system GPS landing system have led to the turning off of most existing microwave landing systems in North America. The microwavelanding-system mode of operation is basically the same as that of the instrument landing system. A microwave-landing-system azimuth antenna provides horizontal guidance with respect to the

The operation of the GPS aircraft navigation system is similar to that of the ubiquitous car GPS navigator. This has two key elements: a GPS receiver, including an antenna; and a geographical information system (GIS). The geographical information system integrates hardware, software, and data, and...
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