Publications

This document presents L-band antenna patterns for a variety of general aviation and air carrier aircraft; these pattern were based on scale-model measurements. The antenna patterns are described by aircraft-coordinate-referenced elevation vs azimuth gain-contour maps. This method of presentation conveniently displays the effects of aircraft configuration on antenna patterns and...

This report provides a discussion of the design of the DABS network management function. Network management is responsible for the interaction between the local sensor and the adjacent connected sensors. Based on a dynamic interpretation of the coverage map and the status of the network, network management determines (a) the...

A ground based system to precisely locate aircraft in three dimensions based on transponder replies has been designed. Field tests have been conducted to validate the design of the elevation performance. This document reports on the principle of operation, experimental hardware and field test of the Precision Altitude and Landing...

The DABS link performance is computed using the present values for the system operating parameters and the available models that describe environment and aircraft antenna effects. The various fade mechanisms are described, and a statistical determination of performance is proposed. The performance is computed for various sets of conditions including...

This report describes the techniques and apparatus used to measure the directional patterns of aircraft ATC transponder antennas (L-Band) using digital techniques and magnetic tapes for data storage. Algorithms involved in data normalization, cross-polarization correction and coordinate conversations are discussed. Some typical applications of the data are illustrated with actual...

A new type of radar digital signal processor for use with ASR radars is described. It features spectral processing accomplished by combining a 3-pulse canceller with an 8-point, weighted, discrete Fourier transform and adaptive thresholds. This combination of circuits provides a 20-dB increase in MTI improvement factor over present ASR's...

This report explains the operation of the DABS uplink encoder and provides information useful in diagnosing its performance. Several techniques which may be useful in analyzing encoder operation are presented. One technique involves only the use of address-parity tables and modulo-2 addition. The address-parity tables included are based upon the...

Radiation patterns are examined for L-Band beacon antennas mounted on aircraft ranging from small, single-engine, general aviation aircraft to the Boeing 747. The data analyzed consists of antenna gain values taken in two degree steps over a spherical surface centered at the antenna location. Data from three representative scale model...

This report provides a full discussion of the design of the DABS channel management function. Channel management regulates all activity on the RF channel, scheduling ATCRBS interrogations and DABS roll-call interrogations and replies. Channel management arranges for multiple interrogations when required to satisfy both the surveillance and the communications functions...

The DABS sensor timing subsystem, which consists of two clocks driven from a common station standard, is the subject of this paper. The subsystem configuration is described and the rationale for this design briefly given. Emphasis is on the techniques for sychronization to an external standard, coordination with other sensors...