Communications: directive radio wave systems and devices (e.g. – Directive – Beacon or receiver
Reexamination Certificate
1999-03-11
2001-05-29
Gregory, Bernarr E. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Beacon or receiver
C342S147000, C342S157000, C342S368000, C342S417000, C342S444000, C342S445000
Reexamination Certificate
active
06239747
ABSTRACT:
FIELD OF INVENTION
The invention relates to an antenna system and method for direction finding.
BACKGROUND ART
Array antennas for direction finding are used to estimate the location of a source of an electromagnetic signal. An Adcock array antenna arranges four antenna elements in an orthogonal pattern for direction finding. For example, a cross is an orthogonal pattern in which each arm of the cross may be defined by two antenna elements. Typically, the antenna elements of an array antenna for direction-finding are mounted to a metallic structure, such as a tower. The tower may reflect the electromagnetic signal before or after it reaches the array antenna causing inaccuracies in measurements associated with the direction of the source of the electromagnetic signal. The electromagnetic signal may be modeled as an electromagnetic field or as a planar wavefront incident upon the antenna. Any other metallic objects in the vicinity of the antenna may perturb the electromagnetic field; hence, degrade the accuracy of direction finding. Thus, a need exists for reducing or eliminating the influence of unwanted reflections from surrounding metallic objects on a direction-finding antenna.
A direction-finding antenna is frequently used in applications where space conservation is of paramount importance. Aesthetic appearance of a direction-finding antenna may be facilitated by disguising the antenna to meet local zoning ordinances or contractual leasing requirements of an antenna site. Even where aesthetic appearance does not, in effect, limit size of the antenna, available space at a crowded antenna site or building roof-top may limit the practical maximum antenna size. Therefore, the direction-finding antenna may need to fit a particular volume constraint or an area constraint for mounting on a building, a tower, a monopole, a vehicle, or an airplane.
Wireless communication systems are expected to incorporate location-determining equipment, such as direction-finding antennas because of emergency “911” service, public safety, and law enforcement concerns. As cellular networks operate side-by-side with personal communication service networks on different frequency bands, person communication service infrastructure costs may be reduced by sharing existing cellular sites. Yet, the full benefit of sharing such infrastructure costs may only be realized with the availability of dual-band products. Thus, a need exists for a dual-band antenna for operation within the cellular band and the newer personal communication service (PCS) bands within the U.S. In addition, similar dual-band antennas are needed for the European cellular band and the newer personal communication network (PCN) in Europe.
SUMMARY OF THE INVENTION
In accordance with the invention, an array antenna for direction finding of received signals includes antenna elements. The antenna elements are arranged to define a triangular outline. The separations between the antenna elements are determined based upon a frequency band of operation. Phase-measuring devices (e.g., correlators) are coupled to the antenna elements for measuring differential phases of signals received between different pairs of the antenna elements. A processing system determines an angle of arrival of an electromagnetic field incident upon the antenna elements, based upon the measured differential phases and a geometric correction factor associated with the actual relationship existing between the antenna elements.
In one aspect of the invention, an array antenna includes antenna elements which define an adjustable triangular outline that may be adjusted to meet space constraints or reduce reflections from mounting conditions associated with the array antenna. The adjustment of the antenna elements is limited to certain geometric configurations with corresponding geometric correction factors to maintain the accuracy of estimating the angle of arrival.
In another aspect of the invention, a compact dual-band array antenna advantageously has common antenna elements which are shared between a first frequency band and a second frequency band. The common antenna elements and adjustable geometry are well-suited for mounting in a spatially confined area or economically serving multiple frequency bands from a single antenna site.
REFERENCES:
patent: 939477 (1976-02-01), Green et al.
patent: 5745078 (1998-04-01), Baghdady
patent: 5995046 (1999-11-01), Belcher et al.
patent: 591867 (1947-09-01), None
H. Alex Romanowitz, “Electrical Fundamentals and Circuit Analysis”, pp. 629-631; John Wiley & Sons; New York; 1966.
P.J.D. Gething, “Radio direction-finding and the resolution of multicomponent wave-fields”, pp. 159-173; Peregrinus Ltd.; Oxford, UK; 1978.
Gregory Bernarr E.
Lucent Technologies - Inc.
LandOfFree
Antenna system and method for direction finding does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Antenna system and method for direction finding, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Antenna system and method for direction finding will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2570555