Communications: radio wave antennas – Antennas – With support for antenna – reflector or director
Reexamination Certificate
1999-05-26
2001-04-03
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
With support for antenna, reflector or director
C343S726000, C343S793000
Reexamination Certificate
active
06211846
ABSTRACT:
The present invention relates to antenna M for radio direction-finding as installed on ast, e.g. the mast of a ship.
BACKGROUND OF THE INVENTION
The systems conventionally used in amplitude radio direction-finding (DF) are systems having crossed loops or systems having parallel loops distributed around the mast, where the latter systems present the advantage over crossed loop systems of making it possible to obtain considerable improvements in terms of the amount of error associated with readings, particularly when the direction of incidence of the electromagnetic wave to be measured coincides with the axis of the ship. As a general rule, crossed loop systems and parallel loop systems include an omnidirectional reference antenna which is a dipole antenna carried by the mast, which extends along the axis said mast, extending it upwards.
The accuracy of such DF systems is very highly affected in the high frequency (HF) range by reflections on obstacles placed in the vicinity of the antennas, and particularly when the system is used on board a ship, by reflections from the superstructure of the ship, its masts and its transmitter antennas.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the invention is to propose a loop type antenna system in which the means which are used for generating the reference signal are decoupled from the mast so that the currents induced in the mast are not transmitted to said reference signal, and in which said means are also completely decoupled from the loop antennas, so that the reference signal is entirely independent of the measurement signals.
The solution of the invention is a system comprising at least two loop antennas and means for generating a reference signal, wherein said means comprise a plurality of dipoles distributed around the mast and parallel thereto, and means for summing the signals output by the various dipoles, the resulting sum signal being used as the reference signal.
The system is advantageously associated with the following characteristics taken singly or in any technically feasible combination:
the dipoles are carried by the loop antennas;
the system comprises a plurality of loop antennas, and the dipoles extend in the planes of said loop antennas;
the system comprises four loop antennas distributed around the mast and parallel in pairs, together with four dipoles which extend parallel to the mast, on the axes of symmetry of said loop antennas;
each of said dipoles is constituted by two segments extending symmetrically rom a midpoint at the bottom of the associated loop;
the loops are tubular elements within which there extends a loop of wire, each of said loops having a gap in its top portion;
the loop antennas and the dipoles are connected to the mast via tubular arms to which said loop antennas and the dipoles are fixed, and cables extend along said arms and the mast to connect the outputs of said antennas to processing means;
the system comprises crossed loops
each loop carries two dipoles which are diametrically opposite and which extend parallel to the axis of the mast, being fixed to said loops substantially halfway up them; and
the HF antenna system is advantageously used on board a ship.
REFERENCES:
patent: 3093827 (1963-06-01), Travers
patent: 3611389 (1971-10-01), Coors et al.
patent: 3665479 (1972-05-01), Silliman
patent: 3721990 (1973-03-01), Gibson et al.
patent: 4207572 (1980-06-01), Hipp et al.
patent: 4916454 (1990-04-01), Bull et al.
patent: 5264862 (1993-11-01), Kumpfbeck
patent: 5300885 (1994-04-01), Bull
patent: 5521608 (1996-05-01), Brandt et al.
patent: 3619028 (1987-12-01), None
patent: 2576152 (1986-07-01), None
Patent abstracts of Japan; vol. 008, No. 059 May 17, 1984.
Blakely & Sokoloff, Taylor & Zafman
Chen Shih-Chao
Societe Technique d'Application et de Recherche Electroniqu
Wong Don
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