Communications: radio wave antennas – Antennas – Spiral or helical type
Patent
1997-11-03
2000-01-25
Wong, Don
Communications: radio wave antennas
Antennas
Spiral or helical type
343754, H01Q 136
Patent
active
060183276
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a spiral antenna constituted by a single wire, and more particularly, to a spiral antenna whereby a tilted beam can be formed.
BACKGROUND ART
Communications using circular polarized waves are commonly conducted in the fields of mobile communications and satellite communications. Helical antennas and spiral antennas capable of transmitting and receiving circular polarized waves are commonly employed in communications using these circular polarized waves.
A helical antenna has maximum directivity in the direction of its helical winding axis, while a primary mode spiral antenna has maximum directivity in a perpendicular direction to the antenna surface. A secondary mode spiral antenna has bidirectional radiation characteristics.
However, in the field of communications, there are cases where a particular communications direction is required, as in satellite communications. If a specific communications direction is required the antenna beam must be set such that it matches the angle of elevation and the azimuth angle thereof.
Therefore, conventionally, the antenna is so constructed that the angle of elevation of the antenna beam can be matched to the angle of elevation of the communications direction by inclining the antenna itself, and the antenna as a whole is rotatable so that when it is mounted in a mobile station, it can be aligned with the azimuth angle of the communications direction.
However, if the antenna itself is inclined such that the beam emitted from the antenna has a specific angle of elevation, then the surface area of the antenna exposed to wind increases and it becomes necessary to strengthen the antenna fixing means. Moreover, the height of the antenna increases and there is a risk that it may exceed a maximum height when it is mounted in a mobile station.
Therefore, it is an object of the present invention to provided a single wire spiral antenna whereby the surface area of the antenna exposed to the wind can be reduced, the height of the device can be reduced, and the radiation beam of a circular polarized wave can be tilted.
SUMMARY OF THE INVENTION
In order to achieve the aforementioned object, in the single wire spiral antenna of the present invention, a single arm spiral antenna constituted by a single wire is positioned above the ground plane at a prescribed interval therefrom and, taking the wavelength used as .lambda., the spiral circumference of said spiral antenna is set to between 2 .lambda. and 3 .lambda..
Furthermore, taking the wavelength used as .lambda. and the spiral circumference of a single arm spiral antenna element constituted by a single wire set to between 2 .lambda. and 3 .lambda., a plurality of said spiral antenna elements are positioned above a reflective plate at a prescribed interval therefrom.
In a single wire spiral antenna according to the present invention of this kind, it is possible to tilt a beam with respect to the axis perpendicular to the antenna surface, and by aligning the angle of elevation of the beam with the communications direction, the spiral antenna can be set up in a horizontal plane. Therefore, the set-up height of a spiral antenna capable of emitting a beam at a desired angle of elevation can be reduced, the surface area of the antenna exposed to wind can be reduced, and the antenna can be prevented from exceeding a height limit even when mounted in a mobile station.
Furthermore, even if an array of single wire spiral antennas of this kind is formed, a plurality of antennas should be arranged in a horizontal direction, so there is no increase in the set-up height of the spiral antenna.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1a is a top view showing the composition of a mode for implementing a single wire spiral antenna according to the present invention; and FIG. 1b is a side view of same;
FIG. 2 shows a radiation pattern in plane Y-Z of a single wire spiral antenna according to the present invention;
FIG. 3 shows a radiation pattern in plane X-Y of a single wire spiral antenna acco
REFERENCES:
patent: 2977594 (1961-03-01), Marston
patent: 3034121 (1962-05-01), Riblet
patent: 3374483 (1968-03-01), Fenwick
patent: 3945016 (1976-03-01), Bizouad et al.
patent: 3956752 (1976-05-01), Phelan et al.
patent: 4243993 (1981-01-01), Lamberty et al.
patent: 5589842 (1996-12-01), Wang et al.
Makino Mitsuya
Nakano Hisamatsu
Clinger James
Nippon Antena Kabushiki Kaisha
Wong Don
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