Variable directivity antenna and variable directivity antenna system using such antennas
First Claim
1. A variable directivity antenna comprising:
- at least two antenna elements each exhibiting a 8-shaped directivity pattern, said antenna elements being disposed generally in parallel with and spaced from each other by a distance shorter than a quarter of a wavelength employed; and
combining means coupled to said at least two antenna elements via associated feeders having different lengths;
the difference in length between said feeders being such that received signals resulting from reception by said at least two antenna elements of radio waves coming from a second direction opposite to a first direction toward and perpendicular to the length direction of said at least two antenna elements can be coupled in generally 180°
out of phase to inputs of said combining means;
said variable directivity antenna further comprising variable phase means disposed between one of said at least two antenna elements and said combining means, said variable phase means being adapted to selectively assume a first state in which said variable phase means couples said received signal from said one antenna element to said combining means without changing the phase of said signal, and a second state in which said variable phase means inverts the phase of said received signal from said one antenna element before coupling to said combining means.
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Accused Products
Abstract
Folded dipole antenna elements (2, 4) are disposed generally in parallel, being spaced by a distance smaller than a quarter of the wavelength employed. The antenna elements (2, 4) are connected to a combiner (16) via feeders (12, 14) having different lengths. The difference in length between the feeders (12, 14) is such that received signals resulting from a radio wave coming to the antenna elements (2, 4) from the front and received by the antenna elements (12, 14) are in phase with each other at the inputs (16a, 16b) of the combiner (16), whereas received signals resulting from a radio wave coming to the antenna elements (2, 4) from the back and received by the antenna elements (12, 14) are 180° out of phase with each other at the inputs (16a, 16b) of the combiner (16). A variable phase device (18) is connected between one of the antenna elements (2, 4) and the combiner (16) to selectively couple the in-phase or 180° out of phase version of the received signal from that one antenna element to the combiner (16).
30 Citations
22 Claims
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1. A variable directivity antenna comprising:
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at least two antenna elements each exhibiting a 8-shaped directivity pattern, said antenna elements being disposed generally in parallel with and spaced from each other by a distance shorter than a quarter of a wavelength employed; and
combining means coupled to said at least two antenna elements via associated feeders having different lengths;
the difference in length between said feeders being such that received signals resulting from reception by said at least two antenna elements of radio waves coming from a second direction opposite to a first direction toward and perpendicular to the length direction of said at least two antenna elements can be coupled in generally 180°
out of phase to inputs of said combining means;
said variable directivity antenna further comprising variable phase means disposed between one of said at least two antenna elements and said combining means, said variable phase means being adapted to selectively assume a first state in which said variable phase means couples said received signal from said one antenna element to said combining means without changing the phase of said signal, and a second state in which said variable phase means inverts the phase of said received signal from said one antenna element before coupling to said combining means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification