Variable directivity antenna and variable directivity antenna system using the antennas
First Claim
1. A variable directivity antenna comprising:
- a first antenna group including first and second antennas for receiving a radio wave in a first frequency band, said first and second antennas being disposed in parallel with and spaced from each other by a distance less than a half of a wavelength in said first frequency band, said first and second antennas exhibiting an 8-shaped directivity along a line perpendicular to the length direction thereof; and
phase shifting means for adjusting phases of received signals from said first and second antennas and combining the phase-adjusted signals in such a manner that the resultant signal selectively assumes a first directivity state in which said resultant signal exhibits a directivity in a first direction which is from said first antenna toward said second antenna, and a second directivity state in which said resultant signal exhibits a directivity in a second direction which is from said second antenna toward said first antenna,wherein said phase shifting means comprises;
combining means to which the received signals from said first and second antennas are supplied;
a first fixed phase shifter disposed between said combining means and said first antenna; and
variable phase shifting means disposed between said second antenna and said combining means;
said variable phase shifting means, in said first directivity state, coupling the received signal from said second antenna as it is to said combining means, and, in said second directivity state, coupling a second fixed phase shifter between said second antenna and said combining means;
said first fixed phase shifter providing such an amount of phase shift that, in said first directivity state, signals coming from said second direction received by said first and second antennas are substantially in opposite phase, said second fixed phase shifter providing such an amount of phase shift that, in said second directivity state, a received signal from said second antenna is substantially in opposite phase with an output signal of said first fixed phase shifter.
1 Assignment
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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 half 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).
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Citations
16 Claims
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1. A variable directivity antenna comprising:
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a first antenna group including first and second antennas for receiving a radio wave in a first frequency band, said first and second antennas being disposed in parallel with and spaced from each other by a distance less than a half of a wavelength in said first frequency band, said first and second antennas exhibiting an 8-shaped directivity along a line perpendicular to the length direction thereof; and phase shifting means for adjusting phases of received signals from said first and second antennas and combining the phase-adjusted signals in such a manner that the resultant signal selectively assumes a first directivity state in which said resultant signal exhibits a directivity in a first direction which is from said first antenna toward said second antenna, and a second directivity state in which said resultant signal exhibits a directivity in a second direction which is from said second antenna toward said first antenna, wherein said phase shifting means comprises; combining means to which the received signals from said first and second antennas are supplied; a first fixed phase shifter disposed between said combining means and said first antenna; and variable phase shifting means disposed between said second antenna and said combining means; said variable phase shifting means, in said first directivity state, coupling the received signal from said second antenna as it is to said combining means, and, in said second directivity state, coupling a second fixed phase shifter between said second antenna and said combining means; said first fixed phase shifter providing such an amount of phase shift that, in said first directivity state, signals coming from said second direction received by said first and second antennas are substantially in opposite phase, said second fixed phase shifter providing such an amount of phase shift that, in said second directivity state, a received signal from said second antenna is substantially in opposite phase with an output signal of said first fixed phase shifter. - View Dependent Claims (2, 3)
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4. A variable directivity antenna comprising:
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a first antenna group including first and second antennas for receiving a radio wave in a first frequency band, said first and second antennas being disposed in parallel with and spaced from each other by a distance less than a half of a wavelength in said first frequency band, said first and second antennas exhibiting an 8-shaped directivity along a line perpendicular to the length direction thereof; and phase shifting means for adjusting phases of received signals from said first and second antennas and combining the phase-adjusted signals in such a manner that the resultant signal selectively assumes a first directivity state in which said resultant signal exhibits a directivity in a first direction which is from said first antenna toward said second antenna, and a second directivity state in which said resultant signal exhibits a directivity in a second direction which is from said second antenna toward said first antenna; wherein said first and second antennas are first and second dipole antennas, respectively, having their entire lengths so selected as to receive a radio wave in said first frequency band;
extension elements are disposed in line with and outward of opposite ends of each said dipole antennas;
the sum of the lengths of said first dipole antenna and said extension elements disposed outward of said first dipole antenna is such as to receive a radio wave in a second frequency band lower than said first frequency band, the sum of the lengths of said second dipole antenna and said extension elements disposed outward of said second dipole being such as to receive a radio wave in said second frequency band; and
switch means are connected between said first dipole antenna and said extension elements disposed outward of said first dipole antenna, and between said second dipole antenna and said extension elements disposed outward of said second dipole antenna.
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5. A variable directivity antenna comprising:
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a first antenna group including first and second antennas for receiving a radio wave in a first frequency band, said first and second antennas being disposed in parallel and spaced by a distance less than a half of a wavelength in said first frequency band, said first and second antennas exhibiting an 8-shaped directivity along a line perpendicular to the length direction thereof; a second antenna group including third and fourth antennas for receiving a radio wave in said first frequency band, said third and fourth antennas being disposed in parallel with and spaced by said distance from each other, and exhibiting an 8-shaped directivity along a line perpendicular to the length direction thereof, said third and fourth antennas being disposed perpendicular to said first and second antennas; first phase shifting means for adjusting phases of received signals from said first and second antennas and combining the phase-adjusted signals in such a manner that the resultant signal selectively assumes a first directivity state in which said resultant signal exhibits a directivity in a first direction which is from said first antenna toward said second antenna, and a second directivity state in which said resultant signal exhibits a directivity in a second direction which is from said second antenna toward said first antenna; second phase shifting means for adjusting phases of received signals from said third and fourth antennas and combining the phase-adjusted signals in such a manner that the resultant signal selectively assumes a third directivity state in which said resultant signal exhibits a directivity in a third direction which is from said third antenna toward said fourth antenna, and a fourth directivity state in which said resultant signal exhibits a directivity in a fourth direction which is from said fourth antenna toward said third antenna; and signal combining means for adjusting in value and combining an output signal of said first phase shifting means in said first or second directivity state and an output signal of said second phase shifting means in said third or fourth directivity state, and providing an output signal exhibiting a directivity in a selected one of said first through fourth directions and directions between said first through fourth directions. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification