Patent ID: 6914558
Filing Date: 2005-07-05
Classification: H01Q

Abstract:
1. A variable directivity antenna apparatus comprising: a first antenna device for receiving radio waves in a first frequency band, comprising first and second antennas each exhibiting an 8-shaped directivity extending along the direction perpendicular to the length direction of said first and second antennas, said first and second antennas being spaced in parallel with each other, with a spacing less than about a quarter of a wavelength of said first frequency band disposed therebetween; a second antenna device for receiving radio waves in said first frequency band, comprising third and fourth antennas each exhibiting an 8-shaped directivity extending along the direction perpendicular to the length direction of said third and fourth antennas, said third and fourth antennas being spaced in parallel with each other, with said spacing disposed therebetween, and extending in the direction perpendicular to said first and second antennas; first phase adjusting means for adjusting phases of reception signals resulting from reception by said first and second antennas of a radio wave and combining the phase adjusted reception signals in such a manner that the resulting combined signal selectively assumes a first directivity state in which the combined signal exhibits directivity toward a first direction perpendicular to said first and second antennas and assumes a second directivity state in which the combined signal exhibits directivity toward a second direction opposite to said first direction, said first direction being such a direction that a radio wave coming in said first direction arriving at said second antenna earlier than said first antenna; second phase adjusting means for adjusting phases of reception signals resulting from reception by said third and fourth antennas of a radio wave and combining the phase adjusted reception signals in such a manner that the resulting combined signal selectively assumes a third directivity state in which the combined signal exhibits directivity toward a third direction perpendicular to said third and fourth antennas and assumes a fourth directivity state in which the combined signal exhibits directivity toward a fourth direction opposite to said third direction, said third direction being such a direction that a radio wave coming in said third direction arriving at said fourth antenna earlier than said third antenna; and signal combining means for adjusting the level of the output signal of said first phase adjusting means in said first or second directivity state and the level of the output signal of said second phase adjusting means in said third or fourth directivity state, and combining the level adjusted output signals of said first and second phase adjusting means for developing an output signal selectively exhibiting directivity oriented toward said first, second, third and fourth directions and the directions between adjacent ones of said first, second, third and fourth directions; wherein: said first phase adjusting means phase shifts one of the reception signals from said first and second antennas by a predetermined amount to thereby produce said first directivity state, and phase shifts the other of the reception signals from said first and second antennas by said predetermined amount to thereby produce said second directivity state; and said second phase adjusting means phase shifts one of the reception signals from said third and fourth antennas by said predetermined amount to thereby produce said third directivity state, and phase shifts the other of the reception signals from said third and fourth antennas by said predetermined amount to thereby produce said fourth directivity state.