Patent ID: 7277063

Claim:
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.