Patent ID: 7620375

Claim:
An apparatus comprising a first antenna system comprising at least first and second antennas installed at respective fixed locations, said first and second antennas each being aimed toward a second antenna system, and transmitter means for applying to said first antenna a first radio-frequency signal having energy in a particular frequency band and representing a first data stream, and for applying to said second antenna a second radio-frequency signal having energy in said particular frequency band and representing a second data stream, said first and second antennas being located with respect to each other and with respect to said second antenna system in such a way that at least two versions of said first radio-frequency signal, having substantially different phases, arrive at said second antenna system and in such a way that at least two versions of said second radio-frequency signal, having substantially different phases, arrive at said second antenna system, wherein said second antenna system comprises at least third and fourth antennas, wherein said at least two versions of said first radio-frequency signal arrive at said third and fourth antennas, respectively, wherein said at least two versions of said second radio-frequency signal arrive at said fourth and third antennas, respectively, and wherein said first antenna system is fixed at a distance D from said second antenna system and said first and second antennas are fixed at a distance L 1 =λD/2 L 2 from one another, where λ is a wavelength within said frequency band and L 2 is the distance between said third and fourth antennas.