Embodiments of the invention relate to
beamforming antennas such as can be used in
space division multiplexing systems.
Space division multiplexing can be used to increase
data capacity in
wireless networks by enabling different base stations to transmit signals within the same
frequency band. Each antenna beam can potentially be used to establish a
communication link within an area of
wireless coverage, and other communication links established on other antenna beams then represent interference to that user. In order to reduce interference, narrow beamwidths are desirable. These are typically achieved by increasing the aperture of the antenna in the
azimuth plane, and in arrangements that require finely divided angular sectors, a greater number of antennas will be required to give three hundred and sixty degree coverage. As a result, there is potentially a large increase in the total surface area of antennas which is undesirable, as it leads to increased wind loading of an antenna
tower. Embodiments of the invention provide an arrangement in which data are transmitted from a first
transmitter to a first
receiver using a first antenna beam, and data are transmitted from a second
transmitter to a second
receiver using a second antenna beam. The first antenna beam is formed by splitting the
signal from the first
transmitter into two parts with a first
phase relationship between the parts, each part being connected to an antenna. A second antenna beam is formed by splitting the
signal from the second transmitter into two parts with a second
phase relationship between the parts, each part being connected to one of the two antennas. An
advantage of embodiments of the invention is that data can be transmitted from different transmitters at the same frequency without interference, while presenting a smaller
antenna aperture than is required with conventional systems.