Array antennas, having a plurality of radiating elements, are increasingly used in adaptive and/or multibeam applications. They are expected to be an important element of future broadband wireless solutions since such antennas enable significant capacity gains to be produced, for example, using accurate beam steering and beam forming.
However, since the amplitude and phase weights of the array elements need to be accurately controlled in order to generate the desired beam patterns, the feed networks of such antennas are complex which means that the antennas are generally expensive to produce. In addition, they generally require multiple rows and columns, resulting in large structures with many piece parts, which are heavy.
With increasing use of such antennas it will become necessary to reduce complexity of manufacture in order achieve a reduction in cost. In order to allow easy mounting of such antennas and to reduce the cost of installation, it is also desirable to reduce the weight of such antennas.
Hitherto, antennas of this type have typically been formed using discrete dipole antennas mounted adjacent a planar reflector. The feed to each antenna has been achieved using a network of coaxial cables. Alternative structures also exist which employ microstrip patch elements and microstrip feed networks.