Broadband Scalable Antenna Arrays With Constant Beamwidths Fed by Frequency-Selective Networks

A novel concept of broadband scalable antenna arrays that allows achieving constant beamwidths across one frequency octave has been proposed. The presented antenna arrays consist of an odd number of broadband antenna elements equally spaced and fed by a frequency-selective feeding network. The feeding network gradually switches the signal between the radiating elements across the bandwidth. The required frequency characteristics for such a selective power divider have been shown and its circuit realization has been proposed. The presented concept has been verified by the design and measurements of an antenna array consisting of five radiating elements in which the beamwidth of around 24° is achieved. The developed antenna operates in the 2-4-GHz frequency range. Moreover, the presented concept has been extended showing the possibility of designing antenna arrays having an arbitrary odd number of effectively radiating elements and constant beamwidths over one frequency octave.