Analysis and design of a multi-band phased array using multi-feed dipole elements

Multifrequency-band phased array antennas are needed for airborne, shipboard, and ground based radar, communication, and EW applications. Such arrays can provide simultaneous, independently-scanned beams for multi-function operations. We have developed a multi-band phased array aperture which utilizes co-planar dipoles with multiple-feed ports to achieve a different effective dipole length for each operating frequency band. The basic geometry is shown. The radiating elements are connected to multiple excitation ports, where band-pass filters an used to achieve open- or short-circuit behavior at the desired operating frequency. Several frequency-selective ground screen layers may be placed behind the radiating layer to improve the match. The principle of operation is shown, using a dual-band cast as an example. In this simple dual-band case, both frequency bands of operation share a common solid ground plane. The analysis of this infinite array of multi-feed dipoles over a ground plane is given. An aperture design for tri-band operation is presented, together with the verification by waveguide simulator experiments. A parametric study of various ground screen effects is also summarized.