ESA antennas are used for a wide range of applications including cellular telephone networks, telemetry systems and automotive, shipboard and airborne radar systems. ESA antennas capable of efficiently radiating over wide bandwidths enable systems having flexibility for multiple mode operation. The growing interest in ultra-wideband (UWB) communications has lead to implementations in which a single ESA antenna is used to accommodate all frequencies of interest. ESA antennas often include an array of notch antenna elements. Each element includes an electrically conductive body having a slot. Generally, the slot includes a feed end which is positioned near a stripline feed and a radiating end which couples the RF signal in the stripline into the air or other medium. The stripline is typically embedded below the surface of a dielectric substrate and extends below the feed end of the slot to enable efficient coupling of an RF signal to be transmitted from the element. The notch antenna element can also be used to couple electromagnetic energy incident at the wide end of the slot into the stripline as a received RF signal. Various parameters affect the frequency content of the RF signal propagating from the element including, for example, the geometries of the base of the notch antenna element and the aperture in a conductive coating on the adjacent surface of the dielectric substrate, and material properties of the dielectric substrate.
Array antennas constructed of slot antennas and TEM horns generally use vertical feeds that are easily accommodated by a brick architecture as is known in the art. A description of brick architectures and tile architectures is provided in section II of the publication of Robert J. Mailloux, Proceedings of the IEEE, Vol. 80, No. 1, January 1992. Typically, array antennas constructed according to the brick architecture are deeper and heavier than array antennas employing the tile architecture where the distribution of RF signals is accomplished in one or more layers that are parallel to the antenna aperture plane. Conventional notch antennas require a feed that extends away from the antenna element so that layered connections are not practical.