A flush-mounted multifunctional slot aperture (combo-antenna) for automotive applications

Two novel antennas: a variable growth, two-arm slot spiral and an annular slot are combined into a single, multicavity backed configuration. The spiral occupies the center/interior region and operates as a second mode circularly polarized (CP) antenna at 2.339 GHz. The annular slot occupies the outer region (at the periphery of the spiral) and is designed to operate as an omnidirectional vertically polarized antenna at 1.472 GHz. This combo antenna is intended for automotive applications and it was designed using the finite element-boundary integral method. Its performance was verified experimentally in a stand alone configuration and while mounted on a vehicle platform.