Design of a multi-functional slot aperture (combo-antenna) for automotive applications

Two conformal, shallow cavity backed, slot antennas are combined into a single configuration to operate at different frequencies and with different electrical characteristics. This new combo-antenna is intended for use in automobile applications and demonstrates a new paradigm in antenna design. A specific design is presented for receiving digital audio broadcasting (DAB $1452-1492 MHz) and satellite digital audio radio system (SDARS - 2332.5-2345 MHz). The antenna consists of a slot spiral and annular ring(s) to deliver patterns that are either circularly or linearly polarised and satisfy various low angle pattern requirements. It is designed using a finite element boundary integral (FE-BI) (see Ozdemir, T. et al., IEE Proc. - Microw. Antennas Propagat., vol.246, no.6, p.447-54, 1999; D. Filipovic, at all., Proc. IEEE APS Int. Symp., p.414-417, 2001) code specially developed for radiating structures with narrow slot lines. The combo antenna is built on inexpensive 0.1575 cm thick FR-4 (ε = 4.25, tanδ = 0.014) substrate.