Microwave radio propagation in automobile engine compartment

With the aim of achieving a wireless harness system in an automobile engine compartment (EC), radio propagation channels from 1.5 to 8 GHz in ECs were characterized with numerous measurements. Because there are many metal objects in EC, the channel´s frequency-distance interdependence was taken into account in the characterization. As a result, the path loss exponents for distance were found to be about 1 and 3 below and above 450 mm, respectively. The exponent for frequency was 0.5 to 1. The delay spread increased as distance increased at a rate of about 3 ns/m. It also exhibited a decreasing trend with increasing frequency at the far distance.