Nicholas DeMinco

Abstract: This paper discusses the basic aspects of radio-wave propagation and antenna modeling in the medium frequency (MF) band. This band covers the frequencies of 300 to 3000 kHz. More specifically, we are concerned with the ground wave and the sky wave in the 300 kHz to 1705 kHz band. The sky wave models described in this paper are valid from 150 kHz to 1705 kHz. The ground wave models described in this paper are valid from 10 kHz to 30 MHz. The AM Broadcast band of 535 to 1605 kHz is in this band and is planned to be used in the Advanced Traveler Information Systems (ATIS) of Intelligent Transportation Systems (ITS) for rural travelers. This system would provide information such as road conditions, road hazards, weather, and incident reporting. The 285 kHz to 325 kHz band is presently being used for a differential correction signal in another application of ITS called the Differential Global Positioning System (DGPS) that will be used for precision location of vehicles. The propagation of radio waves in this band depends on both a ground wave and a sky wave and is quite different from propagation at any other frequency. Antenna modeling in this band is also quite unlike that in other bands. This paper describes radio wave propagation together with antenna modeling in this frequency band so that a better understanding of the phenomena can be obtained for use in design and application of ITS subsystems. The models described here can be used for designing systems and making performance predictions for both of these ITS applications and any other systems that operate in this band. The paper contains descriptions of both sky-wave and ground-wave propagation models in addition to the methodology used to analyze antennas that operate in this band. A method of calculating and normalizing antenna gain for MF systems computations is also discussed. Some comparisons of measured and predicted data are also contained in the descriptions.

Keywords: communications; radio wave propagation; antennas; intelligent transportation systems

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