Method of detecting icy road conditions - uses comparison of HF waves through heated and unheated road sections

摘要

An ultra high frequency transistor or diode generator output is passed to a T divider where it is equally divided and passed along coaxial cables to conical transmission antennas at the roadside. They radiate across the road surface to receiving antennas which receive surface waves guided by conductors in the road surface. One set of conductors is heated by a continuous current source. In the absence of ice received signals are adjusted for phase quadrature at a magic T coupler by a phase shifter. Any unbalance due to icing is detected and amplified for signalling.