Abstract: An ice detection warning system mountable on board an aircraft for inflight monitoring of the airspace ahead of the aircraft comprises: a first plurality of optical elements configured to direct a pulsed laser beam at a first wavelength from a laser source into the airspace ahead of the aircraft; a second plurality of optical elements configured to separate received backscattering of light from the laser beam into a plurality of predetermined wavelengths; a plurality of light detectors for detecting the light of the separated plurality of wavelengths, respectively, and generating respectively corresponding plurality of electrical signals representative of the light detected thereby; and a processor for processing the plurality of electrical signals to determine if airspace conditions ahead of the aircraft are likely to cause ice accretion on the surface of the aircraft, and for generating a warning indicative thereof.

Abstract: A method of determining accurately and expeditiously the frequency of a coherent signal from an incoming electrical signal is disclosed. The method comprises the steps of: generating a time sequence of sampled data signals from the incoming electrical signal; detecting the coherent signal in the time sequence of sampled data signals and generating a frequency estimate thereof; and determining the frequency of the detected coherent signal based on a function of the frequency estimate and a time segment of sampled data signals associated with the coherent signal. A system for performing the same is also disclosed.