Patent ID: 7483800

Claim:
A method for completing a blade measurement for rotating blades within a casing of a turbine engine, comprising the steps of: transmitting microwave energy via an antenna within the casing of the turbine engine; collecting in-phase and quadrature data associated with the microwave energy reflected by the blades and the casing; performing a complex Fast Fourier Transform (FFT) on the in-phase and quadrature data to generate positive frequency components and negative frequency components; separating the positive negative frequency components from the negative frequency components; performing an inverse FFT on each of the positive frequency components and the negative frequency components to generate complex time domain data associated with approaching and recessing velocity components; converting the complex time domain data to magnitude and phase values, the magnitude values comprising approaching and recessing magnitude values and the phase values comprising approaching and recessing phase values; identifying each crossing of the magnitude values with a predetermined threshold to define a blade region associated with a location for one of the blades proximate to the antenna; for the blade region, identifying a zero point velocity as the point where one of the approaching phase values equals one of the recessing phase values, the zero point velocity representing a location of the blade directly beneath the antenna; and processing blade data using the zero point velocity as an index.