| 摘要 |
A method and system of measuring the differential time of flight of a signal transmitted between first and second transducers. First, multiple broadband signal pulses are transmitted in a first direction by the first transducer and received by the second transducer. Then, the received pulses are averaged to form a first received waveform. Next, multiple identical pulses are transmitted in a second direction and the received pulses are again averaged to form a second received waveform. Then, the first and second waveforms are cross-correlated. The peak of the cross-correlation data identifies a coarse measurement of the differential time of flight of the signal. Also, multiple sinusoidal signal pulses are transmitted in each direction and averaged, thereby creating third and fourth received waveforms. A first point is selected on the third waveform and first phase information is generated from a Fourier transform of the center frequency vector beginning at the first point. Then, a second point on the fourth waveform is determined by summing the first point and the coarse measurement. Second phase information is generated from a Fourier transform of the center frequency vector beginning at the second point. The second phase information is subtracted from the first phase information, and the difference is converted into a time value. That time value is added with the coarse measurement, thereby producing a precise differential time of flight measurement. |
