Phase measuring method and apparatus
First Claim
1. A method of obtaining a primary measurement of the differences in the phase relationship between a pair of comparison signals at predetermined different times, the two comparison signals existing simultaneously and having the same comparison frequency, a first of the comparison signals being produced at a first station and a second of the comparison signals being produced at a second station spaced from the first station, which method comprises:
- generating at the first station a first frequency-stable reference signal having a first reference frequency suitably close to the comparison frequency;
generating at the second station a second frequency-stable reference signal having a second reference frequency suitably close to the comparison frequency;
measuring at the first station the phase relationship between the first comparison signal and the first reference signal at each of said predetermined times to provide a first secondary measurement;
measuring at the second station the phase relationship between the second comparison signal and the second reference signal at each of said predetermined times to provide a second secondary measurement; and
bringing together and suitably processing the first and second secondary measurements to extract therefrom said primary measurement.
1 Assignment
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Accused Products
Abstract
A continuous wave electromagnetic distance measuring system comprises a master station 12.3 and a remote station 12.4. A pattern signal having an accurately known pattern frequency is propagated electromagnetically from the master station to the remote station and an auxiliary pattern signal is propogated electromagnetically from the remote station to the master station. Mixing of the pattern and auxiliary pattern signals produces a first comparison signal at the master station and a second comparison signal at the remote station, the comparison signals each having a frequency which is equal to the frequency difference between the pattern and auxiliary pattern signals. The first comparison signal is phase compared with a first reference signal to provide first phase data, and the second comparison signal is phase compared with a second reference signal to provide second phase data. The second phase data is relayed in coded form to the master station. First and second phase data resulting from a plurality of pattern/auxiliary pattern signal combinations is processed at the master station to obtain an accurate indication of the distance between the stations. The pattern signal and the first reference signal are each derived from a first clock signal. Similarly, the auxiliary pattern signal and the second reference signal are each derived from a second clock signal. By selection of suitably stable reference oscillators for producing the clock signals, errors introduced through phase slip between the clock signals can be reduced to negligible proportions. There is disclosed a method of compensating precisely for any such errors by computing and then applying a correction factor. There is also disclosed a method of straddle measuring in which any such errors automatically fall away.
17 Citations
10 Claims
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1. A method of obtaining a primary measurement of the differences in the phase relationship between a pair of comparison signals at predetermined different times, the two comparison signals existing simultaneously and having the same comparison frequency, a first of the comparison signals being produced at a first station and a second of the comparison signals being produced at a second station spaced from the first station, which method comprises:
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generating at the first station a first frequency-stable reference signal having a first reference frequency suitably close to the comparison frequency; generating at the second station a second frequency-stable reference signal having a second reference frequency suitably close to the comparison frequency; measuring at the first station the phase relationship between the first comparison signal and the first reference signal at each of said predetermined times to provide a first secondary measurement; measuring at the second station the phase relationship between the second comparison signal and the second reference signal at each of said predetermined times to provide a second secondary measurement; and bringing together and suitably processing the first and second secondary measurements to extract therefrom said primary measurement. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. Apparatus for obtaining a primary measurement of the differences in the phase relationship between a pair of comparison signals at predetermined different times, the two comparison signals existing simultaneously and having the same comparison frequency, a first of the comparison signals being produced at a first station and a second of the comparison signals being produced at a second station spaced from the first station, which apparatus comprises:
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means at the first station for generating a first frequency-stable reference signal having a first reference frequency suitably close to the comparison frequency; means at the second station for generating a second frequency-stable reference signal having a second reference frequency suitably close to the comparison frequency; means at the first station for measuring the phase relationship between the first comparison signal and the first reference signal at each of said predetermined times to provide a first secondary measurement; means at the second station for measuring the phase relationship between the second comparison signal and the second reference signal at each of said predetermined times, thereby to obtain a second secondary measurement; and means for bringing together and suitably processing the first and second secondary measurements to extract therefrom said primary measurement. - View Dependent Claims (10)
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Specification