Method and apparatus for distance measurement
First Claim
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1. A distance measuring method comprising the steps of:
- transmitting between at least one pair of first and second locations a respective first signal having a first propagation speed, wherein the or each said first signal includes a respective first modulation signal having a repetition period longer than a propagation time of said first signal between the at least one pair of the first and second locations, and wherein the or each said first signal is sequentially transmitted at two carrier frequencies, and said carrier frequencies are selected according to the respective first modulating signal;
transmitting between the or each pair of first and second locations a respective second signal having a second propagation speed higher than the first propagation speed; and
determining the distance between the first and second locations from the difference in propagation time between said first and second signals.
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Abstract
A method and apparatus for distance measurement is disclosed in which first and second signals having different propagation speeds are transmitted between a transmitter (2) at a first location and a receiver (3) at a second location. The distance between the first and second locations is determined from the difference in propagation time between the first and second signals.
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Citations
34 Claims
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1. A distance measuring method comprising the steps of:
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transmitting between at least one pair of first and second locations a respective first signal having a first propagation speed, wherein the or each said first signal includes a respective first modulation signal having a repetition period longer than a propagation time of said first signal between the at least one pair of the first and second locations, and wherein the or each said first signal is sequentially transmitted at two carrier frequencies, and said carrier frequencies are selected according to the respective first modulating signal;
transmitting between the or each pair of first and second locations a respective second signal having a second propagation speed higher than the first propagation speed; and
determining the distance between the first and second locations from the difference in propagation time between said first and second signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A transmitter for a distance measurement system, the transmitter comprising:
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a first emitter for emitting a first signal having a first propagation speed;
a second emitter for emitting a second signal having a second propagation speed higher than the first propagation speed;
first modulating means for modulating said first signal by a first modulation signal having a repetition period longer than a propagation time of the first signal from the first emitter to a detector; and
control means for controlling the delay between emission of said first and second signals, wherein the first emitter in use emits the first signal sequentially at two frequencies selected according to the first modulation signal. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 34)
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24. A detector apparatus for a distance measuring system, the apparatus comprising:
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a first detector for detecting a first signal having a first propagation speed, wherein the first detector in use detects a first modulation signal having a longer repetition period than a transmitter-detector propagation time or the first signal;
frequency discriminator means for detecting the first signal transmitted sequentially at two frequencies selected according to the first modulation signal;
a second detector for detecting a second signal having a second propagation speed higher than the first propagation speed; and
means for determining a transmitter-detector distance from a time interval between detection of said first and second signals. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33)
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Specification