| 摘要 |
A method and a system for detecting and ranging objects utilize summed and difference signals to determine whether a target is present at a predetermined distance from the system. The summed and difference signals represent corresponding points on two discriminator functions that are derived by summing and subtracting two autocorrelation functions. The two autocorrelation functions are identical functions, except that one has been shifted by a one-bit period. By analyzing the summed and difference signals, the system is able to detect objects that cross a boundary zone located at the predetermined distance from the system. In the preferred embodiment, an optical signal is transmitted by a transmitter of the system to detect a target. Preferably, the optical signal is modulated in accordance with a double concatenated eleventh order Barker-based code. The optical signal is received by an associated photodiode after being reflected by the target. The received signal is then cross-correlated to produce the two autocorrelation signals.
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