The Detection of Time-Varying Laser Signals.
Technical rept., 1 Jan 69-30 Jun 70,
JOHNS HOPKINS UNIV BALTIMORE MD CARLYLE BARTON LAB
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A sequential detector is developed for low-intensity, time-varying laser signals. The performance of this detector is superior to that of any fixed-sample-size detector designed for the same purpose. It is shown that all previously-developed detectors are special cases of the sequential detector. The laser signals are first pre-detected by a wide-bandwidth photomultiplier, assumed to be able to resolve the times-of-emissions of the photoelectrons. The joint probability distribution function is derived for these times-of-emissions, which form a non-stationary Poisson process. A truncated sequential probability ratio test for this non-stationary process is devised it is shown to be a generalization of all previously-developed tests for Poisson processes, both sequential and fixed-sample-size. Fundamental differences between this test and those for signals in Gaussian noise are described. A method using stochastic matrices is developed to evaluate the performance of this time-varying sequential test. In many cases, the probabilities of making decisions and the average time to termination can be found exactly. In other cases, no analytical solution is possible thus the performance of the test is evaluated by a digital-computer simulation. Several practical examples are given to illustrate the advantages to be gained in decision time when the sequential detector is used for laser signals. Author
- Optical Detection and Detectors
- Infrared Detection and Detectors
- Non-Radio Communications