An Undergraduate Experiment in Signal Detection

A simple but effective method for extracting periodic signals from noise is discussed, and experimental results of its implementation are given. This method (integration or storage), while only one of many ways in which such signals may be recovered from noise, has the advantage that it is easy to explain and to mechanize and thus is particularly useful in undergraduate signal theory courses and laboratory work. While certain of the components must be designed and constructed, most of the required equipment is readily available in the typical electrical engineering laboratory. The amount of design that is required can be varied and is consistent with undergraduate training. This allows the student to become involved in the planning and construction of the signal extraction system and should be helpful in stimulating the student's interest in random processes which continue to receive increased emphasis. Using the simple system described, it is possible to recover signals that are far below the noise level. A noise-to-signal power ratio of 100:1 presents no difficulties (provided the signal amplitude is sufficiently large) and limited results are given where the noise-tosignal ratio is 2500:1.