Signal analyser for unidentified pseudo-periodic signals - uses recursive filters and processing to determine signal variance compared to noise variance

摘要

A signal, from e.g. an instrumentation sensor, is amplified, filtered and processed as a voltage which varies with time. The output signal is digitised and applied as a sample to a recursive filter (1) and to a processor (2). The difference between the average of the previous samples and the new sample is determined and placed in a memory (3). A second filter (4) calculates the recursive variance of the noise and also receives the difference value from the processor. A memory (5) stores the noise variance signal corresponding to the previous sample and the average of the previous samples. The output of the noise calculation filter (4) passes via a switch (6) controlled by an OR gate (7) at the memory output. This allows its substitution for the previous values in the memory. The OR gate input from an output memory (17) signals that a useful signal is present in the complex signal.