Abstract: A data acquisition system having plural input channels sampled at a first rate by a time division multiplexer applies the samples to a finite impulse response (FIR) discrete filter which generates output samples at a slower rate.The filter forms a set of summations ##EQU1## where Z(t.sub.i) is an input sample at a time t.sub.i, H.sub.i is the i.sup.th value of the filter impulse response, p is a sequence of successive integers, 0, 1, 2, . . . , each of which corresponds to one output sample, K is the length of filter impulse response (number of samples for each output) and R is the ratio of the initial input sample rate to the desired sample rate. A 3 to 1 reduction ratio is achieved with K=31, with the filter forming 11 different overlapping summations, so that after start-up one filtered output sample is outputted after each successive group of 3 inputs.

Abstract: Disclosed is a fully digital spectrum analyzer which includes a digital frequency translator that makes it possible to effectively analyze frequency bands that do not start at zero frequency. With the translator, the available spectral lines can be within the band of interest and not wasted in the range from zero frequency to the start of the band, and as a result the band is examined at optimal resolution. The translation takes place after the signal to be analyzed has been digitized, and the translator time-shares much of the conventional circuitry of the spectrum analyzer, to thereby minimize the cost of translation. Additionally, the spectrum analyzer includes an analog network that reduces the frequency of very fast signals so they can be analyzed by a spectrum analyzer having a relatively low upper frequency limit.

Abstract: A fully digital spectrum analyzer accepting as an input either an analog signal or a series of digital numbers and using time compression and DFT (Discrete Fourier Transform) techniques to provide the spectral component values of the input signal. Novel techniques and means are used in obtaining the power values for selected spectral lines and in averaging these power values. Statistically controlled noise is added to the input of the spectrum analyzer to enhance its resolution beyond the resolution which would be otherwise available. Advanced and efficient techniques are used for generating and applying trigonometric functions in the course of finding the real and imaginary part of Fourier transforms, and for providing running averages of the power spectra.