REAL-TIME MULTI-CHANNEL COMPLEX AMPLITUDE SPECTRUM ANALYZER

摘要

Preprocessing complex amplitude date to an optimum format permits direct complex spectral analysis with a simple and fast algorithm developed by Lowell Technological Institute Research Foundation. While the sine and cosine samples - compressed in a specific logarithmic scale - are read-in from the Fast SAS 4-96 Complex Amplitude Scanner or from magnetic tape, they are digitally filtered in up to 512 spectral bands. Two of four parallel logarithmic products are combined in four simultaneous branches for the real and imaginary components of the positive and the negative spectral frequencies. This bypasses the speed limit of the megabit static shift register memories. All 96 data channels collected by the extremely fast DAASM system are convolved simultaneously either on-line or in playback from tape in the same time as it was recorded. This capability relieves the big computer of this time consuming process and frees it for computing the DAASM maps, showing the structure of the ionosphere, and for statistical investigation of the signal properties.