A flexible FFT algorithm for processing biomedical signals using a personal computer

The aim was to demonstrate the possibility of using personal computer PC-DOS (or generally MS-DOS) for real-time (or quasi real-time) biomedical signal processing by adding a simple A/D conversion card and the mathematical coprocessor XXX87. We have realized an assembly written fast Fourier transform (FFT) routine derived from a radix-4 algorithm, which is autogenerated, i.e. an algorithm modified by another algorithm running off-line according to the number of FFT points. The program is implemented as a subroutine to be called upon by high-level language in different procedures. This approach reduces the computational time, which is particularly useful when many Fourier transforms on different data arrays are required. Reported here are two different applications of the routine as applied to the spectral analysis of Doppler ultrasound velocimetry and surface electromyography.