Abstract A digital computer device for computing an approximation of the Fourier transform of a sequence of m sample pairs having known times of occurrence. An equation expressing the transform is programmed into the computer device. Binary words representing multiplier coefficients are placed in a first cyclically read memory. The m sample pairs are coded into p-digit words in a second memory from which they are simultaneously available. At each first memory reading 2 m multiplier coefficients are applied at the same time as the 2 m sample binary words to 4 m multipliers. The p-digit multiplier outputs are applied to a plurality of binary adders to perform the algebraic additions required by the equation. The device is particularly adapted for computation of Fourier transform approximations in a received signal processing system for a coherent pulse Doppler radar.
A Fourier transform digital computer device for processing a predetermined plurality m, of cylical sample pairs x(ti) and Y(ti) representative of the quadrature outputs of the phase detector of a coherent pulse Doppler Radar system receiver, said samples having known occurrence times ti for a frequency fh, according to the equation:
Claim 2
Dependent Claim
51 words
A Fourier transform digital computer device for processing a predetermined plurality m, of cylical sample pairs x(ti) and Y(ti) representative of the quadrature outputs of the phase detector of a coherent pulse Doppler Radar system receiver, said samples having known occurrence times ti for a frequency fh, according to the equation:
Claim 3
Dependent Claim
85 words
Apparatus according to claim 1 in which said second means includes means assigning approximate values to the sine and cosine terms of said equation, said approximate values ranging between the values +1, + 1/2 , - 1/2 and -1, said means being responsive to the value of said (-Pi-h.pi) angular term as a fraction of 2 pi radians to assign one of said approximate values to each of said sine and cosine terms in accordance with the value of said angular term at any time.
Claim 4
Dependent Claim
36 words
Apparatus according to claim 2 including means for providing said approximate values in two bit digital form ranging from 00 to 11, comprising eight discrete values, one each for each pi /4 of said angular term.