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US 5,179,529 AGranted
High speed fourier transform engine
AssigneeHughes Aircraft Company
InventorMichael V. Nowakowski
Life of this patent
Estimating the term…
Abstract
Fast fourier transforms are performed in digital signal processing using number theoretic transforms. Incoming pulse descriptor words are mapped into a matrix. The first convolution does forward and inverse number transforms on the rows. The second convolution does forward and inverse number transforms on the columns.
Claims33
A method for producing a radar signal description in a desired domain comprising:
- receiving pulsed electromagnetic energy signals at an antenna;
- receiving a set of radar signal pulses from the antenna and measuring at least two predetermined parameters of the received pulses;
- converting the measurements for the set of received pulses to a sequence of pulse descriptor words having a first part and a second part in a predetermined domain;
- employing a fast fourier transform engine with the following steps:
- (i) mapping each pulse descriptor word into a two-dimensional matrix with word sorting means;
- (ii) applying a chirp factor by employing a multiplication means and an up mixing factor to each word, along a defined dimension of the matrix;
- (iii) encoding the matrix by employing encoding means according to the following equations by generating terms for the encoded matrix:
- ##EQU14## where N.sub.1 is the total number of words in the matrix in the defined dimension of the matrix, n.sub.1 is a whole number from 0 to N.sub.1 -1 indicating the position of each word along the defined dimension of the matrix, n.sub.2 indicates the position of each word along any other dimensions of the matrix, xr(n+.sub.1 +n.sub.2) and xi(n.sub.1,n.sub.2) are the first and second parts respectively of a word in the matrix at position (n.sub.1,n.sub.2) and ar(n.sub.1,n.sub.2) and ai(n.sub.1,n.sub.2) are the first and second parts respectively of a word in the encoded matrix at position (n.sub.1,n.sub.2);
- (iv) performing a forward and an inverse transform using a multiplication means along the defined dimension of the matrix;
- (v) decoding the matrix employing decoding means;
- (vi) applying a down mixing factor and a chirp factor to each word along the defined dimension;
- and
- applying each said word characterizing the electromagnetic energy to equipment for additional signal processing.
10 more elements
A method for converting a signal description consisting of a set of signal pulse descriptor words each having a first part and a second part in a first domain to a signal description consisting of a set of signal pulse descriptor words having a first part and a second part in a second domain, the method comprising:
- receiving signals by a sensor from a target;
- receiving signal pulses from an antenna of the sensor;
- converting said signal pulses to analog voltage signals;
- sampling said analog voltage signal with an analog digital converter;
- converting said sampled signals to digital pulse descriptor words;
- using a fast fourier transform engine means employing the following steps:
- (i) mapping each said signal pulse descriptor word serially into a matrix using word sorting means;
- (ii) applying a chirp factor by employing a multiplication means and an up mixing factor to each word along a defined dimension of the matrix;
- (iii) encoding the matrix with encoding means according to the following equations for generating terms for the encoded matrix:
- ##EQU16## where N.sub.1 is the total number of words in the matrix in the defined dimension of the matrix, n.sub.1 is a whole number from 0 to N.sub.1 -1 indicating the position of each word along the defined dimension of the matrix, n.sub.2 indicates the position of each word along any other dimensions of the matrix, xr ((n.sub.1,n.sub.2) and xi (n.sub.1,n.sub.2) are the first and second parts respectively of a word in the matrix at position (n.sub.1,n.sub.2) and ar (n.sub.1,n.sub.2) and ai (n.sub.1,n.sub.2) are the first and second parts respectively of a word in the encoded matrix at position (n.sub.1,n.sub.2);
- (iv) performing a forward and an inverse transform using a multiplication means along the defined dimension of the matrix;
- (v) decoding the matrix with decoding means;
- (vi) applying a down mixing factor and a chirp factor to each word, in the transformed matrix along the defined dimension;
- and
- applying each said word characterizing said target to equipment for processing target characteristics.
12 more elements
A method, incorporated into a system which system has a sensor for receiving signal pulses, for converting a time domain pulse descriptor word set describing a stream of pulses and consisting of set of amplitude versus time pulse descriptor words each having a real and an imaginary part into a frequency domain pulse descriptor word set describing the same stream of pulses and consisting of a set of amplitude versus frequency pulse descriptor words each having a real and an imaginary part comprising:
- receiving said signal pulses by the sensor;
- obtaining said signal pulses from said sensor;
- converting said signal pulses to analog voltage signals;
- sampling said analog voltage signal with an analog digital converter;
- converting said sampled signals to digital pulse descriptor words;
- encoding the matrix using encoding means along the first dimension by applying the following equations to generate the terms of the encoded matrix:
- ##EQU18## where N.sub.1 and N.sub.2 are the number of words along the first and second dimensions of the matrix respectively, n.sub.1 and n.sub.2 are whole numbers from 0 to N.sub.1 -1 and from 0 to N.sub.2 -1 respectively indicative of the position of each word in the first and second dimensions of the matrix respectively, xr(n.sub.1,n.sub.2) and xi(n.sub.1,n.sub.2) are the real and imaginary parts respectively of a word in the matrix at position (n.sub.1,n.sub.2) and ar (n.sub.1,n.sub.2) and ai (n.sub.1,n.sub.2) are the real and imaginary parts respectively of a word in the encoded matrix at position (n.sub.1,n.sub.2);
- performing a forward and an inverse transform using a multiplication means along the first dimension of the matrix;
- decoding the matrix along the first dimension with decoding means;
- applying a down mixing factor and a chirp factor to each word in the matrix after transformation, along the first dimension of the matrix;
- applying a twiddle factor with a multiplication means to each word in the matrix;
- applying a chirp factor and up mixing factor to each word in the matrix along the second dimension of the matrix;
- performing a second forward and a second inverse transform on the second dimension of the matrix;
- decoding the matrix along the second dimension using decoding means;
- applying a down mixing factor and a chirp factor along the second dimension of the matrix;
- and
- applying each said word to equipment for processing.
14 more elements
Dependencies are inferred from the claim text.