Two dimensional fast Fourier transform converter

• US 5,089,982 A
• Filed: 05/24/1990
• Issued: 02/18/1992
• Est. Priority Date: 05/24/1990
• Status: Expired due to Term

• Current Assignee: Grumman Aerospace Corporation (Northrop Grumman Corporation)
• Original Assignee: Grumman Aerospace Corporation (Northrop Grumman Corporation)
• Inventors: Gran, Richard J., Ritucci, Hugo D., Berde, Dennis W.
• Primary Examiner(s): Harkcom, Gary V.
• Assistant Examiner(s): NGUYEN, LONG
• Application Number:
  US07/527,959
• Time in Patent Office: 635 Days
• Field of Search: 364/726, 364/725, 364/518, 382/43
• US Class Current: 708/401
• CPC Class Codes: G06F 17/142 Fast Fourier transforms, e.g. using a Cooley-Tukey type algorithm

Abstract

A two-dimensional fast Fourier transform converter utilizes parallel digital fast Fourier transform processors and a frame serial processing path to convert two-dimensional images of large pixel count (512×512 or higher) and high dynamic range (16 bits of pixel intensity quantization) at a rate equal to or exceeding real time processing rate of 30 frames/second. The parallel processors are organized for performing the row and column transformations in a highly parallel and efficient manner. In one embodiment, a uni-directional processing path with segmented image data busses to streamline the data movement is used. In a second embodiment, a bi-directional processing path is utilized such that the fast Fourier transform processors perform row and column conversions sequentially, thus reducing by a factor of two the number of individual fast Fourier transform processors required. The converter includes three port SRAM working memories, toggled DRAM image frame storage memories, and a data transfer and sequence controller.

Claims

1. A digital fast Fourier transform converter, comprising:

a two-dimensional halfway memory;

a plurality of one-dimensional fast Fourier transform processors connected in parallel to said halfway memory, each processor including means for converting one-dimensional data point sets into one-dimensional fast Fourier transformed data point sets;

data input means for supplying said processors, in sequence, one set at a time per processor, with said one-dimensional data point sets;

transformed data output means for transferring said one-dimensional fast Fourier transformed data point sets, one set at a time per processor, from said processors to said halfway memory to form a partially fast Fourier transformed data frame made up of said one-dimensional fast Fourier transformed data point sets; and

second dimension transform means for transforming said partially fast Fourier transformed data frame into a completely fast Fourier transformed data frame.

2. A converter as claimed in claim 1, wherein said one-dimensional data point sets are lines of a two-dimensional input image frame and said partially transformed data frame is made up of fast Fourier transformed lines of said two-dimensional input image frame.

3. A converter as claimed in claim 1, wherein said second dimension transform means comprises column transfer means for Fourier transforming image data point sets representing columns of said partially transformed data frame;

a two-dimensional image frame memory; and

column storage means for storing fast Fourier transformed columns of said partially transformed data frame into said two-dimensional image memory.

4. A converter as claimed in claim 3, wherein said column transform means comprises a second plurality of one-dimensional fast Fourier transform processors connected in parallel between said halfway memory and said two-dimensional image frame memory.

5. A converter as claimed in claim 3, wherein said column transform means comprises said plurality of one-dimensional fast Fourier transform processors, and said converter further comprises column input means for transferring said columns from said halfway memory to said plurality of one-dimensional fast Fourier transform processors sequentially, one column at a time per processor, and column output means for transferring fast Fourier transformed columns from said plurality of one-dimensional fast Fourier transform processors to said two-dimensional image frame memory.

6. A converter as claimed in claim 5, wherein said transformed data output means and said column input means comprise separate input and output data busses.

7. A converter as claimed in claim 1, wherein said data input means includes means for supplying a complete video image frame made up of said data point sets to said plurality of one-dimensional fast Fourier transform processors in less than 33 milliseconds.

8. A converter as claimed in claim 1, wherein said data point sets each includes at least 512 words, said words representing pixels of a two-dimensional image.

9. A converter as claimed in claim 8, wherein each of said words has a length of at least 16 bits.

10. A converter as claimed in claim 1, further comprising, for each of said plurality of one-dimensional fast Fourier transform processors, a working memory and bus means for transferring data between the working memories and the fast Fourier transform processors.

11. A converter as claimed in claim 10, wherein each of said working memories comprises port means connected to a corresponding one of said processors via said bus means for enabling said corresponding processor to read a data point set stored in said working memory and to write a transformed data point set into said working memory.

12. A converter as claimed in claim 11, wherein each of said one-dimensional fast Fourier transform processors includes means for enabling said processor to make multiple passes via said bus means and said port means in respect to said data point sets for each Fourier transform conversion.

13. A converter as claimed in claim 1, wherein the number of said one-dimensional fast Fourier transform processors is N and the number of said data point sets is greater than N, and further comprising sequencing means for sequencing said processors such that a first of said processors to be supplied with a data point set completes a fast Fourier transform on said data point set at the same time that an Nth data point set is supplied to an Nth processor, the next data point set being supplied to said first processor.

14. A digital fast Fourier transform converter, comprising:

a plurality of fast Fourier transform line processing means for performing fast Fourier transforms sequentially on a plurality of image data point sets to form a plurality of line-transformed image data point sets, each set representing one line of a two-dimensional image frame, in order to generate a line-transformed image frame made up of said line-transformed image data point sets;

a plurality of working line memory means, each connected to one of said plurality of fast Fourier transform line processing means for storing one line of said image frame during processing of said line by a respective line processing means to which the line memory means is connected;

line input means for supplying said working line memory means, sequentially, one line at a time per line processing means, with said image data point sets;

halfway video frame memory means for storing said line-transformed image frame;

line output means connected to said working line memory means and said halfway video frame memory means for receiving said line-transformed data point sets from said working line memory means and storing said line-transformed data point sets in said halfway video frame memory means;

a plurality of fast Fourier transformed column processing means for performing fast Fourier transforms sequentially on a plurality of data point sets to form a plurality of column-transformed data point sets, each data point set representing one column of said line-transformed image frame in order to generate a complete two-dimensional Fourier transformed image frame made up of said column-transformed data point sets;

a plurality of working column memory means, each connected to one of said plurality of fast Fourier transform column processing means for storing one column of said line-transformed image frame during processing by a respective column processing means to which the column memory means is connected;

column input means for supplying said working column memory means, sequentially, one column at a time per column processing means, with image data point sets representing columns of said line-transformed image frame;

two-dimensional video frame memory means for storing said Fourier transformed image frame; and

column output means connected to said column memory means and said two-dimensional video frame memory means for receiving column transformed data point sets from said working column means and storing them in said two-dimensional video frame memory means.

15. A converter as claimed in claim 14, wherein said line input means includes means for supplying a complete frame, line by line in sequence, to said working line memories in less than 33 milliseconds.

16. A converter as claimed in claim 14, wherein said image data point sets each includes at least 512 words of at least 16 bits, each word representing an image pixel.

17. A converter as claimed in claim 14, wherein each of said plurality of fast Fourier transform line processing means comprises a fast Fourier transform line processor and each of said corresponding line memory means includes port means connected to said line processor for enabling said line processor to read a data point set stored in said line memory means and for enabling said line processor to write a transformed data point set into said line memory means.

18. A converter as claimed in claim 17, wherein said line processor includes means for enabling said line processor to make multiple passes in respect to said data point set for each Fourier transform conversion.

19. A converter as claimed in claim 14, wherein each of said line processing means comprises a fast Fourier transform line processor, and wherein each of said working line memory means includes data input port means for receiving a data point set from said line input means and data output port means for supplying a line-transformed data point set to said line output means.

20. A converter as claimed in claim 19, wherein said line memory means further comprises line processor memory control port means connected to a respective one of said line processors for supplying a data point set to said line processor and for receiving a line transformed data point set from said line processor.

21. A converter as claimed in claim 14, wherein each of said plurality of fast Fourier transform column processing means comprises a fast Fourier transform column processor and each of said corresponding column memory means includes port means connected to said column processor for enabling said column processor to read a data point set stored in said column memory means and for enabling said column processor to write a transformed data point set into said column memory means.

22. A converter as claimed in claim 21, wherein said column processor includes means for enabling said column processor to make multiple passes in respect to said data point set for each Fourier transform conversion.

23. A converter as claimed in claim 14, wherein each of said column processing means comprises a fast Fourier transform column processor, and wherein each of said column working memory means includes data input port means for receiving a data point set from said column input means and data output means for supplying a column transformed data point set to said column output means.

24. A converter as claimed in claim 23, wherein said column memory means further comprises column processor memory control port means connected to a respective one of said column processors for supplying a data point set to said column processor and for receiving a column-transformed data point set from said column processor.

25. A converter as claimed in claim 14, wherein said plurality of fast Fourier transform line processor means comprises a plurality of fast Fourier transform line processors, and wherein said line input means includes means for supplying one line of an image frame to each of said plurality of line memory means in sequence, the last of said plurality of line memory means being supplied when a line processor corresponding to a first of said line memory means to be supplied has substantially completed a Fourier transformation on one line of said image frame.

26. A converter as claimed in claim 14, wherein each of said plurality of fast Fourier transform column processing means comprises a fast Fourier transform column processor and wherein said column input means includes means for supplying one column of a line transformed frame to each of said plurality of column memory means in sequence, the last of said plurality of column memory means being supplied when a column processor corresponding to the first of said column memories to be supplied has substantially completed a Fourier transformation on a column of said line transformed frame.

27. A converter as claimed in claim 14, wherein said halfway video frame memory means comprises means for storing two line-transformed image frames, said line input means comprising means for supplying a second frame line by line in sequence to said plurality of line memory means when a first frame has been line-transformed and stored in said halfway video frame memory means by said line output means, and said column input means comprising means for supplying said first frame column by column in sequence from said halfway memory means to said plurality of column memory means while said line input means is supplying said second frame to said plurality of line memory means.

28. A converter as claimed in claim 14, wherein said line memory means and said column memory means include a complex working memory bank for each corresponding line and column processor.

29. A converter as claimed in claim 28, wherein said complex working memory bank is a static random access memory.

30. A converter as claimed in claim 28, wherein said complex working memory bank includes one real working memory and one imaginary working memory, each having a three port input/output interface.

31. A converter as claimed in claim 14, further comprising control means for providing data transfer control signals to synchronously move data point sets along a processing path between said plurality of working line memory means, said plurality of working column memory means, said half-wave video frame memory means, and said two-dimensional video frame memory means.

32. A converter as claimed in claim 31, wherein said control means includes means for providing read, write, select, and enable signals, digital address signals, system initialization commands, standard digital bus control signals, and video dynamic random access memory refresh control signals.

33. A converter as claimed in claim 14, wherein said halfway video frame memory means and said two-dimensional video frame memory means comprise dynamic random access memories.

34. A converter as claimed in claim 14, wherein said halfway video frame memory means and said two-dimensional video frame memory means comprise static random access memories.

35. A method of performing a fast Fourier transform conversion, comprising the steps of:

(a) supplying a plurality of fast Fourier transform line processors, sequentially, one line at a time per processor, with image data point sets each representing one line of a two-dimensional image frame until all lines of said image frame have been supplied;

(b) performing a fast Fourier line transform on each of said image data point sets when they are supplied to said line processors to form a plurality of line-transformed image data point sets;

(c) supplying said line-transformed image data point sets to a halfway video frame memory to form a line-transformed image frame;

(d) supplying image data point sets representing columns of said line-transformed image frame from said halfway video frame memory, sequentially, one column at a time per processor, to a second plurality of fast Fourier transform column processors until all columns of said line-transformed image frame have been supplied;

(e) performing a fast Fourier transform column conversion on each of said image data point sets representing columns when said image data point sets representing columns are supplied to said column processors.

36. A method as claimed in claim 35, further comprising the step of storing column-transformed data point sets in a two-dimension video frame memory to form a two-dimensional fast Fourier transformed image frame.

37. A method as claimed in claim 35, wherein step (a) comprises the steps of supplying one line of said image frame to each of said plurality of line processors in sequence until the last of said line processors is supplied, and subsequently supplying the first of said line processors with the next line in a sequence of said image data point sets, said first fast Fourier transform line conversion having been completed by said first line processor simultaneously with the supplying of said last line processor.

38. A method as claimed in claim 35, further comprising the steps of supplying said column processors with a first line-transformed image frame, sequentially column by column, simultaneously with supplying said line processors with a second image frame sequentially, line by line.

39. A method as claimed in claim 35, further comprising the steps of repeating step (a) simultaneously with the performance of step (d).

40. A method as claimed in claim 35, wherein step (a) comprises the steps of supplying said image data point sets to a plurality of working memories, each corresponding to one of said processors, and supplying said image data point sets to said processors from said memories.

41. A method of performing a fast Fourier transform conversion, comprising the steps of:

(a) supplying a plurality of fast Fourier transform processors, sequentially, one line at a time per processor, with image data point sets each representing one line of a two-dimensional image frame until all lines of said image frame have been supplied;

(b) performing a fast Fourier line transform on each of said image data point sets when they are supplied to said processors to form a plurality of line-transformed image data point sets;

(c) supplying said line-transformed image data point sets to a halfway video frame memory to form a line-transformed image frame;

(d) supplying image data point sets representing columns of said line-transformed image frame from said halfway video frame memory, sequentially, one column at a time per processor, to said processors until all columns of said line-transformed image frame have been supplied;

(e) performing a fast Fourier transform column conversion on each of said image data point sets representing columns when said image data point sets representing columns are supplied to said processors to form a plurality of column-transformed image data point sets.

42. A method as claimed in claim 41, further comprising the step of storing column-transformed data point sets in a two-dimension video frame memory to form a two-dimensional fast Fourier transformed image frame.

43. A method as claimed in claim 41, wherein step (a) comprises the steps of supplying one line of said image frame to each of said plurality of processors in sequence until the last of said processors is supplied, and subsequentially supplying the first of said processors with the next line in the sequence of line data point sets, said first fast Fourier transform line conversions being completed by said first processor simultaneously with the supplying of said last processor.

44. A method as claimed in claim 41, wherein step (a) comprises the steps of supplying image data point sets to a plurality of working memories, each corresponding to one of said processors, and supplying said image data point sets to said processors from said memories.

45. A digital fast Fourier transform converter, comprising:

fast Fourier transform processing means including a plurality of one-dimensional fast Fourier transform processors for performing fast Fourier transforms sequentially on a plurality of image data point sets to form a plurality of line-transformed data point sets;

working memory means comprising a plurality of working memories, each connected to one of said plurality of fast Fourier transform processors for storing one of said data point sets while a respective fast Fourier transform processor to which the respective working memory means is connected performs a fast Fourier transform on one of said data point sets;

halfway video frame memory means for storing a line-transformed image frame;

two-dimensional video frame memory means for storing a Fourier transformed image frame;

a bi-directional internal data bus connected to said plurality of working memory means, said halfway video frame memory means, and said two-dimensional video frame memory means;

line input means connected to said plurality of working memories for supplying said working memories, sequentially, one line at a time per working memory, with image data point sets, each representing one line of a two-dimensional image frame, for processing by the respective processors to which the working memories are connected;

line output means for transferring said line-transformed data point sets from said working line memories to said halfway video frame memory means via said bi-directional internal data bus for storage in said halfway video frame memory means as a line-transformed image frame;

column input means for supplying, via said bi-directional internal data bus, said working memories with image data point sets representing columns of said line-transformed image frame, one column at a time per processor, for processing by the respective processor to which the working memories are connected; and

column output means connected to said working memories for receiving column transformed data point sets from said working memories and storing them in said two-dimensional video frame memory means in order to form a complete two-dimensional Fourier transformed image frame.

46. A converter as claimed in claim 45, wherein the number of said one-dimensional fast Fourier transform processors in N and the number of said data point sets is greater than N, and further comprising sequencing means for sequencing said processors such that a first of said processors to be supplied with a data point set completes a fast Fourier transform on said data point set at the same time that an Nth data point set is supplied to an Nth processor, the next data point set being supplied to said first processor.