Globespan Virata Corporation

Globespan, Inc.

Hughes Electronics Corporation

Yue-Peng Zheng

Daniel Amrany

Wenwei Pan

Yair Aizenberg

Kumar Swaminathan

William J Santulli

Shvetal K Patel

The present invention is generally directed to a novel method of computing a fast Fourier transform (FFT), and an associated circuit that controls the addressing of a data memory of the FFT processing circuit. The novel method operates by computing all complex butterfly operations in a given stage of computations, before computing any of the complex butterfly operations in a subsequent stage. Further, and within any given computation stage, the method performs by computing all other complex butterfly operations in a given stage of computations having a twiddle factor equal to the first twiddle value of that stage, before computing any other complex butterfly operations in the given stage of computations. Thereafter, subsequent computations are performed in the same way. More particularly, after computing a first set of complex butterfly operations (each having the same twiddle value) in a given computation stage, a first complex butterfly operation (having a different twiddle value) of a second set of complex butterfly operations, is computed in that stage. Thereafter, all remaining complex butterfly operations (having the same value) in that stage will be computed. This methodology will be repeated until all butterfly operations are calculated in each stage. An addressing circuit is also provided for addressing a data memory in a system for computing a FFT, the system having a data memory for storing data values and a coefficient memory for storing coefficient values.

Method for computing a fast fourier transform and associated circuit for addressing a data memory

A processing circuit is disclosed for computing a fast Fourier transform (FFT). In one embodiment, the processing circuit includes a memory device, a multiplier, a detector, a state machine, and a circuit for performing the 2's compliment of a coefficient. The memory storage device stores data values and coefficient (or twiddle) values. The detector integrates a data pointer with the state machine. The detector is designed to identify the symmetry lines (by memory address). The state machine, when notified by the detector that a line of symmetry has been encountered, appropriately adjusts either the coefficients, the imaginary sign, or the real sign for input to a multiplier.

Circuit and method for computing a fast fourier transform

The present invention is generally directed to a processing circuit for computing a fast Fourier transform (FFT). The present invention reflects the recognition that excessive reads to and writes from memory consume excessive amounts of power. Accordingly, the circuit of the present is specifically designed to minimize the number of reads and writes to memory. In addition, the circuit is designed so that processing parallelism may be achieved in order to reduce the total number of clock cycles required to compute a FFT. In accordance with one aspect of the invention, the processing circuit includes a data memory for storing data values, and a separate coefficient memory for storing coefficient (or twiddle) values. The circuit further includes a multiplier configured to multiply values received from the coefficient memory and another value retrieved from some other location. The circuit further includes a first adder configured to add a value output from the multiplier with a value retrieved from another location. The circuit further includes a second adder configured to add a value retrieved from the data memory with a value retrieved from another location. Finally, the circuit includes write-back data path disposed between the second adder and the data memory. The write-back data path is configured to write data output from the second adder to the data memory, to a location where a data value was previously retrieved.

Circuit for computing a fast fourier transform

A process circuit is disclosed for computing a fast Fourier transform (FFT). In one embodiment, the processing circuit includes a memory device, a multiplier, a detector, a state machine, and a circuit for performing the 2's compliment of a coefficient. The memory storage device stores data values and coefficient (or twiddle) values. The detector integrates a date pointer with the state machine. The detector is designed to identify the symmetry lines (by memory address). The state machine, when notified by the detector that a line of symmetry has been encountered, appropriately adjusts either the coefficients, the imaginary sign, or the real sign for input to a multiplier.

Disclosed is an RS decoder controller and method, the system comprising a codeword length register to indicate a number of symbols in a number of RS codewords to be decoded by the RS decoder, a error correction capability configuration register to indicate a number of error symbols that are corrected by the RS decoder, and a modulation scheme associated register to indicate a modulation scheme associated employed to generate the RS codewords. The RS decoder controller further includes a number of state machines to control the operation of a Galois field computation unit in the RS decoder.

Configurable Reed-Solomon controller and method

Disclosed is a configurable Galois field computation system and method, the system comprising a read bus and a write bus with a memory coupled therebetween. In addition, a logical circuit is coupled between the read and write busses, the logical circuit having a number of data calculation configurations that are established to generate an n symbol codeword from a number of symbols in a syndrome array. The logical circuit is placed in the various data calculation configurations in order to perform the various operations involved with Reed-Solomon decoding.

Galois field computation system and method

Disclosed is a configurable Reed-Solomon (RS) decoder that comprises a parallel multiply accumulator having a data input to receive at least one RS codeword, the parallel multiply accumulator being configured to generate a syndrome array from the RS codeword. The configurable RS decoder also includes a Galois field computation unit coupled to the parallel multiply accumulator, and an RS decoder controller coupled to the parallel multiply accumulator and the Galois field computation unit, wherein the RS decoder controller controls the operation of the parallel multiply accumulator and the Galois field computation unit. The RS decoder may be configured for different numbers of symbols in the RS codewords, parity symbols in the RS codewords, and modulation types employed in creating the RS codewords.

Configurable decoder and method for decoding a reed-solomon codeword

Disclosed is a configurable Reed-Solomon encoder and method. The configurable Reed-Solomon encoder comprises a multiplexed multiplier-accumulator, a parallel latch bank operatively coupled to the multiplexed multiplier-accumulator, a data/parity multiplexer coupled to the parallel latch bank, and an encoder controller operatively coupled to, and controlling the operation of, the multiplexed multiplier-accumulator, the parallel latch bank, and the data/parity multiplexer. The configurable Reed-Solomon encoder is preferably implemented in an application specific integrated circuit (ASIC), although it may be implemented in software executed by a high-speed digital signal processor, etc.

Configurable encoder and method for generating a Reed-Solomon codeword

An integrated circuit for processing a speech signal in accordance with a CELP standard includes a plurality of processing elements coupled to a data bus in parallel. Each processing element includes a multiplier and an accumulator. The integrated circuit further includes an auxiliary processing element, which is also coupled to the data bus and has a division unit and a comparator. The plurality of processing elements and the auxiliary processing element are also coupled in a pipeline formation.

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Ocean Township, NJ, United States of America

Yue-Peng Zheng