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参数资料
| 型号： | IPR-FFT |
| 厂商： | Altera |
| 文件页数： | 43/70页 |
| 文件大小： | 0K |
| 描述： | IP FFT/IFFT RENEW |
| 标准包装： | 1 |
| 系列： | * |
| 类型： | MegaCore |
| 功能： | 快速傅里叶变换处理器 |
| 许可证： | 续用许可证 |
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3. Functional Description
The discrete Fourier transform (DFT), of length N , calculates the sampled Fourier
transform of a discrete-time sequence at N evenly distributed points ? k = 2 ? k / N on
the unit circle.
The following equation shows the length- N forward DFT of a sequence x( n ):
N – 1
X ? k ? =
?
x ? n ? e
? – j 2 ? nk ? ? N
n = 0
where k = 0, 1, ... N – 1
The following equation shows the length-N inverse DFT:
N – 1
x ? n ? = ? 1 ? N ?
?
X ? k ? e
? j 2 ? nk ? ? N
k = 0
where n = 0, 1, ... N – 1
The complexity of the DFT direct computation can be significantly reduced by using
fast algorithms that use a nested decomposition of the summation in equations one
and two—in addition to exploiting various symmetries inherent in the complex
multiplications. One such algorithm is the Cooley-Tukey radix-r decimation-in-
frequency (DIF) FFT, which recursively divides the input sequence into N/r sequences
of length r and requires log r N stages of computation.
Each stage of the decomposition typically shares the same hardware, with the data
being read from memory, passed through the FFT processor and written back to
memory. Each pass through the FFT processor is required to be performed log r N
times. Popular choices of the radix are r = 2, 4, and 16. Increasing the radix of the
decomposition leads to a reduction in the number of passes required through the FFT
processor at the expense of device resources.
1
The MegaCore function does not apply the scaling factor 1/ N required for a length- N
inverse DFT. You must apply this factor externally.
Buffered, Burst, and Streaming Architectures
A radix-4 decomposition, which divides the input sequence recursively to form
four-point sequences, has the advantage that it requires only trivial multiplications in
the four-point DFT and is the chosen radix in the Altera FFT MegaCore function. This
results in the highest throughput decomposition, while requiring non-trivial complex
multiplications in the post-butterfly twiddle-factor rotations only. In cases where N is
an odd power of two, the FFT MegaCore automatically implements a radix-2 pass on
the last pass to complete the transform.
November 2013
Altera Corporation
FFT MegaCore Function
User Guide
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相关代理商/技术参数 |
参数描述 |
|---|---|
| IPR-FIR | 功能描述:开发软件 FIR Compiler MegaCore RENEWAL RoHS:否 制造商:Atollic Inc. 产品:Compilers/Debuggers 用于:ARM7, ARM9, Cortex-A, Cortex-M, Cortex-R Processors |
| IPR-FIRII | 功能描述:开发软件 FIR Compiler II MegaCore RENEWAL RoHS:否 制造商:Atollic Inc. 产品:Compilers/Debuggers 用于:ARM7, ARM9, Cortex-A, Cortex-M, Cortex-R Processors |
| IPRI2CCMFP001 | 制造商:System Level Solutions (SLS) 功能描述:IP CORE, FPGA, I2C CNTLR, FOR CYCLONE, STRATIX, Software Application:IP CORE, In |
| IPR-ILKN/100G | 功能描述:开发软件 Interlaken - 100G MegaCore RENEWAL RoHS:否 制造商:Atollic Inc. 产品:Compilers/Debuggers 用于:ARM7, ARM9, Cortex-A, Cortex-M, Cortex-R Processors |
| IPR-ILKN/50G | 功能描述:开发软件 Interlaken - 50G MegaCore RENEWAL RoHS:否 制造商:Atollic Inc. 产品:Compilers/Debuggers 用于:ARM7, ARM9, Cortex-A, Cortex-M, Cortex-R Processors |
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