適用於多輸入多輸出正交分頻多工通訊系統之低功率，低記憶體面積及多標準快速傅立葉轉換處理器設計與實現

Design and Implementation of A Low-Power, Small Memory Area, and Multi-Standard FFT Processor for MIMO OFDM Communication System

陳堂政(Tang-Cheng Chen)

指導教授 ： 張慶元

國立清華大學/電機資訊學院/電機工程學系/碩士(2008年)

摘要

現今，無線通訊系統在人們的生活當中扮演非常重要的角色。而快速傅立葉轉換處理器在所有正交分頻多工的通訊系統中是關鍵性的模組。由於大量的複雜運算，傳統的快速傅立葉轉換處理器有較大的面積與較高的功率消耗。因此，低面積與低功率是令人有興趣的主題。
我們提出的快速傅立葉轉換處理器主要是由MRMMDF模組與multibutterfly模組所組合而成。Multibutterfly模組可以根據不同的快速傅立葉轉換的長度而操作radix-2、radix-22、radix-23、或radix-24的蝴蝶圖運算。MRMMDF模組可以同時處理四個128點的快速傅立葉轉換，而且它有較快的操作速度與較高的輸出率。Saturation check單元與block floating-point單元可以適時地截斷較長的字元長度而使資料的字元長度不會連續地增加。常數乘法器可以有效地減少一般乘法器的複雜度、硬體面積及功率消耗。
整個快速傅立葉轉換處理器是使用UMC 90奈米製程所實現。面積是1362x1362 um2。在40 MHz下的功率消耗為16.2 mW，而且它有很高的功率效率。由於在40 MHz下可以正確地運算多個路徑的資料，所以可以支援4x4 MIMO 802.11n and 2x2 MIMO 802.16e兩種標準。在2048點的快速傅立葉轉換下，SQNR為50.45 dB。而且只需要2.25N-word single-port與1.75N-word dual-port的記憶體來完成連續流程的設計。

關鍵字

快速傅立葉轉換 ； 正交分頻多工 ； 多輸入多輸出

並列摘要

Wireless communication plays a significant role in people’s life nowadays. FFT processor is the key module in the all OFDM communication systems. Due to the huge complex computations, the conventional FFT processor has larger area and higher power consumption. Thus, low power and small area are interesting issues.

Our proposed FFT processor is composed of the MRMMDF module and the multibutterfly module. The multibutterfly module can operate the radix-2, radix-22, radix-23, or radix-24 butterfly according to different FFT sizes. The MRMMDF module can deal with simultaneously the four 128-point FFTs, and it has faster operation speed and higher throughput. The saturation check units and block floating-point units truncate timely the longer wordlength such that the wordlength of data are not increased continuously. The constant multiplier reduces helpfully the complexity, hardware area, and power consumption of general multiplier.

The proposed FFT processor is implemented by using Faraday 90nm cell library in UMC 90nm 1P9M process. The core size is 1362x1362 um2. The power consumption is 16.2 mW at 40 MHz, and its power efficiency is very high. It can process correctly multiple data streams at 40 MHz, so it supports 4x4 MIMO 802.11n and 2x2 MIMO 802.16e standards. The SQNR is 50.45 dB when performing the 2048-point FFT. And it only needs 2.25N-word single-port memory and 1.75N-word dual-port memory, where N is 2048, for continuous flow design.

並列關鍵字

FFT ； OFDM ； MIMO

參考文獻

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