| 研究生: |
陳世峻 Chen, Shih-Chun |
|---|---|
| 論文名稱: |
應用於捲積計算的低錯誤固定長度乘法器的設計 Design of Low-Error Fixed-Width Multiplier for Convolution Computations |
| 指導教授: |
郭耀煌
Kuo, Yaw-Huang |
| 學位類別: |
碩士 Master |
| 系所名稱: |
電機資訊學院 - 資訊工程學系 Department of Computer Science and Information Engineering |
| 論文出版年: | 2005 |
| 畢業學年度: | 93 |
| 語文別: | 英文 |
| 論文頁數: | 62 |
| 中文關鍵詞: | 固定長度乘法器 、改進型布斯演算法 、近似進位 |
| 外文關鍵詞: | approximate carry, fixed-width multipliers, modified Booth algorithm |
| 相關次數: | 點閱:180 下載:1 |
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在本篇論文中,我們提出修改Modified Booth為主的固定長度乘法器,根據乘數與被乘數的大小來補償最後乘積的誤差值,以達到較小的誤差和較小的硬體面積。相對於固定長度乘法器,一般的乘法器需要較多的面積及執行時間來完成一個乘法運算,但其精確度卻是絕對零誤差。然而,對於數位訊號處理捲積應用中,運算後的乘積通常不需要低位元部分,為了降低成本及速度的降低,固定長度乘法器的存在是必要的,但其存在的運算誤差及面積大小將是設計的重點,亦是本篇論文的重點。
一個N×N位元(N為偶數)的固定長度乘法運算中,單純的只取前(N/2)×(N/2)位元作乘法運算,將會產生最大的誤差。為了縮減誤差,將根據乘數與被乘數的大小,預測後面(N/2)×(N/2)個位元的進位值。被移除的後面(N/2)×(N/2)個位元,可以分成二部分: LPmajor 與 LPminor。本論文即為預測後面(N/2)×(N/2)個位元的進位值。最新文獻採用卡諾圖來產生S_LPminor的近似值。然而,當輸入的乘數與被乘數很大時,卡諾圖會變的極大,所以此方法並不適用於大bits數的乘數。故本論文提出另一種方法,根據乘數的大小對乘數做分群,不同的群組便有不同的S_LPminor的估計值。經由模擬以及實驗結果,此論文所提出的方法與最新的文獻相較,MSE最多減少了1.1832,而面積也比modified Booth乘法器少了約15%。
The modified Booth fixed-width multiplier receives n-bit input and produces n-bit output. This thesis proposes an error compensation method for a fixed-width multiplier that uses modified Booth algorithm. The truncated part is divided into 2 parts, LPmajor and LPminor. For the reason that LPmajor has dominant effect on the sum of retained cells, S_MP, the sum of LPmajor is computed exactly. The sum of LPminor is computed approximately since it has little contribution on S_MP. Using Karnaugh-map to generate the compensation bias is the first proposed method in this thesis, then another improvement is proposed since it’s time-consuming to draw the K-map from a multiplication of large numbers. The multiplier input values are first classified into several groups and each group is associated with a different compensation bias, which is computed directly from Booth encoder outputs rather than multiplier coefficients. By simulations, the proposed design performs about 2 dB higher PSNR than the existing method. That is, the MSE is reduced up to 1.1832 compared with the state-of-art designs. It saves up to 15% area compared with modified Booth multiplier without truncating any cell.
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