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研究生:王瑞麟
研究生(外文):Jui-Lin Wang
論文名稱:數位音訊廣播接收器中通道解碼及音訊解碼之共用管線式電路設計
論文名稱(外文):Circuit Sharing of OFDM and IMDCT by Modified Pipeline FFT Processor for DAB Receiver
指導教授:戴顯權戴顯權引用關係
指導教授(外文):Shen-Chuan Tai
學位類別:碩士
校院名稱:國立成功大學
系所名稱:電機工程學系碩博士班
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2002
畢業學年度:90
語文別:英文
論文頁數:77
中文關鍵詞:正交分頻多工反向修正離散餘弦轉換數位音訊廣播
外文關鍵詞:OFDMDABIMDCT
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本論文針對數位音訊廣播接收器,採用一個快速演算法,將反向修正離散餘弦轉換(IMDCT)的執行次數降低。相較於其它的快速演算法,我們所提出的方法,可以利用電路分享(Circuit Sharing)的技術輕易的將通道解碼的正交分頻多工(OFDM) 和IMDCT結合共用,以符合數位音訊廣播接收器朝低成本,高整合的趨勢
若和未使用電路分享的方法比較,本設計減少近乎一個IMDCT電路的面積。除此之外,另利用正交分頻多工(OFDM)係數的對稱性,將儲存其值的唯讀記憶體面積減少一半。
在電路架構上,本設計採用單一管線式處理單元,它只包含一個乘法器、一個加法器和一個減法器;並在每四個週期,就算出一筆蝴蝶結運算,以達到低面積高速度的設計要求。
最後,在單一管線式處理單元的模組基礎上,利用上述電路分享的方法,實現供通道解碼及音訊解碼所共用的電路。
In this Thesis, a fast implementation algorithm for inverse modified discrete cosine transform (IMDCT), stated as a 32*64 matrix operation in the DAB receiver is adopted. Comparing to the existed fast algorithm, this fast algorithm is easy to achieve the function of circuit sharing of combining the fast Fourier transform (FFT) circuit in the orthogonal frequency division multiplexing (OFDM) with synthesis filter in the audio decoder to achieve a highly integrated, low gate count and small ROM size DAB receiver.
Verse a not circuit-sharing approach, the design here saves almost an IMDCT circuit. In addition to this, the size of memory for storing 2048-points FFT (OFDM) coefficients is further reduced from 1024 to 512 by using symmetric property of twiddle coefficient.
The design applies pipeline architecture to the butterfly unit. It consists of only one multiplier, one adder, and one subtractor. At the same time, it is capable of computing one butterfly computation every 4 cycles. Then the circuit meets the low area and high speed requirement for DAB receiver.
Finally, we implement the IMDCT and the OFDM circuit that is based on the circuit sharing method by single process element with pipeline structure for DAB receiver.
CONTENTS

List of Figures vi
List of Tables viii
Chapter 1. Introduction 1
1.1 Background 1
1.2 Outline of This Thesis 3

Chapter 2. DAB System 4
2.1 Overview of DAB 4
2.1.1 System Concept 4
2.1.2 Transmission Mode and Frame 5
2.1.3 Single Frequency Network (SFN) 8
2.1.4 Error Correction 9
2.2 OFDM Modulation and Demodulation 11
2.3 ISO/MPEG Audio CODEC 14
2.3.1 Simultaneous and Non-Simultaneous Masking 14
2.3.2 Psychoacoustic Coding 15
2.3.3 ISO/MPEG Audio Layer Models 16
2.3.4 Layer I and Layer II 17
2.3.5 Audio Framing Format 19

Chapter 3. Circuit-Sharing Scheme 21
3.1 Polyphase and Cosine Modulated Filter Banks 21
3.1.1 Polyphase Representation 21
3.1.2 Cosine Modulated Filter Banks 23
3.2 Filter Bank in MPEG-1 Audio 25
3.3 Fast Synthesis Filter 28
3.1.1 IMDCT by DCT 28
3.1.1 DCT by FFT 29
3.4 Proposed Method for Circuit Shring 34

Chapter 4. Hardware Design of Circuit-Sharing 36
4.1 Architecture for Modified FFT Processor 36
4.2 The Modified FFT Processor for Circuit-Sharing in DAB Receiver 40
4.2.1 Interface Unit 41
4.2.2 Address Generation Unit 42
4.2.3 ROM-Sharing Unit 47
4.2.4 Processing Element 48
4.3 Practical Issues of Implementation 57

Chapter 5. Verification and Comparison 59
5.1 Verification of the IMDCT by FFT in Matlab 59
5.2 Circuit-Sharing Scheme Comparison 62
5.3 Gate Count Comparison 63
5.4 Timing Diagram 64

Chapter 6. Conclusion and Future Work 71

Reference 73

List of Figures

Figure 2.1 Overview of DAB system 4
Figure 2.2 DAB transmission frame 6
Figure 2.3 Phase change in symbols 7
Figure 2.4 Symbol structure for mode I 8
Figure 2.5 Long distance multipath 9
Figure 2.6 Viterbi data generation 10
Figure 2.7 Direct and indirect wave travel over different paths 11
Figure 2.8 Signal in multipath 11
Figure 2.9 OFDM and the orthogonality principle 12
Figure 2.10 Time to frequency by sine wave 12
Figure 2.11 Fast Fourier transform 13
Figure 2.12 Simultaneous masking 15
Figure 2.13 Non-simultaneous masking 15
Figure 2.14 Psychoacoustic coder 16
Figure 2.15 MPEG-1 audio modes 17
Figure 2.16 Layer I and layer II coding model 19
Figure 2.17 Layer I and layer II framing format 20
Figure 3.1 Polyphase implementation 23
Figure 3.2 Magnitude response of the prototype and their cosine modulated version 24
Figure 3.3 Analysis filter flow (I) 26
Figure 3.4 Analysis filter flow (II) 26
Figure 3.5 Synthesis filter flow 27
Figure 3.6 64-points IMDCT by 32-points DCT data flow 33
Figure 3.7 32-points DCT by 32-points FFT data flow 33
Figure 3.8 Modified synthesis filter flow 35
Figure 4.1 Single process architecture 37
Figure 4.2 Data format of IMDCT complex sample 38
Figure 4.3 Data format of OFDM complex sample 38
Figure 4.4 Data format of twiddle coefficient complex sample 38
Figure 4.5 8-points DIF FFT data flow 39
Figure 4.6 Block diagram of whole circuit 40
Figure 4.7 Circuit-sharing flow chart 42
Figure 4.8 Block diagram of address generation unit 43
Figure 4.9 ROM-sharing circuit 47
Figure 4.10 Butterfly operation 49
Figure 4.11 Processing element circuit 52
Figure 4.12 Pipeline PE data flow 56
Figure 4.13 Schematic diagram of whole circuit 57
Figure 4.14 Final physical layout of the modified FFT processor 58
Figure 5.1 Timing diagram 64

List of Tables


Table 2.1 DAB transmission mode 5
Table 2.2 Data by phase 7
Table 2.3 MPEG-1 audio support 16
Table 2.4 MPEG-1 audio layer 17
Table 2.5 Changes between DAB and MPEG audio 20
Table 4.1 The relationship between modes and control signals 41
Table 4.2 Binary representation of the base index in a 2048-points FFT 44
Table 4.3 Binary representation of the base index in post-multiply 45
Table 4.4 The relationship between stage counter and increment 46
Table 4.5 Butterfly PE sequence for OFDM and FFT of IMDCT 50
Table 4.6 Butterfly PE sequence for post-multiply of IMDCT 51
Table 5.1 IMDCT by FFT verification by Matlab 59
Table 5.2 Comparison of Different Circuit-Sharing for IMDCT Operation 62
Table 5.3 Gate count comparison between FFT and circuit-sharing 63
REFERENCE

[1]ETSI EN 300 401. ”Radio broadcasting system: Digital Audio Broadcasting (DAB) to Mobile, Portable and Fixed Receivers”, v1.3.2, September 2000.
[2]ISO-IEC JTC1/SC29/WG11 “Coding of Moving Pictures and Associate Audio” 13818-3. Nov. 1994.
[3]P. Shelswell, “The COFDM modulation system: the heart of digital audio broadcasting,” Electronics & Communication Engineering Journal, pp. 127-136, Jun, 1995.
[4]W. Y. Zou, and Y. Wu, “COFDM: An Overview,” IEEE Transactions on Broadcasting, vol. 41, No. 1, pp. 1-8 March 1995.
[5]H. Usuba, S. Kakiuchi, and K. Yamauchi, “A prototype DAB receiver,” in Proc. IEEE International Conference on Consumer Electronics, pp. 52-53, 1996.
[6]T. Fukami, A. Tanaka, K. Fukuaga, K. Momura, and S. Kobayashi, “On-Chip Baseband Decoder for a DAB Receiver,” in Proc. IEEE Custom Integrated Circuit Conference, pp. 400-401, 1998.
[7]A. Delaruelle, J. Huisken, J. V. Loon, and F. Welten, “A Chip Set for a Digital Audio Broadcasting Channel Decoder,” in Proc. IEEE Custom Integrated Circuit Conference, pp. 13.4.1-13.4.4, 1995.
[8]A. Delaruelle, J. Huisken, J. van Loon, and F. Welten, “A Channel Demodulator IC for Digital Audio Broadcasting,” IEEE Custom Integrated Circuits Conference, 1994.
[9]C. Ediz, M. Richard, and K. Izzet, “An extensible complex fast Fourier transform processor chip for real-time spectrum analysis and measurement”, IEEE Transactions on Instrumentation and Measurement, vol. 47, no. 1, pp. 95-99, February 1998.
[10]Tsung-Han Tsai, Thou-Ho Chen, and Liang-Gee Chen, “An MPEG audio decoder chip,” IEEE Trans. on Consumer Electronics, Vol. 41, No. 1, pp. 89-96, Feb, 1995.
[11]Y. Francois, M. Lever and P. Urcun, ” A MUSICAM source codec for digital audio broadcasting and storage ”, IEEE CCITT Conference, 1991.
[12]K. Konstantinides, “Fast subband filtering in MPEG audio coding”, IEEE Signal Processing Letters, vol. 1, no. 2, pp. 26-28, February 1994.
[13]Rao, K. R., “Discrete Cosine Transform: algorithm, advantage, applications”, Academic Press, 1990.
[14]Winnie Lau, Alex chwu, ”A common transform engine for MPEG & AC3 audio decoder”, IEEE, 1997.
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