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研究生：	王瑞麟 Wang, Jui-Lin
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 Circuit Sharing of OFDM and IMDCT by Modified Pipeline FFT Processor for DAB Receiver
指導教授：	戴顯權 Tai, Shen-Chuan
學位類別：	碩士 Master
系所名稱：	電機資訊學院 - 電機工程學系 Department of Electrical Engineering
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：	OFDM, DAB, IMDCT
相關次數：	點閱：239 下載：1
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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.

2003-07-09公開

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