1,720,998 research outputs found
Joint I/Q Imbalance Compensation and Channel Equalization for STBC MISO/MIMO OFDM Systems, and FPGA Design
No full text在這篇論文，提出了實虛部不匹配補償及通道等化之結合演算法與實虛部不
匹配自我偵測及校正的演算法。在這個演算法中，IEEE802.11n 的規格將被用來
做為測試的平台。在實虛部不匹配自我偵測及校正的演算法中，是在一啟動使用
者的傳收端時，及立即做自我的振幅及相位的偵測，使得在使用者端，可以大幅
減少實虛部不匹配的影響，並且可以使得載波頻率不匹配的偵測，更加的可靠。
雖然解決了在使用者端的實虛部不匹配及載波頻率不匹配，但由遠端的傳送端所
引起的實虛部不匹配依然存在，因此，實虛部不匹配補償及通道等化之結合演算
法就是用來解決這方面的問題，這個演算法是採用了MMSE 的準則，使得這個
演算法的表現，比LS 的準則，增進了2 dB 左右。
除此之外，在FPGA 的設計上，採用了SR Transformation 來實現實虛部不
匹配補償及通道等化之結合演算法，這個演算法包含了三個部份: 通道估測，
MISO/MIMO 信號偵測解碼，以及通道及實虛部不匹配資訊之更新; 經過簡化後，
可以減少35%的乘法複雜度。並且可以達到與未經簡化之前的演算法，有相同
SER 的表現。
最後，經過改良後的複數乘法器設計以及適當的記憶體安排，實現此演算法。
在FPGA 的測量上，是透過Altera Stradix EP1S80 FPGA 板，並在Tektronix TLA
715 邏輯分析儀量測，來驗證此演算法的可行性及正確性。In this thesis, the joint I/Q imbalance compensation and channel equalization and
the start up self-calibration algorithm of I/Q imbalance are proposed. The IEEE 802.11n
MISO/MIMO OFDM transceiver is adopted as a test vehicle to demonstrate the presented
algorithm. The self-calibration algorithm is performed at transceiver start-up to
estimate the end user I/Q imbalance parameter, including phase and gain mismatch.
Therefore, the Tx/Rx I/Q imbalance of end user can be alleviated by self calibration
and compensation. In addition, the start-up self calibration and compensation can make
conventional CFO estimation and compensation more reliable under end user Rx I/Q
imbalance impairment. Although Rx I/Q imbalance self compensation and CFO have
been compensated, the remote Tx I/Q imbalance and quasi-static channel variation
degrade the system performance. Therefore, based on MMSE criteria, the joint I/Q imbalance
compensation and channel equalization is presented to minimize the remote Tx
I/Q imbalance and quasi-static channel variation during the physical data transmission.
Consequently, the performance improvement is 2-dB compared with LS algorithm.
On the other hand, the cost-e cient architecture of joint I/Q imbalance compensation
and channel equalization is proposed to reduce hardware complexity based on
strength-reduced transformation. The cost e cient architecture of joint I/Q imbalance
and channel equalization contains three parts: MIMO detection, updating process and
channel estimation. The overall architecture obtains the 35% reduction e ciency in
multiplication. Furthermore, The uncoded SER of this design is the same as the direct
implementation.
Finally, the joint I/Q imbalance compensation and channel equalization is realized by
FPGA board EP1S80 at 40MHz and the system evaluations are measured by Tektronix TLA715 pattern generator and logic analyzer
Injection-locking of Weak-resonant-cavity Laser Diode by Using Gain-saturation SOA Filtered Spectrally Sliced ASE Source for DWDM-PON Transmission
No full text隨著人口的增加，高位元率的傳輸越來越受到重視，應用分波多功的被動光纖網路在光纖到家的系統中，顯然是一個可行又相當便宜的方法。 為了降低分波多功的被動光網路系統的成本，已經有很多應用在分波多功光網路的光源被提出來，如光譜很寬的發光二極體、單模雷射、利用放大後的自發幅射光源注入鎖模費比布洛雷射、雙相注入鎖模的反射性半導體光放大器等等。 儘管利用單模雷射可以使傳輸表現良好，但是因為應用在分波多功光纖網路的單模雷射製造波長沒有辦法控制精準，因此製造成本相當昂貴，且波長會隨溫度的改變而飄移，需要溫度控制器來固定溫度，因此我們使用自發幅射光源注入費比布洛雷射的傳訊器為光網路單位，探討這樣子的分波多功的被動光纖網路系統。 本篇論文討論在200億赫頻寬的陣列波導分波多功器被動光網路系統中，以端面1%反射率的弱共振腔法布里-珀羅雷射為上傳傳訊器，使用223-1 偽隨機二進位序列並以2.488億位元/秒直接調變共振腔法布里-珀羅雷射，分別分析在單向上傳系統以及雙向傳輸系統中，受到自發幅射寬頻光源經過陣列波導濾波器注入鎖模後弱共振腔法布里-珀羅雷射的傳輸表現。 單向上傳系統中：利用自發幅射光源注入雷射達成無色操作時，注入光源的相對強度雜訊以及光源的端面、連接面反射影響傳輸表現甚巨，因此改在光網路單位端使用頻譜切割的自發幅射光源配合一增益飽和之半導體光放大器可有效地分別降低注入光源的相對強度雜訊4.5分貝、端面反射量6.3分貝，可將上傳訊號的消光比從8.9提升到9.6分貝、訊雜比從5.9 提升到6.3分貝。 在這樣的單向上傳系統中，誤碼率為10-9的接收功率在背靠背的傳輸狀態下可達到-26分貝毫瓦，即使經過25公里光纖傳輸，誤碼率為10-9的接收功率仍可達到-24.8分貝毫瓦。 另外，對於弱共振腔法布里-珀羅雷射在自發幅射光源注入鎖模後的增益飽和狀態下，提出訊雜比對於注入功率變化的理論模型，並進一步探討上傳訊號訊雜比與消光比對於誤碼率為10-9的接收功率之影響，可發現對於誤碼率為10-9的接收功率，訊雜比比消光比扮演著更重要的角色。 雙向傳輸系統中：為了可達到波長可獨立操作，不受溫度或外在因素影響，以及降低雙向分波多功的被動光纖網路系統的光源成本，在通訊局端機房使用結合200億赫頻寬的陣列波導分波多功器頻譜切割和增益飽和半導體光放大器濾波技術之自發幅射光源，將其以2.488億位元/秒外部調變後做為下傳訊號；在光網路單位端，藉由另一顆半導體光放大器增益飽和特性搭配弱共振腔法布里-珀羅雷射被注入鎖模後增益飽和之特性，將下傳訊號抹平成近乎連續波光源，用來當作注入光源，然後以2.488億位元/秒直接調變注入鎖模之弱共振腔法布里-珀羅雷射當作上傳訊號，以達到下傳光源的再利用。 在此雙向傳輸系統中，下傳訊號誤碼率為10-9的接收功率在經過25公里光纖傳輸的傳輸狀態下可達到-27.5分貝毫瓦；上傳誤碼率為10-9的接收功率在經過25公里光纖傳輸仍可達到-21.8分貝毫瓦。 同時，探討半導體光放大器操作電流以及下傳訊號功率大小對於抹平後的訊號消光比與過激量之影響，更進一步分析以抹平後的訊號當作注入光源，其消光比與過激量對於上傳訊號品質之響應，可發現抹平後訊號的消光比過激量更能對上傳訊號訊雜比產生影響。鍵字：弱共振腔法布里-珀羅雷射、分波多功被動光纖網路、半導體光放大器、增益飽和、注入鎖模、光纖光通訊、半導體雷射口試委員會審定書 #謝 i文摘要 iiBSTRACT ivONTENTS viIST OF FIGURES viiihapter 1 Introduction 1.1 Introduction 1.2 Motivation 1.3 Structure 3hapter 2 Compromised Extinction and Signal-to-Noise Ratios of WRC-FPLD Transmitter Injection-Locked by AWG Sliced and SOA Bleached ASE Source 4.1 Introduction 4.2 Experiments 5.3 Results and Discussions 7.3.1 Effects of SOA and WRC-FPLD operating conditions on the up-stream transmitted data performances (BER, SNR, and ER) 7.3.2 Theoretical and experimental analyses on the ASE injection power dependent SNR, ER, and BER of WRC-FPLD up-stream data 14.3.3 Distinguishing the influence of SNR and ER to the BER performance of the WRC-FPLD transmitted up-stream data 19.4 Summary 23hapter 3 Injection-Locking of WRC-FPLD Up-stream WDM-PON Transmitter Using the Down-stream AWG Sliced ASE Data Amplitude Squeezing by Gain-saturated SOA 24.1 Introduction 24.2 Experiments 25.3 Results and Discussions 27.3.1 Relative Intensity Noise and Signal-to-Noise Ratio of the Down-stream ASE Source Filtered by Gain-Saturated SOA 27.3.2 Extinction Ratio of the down-stream transmitted data amplitude squeezed by gain-saturated SOA 29.3.3 Distinguished influence of amplitude-squeezed signal to the SNR and BER performances of the WRC-FPLD transmitted up-stream data 34.3.4 The BER performances of the bi-directional data transmission 37.5 Summary 42hapter 4 Conclusion 44.1 Conclusion 44EFERENCE 47者簡介 5
Study of graded-medium properties of process, structure, magnetism, and magnetic recording
No full text 磁記錄媒體必須具有很高的殘留磁化 (Mr，remanent magnetization)，矯頑磁場 (Hc)也要高，才能減少自我消磁效應 (self-demagnetization)以及雜散磁場 (stray fields)的去磁作用。因此，在過去使用CoCrPt基當作記錄媒體的材料，但其記錄密度在接近1 Tb/in2時，將難以再提升以克服熱擾動及雜訊變大的問題。L10-FePt材料由於具有高磁晶異向常數 (~7×107 erg/cm3) 、大的飽和磁化量 (1140 emu/cm3)、大的異向場 (116 kOe)，以及最小穩定的晶粒尺寸大約只有3 nm，所以是個很好的候選材料，因此本研究採用FePt為記錄媒體研究的材料。
在記錄密度不斷提升的同時，由於必須使用大的Ku材料，也產生了資料越來越難寫入的問題，熱輔助磁讀技術因此發展出來，解決寫入場過高的問題。另一個辦法，則是想辦法降低記錄媒體的翻轉場問題，在過去的雙層exchange spring媒體，可以大約降低硬磁層Hc的2倍大小，為了再進一步降低Hc的值，且不降低熱穩定因子的情況下，我們採用多層漸變的exchange spring結構。
本研究之多層漸變的交互彈簧 (exchange spring)結構主要有三種：利用溫度高低、成分變化，以及壓力變化，製作出三種不同的多層漸變的交互彈簧結構。結果顯示，成分漸變的結構將Hc降低了2.6倍；溫度漸變將Hc降低大約2.8倍；而壓力漸變再進一步將Hc降低大約3.3倍。溫度與壓力漸變結構具有相似的磁翻轉行為。而成分漸變結構，在去磁過程，由於不一致的磁旋轉 (non-coherent rotation)產生，會有一個大的可逆翻轉。因此，考慮降低翻轉場及磁翻轉行為，壓力漸變為最佳的漸變膜層結構。 Magnetic recording needs to have high remanent magnetization and high coercivity due to the effects of self-demagnetization and stray fields. Accordingly, in the past CoCrPt was used for the material of recording medium. However, because of larger thermal fluctuation and noise, it is hard to further enhance the areal density if the areal density approaches to 1 Tbit/in2. L10-FePt becomes one of the candidate materials due to the high magnetocrystalline anisotropy constant (Ku ~ 7×107 erg/cm3), high saturation magnetization (~1140 emu/cm3), high anisotropy field (~116 kOe), and minimal stable grain size as small as 3 nm. Therefore, FePt is employed as the material of recording media to be studied. Such high Ku materials also makes writing difficulty resulting to develop the technology of heat-assisted magnetic recording (HAMR) in order to solve the problems of large writing field. The other way is to reduce the switching field. In the past, double-layer of exchange spring media have been used as the recording media to reduce the coercivity by a factor of 2. Our studies concentrate on graded media in order to further decrease the coercivity and maintain the thermal stability factor.
Herein, we explore the magnetic behaviors of L10-FePt graded films three approaches: gradient-temperature (Tg), composition (Cg) and working pressure (Pg). As a result, Hc⊥ can be reduced by a factor of 2.6, 2.8, and 3.3 for the Cg-, Tg- and Pg-L10 FePt layers, respectively. Both Tg- and Pg-FePt have the similar reversal behavior. On the other hand, for Cg-FePt, the magnetization increases sharply upon removal of the applied field. This increment in the magnetization is due to the presence of reversible magnetization switching arising from the non-coherent rotation. Therefore, considering to reduce the switching field and magnetic reversal, Pg-FePt film may has the best gradient performance among these three structures.Contents
Abstract I
Acknowledgement V
Chapter 1 1
Chapter 2 8
2-1 Media Classification 8
2-2 Properties of FePt Perpendicular Anisotropy 9
2-3 Exchange-spring Films 10
2-4 Graded Films 13
Chapter 3 16
3-1 Flow Chart of Experiment 16
3-2 Sample Preparation 16
3-2-1 Equipment 16
3-2-2 Substrate Preparation 17
3-2-3 Target Selection 17
3-3 Fabrication of graded FePt 17
3-3-1 Temperature-graded FePt 17
3-3-2 Composition-graded FePt 18
3-3-3 Pressure-graded FePt 19
3-4 Analysis Technique 20
Chapter 4 24
4-1 Temperature-graded FePt 26
4-2 Composition-graded FePt 33
4-3 Pressure-graded FePt 40
4-4 Comparison of Three Systems 48
4-4(a) Structure Analysis 48
4-4(b) Microstructure Analysis 49
4-4(c) Magnetism Analysis 49
4-5 Summary 51
Chapter 5 96
References 97
Publication List 10
Suppressing Chirp and Power Penalty of Channelized ASE Injection-Locked Mode-Number Tunable Weak-Resonant-Cavity FPLD Transmitter
No full textEffect of thickness of MgO, Co-Fe-B, and Ta layers on perpendicular magnetic anisotropy of [Ta/Co60Fe20B20/MgO](5) multilayered films
No full textStructure and magnetic properties of FePt(001) graded films deposited on glass substrates
No full textsj-pdf-1-imr-10.1177_03000605221108100 - Supplemental material for Correlation between corneal dynamic responses and keratoconus topographic parameters
No full textSupplemental material, sj-pdf-1-imr-10.1177_03000605221108100 for Correlation between corneal dynamic responses and keratoconus topographic parameters by Hsi-Yun Tai, Jun-Ji Lin, Yi-Hung Huang, Po-Jen Shih, I-Jong Wang and Jia-Yush Yen in Journal of International Medical Research</p
Comparison on Injection-Locked Fabry-Perot Laser Diode With Front-Facet Reflectivity of 1% and 30% for Optical Data Transmission in WDM-PON System
No full text
- …
