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Digital I/Q Imbalance Compensation Technique in Multicarrier Low-IF Receiver
No full textI/Q 不平衡是所有I/Q調變系統中都會遭遇到的問題。在接收機前端的類比電路製程變異將會造成電路的不匹配，因此增益不平衡及相位不平衡是不可避免的，數位類比轉換器的電容不匹配也會造成此一問題。I/Q不平衡問題將會造成接收機的鏡像干擾排斥能力大幅降低，鏡像干擾將使得欲接收的信號嚴重失真。
在本篇論文中，提出了一個數位式I/Q不平衡補償技術。使用sign-sign LMS可適性濾波器理論來偵測出I/Q不平衡的參數，然後使用兩個乘法器以及一個直接數位頻率合成器(DDFS)來實現增益不平衡以及相位不平衡的補償。接收機前端的類比電路是使用安捷倫ADS模擬;而數位補償的架構則是使用Matlab Simulink模擬。模擬結果顯示此架構可幾乎完全補償I/Q不平衡，和其他補償方法的比較也顯示此架構提供較好的補償效果及較少的硬提複雜度。最後，我們使用雙通道的類比對數位轉換器(AD9238)及可編程邏輯元件(ALTERA APEX20K1500E)進行驗證，實驗結果顯示:此補償架構可提供高達63dB的鏡像干擾排斥比，合乎了WCDMA以及MCCDMA系統的要求。I/Q imbalance appears in all I/Q communication systems. Process variation in the analog front-end of the receiver will cause mismatches in the components. Gain and phase mismatches between I and Q mixers are unavoidable. The capacitor mismatches in analog-to digital converters also cause this problem. I/Q imbalance problem causes finite rejection in the image frequency band, and the image interference will alias into the desired signal, severe distortion will occur.
In this work, a novel and feasible I/Q imbalance compensation technique is proposed. A sign-sign LMS algorithm is used to detect the imbalance of the analog front-end. After that, two multipliers and a DDFS (Direct Digital Frequency Synthesizer) are employed to perform high precision amplitude and phase imbalance compensation. In this work, the analog front end is simulated by Advanced Design System and the digital compensation architecture is simulated by Matlab Simulink. Simulation results show that this architecture can eliminate I/Q imbalance almost completely without disturb the desired signal. Comparisons between this algorithm and other techniques are also performed, which show that this work can provide better performance with less hardware complexity. Finally, this compensation system is implemented in an ALTERA FPGA(APEX20K1500E) and Analog Device 12-bits dual channel ADC (AD9238). Experiment results show that IRR as high as 63 dB is achieved, which provides sufficient image rejection in both 3GPPWCDMA and MCCDMA system. This algorithm makes low-IF receiver a more attractive candidate in modern receivers.Contents
1 Introduction 1
1.1 Motivation…………………………………………………1
1.2 Organization of The Thesis……………………………1
2 Receiver Architectures…………………………………3
2.1 General Considerations…………………………………3
2.1.1 Intermodulation and Circuit Linearity…………….3
2.1.2 Sensitivity and Noise Figure…………………………3
2.2 Receiver Architectures…………………………………7
2.2.1 Heterodyne Receivers……………………………………7
a Architecture………………………………………………7
b Problems of Heterodyne Receivers………………….9
2.2.2 Homodyne Receivers……………………………………10
a Architecture……………………………10
b Problems of Homodyne Receivers……10
2.2.3 Image Reject Receiver…………………13
2.2.4 Comparison………………………………20
3 OFDM System and Impacts of I/Q Imbalance…………23
3.1 OFDM Systems………………………………………………23
3.1.1 OFDM Basics………………………………………………23
3.1.2 Using IFFT to Generate Orthogonal Subcarriers…25
3.1.3 Guard Time and Cyclic Extension……………………26
3.2 Impacts of I/Q Imbalance in OFDM System…………27
3.2.1 Zero IF Receiver………………………………………27
3.2.2 Low-IF receiver…………………………………………31
4 Proposed Receiver Architecture………………………37
4.1 RF Module…………………………………………………37
4.2 IF Module…………………………………………………42
5 I/Q Imbalance Compensation in Low-IF Receivers…49
5.1 Key Idea of I/Q Imbalance Compensation……………49
5.2 Digital I/Q Imbalance Compensation Techniques…50
5.2.1 Using DDFS for I/Q Imbalance Compensation………50
5.2.2 Blind Image Interference Cancellation……………73
5.3 Comparison…………………………………………………78
6 Experiment Results……………………………………81
6.1 Experiment Result of DDFS phase tuning……………81
6.2 Experiment Result of Sign-Sign LMS Calibration…86
6.3 Experiment Result of ADC and FPGA…………………88
7 Conclusion………………………………………………95
Appendix A Photos of Experiment Equipments………………9
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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