李枝宏特聘教授的個人資料 - Profile of Ju-Hong Lee

李枝宏 Ju-Hong Lee

國立台灣大學電機工程學系 特聘教授
Distinguished Professor, Department of Electrical Engineering, National Taiwan University

主要研究領域:

數位信號處理,智慧型天線與無線通訊信號處理,生醫信號處理,數位影像處理.

Major Research Areas:

Digital Signal Processing, Signal Processing for Smart Antennas and Wireless Communications,Biomedical Signal Processing, Digital Image Processing.

研究領域摘要:

(1) Digital Signal Processing: (1984~至今)

一維及兩維數位信號處理研究: 包含有限脈衝響應(FIR)及無限脈衝響應(IIR)數位濾波器(Digital Filter)與濾波器組(Filter Bank)學理研發與設計等研究,無論在學理上或設計濾波器之係數為連續式、離散式(如2之冪次方)、以及能以-1,0,+1形式適合不需要乘法運算電路硬體合成之理論技術上皆有獨到創新之成就,並針對應用於音訊以及影像訊號處理之數位濾波器組系統相關信號處理技術進行研發。並已有多項研究成果受到國際學術界之肯定而發表於著名之SCI國際性學術期刊如 IEEEIEEDigital Signal ProcessingSignal ProcessingInternational Journal of Circuit Theory and Applications 等。

(2) Digital Signal Processing for Vibration Arthrometry (VAM, 關節振動聽診技術): (1997~2013)

包含 (I) 由國立臺灣大學醫學院骨科部提供人體膝關節病變與運動傷害所產生之振動訊號,應用相關信號處理理論研發建立此振動訊號之數學模型的技術,適合以非侵入性的關節聽診方式來初步診斷,增加臨床醫師判斷的準確率。更協助臨床上分析診斷人體膝關節病變與運動傷害之型態與種類,以期提供醫師進行正確且必要醫療措施所需之資訊。(II) 由國立臺灣大學獸醫學系提供馬匹膝關節病變與老化所產生之振動訊號,應用相關信號處理理論研發建立此振動訊號之數學模型的技術,以協助臨床上分析診斷馬匹膝關節病變與老化之型態與種類,以期提供獸醫師進行正確且必要醫療措施所需之資訊。並已有多項研究成果受到國際學術界之肯定而發表於著名之SCI國際性學術期刊如 IEEEComputers and Electronics in Agriculture 等。

(3) STATISTICAL AND ANTENNA ARRAY Signal Processing: (1985~至今)

一維及兩維可適性陣列信號處理研究:包含一維及兩維可適性陣列波束成型(ADAPTIVE Array Beamforming)之學理研發與處理信號技術之開發等研究。對於可適性陣列信號之有效處理,解決有實際誤差(Mismatch)情形與同頻干擾信號(Coherence Interference)陣列波束成型之問題而研發的強健式技術,在應用上需要具有多重波束(Multiple Beam)成型之技術,以及傳輸之通訊信號具有循環性穩態(Cyclostationarity)特性時之可適性信號處理皆有具體獨到之創新成就,並已有多項研究成果受到國際學術界之肯定而發表於著名之SCI國際性學術期刊如IEEEIEEJournal of the Franklin InstituteSignal Processing等。

(4) MIMO Antenna Arrays and Wireless Communications: (2012~至今)

應用智慧型天線之多重輸入多重輸出(MIMO)無線通訊與雷達天線系統研究: 近年來,基於對應用智慧型陣列天線於無線通訊方面之研究工作,著重於應用智慧型天線之無線通訊系統之相關性能分析與考慮動態環境下,無線通訊系統相關重要之特性改變,進行理論與技術方面之推導與分析。此外也逐漸針對使用大規模智慧型陣列天線於新世代(如5G等)無線通訊系統,在實際應用環境下遭受到誤差因素,致使其性能變壞之問題,進行深入研究與發展解決之相關技術。應用統計信號處理理論與強健式技術於解決使用大規模智慧型陣列天線多重輸入多重輸出無線通訊與多重輸入多重輸出雷達天線系統在實際環境下所面臨之問題,已經漸漸進入有相當之進展階段與產生受到國際相關學術界肯定之研究成果,重要之研究發展與成果已經陸續發表於著名之SCI國際性學術期刊如IEEEJournal of the Franklin InstituteEURASIP Journal on Wireless Communications and Networking等。

近年來逐步以多年來研究成果為基礎,進一步擴展研究領域至下一世代多重輸入多重輸出(MIMO)大規模(MASSIVE)無線通訊系統以及MIMO雷達陣列系統相關應用與技術開發研究. 重點及方向簡述如下:

MIMO無線通訊系統領域,為滿足對無線通道容量日益增加之需求,以達到高傳輸率多媒體資料之接通,然而在現實環境下,完全以數位信號處理環境作為系統設計來執行,對使用大規模天線陣列的MIMO無線通訊系統,尤其針對毫米波MIMO無線通訊系統而言,面臨多種必須解決之困難。

應用統計信號處理理論與強健式技術於解決使用大規模智慧型陣列天線多重輸入多重輸出無線通訊與多重輸入多重輸出雷達天線系統在實際環境下所面臨之其中幾項問題,分別簡述如下: (1)針對使用大規模天線元件之多重輸入多重輸出毫米波無線通訊系統,導致通道狀態訊息或編碼矩陣的係數以完成發射端的空間預編碼急遽上升,而造成頻寬效益下降,進而降低傳送訊號的品質,以及所衍生之天線的問題,研究發展有效的強健式空間預編碼器(Spatial Precoding)之數學理論與新設計技術,進行數學理論分析與公式推導。(2)針對使用大規模天線元件之多重輸入多重輸出無線通訊系統,所衍生之耗費高成本的複雜的硬體設備,以及高功率的耗電量加上天線的問題,研究發展有效的類比與數位混合式(HYBRID)的強健式空間預編碼器之數學理論與新設計技術,進行數學理論分析與公式推導。(3)進行應用統計信號處理理論與強健式技術於解決使用大規模智慧型陣列天線部署的多重輸入多重輸出雷達天線系統在實際環境下運作所衍生之問題,考量MIMO架構雷達系統因開發利用波形分集(Waveform Diversity)之重要功能所形成的虛擬指引向量之特殊架構,研究發展有效的強健式波束成型目標信號接收以及目標信號方位偵測相關技術,進行數學理論分析與公式推導。期望提升運用MIMO架構之雷達天線系統也能分享了MIMO架構帶給無線通訊系統之優點外,特別具有波形分集之重要功能,波形分集之重要功能為可以提供給雷達系統很顯著的區別目標信號源之解析(Resolution)能力、偵測性能(Detection performance)、以及參數估計上的可判別度(Parameter identifiability)。如何進一步發展具體有效改善或解決這些問題的理論與技術以及開發相關領域運用等課題是後續進一步相關研究之挑戰性工作。

 

 

Research Summary:

(1)        Research on One-dimensional (1-D) and Two dimensional (2-D) Digital Signal Processing: Theory and Design of 1-D and 2-D FIR and IIR digital filters and filter banks with continuous filter coefficients or discrete filter coefficients. For many communication and signal processing systems, quadrature mirror filter (QMF) banks have been widely used to achieve the goals of subband coding and short-time spectral analysis. In these applications, a QMF bank is employed to decompose a signal into subbands and the subband signals in the analysis system are decimated by an integer equal to the number of subbands. We have studied and developed theory and design of 1-D, 2-D Filters,  Filter Banks, and Wavelet Filter Banks with linear phase or low group delay response for Applications in Audio, Image, and Video Signal Processing.

(2)        Research on 1-D and 2-D adaptive array signal processing: Theory and Robust techniques for 1-D and 2-D adaptive array beamforming and bearing estimation in the presence of coherence signal sources, array sensor position errors, near field sources, and steering angle error, etc. One of the most important problems in a multiuser asynchronous environment is the inter-user interference, which can degrade the performance quite severely. This is the case also in a practical Code-Division Multiple Access (CDMA) system, because the varying delays of different users induce non-orthogonal codes. The base stations in mobile communication systems have long been using spatial diversity for combating fading due to the severe multipath. However, using an antenna array of several elements introduces extra degrees of freedom, which can be used to obtain higher selectivity. An adaptive receiving array can be steered in the direction of one user at a time, while simultaneously nulling interference from other users, much in the same way as the beamforming techniques. Recently, we also consider the research on OFDMA wireless communication systems. Theory and Techniques have been studied and developed for the adaptive processing of array signals in Smart Antennas with Applications in Wireless, Mobile Communications, and Anti-jamming Communications.

(3)       Analysis and Processing of joint vibration signals for the diagnosis of cartilage pathology: Research on the topics of vibration arthrometry based on the previous studies in this field. They include (a) using physiological patello-femoral crepitus to detect the cartilage integrity of the patellofemoral joint (IEEE Transactions on Biomedical Engineering 47(8):1-3, 2000.). (b) Iatrogenic knee clicks are the most valuable materials for the vibration arthrometric study. Prosthetic wearing signals are useful for a non-invasive diagnosis of the prosthetic wears (metal or polyethelene) (IEEE Transaction Biomedical Engineering 47(2): 219-227, 2000). (c) Analysis of temporomandibular joint vibration signal by mathematical model. (d) Analysis of vibration signals due to subtle lameness and musculoskeletal disorders of horse. We have designed a new diagnostic instrument, Equine Vibration ArthroMetry system (EVAM), which can differentiate horses with musculoskeletal disorders caused by different origins including foreign force damage, chronic laminitis, carpal hygroma, and aged skeletal changes from normal healthy horses. Mathematical algorithms have been developed for the analysis of articular vibration signals of fetlock joints of forelimbs.  We can differentiate between healthy horses and sick horse with musculoskeletal system disorders more easily, economically, and nonivasively.

Another iatrogenic knee click is found for many years by the orthopaedic surgeons who perform cruciate ligament reconstruction for the cruciate ligament deficiency knee. These abnormal noises in the reconstructed knee cause anxiety to the patient. Yet the nature of these noises remains unclear. Through signal analysis, characteristic signal parameters of the abnormal click could be defined and used for a non-invasive diagnosis.

4.  Based on the achievements obtained from (1) and (2), we have been conducting some more advanced researches including the explorations of theories and applications in the areas of multiple-input multiple-output (MIMO) wireless communication systems and MIMO radar systems for the next generation MIMO wireless communications.
 

 

 

 

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