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RISS 인기검색어
- 검색키워드
- 저자 : Roblin, P (검색결과 6 건)
- 무료
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- 유료
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Frequency-Selective Predistortion Linearization of RF Power Amplifiers
Roblin, P.,Suk Keun Myoung,Chaillot, D.,Young Gi Kim,Fathimulla, A.,Strahler, J.,Bibyk, S. IEEE 2008 IEEE transactions on microwave theory and techniqu Vol.56 No.1
<P>This paper presents a frequency-selective RF vector predistortion linearization system for RF multicarrier power amplifiers (PAs) affected by strong differential memory effects. Differential memory effects can be revealed in two-tone experiment by the divergence for increasing tone-spacing of the vector Volterra coefficients associated with the lower and upper intermodulations tones. Using large-signal vector measurement with a large-signal network analyzer, a class-AB LDMOS RF PA is demonstrated to exhibit a strong differential memory effect for modulation bandwidth above 0.3 MHz. New frequency-selective RF and baseband predistortion linearization algorithms are proposed to separately address the linearization requirements of the interband and inband intermodulation products of both the lower and upper sidebands. Theoretical verification of the algorithms are demonstrated with Matlab simulations using a Volterra/Wiener PA model with memory effects. The baseband linearization algorithm is next implemented in a field-programmable gate array and experimentally investigated for the linearization of the class-AB LDMOS PA for two carrier wideband code-division multiple-access signals. The ability of the algorithm to selectively linearize the two interband and four inband intermodulation products is demonstrated. Adjacent channel leakage ratio of up to 45 dBc for inband and interband are demonstrated experimentally at twice the typical fractional bandwidth.</P>
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Poly-Harmonic Modeling and Predistortion Linearization for Software-Defined Radio Upconverters
Xi Yang,Chaillot, D,Roblin, P,Wan-Rone Liou,Jongsoo Lee,Hyo-Dal Park,Strahler, J,Ismail, M IEEE 2010 IEEE transactions on microwave theory and techniqu Vol.58 No.8
<P>This paper presents a new predistortion linearization scheme for single-sideband mixers to be used for removing unwanted harmonics and intermodulation products of the digital IF in an heterodyne transmitter. The proposed algorithm, called poly-harmonic predistortion linearization, relies on an orthogonal expansion in the frequency domain of the nonlinearities for the mixer modeling. It takes into account memory effects that are piece-wise quasi-memoryless and enables the independent cancellation of unwanted spurious sidebands of the digital IF harmonics. The poly-harmonic predistortion linearization scheme for the weak-nonlinear regime was implemented in a field-programmable gate array and experimentally investigated for the linearization of a four-path polyphase single-sideband upconverter. The ability of the poly-harmonic predistortion algorithm to linearize the four-path polyphase mixer for input signals with high envelope fluctuation is demonstrated. -70-dBc/-62-dBc/-60-dBc spurious rejection and 18-dB/10-dB/8-dB linearization improvement of the third-order distortions are achieved for a two-tone RF signal, a 64-tone 10-MHz bandwidth multisine signal and orthogonal frequency-division multiplexing signal, respectively. The combination of the polyphase multipath technique and the poly-harmonic predistortion linearization technique offers an attractive filterless approach for the development of multimode broadband software-defined radio.</P>
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A 8-GHz SiGe HBT VCO Design on a Low Resistive Silicon Substrate Using GSML
Jongsoo Lee,Young-Gi Kim,Eun-Jin Lee,Chang-Woo Kim,Roblin, P. IEEE 2007 IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS PART 1 R Vol.54 No.10
<P>A practical layout method called ground shield microstrip lines (GSML) is investigated for the reliable design of high frequency interconnection lines on a low resistive silicon substrate. GSML facilitates the prediction of parasitic networks at the expense of introducing negligible loss. The microwave performance of a GSML line structure is compared to that of a conventional metal line on the same standard silicon substrate (20 Omegamiddotcm). Then, the GSML structure is applied to an 8-GHz SiGe heterojunction bipolar transistor (HBT) voltage-controlled oscillator (VCO) circuit. The GSML method replaces the post layout simulation and reduces iteration time, increasing design efficiency. A fully integrated differential tuning SiGe HBT 8-GHz VCO is designed and tested. The measured phase noise for the VCO is dBc/Hz at 1-MHz offset with an output power of dBm.</P>
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Park, W.K.,Oh, S.S.,Kang, S.Y.,Roblin, P.,Park, H.D. IET 2009 Electronics letters Vol.45 No.6
<P>A waveguide probe with size-reduced aperture for near-field measurements is proposed. The open-ended waveguide loads the split ring resonator array. The low return loss, high efficiency, and length extension have been achieved by optimising the ring arrangement as well as adopting a double-ridged waveguide and inserting a dielectric material. The proposed probe produces 70% aperture reduction in comparison to conventionally designed probes. The return loss, radiation pattern and gain from the simulation and measurement show good results.</P>
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Nicolas Williet,Radwan Kassir,Francois Casteillo,Violaine Yvorel,Cyril Habougit,Xavier Roblin,Jean-Marc Phelip 대한소화기내시경학회 2019 Clinical Endoscopy Vol.52 No.2
We described for the first time the contrast enhancement of a giant fibrovascular esophageal polyp using ultrasound contrast agent,Sonovue® (Bracco, Milan, Italy) during echoendoscopy. Fine Doppler was unsuccessful in showing vascularization due to the mobilecharacteristic of the tumor. In contrast, via Sonovue® , tissue microcirculation was highlighted inside the entire head of the polyp,leading to better appreciate the risk of bleeding related to its resection. In a second part, we showed the feasibility of classic polypectomyfor this giant polyp (5×5 cm) without complication and results of control endoscopy at 3 months. The present case is summarized in avideo.
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( Francis B. Annor ),( Katherine E. Masyn ),( Ike S. Okosun ),( Douglas W. Roblin ),( Michael Goodman ) 대한신장학회 2015 Kidney Research and Clinical Practice Vol.34 No.3
Background: Psychosocial stress has been hypothesized to impact renal changes, but this hypothesis has not been adequately tested. The aim of this study was to examine the relationship between psychosocial stress and estimated glomerular filtration rate (eGFR) and to examine other predictors of eGFR changes among persons with diabetes mellitus (DM). Methods: Data from a survey conducted in 2005 by a major health maintenance organization located in the southeastern part of the United States, linked to patients’ clinical and pharmacy records (n¼575) from 2005 to 2008, was used. Study participants were working adults aged 25-59 years, diagnosed with DM but without advanced microvascular or macrovascular complications. eGFR was estimated using the Modification of Diet in Renal Disease equation. A latent psychosocial stress variable was created from five psychosocial stress subscales. Using a growth factor model in a structural equation framework, we estimated the association between psychosocial stress and eGFR while controlling for important covariates. Results: The psychosocial stress variable was not directly associated with eGFR in the final model. Factors found to be associated with changes in eGFR were age, race, insulin use, and mean arterial pressure. Conclusion: Among fairly healthy DM patients, we did not find any evidence of a direct association between psychosocial stress and eGFR changes after controlling for important covariates. Predictors of eGFR change in our population included age, race, insulin use, and mean arterial pressure.
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