Theε-Ga_(2)O_(3) thin film was grown on sapphire substrate by using metalorganic chemical vapor deposition(MOCVD)method,and then was used to fabricate a deep-ultraviolet(DUV)photodetector(PD).Theε-Ga_(2)O_(3) thin f...Theε-Ga_(2)O_(3) thin film was grown on sapphire substrate by using metalorganic chemical vapor deposition(MOCVD)method,and then was used to fabricate a deep-ultraviolet(DUV)photodetector(PD).Theε-Ga_(2)O_(3) thin film shown good crystal quality and decent surface morphology.Irradiated by a 254-nm DUV light,the photodetector displayed good optoelectronic performance and high wavelength selectivity,such as photoresponsivity(R)of 175.69 A/W,detectivity(D*)of 2.46×10^(15) Jones,external quantum efficiency(EQE)of 8.6×10^(4)%and good photocurrent-intensity linearity,suggesting decent DUV photosensing performance.At 5 V and under illumination with light intensity of 800μW/cm2,the photocurrent gain is as high as 859 owing to the recycling gain mechanism and delayed carrier recombination;and the photocurrent gain decreases as the incident light intensity increases because of the recombination of photogenerated carriers by the large photon flux.展开更多
A 13bit,pipelined analog-to-digital converter （ADC） designed to achieve high linearity is described. The high linearity is realized by using the passive capacitor error-averaging technique to calibrate the capacitor...A 13bit,pipelined analog-to-digital converter （ADC） designed to achieve high linearity is described. The high linearity is realized by using the passive capacitor error-averaging technique to calibrate the capacitor mismatch error, a gain-boosting opamp to minimize the finite gain error and gain nonlinearity,a bootstrapping switch to reduce the switch on-resistor nonlinearity, and an anti-disturb design to reduce the noise from the digital supply. This ADC is implemented in 0.18μm CMOS technology and occupies a die area of 3.2mm^2 , including pads. Measured performance includes - 0.18/ 0.15LSB of differential nonlinearity, -0.35/0.5LSB of integral nonlinearity, 75.7dB of signal-to-noise plus distortion ratio （SNDR） and 90. 5 dBc of spurious-free dynamic range （SFDR） for 2.4MHz input at 2.5MS/s. At full speed conversion （5MS/s） and for the same 2.4MHz input, the measured SNDR and SFDR are 73.7dB and 83.9 dBc, respectively. The power dissipation including output pad drivers is 21mW at 2.5MS/s and 34mW at 5MS/s,both at 2.7V supply.展开更多
We analyze a wide-band,high-linearity down-conversion mixer for cable receptions that is implemented in 0. 35μm SiGe BiCMOS technology. The bandwidth of the RF （radio frequency） input covers the range from 1 to 1.8...We analyze a wide-band,high-linearity down-conversion mixer for cable receptions that is implemented in 0. 35μm SiGe BiCMOS technology. The bandwidth of the RF （radio frequency） input covers the range from 1 to 1.8GHz. The measured input power at the - 1dB compression point of the mixer reaches ＋ 14.23dBm. The highest voltage conversion gain is 8. 31dB, while the lowest noise figure is 19.4dB. The power consumed is 54mW with a 5V supply. The test result of the down-conversion mixer is outlined.展开更多
A CMOS radio frequency low noise amplifier with high linearity and low operation voltage of less than 1.0V is presented.In this circuit,an auxiliary MOSFET in the triode region is used to boost the linearity.Simulatio...A CMOS radio frequency low noise amplifier with high linearity and low operation voltage of less than 1.0V is presented.In this circuit,an auxiliary MOSFET in the triode region is used to boost the linearity.Simulation shows that this method can boost the input-referred 3rd-order intercept point with much less power dissipation than that of traditional power/linearity tradeoff solution which pays at least 1dB power for 1dB linearity improvement.It is also shown that the size of the common-gate PMOS transistor needs to be optimized to reduce its loaded input impedance so as not to degrade the linearity due to high voltage gain at its source terminal.The simulation is carried out with TSMC 0.18μm RF CMOS technology and SpectreRF.展开更多
A direct conversion CMOS DVB-S front-end employs a T-configuration variable attenuator,a single-to- differential low noise amplifier, and a low noise mixer. By innovative use of the attenuator, the linearity handling ...A direct conversion CMOS DVB-S front-end employs a T-configuration variable attenuator,a single-to- differential low noise amplifier, and a low noise mixer. By innovative use of the attenuator, the linearity handling ability of the system is dramatically improved. The system is designed and fabricated in SMIC 0.18 μm RF CMOS technology. The measurement data show that the front-end provides a total of more than 30rib dynamic range and a noise figure of 5dB in the wide frequency signal band. The prototype front-end consumes only 10mA and achieves an IIP3 of ＋ 20dBm.展开更多
In previous studies about the synchronization of vibrators,the restoring forces of springs are mainly treated as linear directly,whereas the nonlinear features are rarely considered in vibrating systems.To make up thi...In previous studies about the synchronization of vibrators,the restoring forces of springs are mainly treated as linear directly,whereas the nonlinear features are rarely considered in vibrating systems.To make up this drawback,a dynamical model of a nonlinear vibrating mechanical system with double rigid frames(RFs),driven by two vibrators,is proposed to explore the synchronization and stability of the system.In this paper,the nonlinearity is reflected in nonlinear restoring forces of springs characterized by asymmetrical piecewise linear,where the nonlinear stiffness of springs is linearized equivalently using the asymptotic method.Based on the average method and Hamilton’s principle,the theory conditions to achieve synchronization and stability of two vibrators are deduced.After the theory analyses,some numerical qualitative analyses are given to reveal the coupling dynamical characteristics of the system and the relative motion properties between two RFs.Besides,some experiments are carried out to examine the validity of the theoretical results and the correctness of the numerical analyses results.Based on the comparisons of the theory,numeric and experiment,the ideal working regions of the system are suggested.Based on the present work,some new types of vibrating equipment,such as vibrating discharging centrifugal dehydrators/conveyers/screens,can be designed.展开更多
Zero-field single-beam atomic magnetometers with transverse parametric modulation for ultra-weak magnetic field detection have attracted widespread attention recently.In this study,we present a comprehensive response ...Zero-field single-beam atomic magnetometers with transverse parametric modulation for ultra-weak magnetic field detection have attracted widespread attention recently.In this study,we present a comprehensive response model and propose a modification method of conventional first harmonic response by introducing the second harmonic correction.The proposed modification method gives improvement in dynamic range and reduction of linearity error.Additionally,our modification method shows suppression of response instability caused by optical intensity and frequency fluctuations.An atomic magnetometer with single-beam configuration is built to compare the performance between our proposed method and the conventional method.The results indicate that our method’s magnetic field response signal achieves a 5-fold expansion of dynamic range from 2 nT to 10 nT,with the linearity error decreased from 5%to 1%.Under the fluctuations of 5%for optical intensity and±15 GHz detuning of frequency,the proposed modification method maintains intensityrelated instability less than 1%and frequency-related instability less than 8%while the conventional method suffers 15%and 38%,respectively.Our method is promising for future high-sensitive and long-term stable optically pumped atomic sensors.展开更多
Two measurement techniques are investigated to characterize photodetector linearity. A model for the two-tone and three-tone photodetector systems is developed to thoroughly investigate the influences of setup compone...Two measurement techniques are investigated to characterize photodetector linearity. A model for the two-tone and three-tone photodetector systems is developed to thoroughly investigate the influences of setup components on the measurement results. We demonstrate that small bias shifts from the quadrature point of the modulator will induce deviation into measurement results of the two-tone system, and the simulation results correspond well to experimental and calculation results.展开更多
An S-band wideband chirp generator using specially designed fast lock phase lock loop（FL-PLL） was demonstrated.To realize high linearity,structure of direct digital synthesizer（DDS） plus FL-PLL was used.DDS gives ...An S-band wideband chirp generator using specially designed fast lock phase lock loop（FL-PLL） was demonstrated.To realize high linearity,structure of direct digital synthesizer（DDS） plus FL-PLL was used.DDS gives ideal linearity while FL-PLL retains the linearity and provides radio frequency.The system block diagrams were showed and the timing relationships of the components were provided.Two important considerations of the system,wideband loop and wideband voltage control oscillator（VCO）,were discussed;meanwhile,after analyzing the considerations,corresponding solutions were presented.Measurement results show that the generated 2560MHz to 2960MHz chirp reaches a high FM linearity of 0.003%.展开更多
Abstract: The aim of this study was to develop a cheap, locally made and friendly applicable phantom for gamma camera quality control and to test its validity relative to standard results (intrinsic and extrinsic spat...Abstract: The aim of this study was to develop a cheap, locally made and friendly applicable phantom for gamma camera quality control and to test its validity relative to standard results (intrinsic and extrinsic spatial linearity and intrinsic and extrinsic uniformity) of gamma camera SPECT. And the significance of this experimental study was to introduce a multi-purpose phantom for gamma camera which could overcome the risk accompanied by quality control test procedure such as detector crystal damage and the appearance of moiré patterns. The results of the developed phantom showed an average count difference of 0.7% relative to the standard phantom and about 4% in X- to Y-axis directions relative to the standard phantom. Also, the measured absolute linearity was 0.63 mm in X direction and 0.64 mm in Y direction for the UFOV compare with 0.70 mm value of acceptance test. And the I.U. and D.U. of the developed phantom were 3.18% and 2.27% respectively for the UFOV relative to the standard phantom I.U. and D.U. (2.0% and 1.5%) for the UFOV respectively.展开更多
Non-linear dynamics,fractals,periodic oscillations,bifurcations,chaos,and other terminologies have been used to describe human biological systems in the literature for a few decades.The eight manuscripts included in t...Non-linear dynamics,fractals,periodic oscillations,bifurcations,chaos,and other terminologies have been used to describe human biological systems in the literature for a few decades.The eight manuscripts included in this special issue discussed the historical background,展开更多
With the development of our country, the use of simultaneous interpretation also increased greatly. As everyone knows, simultaneous interpreting is a very complex task. Therefore, the interpreters need to grasp some p...With the development of our country, the use of simultaneous interpretation also increased greatly. As everyone knows, simultaneous interpreting is a very complex task. Therefore, the interpreters need to grasp some particular strategies to reduce the difficulty of simultaneous interpreting. Then this thesis aims to discuss the efficiency of Syntactic Linearity in Simultaneous Interpreting.The theory evidence of this thesis comes from the most fundamental principle in Simultaneous Interpreting, that is, syntactic linearity, which helps the interpreters to deal with long and complex sentences even if he or she has no time to hear and remember the whole sentence.展开更多
Translation is by no means a process of bilingual alternating.Practically speaking,translators need to abide by different princi-ples according to different contexts and readers.The emergence of translation theories i...Translation is by no means a process of bilingual alternating.Practically speaking,translators need to abide by different princi-ples according to different contexts and readers.The emergence of translation theories in the world contributes a lot for cross-culturecommunication.With the development and prevalence of the simultaneous interpreting,people tend to shift their eyes from translation tointerpretation.Syntactic linearity makes interpreting easier and more efficient.However,whether this strategy can be applied into writ-ten translation is unknown.This thesis takes Life of Pi as an example to further discuss the feasibility of syntactic linearity used in liter-ary translation,on the basis of interpreting and translating theories.展开更多
Noise and linearity performances are critical characteristics for radio frequency integrated circuits (RFICs), especially for low noise amplifiers (LNAs). In this paper, a detailed analysis of noise and linearity for ...Noise and linearity performances are critical characteristics for radio frequency integrated circuits (RFICs), especially for low noise amplifiers (LNAs). In this paper, a detailed analysis of noise and linearity for the cascode architecture, a widely used circuit structure in LNA designs, is presented. The noise and the linearity improvement techniques for cascode structures are also developed and have been proven by computer simulating experiments. Theoretical analysis and simulation results showed that, for cascode structure LNAs, the first metallic oxide semiconductor field effect transistor (MOSFET) dominates the noise performance of the LNA, while the second MOSFET contributes more to the linearity. A conclusion is thus obtained that the first and second MOSFET of the LNA can be designed to optimize the noise performance and the linearity performance separately, without trade offs. The 1.9GHz Complementary Metal Oxide Semiconductor (CMOS) LNA simulation results are also given as an application of the developed theory.展开更多
An asymmetric Doherty architecture based on three identical transistors is proposed in this paper. This proposed three.way topology reduces the difficulty in designing matching networks brought by the low optimal impe...An asymmetric Doherty architecture based on three identical transistors is proposed in this paper. This proposed three.way topology reduces the difficulty in designing matching networks brought by the low optimal impedance of high power transistors. And the inverted Doherty topology as well as carefully chosen value of load impedance makes it possible to extend the bandwidth of high power amplifiers. Besides, bias networks of this proposed three.way architecture are also carefully considered to improve the linearity. The proposed high power three.way Doherty power amplifier(3W.DPA) is designed and fabricated based on theoretic analysis. Its maximum output power is about 600 Watts and the drain efficiency is above 35.5% at 9d B back off output power level from 1.9GHz to 2.2 GHz and the saturated drain efficiency is above 47% across the whole frequency band. The measured concurrent two.tone results suggest that the linearity of DPA is improved by at least 5d B.展开更多
We demonstrated an AlGaN/GaN high electron mobility transistor(HEMT)namely double-Vthcoupling HEMT(DVC-HEMT)fabricated by connecting different threshold voltage(Vth)values including the slant recess element and planar...We demonstrated an AlGaN/GaN high electron mobility transistor(HEMT)namely double-Vthcoupling HEMT(DVC-HEMT)fabricated by connecting different threshold voltage(Vth)values including the slant recess element and planar element in parallel along the gate width with N;O plasma treatment on the gate region.The comparative studies of DVC-HEMT and Fin-like HEMT fabricated on the same wafer show significantly improved linearity of transconductance(Gm)and radio frequency(RF)output signal characteristics in DVC-HEMT.The fabricated device shows the transconductance plateau larger than 7 V,which yields a flattened fT/fmax-gate bias dependence.At the operating frequency of 30 GHz,the peak power-added efficiency(PAE)of 41%accompanied by the power density(Pout)of 5.3 W/mm.Furthermore,the proposed architecture also features an exceptional linearity performance with 1-d B compression point(P1 d B)of 28 d Bm,whereas that of the Fin-like HEMT is 25.2 d Bm.The device demonstrated in this article has great potential to be a new paradigm for millimeter-wave application where high linearity is essential.展开更多
In the light of some assumptions that are very close to the practical working conditions,a very complicated polishing process of optical element can be simplified as a linear and shift invariant system that is relatd ...In the light of some assumptions that are very close to the practical working conditions,a very complicated polishing process of optical element can be simplified as a linear and shift invariant system that is relatd only to the speed,pres- sure and time of processing.In polishing,the removed material can be represented and entreated by the convolution of the removal function of polishing head and the dwell function.The properties of removal function are presented.The assumptions and methods given by the author have been shown to be correct and applicable by experiments using a ring lap to polish the optical surfac.展开更多
A technique for measuring the linearity of a linearly frequency-modulated continuous wave (LFM-CW) signal is presented. It uses a delay-line and a mixer to sense the slope of the output of a sweep oscillator, so that ...A technique for measuring the linearity of a linearly frequency-modulated continuous wave (LFM-CW) signal is presented. It uses a delay-line and a mixer to sense the slope of the output of a sweep oscillator, so that the original form of frequency function deviated from idealized linear slope is retrieved by means of spectrum analysis. Consequently,the linearity of the LFM signal is determined. The formulation is performed based on the principle that an angle-modulated signal can be approximated by an amplitude-modulated signal if the modulation coefficient is sufficiently small. To examine the validity of the procedure and to study the effect of each parameter on the accuracy of measurement, a number of computer simulations has been made. The results of simulation show that the error of the measurement is less than 2%.展开更多
We investigate the influence of fin architecture on linearity characteristics of AlGaN/GaNFinFET.It is found that the Fin FET with scaled fin dimensions exhibits much flatter Gm characteristics than the one with long ...We investigate the influence of fin architecture on linearity characteristics of AlGaN/GaNFinFET.It is found that the Fin FET with scaled fin dimensions exhibits much flatter Gm characteristics than the one with long fins as well as planar HEMT.According to the comparative study,we provide direct proof that source resistance rather than tri-gate structure itself dominates the Gm behavior.Furthermore,power measurements show that the optimized FinFET is capable of delivering a much higher output power density along with significant improvement in linearity characteristics than conventional planar HEMT.This study also highlights the importance of fin design in GaN-based FinFET for microwave power application,especially high-linearity applications.展开更多
Introduction: Although the Brief Psychiatric Rating Scale (BPRS) is widely used for evaluating patients with schizophrenia, the meaning of the weights of the individual symptoms is ambiguous. The aims of the study wer...Introduction: Although the Brief Psychiatric Rating Scale (BPRS) is widely used for evaluating patients with schizophrenia, the meaning of the weights of the individual symptoms is ambiguous. The aims of the study were 1) to investigate whether the modification of relative weights of items of the BPRS is able to enhance its correlation with the Clinical Global Impression-Schizophrenia scale (CGI-SCH) and 2) to construct a potential modified BPRS. Methods: We evaluated 200 schizophrenia patients using the BPRS and the CGI-SCH and drew the scatter plot distributions of the two scales. Next, univariate regression for the CGI-SCH using individual symptoms of the BPRS was performed. Multivariate regression utilizing the ‘logistic function’ was then conducted to allocate marks to each item and Pearson’s r correlation coefficient and r-squared between the two scales were assessed. After that, we constructed an example of a potential modified BPRS. Results: With the scatter plot for the two scales, a logarithmic curve was obtained;this was described by [CGI-SCH] = 3.2248 × ln[18-item BPRS] – 7.2044 (p i” that could express the relative weights of individual symptoms. Subsequently, modification of point allocations according to “Pi” yielded a Pearson’s r of 0.8491 and an r-squared of 0.7718 (not changed) (both p < 0.001). An example of a potential modified BPRS was constructed. Conclusions: Within the limits of our data, the weightings of items of the BPRS improved the correlation of the BPRS with the CGI-SCH for evaluating schizophrenia.展开更多
基金the National Natural Science Foundation of China(Ganrt No.62004047)。
文摘Theε-Ga_(2)O_(3) thin film was grown on sapphire substrate by using metalorganic chemical vapor deposition(MOCVD)method,and then was used to fabricate a deep-ultraviolet(DUV)photodetector(PD).Theε-Ga_(2)O_(3) thin film shown good crystal quality and decent surface morphology.Irradiated by a 254-nm DUV light,the photodetector displayed good optoelectronic performance and high wavelength selectivity,such as photoresponsivity(R)of 175.69 A/W,detectivity(D*)of 2.46×10^(15) Jones,external quantum efficiency(EQE)of 8.6×10^(4)%and good photocurrent-intensity linearity,suggesting decent DUV photosensing performance.At 5 V and under illumination with light intensity of 800μW/cm2,the photocurrent gain is as high as 859 owing to the recycling gain mechanism and delayed carrier recombination;and the photocurrent gain decreases as the incident light intensity increases because of the recombination of photogenerated carriers by the large photon flux.
文摘A 13bit,pipelined analog-to-digital converter （ADC） designed to achieve high linearity is described. The high linearity is realized by using the passive capacitor error-averaging technique to calibrate the capacitor mismatch error, a gain-boosting opamp to minimize the finite gain error and gain nonlinearity,a bootstrapping switch to reduce the switch on-resistor nonlinearity, and an anti-disturb design to reduce the noise from the digital supply. This ADC is implemented in 0.18μm CMOS technology and occupies a die area of 3.2mm^2 , including pads. Measured performance includes - 0.18/ 0.15LSB of differential nonlinearity, -0.35/0.5LSB of integral nonlinearity, 75.7dB of signal-to-noise plus distortion ratio （SNDR） and 90. 5 dBc of spurious-free dynamic range （SFDR） for 2.4MHz input at 2.5MS/s. At full speed conversion （5MS/s） and for the same 2.4MHz input, the measured SNDR and SFDR are 73.7dB and 83.9 dBc, respectively. The power dissipation including output pad drivers is 21mW at 2.5MS/s and 34mW at 5MS/s,both at 2.7V supply.
文摘We analyze a wide-band,high-linearity down-conversion mixer for cable receptions that is implemented in 0. 35μm SiGe BiCMOS technology. The bandwidth of the RF （radio frequency） input covers the range from 1 to 1.8GHz. The measured input power at the - 1dB compression point of the mixer reaches ＋ 14.23dBm. The highest voltage conversion gain is 8. 31dB, while the lowest noise figure is 19.4dB. The power consumed is 54mW with a 5V supply. The test result of the down-conversion mixer is outlined.
文摘A CMOS radio frequency low noise amplifier with high linearity and low operation voltage of less than 1.0V is presented.In this circuit,an auxiliary MOSFET in the triode region is used to boost the linearity.Simulation shows that this method can boost the input-referred 3rd-order intercept point with much less power dissipation than that of traditional power/linearity tradeoff solution which pays at least 1dB power for 1dB linearity improvement.It is also shown that the size of the common-gate PMOS transistor needs to be optimized to reduce its loaded input impedance so as not to degrade the linearity due to high voltage gain at its source terminal.The simulation is carried out with TSMC 0.18μm RF CMOS technology and SpectreRF.
文摘A direct conversion CMOS DVB-S front-end employs a T-configuration variable attenuator,a single-to- differential low noise amplifier, and a low noise mixer. By innovative use of the attenuator, the linearity handling ability of the system is dramatically improved. The system is designed and fabricated in SMIC 0.18 μm RF CMOS technology. The measurement data show that the front-end provides a total of more than 30rib dynamic range and a noise figure of 5dB in the wide frequency signal band. The prototype front-end consumes only 10mA and achieves an IIP3 of ＋ 20dBm.
基金National Natural Science Foundations of China(Grant No.52075085)Fundamental Research Funds for the Central Universities of China(Grant No.N2103019).
文摘In previous studies about the synchronization of vibrators,the restoring forces of springs are mainly treated as linear directly,whereas the nonlinear features are rarely considered in vibrating systems.To make up this drawback,a dynamical model of a nonlinear vibrating mechanical system with double rigid frames(RFs),driven by two vibrators,is proposed to explore the synchronization and stability of the system.In this paper,the nonlinearity is reflected in nonlinear restoring forces of springs characterized by asymmetrical piecewise linear,where the nonlinear stiffness of springs is linearized equivalently using the asymptotic method.Based on the average method and Hamilton’s principle,the theory conditions to achieve synchronization and stability of two vibrators are deduced.After the theory analyses,some numerical qualitative analyses are given to reveal the coupling dynamical characteristics of the system and the relative motion properties between two RFs.Besides,some experiments are carried out to examine the validity of the theoretical results and the correctness of the numerical analyses results.Based on the comparisons of the theory,numeric and experiment,the ideal working regions of the system are suggested.Based on the present work,some new types of vibrating equipment,such as vibrating discharging centrifugal dehydrators/conveyers/screens,can be designed.
基金Project supported by the National Key R&D Program of China(Grant No.2018YFB2002405)the National Natural Science Foundation of China(Grant No.61903013)。
文摘Zero-field single-beam atomic magnetometers with transverse parametric modulation for ultra-weak magnetic field detection have attracted widespread attention recently.In this study,we present a comprehensive response model and propose a modification method of conventional first harmonic response by introducing the second harmonic correction.The proposed modification method gives improvement in dynamic range and reduction of linearity error.Additionally,our modification method shows suppression of response instability caused by optical intensity and frequency fluctuations.An atomic magnetometer with single-beam configuration is built to compare the performance between our proposed method and the conventional method.The results indicate that our method’s magnetic field response signal achieves a 5-fold expansion of dynamic range from 2 nT to 10 nT,with the linearity error decreased from 5%to 1%.Under the fluctuations of 5%for optical intensity and±15 GHz detuning of frequency,the proposed modification method maintains intensityrelated instability less than 1%and frequency-related instability less than 8%while the conventional method suffers 15%and 38%,respectively.Our method is promising for future high-sensitive and long-term stable optically pumped atomic sensors.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61574019,61674018 and 61674020the Fund of State Key Laboratory of Information Photonics and Optical Communicationsthe Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No 20130005130001
文摘Two measurement techniques are investigated to characterize photodetector linearity. A model for the two-tone and three-tone photodetector systems is developed to thoroughly investigate the influences of setup components on the measurement results. We demonstrate that small bias shifts from the quadrature point of the modulator will induce deviation into measurement results of the two-tone system, and the simulation results correspond well to experimental and calculation results.
基金Supported by the Fund of National Defense Industry Innovative Team (231)
文摘An S-band wideband chirp generator using specially designed fast lock phase lock loop（FL-PLL） was demonstrated.To realize high linearity,structure of direct digital synthesizer（DDS） plus FL-PLL was used.DDS gives ideal linearity while FL-PLL retains the linearity and provides radio frequency.The system block diagrams were showed and the timing relationships of the components were provided.Two important considerations of the system,wideband loop and wideband voltage control oscillator（VCO）,were discussed;meanwhile,after analyzing the considerations,corresponding solutions were presented.Measurement results show that the generated 2560MHz to 2960MHz chirp reaches a high FM linearity of 0.003%.
文摘Abstract: The aim of this study was to develop a cheap, locally made and friendly applicable phantom for gamma camera quality control and to test its validity relative to standard results (intrinsic and extrinsic spatial linearity and intrinsic and extrinsic uniformity) of gamma camera SPECT. And the significance of this experimental study was to introduce a multi-purpose phantom for gamma camera which could overcome the risk accompanied by quality control test procedure such as detector crystal damage and the appearance of moiré patterns. The results of the developed phantom showed an average count difference of 0.7% relative to the standard phantom and about 4% in X- to Y-axis directions relative to the standard phantom. Also, the measured absolute linearity was 0.63 mm in X direction and 0.64 mm in Y direction for the UFOV compare with 0.70 mm value of acceptance test. And the I.U. and D.U. of the developed phantom were 3.18% and 2.27% respectively for the UFOV relative to the standard phantom I.U. and D.U. (2.0% and 1.5%) for the UFOV respectively.
文摘Non-linear dynamics,fractals,periodic oscillations,bifurcations,chaos,and other terminologies have been used to describe human biological systems in the literature for a few decades.The eight manuscripts included in this special issue discussed the historical background,
文摘With the development of our country, the use of simultaneous interpretation also increased greatly. As everyone knows, simultaneous interpreting is a very complex task. Therefore, the interpreters need to grasp some particular strategies to reduce the difficulty of simultaneous interpreting. Then this thesis aims to discuss the efficiency of Syntactic Linearity in Simultaneous Interpreting.The theory evidence of this thesis comes from the most fundamental principle in Simultaneous Interpreting, that is, syntactic linearity, which helps the interpreters to deal with long and complex sentences even if he or she has no time to hear and remember the whole sentence.
文摘Translation is by no means a process of bilingual alternating.Practically speaking,translators need to abide by different princi-ples according to different contexts and readers.The emergence of translation theories in the world contributes a lot for cross-culturecommunication.With the development and prevalence of the simultaneous interpreting,people tend to shift their eyes from translation tointerpretation.Syntactic linearity makes interpreting easier and more efficient.However,whether this strategy can be applied into writ-ten translation is unknown.This thesis takes Life of Pi as an example to further discuss the feasibility of syntactic linearity used in liter-ary translation,on the basis of interpreting and translating theories.
文摘Noise and linearity performances are critical characteristics for radio frequency integrated circuits (RFICs), especially for low noise amplifiers (LNAs). In this paper, a detailed analysis of noise and linearity for the cascode architecture, a widely used circuit structure in LNA designs, is presented. The noise and the linearity improvement techniques for cascode structures are also developed and have been proven by computer simulating experiments. Theoretical analysis and simulation results showed that, for cascode structure LNAs, the first metallic oxide semiconductor field effect transistor (MOSFET) dominates the noise performance of the LNA, while the second MOSFET contributes more to the linearity. A conclusion is thus obtained that the first and second MOSFET of the LNA can be designed to optimize the noise performance and the linearity performance separately, without trade offs. The 1.9GHz Complementary Metal Oxide Semiconductor (CMOS) LNA simulation results are also given as an application of the developed theory.
基金supported in part by the National Basic Research Program of China (Grant No. 2014CB339900)the National Science and Technology Major Project of the Ministry of Science and Technology of China (Grant No. Grant 2015ZX03002002 and Grant 2016ZX03002009, and Grant 2016ZX03001005)+2 种基金the 863 program (Grant No. 2015AA010802)the National Natural Science Foundation of China (Grant No. 61522112, 61331003)the New Century Excellent Talents in University (NCET)
文摘An asymmetric Doherty architecture based on three identical transistors is proposed in this paper. This proposed three.way topology reduces the difficulty in designing matching networks brought by the low optimal impedance of high power transistors. And the inverted Doherty topology as well as carefully chosen value of load impedance makes it possible to extend the bandwidth of high power amplifiers. Besides, bias networks of this proposed three.way architecture are also carefully considered to improve the linearity. The proposed high power three.way Doherty power amplifier(3W.DPA) is designed and fabricated based on theoretic analysis. Its maximum output power is about 600 Watts and the drain efficiency is above 35.5% at 9d B back off output power level from 1.9GHz to 2.2 GHz and the saturated drain efficiency is above 47% across the whole frequency band. The measured concurrent two.tone results suggest that the linearity of DPA is improved by at least 5d B.
基金supported by the National Key Research and Development Program of China(Grant No.2020YFB1804902)the Fundamental Research Funds for the Central Universities+3 种基金the Innovation Fund of Xidian Universitythe National Natural Science Foundation of China(Grant No.61904135)the China Postdoctoral Science Foundation(Grant Nos.2018M640957 and BX20200262)the Research and Development Plan of Key Fields in Guangzhou(Grant No.202103020002)。
文摘We demonstrated an AlGaN/GaN high electron mobility transistor(HEMT)namely double-Vthcoupling HEMT(DVC-HEMT)fabricated by connecting different threshold voltage(Vth)values including the slant recess element and planar element in parallel along the gate width with N;O plasma treatment on the gate region.The comparative studies of DVC-HEMT and Fin-like HEMT fabricated on the same wafer show significantly improved linearity of transconductance(Gm)and radio frequency(RF)output signal characteristics in DVC-HEMT.The fabricated device shows the transconductance plateau larger than 7 V,which yields a flattened fT/fmax-gate bias dependence.At the operating frequency of 30 GHz,the peak power-added efficiency(PAE)of 41%accompanied by the power density(Pout)of 5.3 W/mm.Furthermore,the proposed architecture also features an exceptional linearity performance with 1-d B compression point(P1 d B)of 28 d Bm,whereas that of the Fin-like HEMT is 25.2 d Bm.The device demonstrated in this article has great potential to be a new paradigm for millimeter-wave application where high linearity is essential.
文摘In the light of some assumptions that are very close to the practical working conditions,a very complicated polishing process of optical element can be simplified as a linear and shift invariant system that is relatd only to the speed,pres- sure and time of processing.In polishing,the removed material can be represented and entreated by the convolution of the removal function of polishing head and the dwell function.The properties of removal function are presented.The assumptions and methods given by the author have been shown to be correct and applicable by experiments using a ring lap to polish the optical surfac.
文摘A technique for measuring the linearity of a linearly frequency-modulated continuous wave (LFM-CW) signal is presented. It uses a delay-line and a mixer to sense the slope of the output of a sweep oscillator, so that the original form of frequency function deviated from idealized linear slope is retrieved by means of spectrum analysis. Consequently,the linearity of the LFM signal is determined. The formulation is performed based on the principle that an angle-modulated signal can be approximated by an amplitude-modulated signal if the modulation coefficient is sufficiently small. To examine the validity of the procedure and to study the effect of each parameter on the accuracy of measurement, a number of computer simulations has been made. The results of simulation show that the error of the measurement is less than 2%.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61504125,61474101,and 61505181)
文摘We investigate the influence of fin architecture on linearity characteristics of AlGaN/GaNFinFET.It is found that the Fin FET with scaled fin dimensions exhibits much flatter Gm characteristics than the one with long fins as well as planar HEMT.According to the comparative study,we provide direct proof that source resistance rather than tri-gate structure itself dominates the Gm behavior.Furthermore,power measurements show that the optimized FinFET is capable of delivering a much higher output power density along with significant improvement in linearity characteristics than conventional planar HEMT.This study also highlights the importance of fin design in GaN-based FinFET for microwave power application,especially high-linearity applications.
文摘Introduction: Although the Brief Psychiatric Rating Scale (BPRS) is widely used for evaluating patients with schizophrenia, the meaning of the weights of the individual symptoms is ambiguous. The aims of the study were 1) to investigate whether the modification of relative weights of items of the BPRS is able to enhance its correlation with the Clinical Global Impression-Schizophrenia scale (CGI-SCH) and 2) to construct a potential modified BPRS. Methods: We evaluated 200 schizophrenia patients using the BPRS and the CGI-SCH and drew the scatter plot distributions of the two scales. Next, univariate regression for the CGI-SCH using individual symptoms of the BPRS was performed. Multivariate regression utilizing the ‘logistic function’ was then conducted to allocate marks to each item and Pearson’s r correlation coefficient and r-squared between the two scales were assessed. After that, we constructed an example of a potential modified BPRS. Results: With the scatter plot for the two scales, a logarithmic curve was obtained;this was described by [CGI-SCH] = 3.2248 × ln[18-item BPRS] – 7.2044 (p i” that could express the relative weights of individual symptoms. Subsequently, modification of point allocations according to “Pi” yielded a Pearson’s r of 0.8491 and an r-squared of 0.7718 (not changed) (both p < 0.001). An example of a potential modified BPRS was constructed. Conclusions: Within the limits of our data, the weightings of items of the BPRS improved the correlation of the BPRS with the CGI-SCH for evaluating schizophrenia.
