Pulsar glitches, i.e. the sudden spin-ups of pulsars, have been detected for most known pulsars.The mechanism giving rise to this kind of phenomenon is uncertain, although a large data set has been built.In the framew...Pulsar glitches, i.e. the sudden spin-ups of pulsars, have been detected for most known pulsars.The mechanism giving rise to this kind of phenomenon is uncertain, although a large data set has been built.In the framework of the starquake model, based on Baym & Pines, the glitch sizes(the relative increases of spin-frequencies during glitches) △Ω/Ω depend on the released energies during glitches, with less released energies corresponding to smaller glitch sizes. On the other hand, as one of the dark matter candidates,our Galaxy might be filled with so called strange nuggets(SNs) which are relics from the early Universe.In this case collisions between pulsars and SNs are inevitable, and these collisions would lead to glitches when enough elastic energy has been accumulated during the spin-down process. The SN-triggered glitches could release less energy, because the accumulated elastic energy would be less than that in the scenario of glitches without SNs. Therefore, if a pulsar is hit frequently by SNs, it would tend to have more small glitches, whose values of ??/? are smaller than those in the standard starquake model(with larger amounts of released energy). Based on the assumption that in our Galaxy the distribution of SNs is similar to that of dark matter, as well as on the glitch data in the ATNF Pulsar Catalogue and Jodrell Bank glitch table, we find that in our Galaxy the incidences of small glitches exhibit tendencies consistent with the collision rates between pulsars and SNs. Further testing of this scenario is expected by detecting more small glitches(e.g.,by the Square Kilometre Array).展开更多
Pulsar glitches are sudden increases in the rotation rate which probably result from angular momentum transfer within the neutron star. We review the observational features of the 39 glitches detected at Nanshan from ...Pulsar glitches are sudden increases in the rotation rate which probably result from angular momentum transfer within the neutron star. We review the observational features of the 39 glitches detected at Nanshan from 2000 to 2008, including several events which appear to be slow glitches. A wide variety of post-glitch behavior is observed with very little recovery in some pulsars and over-recovery in others. Analysis of the whole sample of known glitches shows that fractional glitch amplitudes are correlated with characteristic age with a peak at about 105 years, but there is a spread of two or three orders of magnitude at all ages. For individual pulsars with many glitches, the time until the next glitch is sometimes proportional to the fractional glitch amplitude.展开更多
针对LBlock算法在侧信道攻击前脆弱的问题,文章提出一种可以抵抗一阶和二阶差分功耗攻击(Differential Power Analysis,DPA)的门限防护方案。该方案以秘密共享原理为基础理论,并且在算法进行运算时采用了复合域的概念,将算法的运算域由G...针对LBlock算法在侧信道攻击前脆弱的问题,文章提出一种可以抵抗一阶和二阶差分功耗攻击(Differential Power Analysis,DPA)的门限防护方案。该方案以秘密共享原理为基础理论,并且在算法进行运算时采用了复合域的概念,将算法的运算域由GF(24)转移到GF(22)上,减少硬件消耗的同时,又提高了算法的安全性。在乘法器分组中采用虚拟值方法,以保证满足门限方案的均匀性,并在反相器中引入分解法,以保证各信息分组相关独立且线性无关。分析验证表明,方案满足门限方案所需要的各项性质,并且可以抵御一阶、二阶DPA攻击。所有的信息分组都是独立且无联系的,所以该方案对于glitch攻击也具有相应的防护能力,具有较好的实用性。展开更多
The Crab Nebula and its pulsar PSR B0531 + 21 is the space laboratory for the study of fundamental physical processes. From the beginning of the current century up to date, the giant pulses of the pulsar in the Crab N...The Crab Nebula and its pulsar PSR B0531 + 21 is the space laboratory for the study of fundamental physical processes. From the beginning of the current century up to date, the giant pulses of the pulsar in the Crab Nebula are regularly observed on the Large Phased Array of the Pushchino Radio Astronomy Observatory of the Lebedev Physical Institute at a frequency 111 MHz. The connection between the scattering time scale of radio pulses and the dispersion measure of the pulsar, which was established earlier together with Jodrell Bank, is confirmed. The observed variations in the scattering of radio pulses and their partial correlation with the dispersion measure are explained by the eclipse of the pulsar by dense plasma clouds with fluctuations in the electron density significantly exceeding the corresponding fluctuations in the interstellar medium. The question of a possible connection between period failers (glitches), dispersion measure variations, radio pulses scattering and gamma-ray flares is discussed.展开更多
Objective:Resident microorganisms live in dynamic harmony with their hosts to influence various physical and psychological health aspects.The majority of the resident microbes are found in the digestive tract,aka the ...Objective:Resident microorganisms live in dynamic harmony with their hosts to influence various physical and psychological health aspects.The majority of the resident microbes are found in the digestive tract,aka the gut of mammals.If and when perturbed,the composition of gut microbiota could jeopardize the physiological balance or homeostasis.In this article,we aim to establish how different diseases could be accompanied by notable changes in gut microbial composition and lend insight into microbial regulation of health.Methods:Literature search was done in PubMed using relevant keywords and summarized in tabular form as well as in narration.Results:We try to focus on the concept of microbial and metabolite biomarkers for diseases.We also try to capture the renewed perspective of good and harmful microorganisms in the context of host health.We have presented a comparative network analysis of microbial roles in select diseases.Recent findings also suggested that the growth of some traditionally disease-causing pathogenic microorganisms promotes health in other human communities.We have listed major taxa of gut microbes in communities worldwide,which signifies that gut microbiota can be healthy or harmful depending on the urbanization and ethnicity of the hosts.The traditional and current schools of thoughts are both limited by the technology of metagenomic studies;we have elucidated some of their shortcomings.Conclusion:Research in the field of gut microbiota must take into account the different populations and the changing narrative of healthy and harmful microbes.展开更多
研究了在Burgers方程跨声速稀疏波计算中遇到的sonic point glitch问题,对它产生的原因及其与数值格式熵条件的关系进行了分析.对若干著名格式,按照是否满足熵条件进行了分类.为了消除sonic point glitch现象,提出了一种新的两步分裂方...研究了在Burgers方程跨声速稀疏波计算中遇到的sonic point glitch问题,对它产生的原因及其与数值格式熵条件的关系进行了分析.对若干著名格式,按照是否满足熵条件进行了分类.为了消除sonic point glitch现象,提出了一种新的两步分裂方法,并用这种方法改进了一系列典型格式.数值试验表明这是一种很好的消除sonic point glitch的方法.展开更多
We investigate the masses of glitching pulsars in order to constrain their equation of state(EOS). The observations of glitches(sudden jumps in rotational frequency) may provide information on the interior physics of ...We investigate the masses of glitching pulsars in order to constrain their equation of state(EOS). The observations of glitches(sudden jumps in rotational frequency) may provide information on the interior physics of neutron stars. With the assumption that glitches are triggered by superfluid neutrons, the masses of glitching neutron stars can be estimated using observations of maximum glitches.Together with the observations of thermal emission from glitching pulsars Vela and J1709–4429, the slope of symmetry energy and incompressibility of nuclear matter at saturation density can be constrained.The slope of symmetry energy L should be larger than 67 MeV while the lower limit of incompressibility for symmetric nuclear matter K_0 is 215 MeV. We also obtain a relationship between L and K_0:6.173 MeV + 0.283 K_0≤ L ≤ 7.729 MeV + 0.291 K_0. The restricted EOSs are consistent with the observations of 2-solar-mass neutron stars and gravitational waves from a binary neutron star inspiral.展开更多
The problem of glitch crisis has been a great deal of debate recently. It might challenge the standard two- component model, where glitches are thought to be triggered by the sudden unpinning of superfluid vortices in...The problem of glitch crisis has been a great deal of debate recently. It might challenge the standard two- component model, where glitches are thought to be triggered by the sudden unpinning of superfluid vortices in the neutron-star crust. It says that due to crustal entrainment the amount of superfluid in the crust cannot explain the changes in angular momentum required to account for the glitches. However7 the argument of this crisis is based on the assumption that the core superfluid is completely coupled to the crust when a glitch happens. The fraction of the coupled core part is actually a quite uncertain problem so far. In this work, we take three possible values for the fraction of the coupled core part and study in detail the crisis problem for a 1.4M⊙ canonical star, based on a microscopic equation of state for the neutron star's core using the Brueckner-Hartree-Fock approach. For this purpose, two requisite parameters are chosen as follows: the core-crust transition pressure is in the range of Pt = 0.2-0.65 MeV/fm3, and the fractional crust radius AR/R = 0.082 based on experiments. To account for the possibility of a heavier star, a larger value of AR/R = 0.15 is also chosen for comparison. Then we take the crustal entrainment into account, and evaluate the predictions for the fractional moment of inertia at various conditions. The results show that there is commonly no such glitch crisis, as long as one considers only a small fraction of the core neutron superfluid will contribute to the charged component of the star. Only if the core-crust transition pressure is determined to be a low value, the crisis problem may appear for complete core-crust coupling. This is consistent with a recent study in a phenomenological model.展开更多
Glitches represent a category of non-Gaussian and transient noise that frequently intersects with gravitational wave(GW)signals,thereby exerting a notable impact on the processing of GW data.The inference of GW parame...Glitches represent a category of non-Gaussian and transient noise that frequently intersects with gravitational wave(GW)signals,thereby exerting a notable impact on the processing of GW data.The inference of GW parameters,crucial for GW astronomy research,is particularly susceptible to such interference.In this study,we pioneer the utilization of a temporal and time-spectral fusion normalizing flow for likelihood-free inference of GW parameters,seamlessly integrating the high temporal resolution of the time domain with the frequency separation characteristics of both time and frequency domains.Remarkably,our findings indicate that the accuracy of this inference method is comparable to that of traditional non-glitch sampling techniques.Furthermore,our approach exhibits a greater efficiency,boasting processing times on the order of milliseconds.In conclusion,the application of a normalizing flow emerges as pivotal in handling GW signals affected by transient noises,offering a promising avenue for enhancing the field of GW astronomy research.展开更多
We investigate the effects of theσmeson mass(m_(σ)),symmetry energy,and slope of the symmetry energy on the neutron star core-crust transition density and the crustal moment of inertia(ΔI/I)in the nonlinear relativ...We investigate the effects of theσmeson mass(m_(σ)),symmetry energy,and slope of the symmetry energy on the neutron star core-crust transition density and the crustal moment of inertia(ΔI/I)in the nonlinear relativistic Hartree approach(RHA),which includes vacuum polarization.Although the core-crust transition density(ρ_(t)),pressure(P_(t)),and neutron star radius(R),which are all dependent on the symmetry energy,contribute to determiningΔI/I,we find that changing only the slope of symmetry energy within a reasonable range is not sufficient to reachΔI/I≥7%to achieve the large glitches of the Vela pulsar.However,since all three factors(ρ_(t),P_(t),and R)increase with the increase in mσthrough scalar vacuum polarization,adjusting mσcan easily achieveΔI/I≥7%.展开更多
We adopt the Nambu–Jona-Lasinio(NJL) model to study the crust-core transition properties in neutron stars(NSs). For a given momentum cutoff and symmetry energy of saturation density in the NJL model, decreasing the s...We adopt the Nambu–Jona-Lasinio(NJL) model to study the crust-core transition properties in neutron stars(NSs). For a given momentum cutoff and symmetry energy of saturation density in the NJL model, decreasing the slope of the symmetry energy gives rise to an increase in the crust-core transition density and transition pressure.Given the slope of the symmetry energy at saturation density, the transition density and corresponding transition pressure increase with increasing symmetry energy. The increasing trend between the fraction of the crustal moment of inertia and the slope of symmetry energy at saturation density indicates that a relatively large momentum cutoff of the NJL model is preferred. For a momentum cutoff of 500 Me V, the fraction of the crustal moment of inertia clearly increases with the slope of symmetry energy at saturation density. Thus, at the required fraction(7%) of the crustal moment of inertia, the NJL model with momentum cutoff of 500 Me V and a large slope of the symmetry energy of saturation density can give the upper limit of the mass of the Vela pulsar to be above 1.40 M.展开更多
This paper presents a low phase noise and low reference spur quadrature phase-locked loop (QPLL) circuit that is implemented as a part ofa fi'equency synthesizer for China UWB standard systems. A glitch-suppressed ...This paper presents a low phase noise and low reference spur quadrature phase-locked loop (QPLL) circuit that is implemented as a part ofa fi'equency synthesizer for China UWB standard systems. A glitch-suppressed charge pump (CP) is employed for reference spur reduction. By forcing the phase frequency detector and CP to operate in a linear region of its transfer function, the linearity of the QPLL is further improved. With the proposed series-quadrature voltage-controlled oscillator, the phase accuracy of the QPLL is guaranteed. The circuit is fab- ricated in the TSMC 0.13/Jm CMOS process and operated at 1.2-V supply voltage. The QPLL measures a phase noise of -95 dBc/Hz at 100-kHz offset and a reference spur of-71 dBc. The fully-integrated QPLL dissipates a current of 13 mA.展开更多
A 12-bit, 100-MHz CMOS current-steering D/A converter for CNC (computer number control) systems is presented. To reduce the glitch and increase the SFDR (spurious-free dynamic range), a low crosspoint switch drive...A 12-bit, 100-MHz CMOS current-steering D/A converter for CNC (computer number control) systems is presented. To reduce the glitch and increase the SFDR (spurious-free dynamic range), a low crosspoint switch driver and a special dummy switch are applied. In addition, a 4-5-3 segmental structure is used to optimize the performance and layout area. After improvement, the biggest glitch energy decreased from 6.7 pVs to 1.7 pVs, the INL decreased from 2 LSB to 0.8 LSB, the SFDR is 78 dB at a 100-MSPS clock rate and 1 MHz output frequency. This DAC can deliver up to 20.8 mA full-scale current into a 50 Ω load. The power when operating at full-scale current is 163 mW. The layout area is 1.8 × 1.8 mm2 in a standard 0.35-um CMOS technology.展开更多
基金supported by the National Natural Science Foundation of China (11203018)the West Light Foundation (XBBS-2014-23)+1 种基金the Science Project of Universities in Xinjiang (XJEDU2012S02)the Doctoral Science Foundation of Xinjiang University (BS120107)
文摘Pulsar glitches, i.e. the sudden spin-ups of pulsars, have been detected for most known pulsars.The mechanism giving rise to this kind of phenomenon is uncertain, although a large data set has been built.In the framework of the starquake model, based on Baym & Pines, the glitch sizes(the relative increases of spin-frequencies during glitches) △Ω/Ω depend on the released energies during glitches, with less released energies corresponding to smaller glitch sizes. On the other hand, as one of the dark matter candidates,our Galaxy might be filled with so called strange nuggets(SNs) which are relics from the early Universe.In this case collisions between pulsars and SNs are inevitable, and these collisions would lead to glitches when enough elastic energy has been accumulated during the spin-down process. The SN-triggered glitches could release less energy, because the accumulated elastic energy would be less than that in the scenario of glitches without SNs. Therefore, if a pulsar is hit frequently by SNs, it would tend to have more small glitches, whose values of ??/? are smaller than those in the standard starquake model(with larger amounts of released energy). Based on the assumption that in our Galaxy the distribution of SNs is similar to that of dark matter, as well as on the glitch data in the ATNF Pulsar Catalogue and Jodrell Bank glitch table, we find that in our Galaxy the incidences of small glitches exhibit tendencies consistent with the collision rates between pulsars and SNs. Further testing of this scenario is expected by detecting more small glitches(e.g.,by the Square Kilometre Array).
基金supported by the National Basic Research Program of China (Grant No. 2009CB824800)the National Natural Science Foundation of China (Grant No. 10673021)the Knowledge Innovation Program of CAS Project (Grant No. KJCX2-YW-T09)
文摘Pulsar glitches are sudden increases in the rotation rate which probably result from angular momentum transfer within the neutron star. We review the observational features of the 39 glitches detected at Nanshan from 2000 to 2008, including several events which appear to be slow glitches. A wide variety of post-glitch behavior is observed with very little recovery in some pulsars and over-recovery in others. Analysis of the whole sample of known glitches shows that fractional glitch amplitudes are correlated with characteristic age with a peak at about 105 years, but there is a spread of two or three orders of magnitude at all ages. For individual pulsars with many glitches, the time until the next glitch is sometimes proportional to the fractional glitch amplitude.
文摘针对LBlock算法在侧信道攻击前脆弱的问题,文章提出一种可以抵抗一阶和二阶差分功耗攻击(Differential Power Analysis,DPA)的门限防护方案。该方案以秘密共享原理为基础理论,并且在算法进行运算时采用了复合域的概念,将算法的运算域由GF(24)转移到GF(22)上,减少硬件消耗的同时,又提高了算法的安全性。在乘法器分组中采用虚拟值方法,以保证满足门限方案的均匀性,并在反相器中引入分解法,以保证各信息分组相关独立且线性无关。分析验证表明,方案满足门限方案所需要的各项性质,并且可以抵御一阶、二阶DPA攻击。所有的信息分组都是独立且无联系的,所以该方案对于glitch攻击也具有相应的防护能力,具有较好的实用性。
文摘The Crab Nebula and its pulsar PSR B0531 + 21 is the space laboratory for the study of fundamental physical processes. From the beginning of the current century up to date, the giant pulses of the pulsar in the Crab Nebula are regularly observed on the Large Phased Array of the Pushchino Radio Astronomy Observatory of the Lebedev Physical Institute at a frequency 111 MHz. The connection between the scattering time scale of radio pulses and the dispersion measure of the pulsar, which was established earlier together with Jodrell Bank, is confirmed. The observed variations in the scattering of radio pulses and their partial correlation with the dispersion measure are explained by the eclipse of the pulsar by dense plasma clouds with fluctuations in the electron density significantly exceeding the corresponding fluctuations in the interstellar medium. The question of a possible connection between period failers (glitches), dispersion measure variations, radio pulses scattering and gamma-ray flares is discussed.
文摘Objective:Resident microorganisms live in dynamic harmony with their hosts to influence various physical and psychological health aspects.The majority of the resident microbes are found in the digestive tract,aka the gut of mammals.If and when perturbed,the composition of gut microbiota could jeopardize the physiological balance or homeostasis.In this article,we aim to establish how different diseases could be accompanied by notable changes in gut microbial composition and lend insight into microbial regulation of health.Methods:Literature search was done in PubMed using relevant keywords and summarized in tabular form as well as in narration.Results:We try to focus on the concept of microbial and metabolite biomarkers for diseases.We also try to capture the renewed perspective of good and harmful microorganisms in the context of host health.We have presented a comparative network analysis of microbial roles in select diseases.Recent findings also suggested that the growth of some traditionally disease-causing pathogenic microorganisms promotes health in other human communities.We have listed major taxa of gut microbes in communities worldwide,which signifies that gut microbiota can be healthy or harmful depending on the urbanization and ethnicity of the hosts.The traditional and current schools of thoughts are both limited by the technology of metagenomic studies;we have elucidated some of their shortcomings.Conclusion:Research in the field of gut microbiota must take into account the different populations and the changing narrative of healthy and harmful microbes.
文摘研究了在Burgers方程跨声速稀疏波计算中遇到的sonic point glitch问题,对它产生的原因及其与数值格式熵条件的关系进行了分析.对若干著名格式,按照是否满足熵条件进行了分类.为了消除sonic point glitch现象,提出了一种新的两步分裂方法,并用这种方法改进了一系列典型格式.数值试验表明这是一种很好的消除sonic point glitch的方法.
基金supported by the National Basic Research Program of China (2014CB845800)the National Natural Science Foundation of China (Grant No. 11573014)
文摘We investigate the masses of glitching pulsars in order to constrain their equation of state(EOS). The observations of glitches(sudden jumps in rotational frequency) may provide information on the interior physics of neutron stars. With the assumption that glitches are triggered by superfluid neutrons, the masses of glitching neutron stars can be estimated using observations of maximum glitches.Together with the observations of thermal emission from glitching pulsars Vela and J1709–4429, the slope of symmetry energy and incompressibility of nuclear matter at saturation density can be constrained.The slope of symmetry energy L should be larger than 67 MeV while the lower limit of incompressibility for symmetric nuclear matter K_0 is 215 MeV. We also obtain a relationship between L and K_0:6.173 MeV + 0.283 K_0≤ L ≤ 7.729 MeV + 0.291 K_0. The restricted EOSs are consistent with the observations of 2-solar-mass neutron stars and gravitational waves from a binary neutron star inspiral.
基金Supported by the National Natural Science Foundation of China under Grant No U1431107
文摘The problem of glitch crisis has been a great deal of debate recently. It might challenge the standard two- component model, where glitches are thought to be triggered by the sudden unpinning of superfluid vortices in the neutron-star crust. It says that due to crustal entrainment the amount of superfluid in the crust cannot explain the changes in angular momentum required to account for the glitches. However7 the argument of this crisis is based on the assumption that the core superfluid is completely coupled to the crust when a glitch happens. The fraction of the coupled core part is actually a quite uncertain problem so far. In this work, we take three possible values for the fraction of the coupled core part and study in detail the crisis problem for a 1.4M⊙ canonical star, based on a microscopic equation of state for the neutron star's core using the Brueckner-Hartree-Fock approach. For this purpose, two requisite parameters are chosen as follows: the core-crust transition pressure is in the range of Pt = 0.2-0.65 MeV/fm3, and the fractional crust radius AR/R = 0.082 based on experiments. To account for the possibility of a heavier star, a larger value of AR/R = 0.15 is also chosen for comparison. Then we take the crustal entrainment into account, and evaluate the predictions for the fractional moment of inertia at various conditions. The results show that there is commonly no such glitch crisis, as long as one considers only a small fraction of the core neutron superfluid will contribute to the charged component of the star. Only if the core-crust transition pressure is determined to be a low value, the crisis problem may appear for complete core-crust coupling. This is consistent with a recent study in a phenomenological model.
基金the National SKA Program of China(2022SKA0110200,2022SKA0110203)the National Natural Science Foundation of China(11975072,11875102,11835009)the National 111 Project(B16009)。
文摘Glitches represent a category of non-Gaussian and transient noise that frequently intersects with gravitational wave(GW)signals,thereby exerting a notable impact on the processing of GW data.The inference of GW parameters,crucial for GW astronomy research,is particularly susceptible to such interference.In this study,we pioneer the utilization of a temporal and time-spectral fusion normalizing flow for likelihood-free inference of GW parameters,seamlessly integrating the high temporal resolution of the time domain with the frequency separation characteristics of both time and frequency domains.Remarkably,our findings indicate that the accuracy of this inference method is comparable to that of traditional non-glitch sampling techniques.Furthermore,our approach exhibits a greater efficiency,boasting processing times on the order of milliseconds.In conclusion,the application of a normalizing flow emerges as pivotal in handling GW signals affected by transient noises,offering a promising avenue for enhancing the field of GW astronomy research.
基金Supported in part by the National Natural Science Foundation of China (11775049,12375112)。
文摘We investigate the effects of theσmeson mass(m_(σ)),symmetry energy,and slope of the symmetry energy on the neutron star core-crust transition density and the crustal moment of inertia(ΔI/I)in the nonlinear relativistic Hartree approach(RHA),which includes vacuum polarization.Although the core-crust transition density(ρ_(t)),pressure(P_(t)),and neutron star radius(R),which are all dependent on the symmetry energy,contribute to determiningΔI/I,we find that changing only the slope of symmetry energy within a reasonable range is not sufficient to reachΔI/I≥7%to achieve the large glitches of the Vela pulsar.However,since all three factors(ρ_(t),P_(t),and R)increase with the increase in mσthrough scalar vacuum polarization,adjusting mσcan easily achieveΔI/I≥7%.
基金Supported by National Natural Science Foundation of China(11775049,11275048)the China Jiangsu Provincial Natural Science Foundation(BK20131286)
文摘We adopt the Nambu–Jona-Lasinio(NJL) model to study the crust-core transition properties in neutron stars(NSs). For a given momentum cutoff and symmetry energy of saturation density in the NJL model, decreasing the slope of the symmetry energy gives rise to an increase in the crust-core transition density and transition pressure.Given the slope of the symmetry energy at saturation density, the transition density and corresponding transition pressure increase with increasing symmetry energy. The increasing trend between the fraction of the crustal moment of inertia and the slope of symmetry energy at saturation density indicates that a relatively large momentum cutoff of the NJL model is preferred. For a momentum cutoff of 500 Me V, the fraction of the crustal moment of inertia clearly increases with the slope of symmetry energy at saturation density. Thus, at the required fraction(7%) of the crustal moment of inertia, the NJL model with momentum cutoff of 500 Me V and a large slope of the symmetry energy of saturation density can give the upper limit of the mass of the Vela pulsar to be above 1.40 M.
基金supported by the National Science & Technology Major Projects of China(Nos.2009ZX03006-007-01,2009ZX03007-001, 2009ZX03006-009)the National High Tech R&D Program of China(No.2009AA01Z261 )
文摘This paper presents a low phase noise and low reference spur quadrature phase-locked loop (QPLL) circuit that is implemented as a part ofa fi'equency synthesizer for China UWB standard systems. A glitch-suppressed charge pump (CP) is employed for reference spur reduction. By forcing the phase frequency detector and CP to operate in a linear region of its transfer function, the linearity of the QPLL is further improved. With the proposed series-quadrature voltage-controlled oscillator, the phase accuracy of the QPLL is guaranteed. The circuit is fab- ricated in the TSMC 0.13/Jm CMOS process and operated at 1.2-V supply voltage. The QPLL measures a phase noise of -95 dBc/Hz at 100-kHz offset and a reference spur of-71 dBc. The fully-integrated QPLL dissipates a current of 13 mA.
基金Project supported by the Hubei Natural Science Foundation of China(No.2010CDB02706)
文摘A 12-bit, 100-MHz CMOS current-steering D/A converter for CNC (computer number control) systems is presented. To reduce the glitch and increase the SFDR (spurious-free dynamic range), a low crosspoint switch driver and a special dummy switch are applied. In addition, a 4-5-3 segmental structure is used to optimize the performance and layout area. After improvement, the biggest glitch energy decreased from 6.7 pVs to 1.7 pVs, the INL decreased from 2 LSB to 0.8 LSB, the SFDR is 78 dB at a 100-MSPS clock rate and 1 MHz output frequency. This DAC can deliver up to 20.8 mA full-scale current into a 50 Ω load. The power when operating at full-scale current is 163 mW. The layout area is 1.8 × 1.8 mm2 in a standard 0.35-um CMOS technology.