The design and implementation of a novel ADC architecture called ring-ADC for digital voltage regulator module controllers are presented. Based on the principle of voltage-controlled oscillators＇ transform from volta...The design and implementation of a novel ADC architecture called ring-ADC for digital voltage regulator module controllers are presented. Based on the principle of voltage-controlled oscillators＇ transform from voltage to frequency,the A/D conversion of ring-ADC achieves good linearity and precise calibration against process variations compared with the delay-line ADC. A differential pulse counting discriminator also helps decrease the power consumption of the ring-ADC. It is fabricated with a Chartered 0.35μm CMOS process, and the measurement results of the integral and differential nonlinearity performance are 0.92LSB and 1.2LSB respectively. The maximum gain error measured in ten sample chips is ± 3.85%. With sampling rate of 500kHz and when the voltage regulator module （VRM） works in steady state, the ring-ADC＇s average power consumption is 2.56mW. The ring-ADC is verified to meet the requirements for digital VRM controller application.展开更多
One of the principal disadvantages of Orthogonal Frequency Division Multiplexing (OFDM) is very sensitive to carrier frequency offset. The integer frequency offset has no effect on the orthogonality among the subcarri...One of the principal disadvantages of Orthogonal Frequency Division Multiplexing (OFDM) is very sensitive to carrier frequency offset. The integer frequency offset has no effect on the orthogonality among the subcarriers, but it causes a circular shift and phase rotation of the received data symbols sequence, resulting in a Bit Error Rate(BER) of 0.5. In this paper,a novel integer frequency offset estimator for OFDM is derived based on maximum likelihood estimation technique and exploration of the differential relation between two consecutive OFDM data symbol sequences in frequency domain. Its performance is compared with the conventional method by computer simulations for the additive white Gaussian noise channel and a multipath fading channel. Simulation results show that the performance of the proposed estimator is better than the conventional estimator.展开更多
The relation between diffractive beam parameters and normalized frequency is analyzed that leads to two improved Tormulas for two kinds of mode-field halT-widths and several formulas for divergence angle as well as be...The relation between diffractive beam parameters and normalized frequency is analyzed that leads to two improved Tormulas for two kinds of mode-field halT-widths and several formulas for divergence angle as well as beam propagation factor. The numerical calculation indicates that the maximal relative error is less than 0.5% within a reasonable parameter range.展开更多
The effect of the microstrip bend on the propagation characteristics of a microstrip line was investigated based on the Finite-Difference Time-Domain(FDTD)method.The dispersive characteristics of a microstrip line wit...The effect of the microstrip bend on the propagation characteristics of a microstrip line was investigated based on the Finite-Difference Time-Domain(FDTD)method.The dispersive characteristics of a microstrip line with a bend are quite different from that of a uniform straight microstrip line.The effect of bend discontinuity on propagation constants deceases exponentially with the distance form the corner of the bend.This can be explained by the fact that the higher order modes excited by the bend discontinuities have intrinsic properties of exponentially decay with the distance from the bend discontinuities.This effect can be negligible(less than five percent)when the distance is beyond ten times of conductor strip width.The S parameters and propagation constants comparison between unmitered and mitered bends are also presented.The proposed method which takes advantage of the FDTD algorithm and the Root Mean Square Deviation(RMSD)analysis is also an effective way for analyzing the dispersion characteristics of other planar transmission lines.展开更多
The present study reports on the use of the high-frequency verb do in written English performance based on the Chinese Learner English Corpus (CLEC). The native English corpus for comparison is the Louvain Corpus of N...The present study reports on the use of the high-frequency verb do in written English performance based on the Chinese Learner English Corpus (CLEC). The native English corpus for comparison is the Louvain Corpus of Native English Essays (LOCNESS). A corpus-based Contrastive Interlanguage Analysis (CIA) approach has been adopted in the study. A comparison is made between Band 4 and 8 English majors' writings in CLEC and the native college students' writings in LOCNESS. Results indicate that as far as the overall frequency of do is concerned, there is no significant difference between Band 8 English majors and the native speakers, but Band 4 English majors use less than native speakers. With regard to the different uses of do, marked differences have been found between Chinese learners and native speakers, especially when do is used as an auxiliary verb or a delexical verb. To be specific, Chinese learners show a strong tendency to underuse do as an auxiliary verb to form an interrogative, negative or inverted sentence. Moreover, they tend to overuse do as a delexical verb, allowing it more freedom to collocate with a wider range of nouns. The underlying reasons might be mother-tongue interference, intralingual transfer, and overgeneralization, etc. In conclusion, the pedagogical implications of the study are discussed and suggestions made for adopting corpus-based exercises as a way of raising learners' awareness of the use of high-frequency words.展开更多
文摘The design and implementation of a novel ADC architecture called ring-ADC for digital voltage regulator module controllers are presented. Based on the principle of voltage-controlled oscillators＇ transform from voltage to frequency,the A/D conversion of ring-ADC achieves good linearity and precise calibration against process variations compared with the delay-line ADC. A differential pulse counting discriminator also helps decrease the power consumption of the ring-ADC. It is fabricated with a Chartered 0.35μm CMOS process, and the measurement results of the integral and differential nonlinearity performance are 0.92LSB and 1.2LSB respectively. The maximum gain error measured in ten sample chips is ± 3.85%. With sampling rate of 500kHz and when the voltage regulator module （VRM） works in steady state, the ring-ADC＇s average power consumption is 2.56mW. The ring-ADC is verified to meet the requirements for digital VRM controller application.
基金Supported by the National Natural Science Foundation of China (No.60372048) Mi-crosoft Research Asia, Key Project of National Natural Science Foundation of China (No.60496316)National "863" Program of China (No.2005AA123910)Teaching Research Award Program for Outstanding Young Teachers in Higher Education Institutions of MOE, P.R.C.Key Project of Chinese Ministry of Education (No.104171).
文摘One of the principal disadvantages of Orthogonal Frequency Division Multiplexing (OFDM) is very sensitive to carrier frequency offset. The integer frequency offset has no effect on the orthogonality among the subcarriers, but it causes a circular shift and phase rotation of the received data symbols sequence, resulting in a Bit Error Rate(BER) of 0.5. In this paper,a novel integer frequency offset estimator for OFDM is derived based on maximum likelihood estimation technique and exploration of the differential relation between two consecutive OFDM data symbol sequences in frequency domain. Its performance is compared with the conventional method by computer simulations for the additive white Gaussian noise channel and a multipath fading channel. Simulation results show that the performance of the proposed estimator is better than the conventional estimator.
基金Supported by the Program of Fujian Education Department under Grant No. JB09069the Natural Science Fund of Fujian Province under Grant No. 2009J01275
文摘The relation between diffractive beam parameters and normalized frequency is analyzed that leads to two improved Tormulas for two kinds of mode-field halT-widths and several formulas for divergence angle as well as beam propagation factor. The numerical calculation indicates that the maximal relative error is less than 0.5% within a reasonable parameter range.
基金supported by basic research item of National Key Lab of Electronic Measurement Technology and National Natural Science Foundation of China(No.60876028,60633060)
文摘The effect of the microstrip bend on the propagation characteristics of a microstrip line was investigated based on the Finite-Difference Time-Domain(FDTD)method.The dispersive characteristics of a microstrip line with a bend are quite different from that of a uniform straight microstrip line.The effect of bend discontinuity on propagation constants deceases exponentially with the distance form the corner of the bend.This can be explained by the fact that the higher order modes excited by the bend discontinuities have intrinsic properties of exponentially decay with the distance from the bend discontinuities.This effect can be negligible(less than five percent)when the distance is beyond ten times of conductor strip width.The S parameters and propagation constants comparison between unmitered and mitered bends are also presented.The proposed method which takes advantage of the FDTD algorithm and the Root Mean Square Deviation(RMSD)analysis is also an effective way for analyzing the dispersion characteristics of other planar transmission lines.
文摘The present study reports on the use of the high-frequency verb do in written English performance based on the Chinese Learner English Corpus (CLEC). The native English corpus for comparison is the Louvain Corpus of Native English Essays (LOCNESS). A corpus-based Contrastive Interlanguage Analysis (CIA) approach has been adopted in the study. A comparison is made between Band 4 and 8 English majors' writings in CLEC and the native college students' writings in LOCNESS. Results indicate that as far as the overall frequency of do is concerned, there is no significant difference between Band 8 English majors and the native speakers, but Band 4 English majors use less than native speakers. With regard to the different uses of do, marked differences have been found between Chinese learners and native speakers, especially when do is used as an auxiliary verb or a delexical verb. To be specific, Chinese learners show a strong tendency to underuse do as an auxiliary verb to form an interrogative, negative or inverted sentence. Moreover, they tend to overuse do as a delexical verb, allowing it more freedom to collocate with a wider range of nouns. The underlying reasons might be mother-tongue interference, intralingual transfer, and overgeneralization, etc. In conclusion, the pedagogical implications of the study are discussed and suggestions made for adopting corpus-based exercises as a way of raising learners' awareness of the use of high-frequency words.
