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A Σ-Δ Fractional-N PLL Frequency Synthesizer with AFC for SRD Applications 被引量:1
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作者 章华江 胡康敏 洪志良 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2008年第7期1298-1304,共7页
A fractional-N frequency synthesizer for 433/868MHz SRD applications is implemented in a 0.3μm CMOS process. A wide-band VCO and an AFC are used to cover the desired bands. A 3bit third order sigma-delta modulator is... A fractional-N frequency synthesizer for 433/868MHz SRD applications is implemented in a 0.3μm CMOS process. A wide-band VCO and an AFC are used to cover the desired bands. A 3bit third order sigma-delta modulator is adopted to reduce the out-band phase noise. The measurements show a VCO tuning range from 1.31 to 1.88GHz with AFC working correctly,an out-band phase noise of -139dBc/Hz at 3MHz offset frequency, and a fractional spur of less than - 60dBc. The chip area is 1.5mm × 1.2mm and the total current dissipation including LO buffers is 19mA from a single 3.0V supply voltage. 展开更多
关键词 short range device phase locked loop adaptive frequency calibration frequency synthesizer SIGMA-DELTA
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Adaptive Time Frequency Distribution Based on Linear Chirp Modulated Gaussian Functions 被引量:3
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作者 Shi-wei Ma Guang-hua Chen +1 位作者 Jia-mei Deng Jia-lin Cao 《Advances in Manufacturing》 2000年第1期31-37,共7页
We propose a method that uses linear chirp modulated Gaussian functions as the elementary functions, by adaptively adjusting variances, time frequency centers and sweep rates, to decompose signals. By taking WVD, an ... We propose a method that uses linear chirp modulated Gaussian functions as the elementary functions, by adaptively adjusting variances, time frequency centers and sweep rates, to decompose signals. By taking WVD, an improved adaptive time frequency distribution is developed, which is non negative, free of cross term interference, and of better time frequency resolution. The paper presents an effective numerical algorithm to estimate the optimal parameters of the basis. Simulations indicate that the proposed approach is effective in analyzing signal's time frequency behavior. 展开更多
关键词 adaptive time frequency distribution elementary function subspace decomposition STFT WVD
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IMPROVED METHOD FOR HILBERT INSTANTANEOUS FREQUENCY ESTIMATION 被引量:3
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作者 BO Lin LIU Xiaofeng QIN Shuren 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2007年第6期94-98,共5页
In the mechanical fault detection and diagnosis field, it is more and more important to analyze the instantaneous frequency (IF) character of complex vibration signal. The improved IF estimation method is put forwar... In the mechanical fault detection and diagnosis field, it is more and more important to analyze the instantaneous frequency (IF) character of complex vibration signal. The improved IF estimation method is put forward aiming at the shortage of traditional Hilbert transform. It is based on Hilbert transform in wavelet domain. With the help of relationship between the real part and the imaginary part obtained from the complex coefficient of continuous wavelet transform or the analyti- cal signal reconstructed in wavelet packet decomposition, the instantaneous phase function of the subcomponent is extracted. In order to improve the precise of IF estimated out, some means such as Linear regression, adaptive filtering, resampling are applied into the instantaneous phase obtained, then, the central differencing operator is used to get desired IF. Simulation results with synthetic and gearbox fault signals are included to illustrate the proposed method. 展开更多
关键词 Instantaneous frequency Hilbert transform Wavelet transform Linear regression Adaptive filtering Resampling
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Towards frequency adaptation for delayed feedback deep brain stimulations
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作者 Mohammad Daneshzand Miad Faezipour Buket D.Barkana 《Neural Regeneration Research》 SCIE CAS CSCD 2018年第3期408-409,共2页
In neurodegenerative disorders such as Parkinson's disease (PD), deep brain stimulation (DBS) is a desirable approach when the medication is less effective for treating the symptoms. DBS incorporates transferring... In neurodegenerative disorders such as Parkinson's disease (PD), deep brain stimulation (DBS) is a desirable approach when the medication is less effective for treating the symptoms. DBS incorporates transferring electrical pulses to a specific tissue of the central nervous system, obtaining therapeutic results by modulating the neuronal activity of that region. DBS has certain advantages such as reversibility and adjustability features over medication, since the neuronal firing patterns can be recorded and used to alter the parameters of the DBS signal (Benabid et al., 2009). One of the DBS indications is its ability to suppress the abnormal neuronal activity to treat symptoms like tremor, akinesia and dystonia. 展开更多
关键词 FIGURE DBS Towards frequency adaptation for delayed feedback deep brain stimulations STN HFS
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New lumped-mass-stick model based on modal characteristics of structures: development and application to a nuclear containment building 被引量:8
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作者 Hwasung Roh Huseok Lee Jong Seh Lee 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2013年第2期307-317,共11页
In this study, a new lumped-mass-stick model (LMSM) is developed based on the modal characteristics of a structure such as eigenvalues and eigenvectors. The simplified model, named the "frequency adaptive lumped-ma... In this study, a new lumped-mass-stick model (LMSM) is developed based on the modal characteristics of a structure such as eigenvalues and eigenvectors. The simplified model, named the "frequency adaptive lumped-massstick model," hasonly a small number of stick elements and nodes to provide the same natural frequencies of the structure and is applied to a nuclear containment building. To investigate the numerical performance of the LMSM, a time history analysis is carried out on both the LMSM and the finite element model (FEM) for a nuclear containment building. A comparison of the results shows that the dynamic responses of the LMSM in terms of displacement and acceleration are almost identical to those of the FEM. In addition, the results in terms of floor response spectra at certain elevations are also in good agreement. 展开更多
关键词 new lumped-mass-stick model frequency adaptive nuclear containment buildings seismic response floor response spectrum
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Narrow-band interference excision in spread-spectrum systems using new N-sigma algorithm based on fuzzy threshold 被引量:4
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作者 Feng Jining Wu Siliang Wang Ju 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2009年第1期20-26,共7页
The key to narrow-band interference excision in frequency domain is to determine the excision thresh- old in direct-sequence spread-spectrum (DS-SS) systems. The excision threshold is a non-linear function related t... The key to narrow-band interference excision in frequency domain is to determine the excision thresh- old in direct-sequence spread-spectrum (DS-SS) systems. The excision threshold is a non-linear function related to the number and the power of interference, and attempting to get the exact relation of threshold related to the number and the power of interference is almost impossible. The N-sigma algorithm determines the excision threshold using subsection function; however, the excision threshold determined by this method is not exact. A new method to determine the threshold of N-sigma algorithm is proposed. The new method modifies the scale factor N by use of the membership function. The threshold determined by this method is consecutive and smooth, and it is closer to the fact than that of the initial N-sigma algorithm. The GPS signal and single-tone (CW) interference (that is, typical narrow-band interference) are implemented in the simulation, and the results are presented to demonstrate the validity of the new algorithm. 展开更多
关键词 direct-sequence spread-spectrum systems adaptive frequency domain interference suppression fuzzyfunction GPS signal.
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Adaptive resource allocation for multi-user multi-server power-line communication OFDM systems
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作者 徐志强 翟明岳 +1 位作者 崔翔 赵宇明 《Journal of Central South University》 SCIE EI CAS 2011年第2期479-489,共11页
The bits and power allocation model of adaptive power-rate mixture for multi-user multi-server power-line communication systems was analyzed with the restrictions of maximal total power,fixed rate for each real time (... The bits and power allocation model of adaptive power-rate mixture for multi-user multi-server power-line communication systems was analyzed with the restrictions of maximal total power,fixed rate for each real time (RT) user,minimal rate for each non-real time (NRT) user,maximal bits and power for each subcarrier in each orthogonal frequency division multiplexing (OFDM) symbol. An algorithm of resource dynamic allocation in the first OFDM symbol of each frame and resource optimal adjustment in the latter OFDM symbol of each frame was proposed. In the first OFDM symbol of every frame,resource is firstly assigned for RT users so as to minimize their total used power until satisfying their fixed rates; secondly the remainder resource of power and subcarriers are assigned for NRT users so as to minimize their total used power until satisfying their minimal rates also; lastly the remainder resource is again assigned for NRT users according to the proportional fairness strategy so as to maximize their total assigning rate. In the latter OFDM symbol of each frame,bits are swapped and power is adjusted for every user based on the resource allocation results of anterior OFDM symbol. The algorithm is tested in the typical power-line channel scenarios and the simulation results indicate that the proposed algorithm has better performances than the classical multi-user resource allocation algorithms and it realizes the multiple aims of multi-user multi-server resource allocation for power-line communication systems. 展开更多
关键词 power-line communications adaptive orthogonal frequency division multiplexing resource allocation user priority swapadjustment
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New Channel Simulator for Adaptive HF Communication Systems
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作者 张玉冰 匡镜明 刘家康 《Journal of Beijing Institute of Technology》 EI CAS 2003年第4期412-415,共4页
The high frequency (HF) channel simulators with time-varying parameters based on the Watterson model are analyzed. The methods of simulating the HF channel with time-varying parameters are proposed. The linearly time-... The high frequency (HF) channel simulators with time-varying parameters based on the Watterson model are analyzed. The methods of simulating the HF channel with time-varying parameters are proposed. The linearly time-varying delay spread is introduced into the channel simulators to simulate the transition states between two channel modes of CCIR520-1. Two signals, including a 500 Hz and a 1 000 Hz bandwidth signal are respectively input into the standard Watterson HF channel model and the proposed channel model with time-varying parameters. Some simulation results prove that the proposed HF channel model with time-varying parameters can reflect the time-varying characteristics of frequency selected fading of HF channel. 展开更多
关键词 high frequency channel simulator Watterson model adaptive high frequency communications
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SR-AFU: super-resolution network using adaptive frequency component upsampling and multi-resolution features
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作者 Ke-Jia CHEN Mingyu WU +1 位作者 Yibo ZHANG Zhiwei CHEN 《Frontiers of Computer Science》 SCIE EI CSCD 2023年第1期123-132,共10页
Image super-resolution (SR) is one of the classic computer vision tasks. This paper proposes a super-resolution network based on adaptive frequency component upsampling, named SR-AFU. The network is composed of multip... Image super-resolution (SR) is one of the classic computer vision tasks. This paper proposes a super-resolution network based on adaptive frequency component upsampling, named SR-AFU. The network is composed of multiple cascaded dilated convolution residual blocks (CDCRB) to extract multi-resolution features representing image semantics, and multiple multi-size convolutional upsampling blocks (MCUB) to adaptively upsample different frequency components using CDCRB features. The paper also defines a new loss function based on the discrete wavelet transform, making the reconstructed SR images closer to human perception. Experiments on the benchmark datasets show that SR-AFU has higher peak signal to noise ratio (PSNR), significantly faster training speed and more realistic visual effects compared with the existing methods. 展开更多
关键词 SUPER-RESOLUTION multi-resolution features adaptive frequency upsampling wavelet transformation
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Comparative Study of Low-Pass Filter and Phase-Locked Loop Type Speed Filters for Sensorless Control of AC Drives
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作者 Dong Wang Kaiyuan Lu +1 位作者 Peter Omand Rasmussen Zhenyu Yang 《CES Transactions on Electrical Machines and Systems》 2017年第2期207-215,共9页
High quality speed information is one of the key issues in machine sensorless drives,which often requires proper filtering of the estimated speed.This paper comparatively studies typical low-pass filters(LPF)and phase... High quality speed information is one of the key issues in machine sensorless drives,which often requires proper filtering of the estimated speed.This paper comparatively studies typical low-pass filters(LPF)and phase-locked loop(PLL)type filters with respect to ramp speed reference tracking and steady-state performances,as well as the achievement of adaptive cutoff frequency control.An improved LPF-based filter structure with no ramping and steady-state errors caused by filter parameter quantization effects is proposed,which is suitable for applying LPF for sensorless drives of AC machines,especially when fixed-point digital signal processor is selected e.g.in mass production.Furthermore,the potential of adopting PLL for speed filtering is explored.It is demonstrated that PLL type filters can well maintain the advantages offered by the improved LPF.Moreover,it is found that the PLL type filters exhibit almost linear relationship between the cutoff frequency of the PLL filter and its proportional-integral(PI)gains,which can ease the realization of speed filters with adaptive cutoff frequency for improving the speed transient performance.The proposed filters are verified experimentally.The PLL type filter with adaptive cutoff frequency can provide satisfactory performances under various operating conditions and is therefore recommended. 展开更多
关键词 Adaptive cutoff frequency low-pass filter machine sensorless drive phase-locked loop speed filter static error
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A fast lock frequency synthesizer using an improved adaptive frequency calibration 被引量:2
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作者 阴亚东 阎跃鹏 +1 位作者 梁伟伟 杜占坤 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2010年第6期131-136,共6页
An improved adaptive frequency calibration(AFC) has been employed to implement a fast lock phaselocked loop based frequency synthesizer in a 0.18μm CMOS process.The AFC can work in two modes:the frequency calibrat... An improved adaptive frequency calibration(AFC) has been employed to implement a fast lock phaselocked loop based frequency synthesizer in a 0.18μm CMOS process.The AFC can work in two modes:the frequency calibration mode and the store/load mode.In the frequency calibration mode,a novel frequency-detector is used to reduce the frequency calibration time to 16 us typically.In the store/load mode,the AFC makes the voltage-controlled oscillator(VCO) return to the calibrated frequency in about 1μs by loading the calibration result stored after the frequency calibration.The experimental results show that the VCO tuning frequency range is about 620-920 MHz and the in-band phase noise within the loop bandwidth of 10 kHz is-82 dBc/Hz.The lock time is about 20μs in frequency calibration mode and about 5 us in store/load mode.The synthesizer consumes 12 mA from a single 1.8 V supply voltage when steady. 展开更多
关键词 adaptive frequency calibration frequency detector frequency synthesizer phase-locked loop
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AMC-based resource allocation in adaptive frequency reused OFDMA-relay networks 被引量:1
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作者 CHEN Yu FANG Xu-ming 《The Journal of China Universities of Posts and Telecommunications》 EI CSCD 2011年第2期59-64,71,共7页
In orthogonal frequency division multiple access(OFDMA) relay system,for supporting relay transmission,the base station(BS)-the relay station(RS) link must consume an extra part of resource,which may result in s... In orthogonal frequency division multiple access(OFDMA) relay system,for supporting relay transmission,the base station(BS)-the relay station(RS) link must consume an extra part of resource,which may result in serious resource shortage.In order to improve resource utilization,this paper proposes a dynamic resource allocation scheme in adaptive frequency reused OFDMA-relay system based on adaptive modulation and coding(AMC) technology.In this scheme,relay nodes have two independent antennas and operate in decode-and-forward(DF) and full-duplex mode.Then the BS and RSs share the same subcarriers by spatial multiplexing by two independent antennas.The resource allocation problem is formulated for system downlink throughput maximization.Since the optimal solution couldn't be obtained easily,a sub-optimal algorithm is proposed.The adaptive frequency reused algorithm with two independent antennas RS improves the system throughput about 24.3 % compared with the orthogonal frequency allocation with single-antenna model,and increases the system throughput 10.4 % compared with adaptive frequency reused algorithms with single-antenna RS.It is proved that both of the RS with two-antenna model and adaptive frequency reused scheme can improve the system throughput significantly. 展开更多
关键词 AMC resource allocation adaptive frequency reuse OFDMA RELAY
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Design of a constant-voltage and constant-current controller with dual-loop and adaptive switching frequency control
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作者 陈映平 李志谦 《Journal of Semiconductors》 EI CAS CSCD 2015年第5期104-110,共7页
A 5.0-V 2.0-A flyback power supply controller providing constant-voltage (CV) and constant-current (CC) output regulation without the use of an optical coupler is presented. Dual-close-loop control is proposed her... A 5.0-V 2.0-A flyback power supply controller providing constant-voltage (CV) and constant-current (CC) output regulation without the use of an optical coupler is presented. Dual-close-loop control is proposed here due to its better regulation performance of tolerance over process and temperature compared with open loop control used in common. At the same time, the two modes, CC and CV, could switch to each other automatically and smoothly according to the output voltage level not sacrificing the regulation accuracy at the switching phase, which overcomes the drawback of the digital control scheme depending on a hysteresis comparator to change the mode. On-chip compensation using active capacitor multiplier technique is applied to stabilize the voltage loop, eliminate an additional package pin, and save on the die area. The system consumes as little as 100 mW at no-load condition without degrading the transient response performance by utilizing the adaptive switching frequency control mode. The proposed controller has been implemented in a commercial 0.35μm 40-V BCD process, and the active chip area is 1.5×1.0 mm^2. The total error of the output voltage due to line and load variations is less than 4-1.7%. 展开更多
关键词 constant voltage constant current DUAL-LOOP adaptive switching frequency
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A wide range sigma-delta fractional-N frequency synthesizer with adaptive frequency calibration
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作者 魏建军 姜汉钧 +4 位作者 张凌伟 董晶晶 李福乐 王志华 张春 《Journal of Semiconductors》 EI CAS CSCD 2013年第6期97-101,共5页
A wide range fractional-N frequency synthesizer in 0.18μm RF CMOS technology is implemented. A switched-capacitors bank LC-tank VCO and an adaptive frequency calibration technique are used to expand the frequency ran... A wide range fractional-N frequency synthesizer in 0.18μm RF CMOS technology is implemented. A switched-capacitors bank LC-tank VCO and an adaptive frequency calibration technique are used to expand the frequency range.A 16-bit third-order sigma-delta modulator with dither is used to randomize the fractional spur. The active area is 0.6 mm;.The experimental results show the proposed frequency synthesizer consumes 4.3 raA from a single 1.8 V supply voltage except for buffers.The frequency range is 1.44-2.11 GHz and the frequency resolution is less than 0.4 kHz.The phase noise is -94 dBc/Hz @ 100 kHz and -121 dBc/Hz @ 1 MHz at the output of the prescaler with a loop bandwidth of approximately 120 kHz.The performance meets the requirements for the multi-band and multi-mode transceiver applications. 展开更多
关键词 adaptive frequency calibration fractional frequency synthesizer wide frequency range
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An approach for parameter estimation of combined CPPM and LFM radar signal 被引量:3
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作者 Zhang Wei Xiong Ying +2 位作者 Wang Pei Wang Jun Tang Bin 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2013年第4期986-992,共7页
In this paper, the problem of parameter estimation of the combined radar signal adopting chaotic pulse position modulation (CPPM) and linear frequency modulation (LFM), which can be widely used in electronic count... In this paper, the problem of parameter estimation of the combined radar signal adopting chaotic pulse position modulation (CPPM) and linear frequency modulation (LFM), which can be widely used in electronic countermeasures, is addressed. An approach is proposed to estimate the initial frequency and chirp rate of the combined signal by exploiting the second-order cyclostationarity of the intra-pulse signal. In addition, under the condition of the equal pulse width, the pulse repetition interval (PRI) of the combined signal is predicted using the low-order Volterra adaptive filter. Simulations demonstrate that the proposed cyclic autocorrelation Hough transform (CHT) algorithm is theoretically tolerant to additive white Gaussian noise. When the value of signal noise to ratio (SNR) is less than 4 dB, it can still estimate the intra-pulse parameters well. When SNR = 3 dB, a good prediction of the PRI sequence can be achieved by the Volterra adaptive filter algorithm, even only 100 training samples. 展开更多
关键词 Chaotic pulse position modulation Combined radar signal Cyclic autocorrelation Electronic countermeasures Hough transform Linear frequency modulation Volterra adaptive filter
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A 3.96 GHz phase-locked loop for mode-1 MB-OFDM UWB hopping carrier generation
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作者 郑永正 李伟男 +2 位作者 夏玲琍 黄煜梅 洪志良 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2009年第7期91-95,共5页
A fully integrated phase-locked loop(PLL) is presented for a single quadrature output frequency of 3.96 GHz.The proposed PLL can be applied to mode-1 MB-OFDM UWB hopping carrier generation.An adaptive frequency cali... A fully integrated phase-locked loop(PLL) is presented for a single quadrature output frequency of 3.96 GHz.The proposed PLL can be applied to mode-1 MB-OFDM UWB hopping carrier generation.An adaptive frequency calibration loop is incorporated into the PLL.The capacitance area in the loop filter is largely reduced through a capacitor multiplier.Implemented in a CMOS process, this PLL draws 13.0 mA current from a single 1.2 V supply while occupying 0.55 mm2 die area.Measurement results show that the PLL achieves a phase noise of-70 dBc/Hz at 10 kHz offset and-113 dBc/Hz at 1 MHz offset.The integrated RMS jitter from 1 kHz to 10 MHz is 2.2 ps.The reference spur level is less than-68 dBc. 展开更多
关键词 phase-locked loop adaptive frequency calibration loop filter CMOS UWB
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A Necessary Condition about the Optimum Partition on a Finite Set of Samples and Its Application to Clustering Analysis
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作者 叶世伟 史忠植 《Journal of Computer Science & Technology》 SCIE EI CSCD 1995年第6期545-556,共12页
This paper presents another necessary condition about the optimum parti-tion on a finite set of samples. From this condition, a corresponding generalized sequential hao f k-means (GSHKM) clustering algorithm is built ... This paper presents another necessary condition about the optimum parti-tion on a finite set of samples. From this condition, a corresponding generalized sequential hao f k-means (GSHKM) clustering algorithm is built and many well-known clustering algorithms are found to be included in it. Under some assumptions the well-known MacQueen's SHKM (Sequential Hard K-Means)algorithm, FSCL (Frequency Sensitive Competitive Learning) algorithm and RPCL (Rival Penalized Competitive Learning) algorithm are derived. It is shown that FSCL in fact still belongs to the kind of GSHKM clustering algth rithm and is more suitable for producing means of K-partition of sample data,which is illustrated by numerical experiment. Meanwhile, some improvements on these algorithms are also given. 展开更多
关键词 Cluster analysis MacQueen's sequential hard K-means clustering algorithm frequency sensitive competitive learning adaptive frequency K-means clustering
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A VHF RFPGA with adaptive phase-correction technique
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作者 程序 郭桂良 +2 位作者 阎跃鹏 刘荣江 姜宇 《Journal of Semiconductors》 EI CAS CSCD 2013年第8期183-187,共5页
This paper presents a VHF(30-300 MHz) RF programmable gain amplifier(PGA) with an adaptive phase correction technique.The proposed technique effectively mitigates phase errors over the VHF band,and the RFPGA as a ... This paper presents a VHF(30-300 MHz) RF programmable gain amplifier(PGA) with an adaptive phase correction technique.The proposed technique effectively mitigates phase errors over the VHF band,and the RFPGA as a whole satisfies all the specifications of the China mobile multimedia broadcasting VHF band applications.The RFPGA is implemented with a TSMC 0.25μm CMOS process.Measurement results reveal a gain range of around 61 dB,an ⅡP3 of-7 dBm at maximum gain,a power consumption of 10.2 mA at maximum gain,and a phase imbalance of less than 0.3 degrees. 展开更多
关键词 programmable gain amplifier very high frequency adaptive phase correction technique phase imbalance china mobile multimedia broadcasting
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On-Line Adaptive Repetitive Controller for Power Factor Correction Systems
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作者 鞠嘉凌 刘斌 +2 位作者 李俊 胡质良 万海燕 《Journal of Shanghai Jiaotong university(Science)》 EI 2016年第3期263-269,共7页
When the fundamental frequency is shifting, it is hard for traditional repetitive controller to work at the resonant frequencies. In this paper, a novel adaptive repetitive controller for power factor correction syste... When the fundamental frequency is shifting, it is hard for traditional repetitive controller to work at the resonant frequencies. In this paper, a novel adaptive repetitive controller for power factor correction systems is proposed to suppress the current harmonics. Through the controller, the shifting sampling times of the repetitive controller in a fundamental period can be obtained. Mathematical analysis, simulations and physical experiments have validated the effectiveness of the adaptive repetitive controller. 展开更多
关键词 frequency shifting harmonics adaptive repetitive controller
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