A compact direct digital frequency synthesizer （DDFS） for system-on-chip implementation of the high precision rubidium atomic frequency standard is developed. For small chip size and low power consumption, the phase...A compact direct digital frequency synthesizer （DDFS） for system-on-chip implementation of the high precision rubidium atomic frequency standard is developed. For small chip size and low power consumption, the phase to sine mapping data is compressed using sine symmetry technique, sine-phase difference technique, quad line approximation technique,and quantization and error read only memory （QE-ROM） technique. The ROM size is reduced by 98% using these techniques. A compact DDFS chip with 32bit phase storage depth and a 10bit on-chip digital to analog converter has been successfully implemented using a standard 0.35μm CMOS process. The core area of the DDFS is 1.6mm^2. It consumes 167mW at 3.3V,and its spurious free dynamic range is 61dB.展开更多
This paper addresses a unified approach of the PID controller design for low as well as high order unstable processes with time delay.The design method is based on the direct synthesis(DS)approach to achieve the enhan...This paper addresses a unified approach of the PID controller design for low as well as high order unstable processes with time delay.The design method is based on the direct synthesis(DS)approach to achieve the enhanced load disturbance rejection.To improve the servo response,a two-degree of freedom control scheme has been considered.A suitable guideline has been provided to select the desired reference model in the DS scheme.The direct synthesis controller has been approximated to the PID controller using the frequency response matching method.A consistently better performance has been obtained in comparison with the recently reported methods.展开更多
Indirect association is a high level relationship between items and frequent item sets in data. There are many potential applications for indirect associations, such as database marketing, intelligent data analysis, w...Indirect association is a high level relationship between items and frequent item sets in data. There are many potential applications for indirect associations, such as database marketing, intelligent data analysis, web -log analysis, recommended system, etc. Existing indirect association mining algorithms are mostly based on the notion of post - processing of discovery of frequent item sets. In the mining process, all frequent item sets need to be generated first, and then they are fihered and joined to form indirect associations. We have presented an indirect association mining algorithm （NIA） based on anti -monotonicity of indirect associations whereas k candidate indirect associations can be generated directly from k - 1 candidate indirect associations, without all frequent item sets generated. We also use the frequent itempair support matrix to reduce the time and memory space needed by the algorithm. In this paper, a novel algorithm （NIA2） is introduced based on the generation of indirect association patterns between itempairs through one item mediator sets from frequent itempair support matrix. A notion of mediator set support threshold is also presented. NIA2 mines indirect association patterns directly from the dataset, without generating all frequent item sets. The frequent itempair support matrix and the notion of using tm as the support threshold for mediator sets can significantly reduce the cost of joint operations and the search process compared with existing algorithms. Results of experiments on a real - word web log dataset have proved NIA2 one order of magnitude faster than existing algorithms.展开更多
Direct Digital Synthesis （DDS） chip was used in the design of program controlled power source in this paper. With the accurate control of Dual DDS chips by Micro Controller Unit （MCU）, illter and power amplifier, ...Direct Digital Synthesis （DDS） chip was used in the design of program controlled power source in this paper. With the accurate control of Dual DDS chips by Micro Controller Unit （MCU）, illter and power amplifier, this power source can generate voltage and corrent output with variable frequency, amplitude and phase. There are several advantages of this power source such as high power, high accuiracy, output stable, light and conveaient.展开更多
Amplitude quantization is one of the main sources of spurious noise frequencies in Direct Digital Frequency Synthesizers (DDFSs), which affect their application to many wireless telecommu- nication systems. In this pa...Amplitude quantization is one of the main sources of spurious noise frequencies in Direct Digital Frequency Synthesizers (DDFSs), which affect their application to many wireless telecommu- nication systems. In this paper, two different kinds of spurious signals due to amplitude quantization in DDFSs are exactly formulated in the time domain and detailedly compared in the frequency do- main, and the effects of the DDFS parameter variations on the spurious performance are thoroughly studied. Then the spectral properties and power levels of the amplitude-quantization spurs in the absence of phase-accumulator truncation are emphatically analyzed by waveform estimation and computer simulation, and several important conclusions are derived which can provide theoretical support for parameter choice and spurious performance evaluation in the application of DDFSs.展开更多
This paper proposes the design and research on the high bandwidth linear frequency sweep signal source involved in the readout unit module of the wireless passive pressure sensor in high temperature based on the princ...This paper proposes the design and research on the high bandwidth linear frequency sweep signal source involved in the readout unit module of the wireless passive pressure sensor in high temperature based on the principle of mutual inductance coupling which is applied widely at present. The operating principle of the linear sweep frequency source based on the direct digital frequency synthesis （DDS） technology is introduced, and the implementation method of the hardware circuit and logic sequential control process required in our system has been realized utilizing this technology. Through the experiments under different conditions of the step value, the sweep range and other related design indicators, the influence on the extraction method of resonance frequency information, extraction accuracy, and others during the readout system of the mutual inductance coupling sensor are analyzed and studied. The design of the linear frequency sweep signal source is realized with a resonance frequency change resolution of 6 kHz, a minimum step value of 1 kHz, and a precision of frequency for 0.116 Hz within the sweep width of 1 MHz - 100MHz. Due to the use of the integrated commercial chip, the linear sweep frequency source is made small in size, high working frequency, high resolution and low step values for the readout unit modularized of a higher application value.展开更多
We present a low cost radio-frequency （RF） generator suitable for experiments with cold atoms. The RF source achieves a sub-hertz frequency with tunable resolution from 0 MHz to 400 MHz and a maximum output power of...We present a low cost radio-frequency （RF） generator suitable for experiments with cold atoms. The RF source achieves a sub-hertz frequency with tunable resolution from 0 MHz to 400 MHz and a maximum output power of 33 dBm. Based on a direct digital synthesizer （DDS） chip, we implement a ramping capability for frequency, ampli- tude and phase. The system can also operate as an arbitrary waveform generator. By measuring the stability in a dura- tion of 600 s, we fred the presented device performs comparably as Agilent33522A in terms of short-term stability. Due to its excellent performance, the RF generator has been already applied to cold atom trapping experiments.展开更多
文摘A compact direct digital frequency synthesizer （DDFS） for system-on-chip implementation of the high precision rubidium atomic frequency standard is developed. For small chip size and low power consumption, the phase to sine mapping data is compressed using sine symmetry technique, sine-phase difference technique, quad line approximation technique,and quantization and error read only memory （QE-ROM） technique. The ROM size is reduced by 98% using these techniques. A compact DDFS chip with 32bit phase storage depth and a 10bit on-chip digital to analog converter has been successfully implemented using a standard 0.35μm CMOS process. The core area of the DDFS is 1.6mm^2. It consumes 167mW at 3.3V,and its spurious free dynamic range is 61dB.
文摘This paper addresses a unified approach of the PID controller design for low as well as high order unstable processes with time delay.The design method is based on the direct synthesis(DS)approach to achieve the enhanced load disturbance rejection.To improve the servo response,a two-degree of freedom control scheme has been considered.A suitable guideline has been provided to select the desired reference model in the DS scheme.The direct synthesis controller has been approximated to the PID controller using the frequency response matching method.A consistently better performance has been obtained in comparison with the recently reported methods.
文摘Indirect association is a high level relationship between items and frequent item sets in data. There are many potential applications for indirect associations, such as database marketing, intelligent data analysis, web -log analysis, recommended system, etc. Existing indirect association mining algorithms are mostly based on the notion of post - processing of discovery of frequent item sets. In the mining process, all frequent item sets need to be generated first, and then they are fihered and joined to form indirect associations. We have presented an indirect association mining algorithm （NIA） based on anti -monotonicity of indirect associations whereas k candidate indirect associations can be generated directly from k - 1 candidate indirect associations, without all frequent item sets generated. We also use the frequent itempair support matrix to reduce the time and memory space needed by the algorithm. In this paper, a novel algorithm （NIA2） is introduced based on the generation of indirect association patterns between itempairs through one item mediator sets from frequent itempair support matrix. A notion of mediator set support threshold is also presented. NIA2 mines indirect association patterns directly from the dataset, without generating all frequent item sets. The frequent itempair support matrix and the notion of using tm as the support threshold for mediator sets can significantly reduce the cost of joint operations and the search process compared with existing algorithms. Results of experiments on a real - word web log dataset have proved NIA2 one order of magnitude faster than existing algorithms.
文摘Direct Digital Synthesis （DDS） chip was used in the design of program controlled power source in this paper. With the accurate control of Dual DDS chips by Micro Controller Unit （MCU）, illter and power amplifier, this power source can generate voltage and corrent output with variable frequency, amplitude and phase. There are several advantages of this power source such as high power, high accuiracy, output stable, light and conveaient.
基金Supported by National High-Technology Research and Development Plan of China (Grant No.2006AA01Z452)
文摘Amplitude quantization is one of the main sources of spurious noise frequencies in Direct Digital Frequency Synthesizers (DDFSs), which affect their application to many wireless telecommu- nication systems. In this paper, two different kinds of spurious signals due to amplitude quantization in DDFSs are exactly formulated in the time domain and detailedly compared in the frequency do- main, and the effects of the DDFS parameter variations on the spurious performance are thoroughly studied. Then the spectral properties and power levels of the amplitude-quantization spurs in the absence of phase-accumulator truncation are emphatically analyzed by waveform estimation and computer simulation, and several important conclusions are derived which can provide theoretical support for parameter choice and spurious performance evaluation in the application of DDFSs.
文摘This paper proposes the design and research on the high bandwidth linear frequency sweep signal source involved in the readout unit module of the wireless passive pressure sensor in high temperature based on the principle of mutual inductance coupling which is applied widely at present. The operating principle of the linear sweep frequency source based on the direct digital frequency synthesis （DDS） technology is introduced, and the implementation method of the hardware circuit and logic sequential control process required in our system has been realized utilizing this technology. Through the experiments under different conditions of the step value, the sweep range and other related design indicators, the influence on the extraction method of resonance frequency information, extraction accuracy, and others during the readout system of the mutual inductance coupling sensor are analyzed and studied. The design of the linear frequency sweep signal source is realized with a resonance frequency change resolution of 6 kHz, a minimum step value of 1 kHz, and a precision of frequency for 0.116 Hz within the sweep width of 1 MHz - 100MHz. Due to the use of the integrated commercial chip, the linear sweep frequency source is made small in size, high working frequency, high resolution and low step values for the readout unit modularized of a higher application value.
基金This work has been supported by the National Natural Science Foundation of China(No.51275523)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20134307110009)
文摘We present a low cost radio-frequency （RF） generator suitable for experiments with cold atoms. The RF source achieves a sub-hertz frequency with tunable resolution from 0 MHz to 400 MHz and a maximum output power of 33 dBm. Based on a direct digital synthesizer （DDS） chip, we implement a ramping capability for frequency, ampli- tude and phase. The system can also operate as an arbitrary waveform generator. By measuring the stability in a dura- tion of 600 s, we fred the presented device performs comparably as Agilent33522A in terms of short-term stability. Due to its excellent performance, the RF generator has been already applied to cold atom trapping experiments.
