Central nerve signal evoked by thoughts can be directly used to control a robot or prosthetic devices without the involvement of the peripheral nerve and muscles.This is a new strategy of human-computer interaction.A ...Central nerve signal evoked by thoughts can be directly used to control a robot or prosthetic devices without the involvement of the peripheral nerve and muscles.This is a new strategy of human-computer interaction.A method of electroencephalogram(EEG) phase synchronization combined with band energy was proposed to construct a feature vector for pattern recognition of brain-computer interaction based on EEG induced by motor imagery in this paper,rhythm and beta rhythm were first extracted from EEG by band pass filter and then the frequency band energy was calculated by the sliding time window;the instantaneous phase values were obtained using Hilbert transform and then the phase synchronization feature was calculated by the phase locking value(PLV) and the best time interval for extracting the phase synchronization feature was searched by the distribution of the PLV value in the time domain.Finally,discrimination of motor imagery patterns was performed by the support vector machine(SVM).The results showed that the phase synchronization feature more effective in4s-7s and the correct classification rate was 91.4%.Compared with the results achieved by a single EEG feature related to motor imagery,the correct classification rate was improved by 3.5 and4.3 percentage points by combining phase synchronization with band energy.These indicate that the proposed method is effective and it is expected that the study provides a way to improve the performance of the online real-time brain-computer interaction control system based on EEG related to motor imagery.展开更多
This paper presents a high efficiency Doherty power amplifier suitable for TV band applications. A class AB power amplifier is firstly implemented using a commercial GaN HEMT from Cree Incorporation, achieving a high ...This paper presents a high efficiency Doherty power amplifier suitable for TV band applications. A class AB power amplifier is firstly implemented using a commercial GaN HEMT from Cree Incorporation, achieving a high power-added-efficiency of 77.78% and a 40.593 dBm output power with an associated gain of 21.65 dB. The Doherty amplifier has then been designed following the previous class AB scheme for the main amplifier and a class C scheme for the peak one. This amplifier attained a high power-added-efficiency of 81.94%, a 42.77 dBm output power, an associated gain of 21.32 dB, and an operating frequency bandwidth between 550 and 1000 MHz (58.06% fractional bandwidth) which made it suitable for TV band applications.展开更多
The gradient doping regions were employed in the emitter layer and the base layer of GaAs based laser power converters(LPCs).Silvaco TCAD was used to numerically simulate the linear gradient doping and exponential gra...The gradient doping regions were employed in the emitter layer and the base layer of GaAs based laser power converters(LPCs).Silvaco TCAD was used to numerically simulate the linear gradient doping and exponential gradient doping structure,and analyze the transport process of photogenerated carriers.Energy band adjustment via gradient doping improved the separation and transport efficiency of photogenerated carriers and reduced the total recombination rate of GaAs LPCs.Compared with traditional structure of LPCs,the photoelectric conversion efficiency of LPCs with linear and exponential gradient doping structure were improved from 52.7%to 57.2%and 57.7%,respectively,under 808 nm laser light at the power density of 1 W/cm^(2).展开更多
The current study examined the effects of band therapy using music on grasping power, depression, and personal relationships among residents of a nursing home. Thirty subjects participated in the study. The band thera...The current study examined the effects of band therapy using music on grasping power, depression, and personal relationships among residents of a nursing home. Thirty subjects participated in the study. The band therapy included greetings, warm-up exercises with music, singing with dance, playing instruments, closing speech, and stretching with background music. Band therapy was held for 40 minutes once per week, for a total of four sessions, in the activity room of the nursing home. Findings showed that grasping power, depression, and personal relationships were improved at posttest, but the differences were not statistically significant. A better study design to compare the effects of band therapy with the other group, and a more simple and repeated intervention for the elderly to follow without stress might be necessary.展开更多
In this paper,we present the general design methods and parameter measurements of a 1-k W solidstate radio frequency(RF) power amplifier at 2856 MHz,for the soft X-ray free electron laser facility.Three-stage amplific...In this paper,we present the general design methods and parameter measurements of a 1-k W solidstate radio frequency(RF) power amplifier at 2856 MHz,for the soft X-ray free electron laser facility.Three-stage amplification with a 4-way combination is used.An RF switch module is integrated with the solid-state RF power amplifier to convert the continuous wave(CW) signal into pulse signal,with adjustable pulse width.The power gain is measured at 57.7 d B at 60 d Bm output.The RF phase noise,which is measured by the low-level RF system,is\0.015 degree(RMS),while the pulse frontier jitter is\5 ns.展开更多
Advanced wireless standards of communication like 3GPP and LTE are becoming more and more efficient and with this evolution of communication systems mobile equipment is also become smaller and smaller. Power amplifier...Advanced wireless standards of communication like 3GPP and LTE are becoming more and more efficient and with this evolution of communication systems mobile equipment is also become smaller and smaller. Power amplifier designing has become a very crucial task in this era where efficiency and size are the main concern of any designer. In this paper we have design and analyzed X-band Class E Metal-semiconductor field effect transistor(MESFET) based Power Amplifier. This device targets the devices which use OFDM technique to improve their spectral efficiency for the next generation communication systems. Microstrip lines are used to achieve small size for our design instead of lumped components. Load Pull measurements are used to get MESFET input and output impedances optimum values. For linear and non linear operation small signal mathematical model of the design is used. To reduce thermal losses FR4 substrate is used to increase PA efficiency. Our designs shows small values of input and output return loss of about-22.3d B and-23.716 d B achieving a high gain of about25.6 d B respectively, with PAE of about 30 % having stability factor greater than 1 and 21.894 d Bm of output power.展开更多
The rapid pace of change in the wide band gap(WBG)power semiconductor area has led to an explosion in potential uses for WBG devices in a huge variety of applications.The applications include automotive,aerospace and ...The rapid pace of change in the wide band gap(WBG)power semiconductor area has led to an explosion in potential uses for WBG devices in a huge variety of applications.The applications include automotive,aerospace and traction applications,as well as grid related or charging systems,with the potential to provide paradigm shifts in performance and efficiency over Silicon devices in current use today.Despite these exciting developments,however,there are still many outstanding challenges for both researchers and industry to solve before WBG technology becomes pervasive.In this paper we will explore some of these challenges and highlight the strengths of WBG devices,some of the specific issues for machine drives and develop some potential solutions for future developments in power electronics.展开更多
In this paper, the synchronous concurrent dual-band RF signal is used to drive the RF Power Amplifier (PA). The nonlinear characterization of a concurrent dual-band RF PA is discussed while two band signals in the dua...In this paper, the synchronous concurrent dual-band RF signal is used to drive the RF Power Amplifier (PA). The nonlinear characterization of a concurrent dual-band RF PA is discussed while two band signals in the dual-band are modulated by CDMA2000 and WCDMA signals. When the two band signals in the dual-band of the PA are modulated with the same signals, it is found that the nonlinearity of the PA can be expressed by any of the two corresponding baseband data. On the other hand, when the two band signals in the dual-band of the PA are modulated with two different signals, the PA nonlinearity cannot be characterized by any of the two corresponding baseband data. In this case, its nonlinearity has to be denoted by a composite signals consisting of the two baseband signals. Consequently, the requirements for the speed of the A/D converter can be largely reduced. The experimental results with CDMA2000 and WCDMA signals demonstrate the speed of the A/D converter required is only 30 M Sample Per Second (SaPS), but it will be at least 70 M SaPS for the conventional method.展开更多
An X-band inverse class-F power amplifier is realized by a 1-mm Al Ga N/Ga N high electron mobility transistor(HEMT).The intrinsic and parasitic components inside the transistor,especially output capacitor Cds,influ...An X-band inverse class-F power amplifier is realized by a 1-mm Al Ga N/Ga N high electron mobility transistor(HEMT).The intrinsic and parasitic components inside the transistor,especially output capacitor Cds,influence the harmonic impedance heavily at the X-band,so compensation design is used for meeting the harmonic condition of inverse class-F on the current source plane.Experiment results show that,in the continuous-wave mode,the power amplifier achieves 61.7% power added efficiency(PAE),which is 16.3% higher than the class-AB power amplifier realized by the same kind of HEMT.To the best of our knowledge,this is the first inverse class-F Ga N internally-matched power amplifier,and the PAE is quite high at the X-band.展开更多
In order to satisfy increasingly greater demand for the performance of communication systems, a throughput efficient wireless system based on the extended binary phase shift keying (EBPSK) modulation is presented. S...In order to satisfy increasingly greater demand for the performance of communication systems, a throughput efficient wireless system based on the extended binary phase shift keying (EBPSK) modulation is presented. Simultaneously, corresponding analysis of power spectra is also given with a brief process. The optimal waveform is proposed without useful information loss, by removing linear spectra presenting periodic components. On this basis, the reasonable definition of bandwidth is discussed, which indicates that the EBPSK belongs to the category of the ultra narrow band (UNB) throughput-efficient communication. Meanwhile, the modulation parameters' effects on bandwidth, transmission rate and transmission performance are analyzed. Results illustrate the validity of theoretical analysis and spectrum optimization. Results also prove that this UNB system can obtain good bit error rate (BER) performance with high spectra efficiency.展开更多
A CMOS dual-band low noise amplifer (LNA) design is presented.The purpose of th is work is intended to substitute only one LNA for two individual LNA's in dual -band transceivers for applications such as wireless ...A CMOS dual-band low noise amplifer (LNA) design is presented.The purpose of th is work is intended to substitute only one LNA for two individual LNA's in dual -band transceivers for applications such as wireless local area network complying with both IEEE 802.11a and 802.11b/g.Dua l-band simultaneous input power and noise matching and load shaping are discuss ed.The chip is implemented in 0.25μm CMOS mixed and RF process.The measured pe rformance is summarized and discussed.展开更多
The Peak to Average power Ratio (PAR) of a Multi-Band Orthogonal Frequency-Division Multiplexing (MB-OFDM) Ultra-Wide Band (UWB) signals can be substantially larger than that of single carrier or carrier-less ultra-wi...The Peak to Average power Ratio (PAR) of a Multi-Band Orthogonal Frequency-Division Multiplexing (MB-OFDM) Ultra-Wide Band (UWB) signals can be substantially larger than that of single carrier or carrier-less ultra-wideband signals. In this letter, a novel PAR reduction scheme for the MB-OFDM UWB system based on spreading and interleaving is proposed. By spreading the coded bits over each subcarrier in corresponding band and interleaving the spread symbols across all bands, the PAR statistics of the MB-OFDM signals can be improved and the PAR is reduced obviously. In the PAR reduction scheme, there is no loss in transmission data rate or Bit Error Rate (BER) performance decreasing. Since the spreading and interleaving operation are implemented by unitary Hadamard sequences and used for an approach to provide the robustness of the UWB system to narrowband interference, there is no additional implementation burden. Simulation results show that the investigated scheme gives the PAR reduction of 3dB compared with that of the original MB-OFDM signals.展开更多
A C-band RF pulse compressor is in development at SINAP It comprises of two resonant cavities,two mode convertors and a 3 dB power divider.TE_(0.1.15)mode is selected for obtaining higher quality factor Q_0 of the RF ...A C-band RF pulse compressor is in development at SINAP It comprises of two resonant cavities,two mode convertors and a 3 dB power divider.TE_(0.1.15)mode is selected for obtaining higher quality factor Q_0 of the RF pulse compressor cavities,so that the power gain factor can be 3.2,which is supposed to multiply the RF power from 50 MW to 1 60 MW.In this paper,we report our work on C-band RF pulse compressor,namely the design simulation and cold test results.展开更多
Wind turbines are usually designed and operated with fixed startup speed. It could perform startup and shutdown operations repeatedly when the wind fluctuates around the startup speed. The excessive stress induced by ...Wind turbines are usually designed and operated with fixed startup speed. It could perform startup and shutdown operations repeatedly when the wind fluctuates around the startup speed. The excessive stress induced by frequent startup and shutdown could enhance the likelihood of component failure and hence negatively impact the availability of a wind turbine. Startup speed with dead band is proposed in this article to prevent the wind turbine from frequent startup. 22 years wind data from the Cheung Chau wind station in Hong Kong are analyzed to evaluate the reduction in the number of startup and potential loss of wind power production using the proposed approach. Numerical simulation suggests that the number of startup could be reduced by half with trivial reduction in potential wind power generation in most of investigated sites once an appropriate dead band is adopted.展开更多
Power semiconductor devices are the key technology driver for all power electronic system engineering.The main development trend for power devices is going towards higher power handling capability at even smaller Sivo...Power semiconductor devices are the key technology driver for all power electronic system engineering.The main development trend for power devices is going towards higher power handling capability at even smaller Sivolume, faster switching performance,advanced ruggedness and reliability at elevated operating temperature and extended SOA diagrams.To cover all applications in the various fields of industry,consumer,computing and automotive the device optimization is different for low voltage power MOSFET,for high voltage MOSFET,for plasma modulated devices and components based on wide bandgap(WB) material.In the paper,the main development trends will be described and discussed.展开更多
This paper presents a fuzzy logic based three phase four wire four-leg shunt active power filter to suppress harmonic currents. Modified instantaneous p-q theory is adopted for calculating the compensating current. Fu...This paper presents a fuzzy logic based three phase four wire four-leg shunt active power filter to suppress harmonic currents. Modified instantaneous p-q theory is adopted for calculating the compensating current. Fuzzy-adaptive hysteresis band technique is applied for the current control to derive the switching signals for the voltage source inverter. A fuzzy logic controller is developed to control the voltage of the DC capacitor. Computer simulations are carried out on a sample power system to demonstrate the suitability of the proposed control strategy, for harmonic reduction under three different conditions namely, ideal, unbalance, unbalance and distorted source voltage conditions. The proposed control strategy is found to be effective to reduce the harmonics and compensate reactive power and neutral current and balance load currents under ideal and non-ideal source voltage conditions.展开更多
A novel dual-band and diverse radiation pattern antenna is proposed for power efficient on-body and off-body communications intended for various applications in healthcare and sport monitoring. The antenna is dual ban...A novel dual-band and diverse radiation pattern antenna is proposed for power efficient on-body and off-body communications intended for various applications in healthcare and sport monitoring. The antenna is dual band at 2.45 GHz (ISM band) with omnidirectional radiation pattern over the body surface to communicate power efficiently with other co-located body worn devices and at 1.9 GHz (PCS band), it has directive radiation pattern towards off the body to communicate from on-body device to off-body devices. The free space and on-body performances of the antenna are investigated by both simulation and experiment. The antenna shows very good on-body radiation efficiency of 58% at 2.45 GHz and 61% at 1.9 GHz. Good on-body gain is noticed at both frequency bands. Results show that the gain of the proposed antenna increases by 4.7% at 2.45 GHz and 3.2% at 1.9 GHz when placed on the body.展开更多
Experiments were conducted to investigate the effects of low power microwave radiation on germination and growth rate in seeds. In the present paper, the bioeffects of low power (non-thermal intensity) microwave modul...Experiments were conducted to investigate the effects of low power microwave radiation on germination and growth rate in seeds. In the present paper, the bioeffects of low power (non-thermal intensity) microwave modulated with 1 KHz square wave have been studied. Experiments were performed in X-band frequencies using klystron based microwave test bench. Microwave parameters like frequency, power, exposure time and power density were varied while irradiating seed samples to study their influence on germination. The seed samples used for the experiment included wheat (Triticum aestivum), bengal gram (Cicer arietinum), green gram (Vigna radiate) and moth bean (Vigna Aconitifolia). Seed germination %, plant height, root length and dry matter % (biomass %) were recorded and compared with control seeds. The effects of different treatments were found to be stimulating the germination and seedling vigour of plants especially in power and exposure time treatments while increase in frequency and power density has reduced the seed germination and seedling vigour. The effect also varied with the nature of seeds.展开更多
The damage effect characteristics of GaAs pseudomorphic high electron mobility transistor(pHEMT)under the irradiation of C band high-power microwave(HPM)is investigated in this paper.Based on the theoretical analysis,...The damage effect characteristics of GaAs pseudomorphic high electron mobility transistor(pHEMT)under the irradiation of C band high-power microwave(HPM)is investigated in this paper.Based on the theoretical analysis,the thermoelectric coupling model is established,and the key damage parameters of the device under typical pulse conditions are predicted,including the damage location,damage power,etc.By the injection effect test and device microanatomy analysis through using scanning electron microscope(SEM)and energy dispersive spectrometer(EDS),it is concluded that the gate metal in the first stage of the device is the vulnerable to HPM damage,especially the side below the gate near the source.The damage power in the injection test is about 40 dBm and in good agreement with the simulation result.This work has a certain reference value for microwave damage assessment of pHEMT.展开更多
基金supported by the National Natural Science Foundation of China(81470084,61463024)the Research Project for Application Foundation of Yunnan Province(2013FB026)+2 种基金the Cultivation Program of Talents of Yunnan Province(KKSY201303048)the Focal Program for Education Department of Yunnan Province(2013Z130)the Brain Information Processing and Brain-computer Interaction Fusion Control of Kunming University Scienceand Technology(Fund of Discipline Direction Team)
文摘Central nerve signal evoked by thoughts can be directly used to control a robot or prosthetic devices without the involvement of the peripheral nerve and muscles.This is a new strategy of human-computer interaction.A method of electroencephalogram(EEG) phase synchronization combined with band energy was proposed to construct a feature vector for pattern recognition of brain-computer interaction based on EEG induced by motor imagery in this paper,rhythm and beta rhythm were first extracted from EEG by band pass filter and then the frequency band energy was calculated by the sliding time window;the instantaneous phase values were obtained using Hilbert transform and then the phase synchronization feature was calculated by the phase locking value(PLV) and the best time interval for extracting the phase synchronization feature was searched by the distribution of the PLV value in the time domain.Finally,discrimination of motor imagery patterns was performed by the support vector machine(SVM).The results showed that the phase synchronization feature more effective in4s-7s and the correct classification rate was 91.4%.Compared with the results achieved by a single EEG feature related to motor imagery,the correct classification rate was improved by 3.5 and4.3 percentage points by combining phase synchronization with band energy.These indicate that the proposed method is effective and it is expected that the study provides a way to improve the performance of the online real-time brain-computer interaction control system based on EEG related to motor imagery.
文摘This paper presents a high efficiency Doherty power amplifier suitable for TV band applications. A class AB power amplifier is firstly implemented using a commercial GaN HEMT from Cree Incorporation, achieving a high power-added-efficiency of 77.78% and a 40.593 dBm output power with an associated gain of 21.65 dB. The Doherty amplifier has then been designed following the previous class AB scheme for the main amplifier and a class C scheme for the peak one. This amplifier attained a high power-added-efficiency of 81.94%, a 42.77 dBm output power, an associated gain of 21.32 dB, and an operating frequency bandwidth between 550 and 1000 MHz (58.06% fractional bandwidth) which made it suitable for TV band applications.
基金This work was supported by the National Key R&D Program of China(No.2018YFB1500500)also supported by Ally Fund of Chinese Academy of Sciences(No.Y072051002).
文摘The gradient doping regions were employed in the emitter layer and the base layer of GaAs based laser power converters(LPCs).Silvaco TCAD was used to numerically simulate the linear gradient doping and exponential gradient doping structure,and analyze the transport process of photogenerated carriers.Energy band adjustment via gradient doping improved the separation and transport efficiency of photogenerated carriers and reduced the total recombination rate of GaAs LPCs.Compared with traditional structure of LPCs,the photoelectric conversion efficiency of LPCs with linear and exponential gradient doping structure were improved from 52.7%to 57.2%and 57.7%,respectively,under 808 nm laser light at the power density of 1 W/cm^(2).
文摘The current study examined the effects of band therapy using music on grasping power, depression, and personal relationships among residents of a nursing home. Thirty subjects participated in the study. The band therapy included greetings, warm-up exercises with music, singing with dance, playing instruments, closing speech, and stretching with background music. Band therapy was held for 40 minutes once per week, for a total of four sessions, in the activity room of the nursing home. Findings showed that grasping power, depression, and personal relationships were improved at posttest, but the differences were not statistically significant. A better study design to compare the effects of band therapy with the other group, and a more simple and repeated intervention for the elderly to follow without stress might be necessary.
文摘In this paper,we present the general design methods and parameter measurements of a 1-k W solidstate radio frequency(RF) power amplifier at 2856 MHz,for the soft X-ray free electron laser facility.Three-stage amplification with a 4-way combination is used.An RF switch module is integrated with the solid-state RF power amplifier to convert the continuous wave(CW) signal into pulse signal,with adjustable pulse width.The power gain is measured at 57.7 d B at 60 d Bm output.The RF phase noise,which is measured by the low-level RF system,is\0.015 degree(RMS),while the pulse frontier jitter is\5 ns.
基金supported by the National Natural Science Foundation of China (Grant no.61571063, 61472357, 61501100)
文摘Advanced wireless standards of communication like 3GPP and LTE are becoming more and more efficient and with this evolution of communication systems mobile equipment is also become smaller and smaller. Power amplifier designing has become a very crucial task in this era where efficiency and size are the main concern of any designer. In this paper we have design and analyzed X-band Class E Metal-semiconductor field effect transistor(MESFET) based Power Amplifier. This device targets the devices which use OFDM technique to improve their spectral efficiency for the next generation communication systems. Microstrip lines are used to achieve small size for our design instead of lumped components. Load Pull measurements are used to get MESFET input and output impedances optimum values. For linear and non linear operation small signal mathematical model of the design is used. To reduce thermal losses FR4 substrate is used to increase PA efficiency. Our designs shows small values of input and output return loss of about-22.3d B and-23.716 d B achieving a high gain of about25.6 d B respectively, with PAE of about 30 % having stability factor greater than 1 and 21.894 d Bm of output power.
文摘The rapid pace of change in the wide band gap(WBG)power semiconductor area has led to an explosion in potential uses for WBG devices in a huge variety of applications.The applications include automotive,aerospace and traction applications,as well as grid related or charging systems,with the potential to provide paradigm shifts in performance and efficiency over Silicon devices in current use today.Despite these exciting developments,however,there are still many outstanding challenges for both researchers and industry to solve before WBG technology becomes pervasive.In this paper we will explore some of these challenges and highlight the strengths of WBG devices,some of the specific issues for machine drives and develop some potential solutions for future developments in power electronics.
基金Supported by the National Science and Technology Major Project of China (2010ZX03007-003-04)the National Natural Science Foundation of China (No. 61171040)+4 种基金the Key Project of International Cooperation of the Provincial Science and Technology Major Projects of Zhejiang (2010C14007)the Provincial Natural Science Foundation of Zhejiang (Y1101270)the Natural Science Foundation of Ningbo (2011A610188)Key Project of International Scientific and Technical Cooperation of Yunnan (2009AC010)Excellent Papers Engagement Fund of Ningbo University (PY20100004)
文摘In this paper, the synchronous concurrent dual-band RF signal is used to drive the RF Power Amplifier (PA). The nonlinear characterization of a concurrent dual-band RF PA is discussed while two band signals in the dual-band are modulated by CDMA2000 and WCDMA signals. When the two band signals in the dual-band of the PA are modulated with the same signals, it is found that the nonlinearity of the PA can be expressed by any of the two corresponding baseband data. On the other hand, when the two band signals in the dual-band of the PA are modulated with two different signals, the PA nonlinearity cannot be characterized by any of the two corresponding baseband data. In this case, its nonlinearity has to be denoted by a composite signals consisting of the two baseband signals. Consequently, the requirements for the speed of the A/D converter can be largely reduced. The experimental results with CDMA2000 and WCDMA signals demonstrate the speed of the A/D converter required is only 30 M Sample Per Second (SaPS), but it will be at least 70 M SaPS for the conventional method.
基金Project supported by the National High Technology Research and Development Program of China(Grant No.2015AA016801)
文摘An X-band inverse class-F power amplifier is realized by a 1-mm Al Ga N/Ga N high electron mobility transistor(HEMT).The intrinsic and parasitic components inside the transistor,especially output capacitor Cds,influence the harmonic impedance heavily at the X-band,so compensation design is used for meeting the harmonic condition of inverse class-F on the current source plane.Experiment results show that,in the continuous-wave mode,the power amplifier achieves 61.7% power added efficiency(PAE),which is 16.3% higher than the class-AB power amplifier realized by the same kind of HEMT.To the best of our knowledge,this is the first inverse class-F Ga N internally-matched power amplifier,and the PAE is quite high at the X-band.
基金The National Natural Science Foundation of China(No.60472054)the Natural Science Foundation of Jiangsu Province(No.BK2007103)
文摘In order to satisfy increasingly greater demand for the performance of communication systems, a throughput efficient wireless system based on the extended binary phase shift keying (EBPSK) modulation is presented. Simultaneously, corresponding analysis of power spectra is also given with a brief process. The optimal waveform is proposed without useful information loss, by removing linear spectra presenting periodic components. On this basis, the reasonable definition of bandwidth is discussed, which indicates that the EBPSK belongs to the category of the ultra narrow band (UNB) throughput-efficient communication. Meanwhile, the modulation parameters' effects on bandwidth, transmission rate and transmission performance are analyzed. Results illustrate the validity of theoretical analysis and spectrum optimization. Results also prove that this UNB system can obtain good bit error rate (BER) performance with high spectra efficiency.
文摘A CMOS dual-band low noise amplifer (LNA) design is presented.The purpose of th is work is intended to substitute only one LNA for two individual LNA's in dual -band transceivers for applications such as wireless local area network complying with both IEEE 802.11a and 802.11b/g.Dua l-band simultaneous input power and noise matching and load shaping are discuss ed.The chip is implemented in 0.25μm CMOS mixed and RF process.The measured pe rformance is summarized and discussed.
基金Supported by the National 863 High Technology Research Program of China (N0.2005AA123320)Universities Natural Science Research Project of Jiangsu Province (No.05KJB510101).
文摘The Peak to Average power Ratio (PAR) of a Multi-Band Orthogonal Frequency-Division Multiplexing (MB-OFDM) Ultra-Wide Band (UWB) signals can be substantially larger than that of single carrier or carrier-less ultra-wideband signals. In this letter, a novel PAR reduction scheme for the MB-OFDM UWB system based on spreading and interleaving is proposed. By spreading the coded bits over each subcarrier in corresponding band and interleaving the spread symbols across all bands, the PAR statistics of the MB-OFDM signals can be improved and the PAR is reduced obviously. In the PAR reduction scheme, there is no loss in transmission data rate or Bit Error Rate (BER) performance decreasing. Since the spreading and interleaving operation are implemented by unitary Hadamard sequences and used for an approach to provide the robustness of the UWB system to narrowband interference, there is no additional implementation burden. Simulation results show that the investigated scheme gives the PAR reduction of 3dB compared with that of the original MB-OFDM signals.
基金the Accelerator Laboratory of Tsinghua University for experiment supports
文摘A C-band RF pulse compressor is in development at SINAP It comprises of two resonant cavities,two mode convertors and a 3 dB power divider.TE_(0.1.15)mode is selected for obtaining higher quality factor Q_0 of the RF pulse compressor cavities,so that the power gain factor can be 3.2,which is supposed to multiply the RF power from 50 MW to 1 60 MW.In this paper,we report our work on C-band RF pulse compressor,namely the design simulation and cold test results.
文摘Wind turbines are usually designed and operated with fixed startup speed. It could perform startup and shutdown operations repeatedly when the wind fluctuates around the startup speed. The excessive stress induced by frequent startup and shutdown could enhance the likelihood of component failure and hence negatively impact the availability of a wind turbine. Startup speed with dead band is proposed in this article to prevent the wind turbine from frequent startup. 22 years wind data from the Cheung Chau wind station in Hong Kong are analyzed to evaluate the reduction in the number of startup and potential loss of wind power production using the proposed approach. Numerical simulation suggests that the number of startup could be reduced by half with trivial reduction in potential wind power generation in most of investigated sites once an appropriate dead band is adopted.
文摘Power semiconductor devices are the key technology driver for all power electronic system engineering.The main development trend for power devices is going towards higher power handling capability at even smaller Sivolume, faster switching performance,advanced ruggedness and reliability at elevated operating temperature and extended SOA diagrams.To cover all applications in the various fields of industry,consumer,computing and automotive the device optimization is different for low voltage power MOSFET,for high voltage MOSFET,for plasma modulated devices and components based on wide bandgap(WB) material.In the paper,the main development trends will be described and discussed.
文摘This paper presents a fuzzy logic based three phase four wire four-leg shunt active power filter to suppress harmonic currents. Modified instantaneous p-q theory is adopted for calculating the compensating current. Fuzzy-adaptive hysteresis band technique is applied for the current control to derive the switching signals for the voltage source inverter. A fuzzy logic controller is developed to control the voltage of the DC capacitor. Computer simulations are carried out on a sample power system to demonstrate the suitability of the proposed control strategy, for harmonic reduction under three different conditions namely, ideal, unbalance, unbalance and distorted source voltage conditions. The proposed control strategy is found to be effective to reduce the harmonics and compensate reactive power and neutral current and balance load currents under ideal and non-ideal source voltage conditions.
文摘A novel dual-band and diverse radiation pattern antenna is proposed for power efficient on-body and off-body communications intended for various applications in healthcare and sport monitoring. The antenna is dual band at 2.45 GHz (ISM band) with omnidirectional radiation pattern over the body surface to communicate power efficiently with other co-located body worn devices and at 1.9 GHz (PCS band), it has directive radiation pattern towards off the body to communicate from on-body device to off-body devices. The free space and on-body performances of the antenna are investigated by both simulation and experiment. The antenna shows very good on-body radiation efficiency of 58% at 2.45 GHz and 61% at 1.9 GHz. Good on-body gain is noticed at both frequency bands. Results show that the gain of the proposed antenna increases by 4.7% at 2.45 GHz and 3.2% at 1.9 GHz when placed on the body.
文摘Experiments were conducted to investigate the effects of low power microwave radiation on germination and growth rate in seeds. In the present paper, the bioeffects of low power (non-thermal intensity) microwave modulated with 1 KHz square wave have been studied. Experiments were performed in X-band frequencies using klystron based microwave test bench. Microwave parameters like frequency, power, exposure time and power density were varied while irradiating seed samples to study their influence on germination. The seed samples used for the experiment included wheat (Triticum aestivum), bengal gram (Cicer arietinum), green gram (Vigna radiate) and moth bean (Vigna Aconitifolia). Seed germination %, plant height, root length and dry matter % (biomass %) were recorded and compared with control seeds. The effects of different treatments were found to be stimulating the germination and seedling vigour of plants especially in power and exposure time treatments while increase in frequency and power density has reduced the seed germination and seedling vigour. The effect also varied with the nature of seeds.
基金Project supported by the Foundation Enhancement Planthe National Natural Science Foundation of China (Grant No. 61974116)
文摘The damage effect characteristics of GaAs pseudomorphic high electron mobility transistor(pHEMT)under the irradiation of C band high-power microwave(HPM)is investigated in this paper.Based on the theoretical analysis,the thermoelectric coupling model is established,and the key damage parameters of the device under typical pulse conditions are predicted,including the damage location,damage power,etc.By the injection effect test and device microanatomy analysis through using scanning electron microscope(SEM)and energy dispersive spectrometer(EDS),it is concluded that the gate metal in the first stage of the device is the vulnerable to HPM damage,especially the side below the gate near the source.The damage power in the injection test is about 40 dBm and in good agreement with the simulation result.This work has a certain reference value for microwave damage assessment of pHEMT.