A new low-cost demodulator for ZigBee receivers satisfying requirements of IEEE802.15.4 standard is presented,which is designed for ISM 2.4 GHz band and based on Zero-IF receivers.This demodulator extracts symbols dir...A new low-cost demodulator for ZigBee receivers satisfying requirements of IEEE802.15.4 standard is presented,which is designed for ISM 2.4 GHz band and based on Zero-IF receivers.This demodulator extracts symbols directly from baseband signal rather than recovering PN code chips,so its structure is simple.Two main techniques are used to improve the performance of demodulator.One is Phase-Axis Crossing Detector(PACD) which detects the phase correlation of baseband signal.The other is symbol synchronization and sampling clock correction algorithm.The result shows that this demodulator performance,Symbol Error Rate(SER) and Packet Error Rate(PER) meet IEEE 802.15.4TM standard requirements and the demodulator can handle frequency offset in excess of 200 kHz,involving a Zero-IF receiver with a Noise Figure(NF) lower than 17 dB,which is easily imple-mented in standard CMOS technology.展开更多
A model of curvature and tip deflection of multilayer thermal cantilever actuators is derived.The sim-plified expression received from the model avoids inverting complex matrices enhances understanding and makes it ea...A model of curvature and tip deflection of multilayer thermal cantilever actuators is derived.The sim-plified expression received from the model avoids inverting complex matrices enhances understanding and makes it easier to optimize the structure parameters.Experiment is performed,the modeled and experimental results demonstrate the validity of the model,and it also indicates that Young's module makes great contribution to the deflection;therefore,thin layers cannot be ignored arbitrarily.展开更多
GaAs-based metamorphic HEMTs (MHEMT) consist of GaAs substrates and InP-based epitaxial structure, and have the advantages of both InP HEMT's excellent performances and GaAs-based HEMT's mature processes. GaAs...GaAs-based metamorphic HEMTs (MHEMT) consist of GaAs substrates and InP-based epitaxial structure, and have the advantages of both InP HEMT's excellent performances and GaAs-based HEMT's mature processes. GaAs-based MHEMTs were applied to millimeter-wave low-noise, high-power applications and systems. The current gain cut-off frequency (fT) and the maximum oscillation frequency (fmax) are important performance parameter of GaAs-based MHEMTs, and they are limited by the gate-length mainly. Electron beam lithography is one of the lithography technologies which can be used to realize the deep submicron gate-length. The 200 nm gate-length GaAs-based MHEMTs have been fabricated by electron beam lithography. In order to reduce the parasite gate capacitance and gate resistance, a trilayer resist structure was used to pattern the T-gate resist profile. Excellent DC, high frequency and power performances have been obtained. FT and fmax are 105 GHz, 70 GHz respectively. The research is very helpful to obtain higher performance GaAs-based MHEMTs.展开更多
The ultra-small textured surface of multicrystalline silicon solar cell,prepared by electroless chemical-etching method,shows an excellent anti-reflection property over a wide spectral bandwidth.A novel back surface p...The ultra-small textured surface of multicrystalline silicon solar cell,prepared by electroless chemical-etching method,shows an excellent anti-reflection property over a wide spectral bandwidth.A novel back surface protection method and front surface passivation method have been used in the multicrystalline solar cells with ultra-small textured surfaces.With these improvements,the back surface remains intact after the etch process and the efficient minority lifetime is apparently increased.The test result shows that the solar cell with ultra-small textured surface can obtain better electrical performances by these improvements.展开更多
Nanostructure-textured solar cell owns unique properties but has some shortages especially in its fabrication and passivation.In this paper,nanostructures for crystalline silicon solar cell have been synthesized by co...Nanostructure-textured solar cell owns unique properties but has some shortages especially in its fabrication and passivation.In this paper,nanostructures for crystalline silicon solar cell have been synthesized by controllable method based on silver catalyzed chemical etching.In this way,only the front surface of cell is etched and rear surface is protected.It was found that cells textured via the new method obtained equally excellent optical while superior electrical properties compared with those textured via traditional HF/AgNO3 etching.The V OC and I SC of the cell were improved by 6% and 11%,respectively.Then the cells were passivated via a bi-layer passivation(SiO2 & SiN x),in contrast to traditional SiN x passivation.It was also found that cells with new passivation exhibited improved V OC and I SC by 4% and 25%,respectively.The encouraging results can provide fundamental data for developing the nanostructure-textured crystalline silicon solar cell in following researches.展开更多
We report on a demonstration of top-gated graphene field-effect transistors(FETs) fabricated on epitaxial SiC substrate.Composite stacks,benzocyclobutene and atomic layer deposition Al2O3,are used as the gate dielectr...We report on a demonstration of top-gated graphene field-effect transistors(FETs) fabricated on epitaxial SiC substrate.Composite stacks,benzocyclobutene and atomic layer deposition Al2O3,are used as the gate dielectrics to maintain intrinsic carrier mobility of graphene.All graphene FETs exhibit n-type transistor characteristics and the drain current is nearly linear dependence on gate and drain voltages.Despite a low field-effect mobility of 40 cm2/(V s),a maximum cutoff frequency of 4.6 GHz and a maximum oscillation frequency of 1.5 GHz were obtained for the graphene devices with a gate length of 1 μm.展开更多
On the basis of opto-mechanical effect and micro electromechanical system(MEMS)technology,a novel substrate-free focal plane array(FPA)with the thermal isolated structure for uncooled infrared imaging is developed,eve...On the basis of opto-mechanical effect and micro electromechanical system(MEMS)technology,a novel substrate-free focal plane array(FPA)with the thermal isolated structure for uncooled infrared imaging is developed,even as alternate evaporated Au on SiN cantilever is used for thermal isolation.A human thermal image is obtained successfully by using the infrared imaging system composed of the FPA and optical detecting system.The experiment results show that the realization of thermal isolation structure in substrate-free FPA increases the temperature rise of the deflecting leg effectively,whereas the noise equivalent temperature difference(NETD)is about 200 mK.展开更多
基金Supported by Zhejiang Province Important Sci-Tech Foundation Item (No.2006C11107)
文摘A new low-cost demodulator for ZigBee receivers satisfying requirements of IEEE802.15.4 standard is presented,which is designed for ISM 2.4 GHz band and based on Zero-IF receivers.This demodulator extracts symbols directly from baseband signal rather than recovering PN code chips,so its structure is simple.Two main techniques are used to improve the performance of demodulator.One is Phase-Axis Crossing Detector(PACD) which detects the phase correlation of baseband signal.The other is symbol synchronization and sampling clock correction algorithm.The result shows that this demodulator performance,Symbol Error Rate(SER) and Packet Error Rate(PER) meet IEEE 802.15.4TM standard requirements and the demodulator can handle frequency offset in excess of 200 kHz,involving a Zero-IF receiver with a Noise Figure(NF) lower than 17 dB,which is easily imple-mented in standard CMOS technology.
基金Supported by the National Natural Science Foundation of China (Grant No. 60576053)Hi-Tech Research and Development Program of China (Grant No. 2007AA03Z333)
文摘A model of curvature and tip deflection of multilayer thermal cantilever actuators is derived.The sim-plified expression received from the model avoids inverting complex matrices enhances understanding and makes it easier to optimize the structure parameters.Experiment is performed,the modeled and experimental results demonstrate the validity of the model,and it also indicates that Young's module makes great contribution to the deflection;therefore,thin layers cannot be ignored arbitrarily.
基金the National Basic Research Program of China (Grant No. G2002CB311901)Equipment Advance Research Project (Grant No. 61501050401C)Institute of Microelectronics, Chinese Academy of Sciences, Dean Fund (Grant No. 06SB124004)
文摘GaAs-based metamorphic HEMTs (MHEMT) consist of GaAs substrates and InP-based epitaxial structure, and have the advantages of both InP HEMT's excellent performances and GaAs-based HEMT's mature processes. GaAs-based MHEMTs were applied to millimeter-wave low-noise, high-power applications and systems. The current gain cut-off frequency (fT) and the maximum oscillation frequency (fmax) are important performance parameter of GaAs-based MHEMTs, and they are limited by the gate-length mainly. Electron beam lithography is one of the lithography technologies which can be used to realize the deep submicron gate-length. The 200 nm gate-length GaAs-based MHEMTs have been fabricated by electron beam lithography. In order to reduce the parasite gate capacitance and gate resistance, a trilayer resist structure was used to pattern the T-gate resist profile. Excellent DC, high frequency and power performances have been obtained. FT and fmax are 105 GHz, 70 GHz respectively. The research is very helpful to obtain higher performance GaAs-based MHEMTs.
基金supported by the National Basic Research Program of China("973" Project) (Grant No. 2009CB939703)the National Natural Science Foundation of China (Grant Nos. 11104319,51172268)the Chinese Academy of Solar Energy Action Plan and by Beijing Science and Technology Project (Grant No. Y2BK024001)
文摘The ultra-small textured surface of multicrystalline silicon solar cell,prepared by electroless chemical-etching method,shows an excellent anti-reflection property over a wide spectral bandwidth.A novel back surface protection method and front surface passivation method have been used in the multicrystalline solar cells with ultra-small textured surfaces.With these improvements,the back surface remains intact after the etch process and the efficient minority lifetime is apparently increased.The test result shows that the solar cell with ultra-small textured surface can obtain better electrical performances by these improvements.
基金supported by the National Basic Research Program of China ("973" Project)(Grant No. 2009CB939703)the National Natural Science Foundation of China (Grant Nos. 11104319,51172268)the Chinese Academy of Solar Energy Action Plan
文摘Nanostructure-textured solar cell owns unique properties but has some shortages especially in its fabrication and passivation.In this paper,nanostructures for crystalline silicon solar cell have been synthesized by controllable method based on silver catalyzed chemical etching.In this way,only the front surface of cell is etched and rear surface is protected.It was found that cells textured via the new method obtained equally excellent optical while superior electrical properties compared with those textured via traditional HF/AgNO3 etching.The V OC and I SC of the cell were improved by 6% and 11%,respectively.Then the cells were passivated via a bi-layer passivation(SiO2 & SiN x),in contrast to traditional SiN x passivation.It was also found that cells with new passivation exhibited improved V OC and I SC by 4% and 25%,respectively.The encouraging results can provide fundamental data for developing the nanostructure-textured crystalline silicon solar cell in following researches.
基金supported by the National Science and Technology Major Project(2011ZX02707.3)the National Basic Research Program of China(2011CB932700)the National Natural Science Foundation of China(61136005,50972162,51072223 and 61006063)
文摘We report on a demonstration of top-gated graphene field-effect transistors(FETs) fabricated on epitaxial SiC substrate.Composite stacks,benzocyclobutene and atomic layer deposition Al2O3,are used as the gate dielectrics to maintain intrinsic carrier mobility of graphene.All graphene FETs exhibit n-type transistor characteristics and the drain current is nearly linear dependence on gate and drain voltages.Despite a low field-effect mobility of 40 cm2/(V s),a maximum cutoff frequency of 4.6 GHz and a maximum oscillation frequency of 1.5 GHz were obtained for the graphene devices with a gate length of 1 μm.
基金supported by the National Natural Science Foundation of China(Grant No.60236010)the National Technology Research Development Program of China(No.2005AA404210).
文摘On the basis of opto-mechanical effect and micro electromechanical system(MEMS)technology,a novel substrate-free focal plane array(FPA)with the thermal isolated structure for uncooled infrared imaging is developed,even as alternate evaporated Au on SiN cantilever is used for thermal isolation.A human thermal image is obtained successfully by using the infrared imaging system composed of the FPA and optical detecting system.The experiment results show that the realization of thermal isolation structure in substrate-free FPA increases the temperature rise of the deflecting leg effectively,whereas the noise equivalent temperature difference(NETD)is about 200 mK.
