The frequency band between 5 010 MHz and 5 030 MHz allocated as C band has been used as a candidate in the global navigation satellite systems （GNSS） along with more and more naviga- tion services in L band. The pot...The frequency band between 5 010 MHz and 5 030 MHz allocated as C band has been used as a candidate in the global navigation satellite systems （GNSS） along with more and more naviga- tion services in L band. The potential benefits and technical requirements of C band for satellite navi- gation have been analyzed before. However the degradation of effective carrier-power-to-noise densi- ty ratio（ A （C/No ）eu） based on code tracking spectral sensitivity coefficient（ CT_SSC ） as a compati- bility assessment methodology for potential GNSS radio frequency compatibility in C-Band has not been discussed clearly. So the compatibility of the signals in the C band between BeiDou （BD） B1 C and GPS L1C, L1C/A, Galileo E1Os as the interoperability or classical signals in L band is analyzed. Simulation results reveal the interference degree between BD III B1C and GPS L1C/A, L1C, Galileo E1OS. The results can also reveal that the multiplexed binary offset carrier （MBOC） and binary phase shift keying （BPSK） modulation is not appropriate for C band.展开更多
EAST （experimental advanced superconducting tokamak） fast control power supply is a high-capacity single-phase AC/DC/AC inverter power supply, which traces the displacement signal of plasma, and excites coils in a v...EAST （experimental advanced superconducting tokamak） fast control power supply is a high-capacity single-phase AC/DC/AC inverter power supply, which traces the displacement signal of plasma, and excites coils in a vacuum vessel to produce a magnetic field that realizes plasma stabilization. To meet the requirements of a large current and fast response, the multi- ple structure of the carrier phase-shift three-level inverter is presented, which realizes parallelled multi-inverters, raises the equivalent switching frequency of the inverters and improves the per- formance of output waves. In this work the design scheme is analyzed, and the output harmonic characteristic of parallel inverters is studied. The simulation and experimental results confirm that the scheme and control strategy is valid. The power supply system can supply a large current, and has a perfect performance on harmonic features as well as the ability of a fast response.展开更多
A backside illuminated mesa-structure In Ga As/In P modified uni-traveling-carrier photodiode（MUTC-PD） with wide bandwidth and high saturation power is fabricated and investigated. The device structure is optimized ...A backside illuminated mesa-structure In Ga As/In P modified uni-traveling-carrier photodiode（MUTC-PD） with wide bandwidth and high saturation power is fabricated and investigated. The device structure is optimized to reduce the capacitance and resistance. For the 22-μm-diameter device, the maximum responsivity at 1.55 μm is 0.5 A/W, and the 3-d B cutoff frequency reaches up to 28 GHz. The output photocurrent at the 1-d B compression point is measured to be 54 m A at 25 GHz, with a corresponding output radio frequency（RF） power of up to 15.5 d Bm. The saturation characteristics of the MUTC-PD are also verified by the electric field simulation, and electric field collapse is found to be the cause of the saturation phenomenon.展开更多
In the present communication, the hydrodynamic model is used to investigate the amplitude modulation as well as demodulation of an electromagnetic wave of high power helicon pump wave into another helicon wave in stra...In the present communication, the hydrodynamic model is used to investigate the amplitude modulation as well as demodulation of an electromagnetic wave of high power helicon pump wave into another helicon wave in strain dependent dielectric material incorporating carrier heating (CH) effects. The consideration of CH in modulation and demodulation is prime importance for the adding of new dimension in analysis of amplification of acoustic helicon wave. By using the dispersion relation, threshold pump electric filed and growth rate of unstable mode from the modulation and demodulation of the high power helicon wave well above from the threshold value will be discussed in the present analysis. The numerical analysis is applied to a strain dependent dielectric material, BaTiO3 at room temperature and irradiated with high power helicon wave of frequency 1.78 × 1014 Hz. This material is very sensitive to the pump intensities, therefore during studies, Gaussian shape of the helicon pump wave is considered during the propagation in stain dependent dielectric material and opto-acoustic wave in the form of Gaussian profile (ω0,κ0) is induced longitudinally along the crystallographic plane of BaTiO3. Its variation is caused by the available magnetic field (ωc), interaction length (z) and pulsed duration of interaction (τ). From the analysis of numerical results, the incorporation of CH effect can effectively modify the magnitude of modulation or demodulation of the amplitude of high power helicon laser wave through diffusion process. Not only the amplitude modulation and demodulation of the wave, the diffusion of the CH effectively modifies the growth rate of unstable mode of frequency in BaTiO3. The propagation of the threshold electric field shows the sinusoidal or complete Gaussian profile, whereas this profile is found to be completely lost in growth of unstable mode. It has also been seen that the growth rate is observed to be of the order of 108 - 1010 s-1 but from diffusion of carrier heating, and that its order is enhanced from 1010 - 1012 s-1 with the variation of the magnetized frequency from 1 to 2.5 × 1014 Hz.展开更多
Since the lower power requirement of code division multiple access(CDMA) than that of other multiple access, the CDMA technology is suitable to be used in low earth orbit(LEO) satellite communication system whose spac...Since the lower power requirement of code division multiple access(CDMA) than that of other multiple access, the CDMA technology is suitable to be used in low earth orbit(LEO) satellite communication system whose space power is limited due to the small size of satellite. The pilot channel of CDMA technology is very important for earth mobile station(EMS) in LEO system to recover carrier and code, but the power requirement of pilot channel is very higher than that of other channels. In this paper, a power reduction method for pilot channel is proposed. By the new method, the power of pilot channel transmitted from LEO satellite is reduced to a lower level. For improving the signal to noise ratio(SNR) of pilot channel with lower power, coherent integration is employed in EMS at the pre-processing stage. Considering the high dynamic situation of LEO satellite, the long period of time for integration will deteriorate the receiving performance of EMS, therefore, a dynamic compensation module is added to carrier tracking loop against the high dynamic. Meanwhile, the transfer function of the new tracking loop and the condition for steadystate zero error are deduced. Numerical examples are provided to demonstrate effectiveness of the proposed approach.展开更多
When solving the routing problem with traditional ant colony algorithm, there is scarce in initialize pheromone and a slow convergence and stagnation for the complex network topology and the time-varying characteristi...When solving the routing problem with traditional ant colony algorithm, there is scarce in initialize pheromone and a slow convergence and stagnation for the complex network topology and the time-varying characteristics of channel in power line carrier communication of low voltage distribution grid. The algorithm is easy to fall into premature and local optimization. Proposed an automatic network algorithm based on improved transmission delay and the load factor as the evaluation factors. With the requirements of QoS, a logical topology of power line communication network is established. By the experiment of MATLAB simulation, verify that the improved Dynamic hybrid ant colony genetic algorithm (DH_ACGA) algorithm has improved the communication performance, which solved the QoS routing problems of power communication to some extent.展开更多
The orthogonality between the subcarriers of multipleinput multiple-output orthogonal frequency division multiplexing( MIMO-OFDM) systems is destroyed due to the Doppler frequency offset,particularly in the high-speed...The orthogonality between the subcarriers of multipleinput multiple-output orthogonal frequency division multiplexing( MIMO-OFDM) systems is destroyed due to the Doppler frequency offset,particularly in the high-speed train( HST) environment,which leads to severe inter-carrier interference( ICI). Therefore,it is necessary to analyze the mechanism and influence factor of ICI in HST environment. In this paper, by using a non-stationary geometry-based stochastic model( GBSM) for MIMO HST channels, ICI is analyzed through investigating the channel coefficients and the carrier-to-interference power ratio( CIR). It is a fact that most of signal energy spreads on itself and its several neighborhood subcarriers. By investigating the amplitude of subcarriers, CIR is used to evaluate the ICI power level. The simulation results show that the biggest impact factor for the CIR is the multipath number L and the minimum impact factor K; when the train speed υR> 400 km / h,the normalized Doppler frequency offset ε > 0. 35,the CIR tends to zero,and the communication quality will be very poor at this condition. Finally,bit error rate( BER) is investigated by simulating a specific channel environment.展开更多
基金Supported by the National High Technology Research and Development Program of China(863Program)(2011AA120502)
文摘The frequency band between 5 010 MHz and 5 030 MHz allocated as C band has been used as a candidate in the global navigation satellite systems （GNSS） along with more and more naviga- tion services in L band. The potential benefits and technical requirements of C band for satellite navi- gation have been analyzed before. However the degradation of effective carrier-power-to-noise densi- ty ratio（ A （C/No ）eu） based on code tracking spectral sensitivity coefficient（ CT_SSC ） as a compati- bility assessment methodology for potential GNSS radio frequency compatibility in C-Band has not been discussed clearly. So the compatibility of the signals in the C band between BeiDou （BD） B1 C and GPS L1C, L1C/A, Galileo E1Os as the interoperability or classical signals in L band is analyzed. Simulation results reveal the interference degree between BD III B1C and GPS L1C/A, L1C, Galileo E1OS. The results can also reveal that the multiplexed binary offset carrier （MBOC） and binary phase shift keying （BPSK） modulation is not appropriate for C band.
基金supported by Key Project of National Ninth Five-Year Research Program of China[(1998)1303]
文摘EAST （experimental advanced superconducting tokamak） fast control power supply is a high-capacity single-phase AC/DC/AC inverter power supply, which traces the displacement signal of plasma, and excites coils in a vacuum vessel to produce a magnetic field that realizes plasma stabilization. To meet the requirements of a large current and fast response, the multi- ple structure of the carrier phase-shift three-level inverter is presented, which realizes parallelled multi-inverters, raises the equivalent switching frequency of the inverters and improves the per- formance of output waves. In this work the design scheme is analyzed, and the output harmonic characteristic of parallel inverters is studied. The simulation and experimental results confirm that the scheme and control strategy is valid. The power supply system can supply a large current, and has a perfect performance on harmonic features as well as the ability of a fast response.
基金Project supported by the National Basic Research Program of China(Grant Nos.2012CB315605 and 2014CB340002)the National Natural Science Foundation of China(Grant Nos.61176015,61176059,61210014,61321004,and 61307024)the Open Fund of State Key Laboratory on Integrated Optoelectronics,China(Grant Nos.IOSKL2012KF08 and IOSKL2014KF09)
文摘A backside illuminated mesa-structure In Ga As/In P modified uni-traveling-carrier photodiode（MUTC-PD） with wide bandwidth and high saturation power is fabricated and investigated. The device structure is optimized to reduce the capacitance and resistance. For the 22-μm-diameter device, the maximum responsivity at 1.55 μm is 0.5 A/W, and the 3-d B cutoff frequency reaches up to 28 GHz. The output photocurrent at the 1-d B compression point is measured to be 54 m A at 25 GHz, with a corresponding output radio frequency（RF） power of up to 15.5 d Bm. The saturation characteristics of the MUTC-PD are also verified by the electric field simulation, and electric field collapse is found to be the cause of the saturation phenomenon.
文摘In the present communication, the hydrodynamic model is used to investigate the amplitude modulation as well as demodulation of an electromagnetic wave of high power helicon pump wave into another helicon wave in strain dependent dielectric material incorporating carrier heating (CH) effects. The consideration of CH in modulation and demodulation is prime importance for the adding of new dimension in analysis of amplification of acoustic helicon wave. By using the dispersion relation, threshold pump electric filed and growth rate of unstable mode from the modulation and demodulation of the high power helicon wave well above from the threshold value will be discussed in the present analysis. The numerical analysis is applied to a strain dependent dielectric material, BaTiO3 at room temperature and irradiated with high power helicon wave of frequency 1.78 × 1014 Hz. This material is very sensitive to the pump intensities, therefore during studies, Gaussian shape of the helicon pump wave is considered during the propagation in stain dependent dielectric material and opto-acoustic wave in the form of Gaussian profile (ω0,κ0) is induced longitudinally along the crystallographic plane of BaTiO3. Its variation is caused by the available magnetic field (ωc), interaction length (z) and pulsed duration of interaction (τ). From the analysis of numerical results, the incorporation of CH effect can effectively modify the magnitude of modulation or demodulation of the amplitude of high power helicon laser wave through diffusion process. Not only the amplitude modulation and demodulation of the wave, the diffusion of the CH effectively modifies the growth rate of unstable mode of frequency in BaTiO3. The propagation of the threshold electric field shows the sinusoidal or complete Gaussian profile, whereas this profile is found to be completely lost in growth of unstable mode. It has also been seen that the growth rate is observed to be of the order of 108 - 1010 s-1 but from diffusion of carrier heating, and that its order is enhanced from 1010 - 1012 s-1 with the variation of the magnetized frequency from 1 to 2.5 × 1014 Hz.
基金supported by the National High Technology Research and Development Program of China (863 Program) (No.2012AA01A502)the National Natural Science Foundation of China (No.61179006)the Science and Technology Support Program of Sichuan Province (No.2014GZX0004)
文摘Since the lower power requirement of code division multiple access(CDMA) than that of other multiple access, the CDMA technology is suitable to be used in low earth orbit(LEO) satellite communication system whose space power is limited due to the small size of satellite. The pilot channel of CDMA technology is very important for earth mobile station(EMS) in LEO system to recover carrier and code, but the power requirement of pilot channel is very higher than that of other channels. In this paper, a power reduction method for pilot channel is proposed. By the new method, the power of pilot channel transmitted from LEO satellite is reduced to a lower level. For improving the signal to noise ratio(SNR) of pilot channel with lower power, coherent integration is employed in EMS at the pre-processing stage. Considering the high dynamic situation of LEO satellite, the long period of time for integration will deteriorate the receiving performance of EMS, therefore, a dynamic compensation module is added to carrier tracking loop against the high dynamic. Meanwhile, the transfer function of the new tracking loop and the condition for steadystate zero error are deduced. Numerical examples are provided to demonstrate effectiveness of the proposed approach.
文摘When solving the routing problem with traditional ant colony algorithm, there is scarce in initialize pheromone and a slow convergence and stagnation for the complex network topology and the time-varying characteristics of channel in power line carrier communication of low voltage distribution grid. The algorithm is easy to fall into premature and local optimization. Proposed an automatic network algorithm based on improved transmission delay and the load factor as the evaluation factors. With the requirements of QoS, a logical topology of power line communication network is established. By the experiment of MATLAB simulation, verify that the improved Dynamic hybrid ant colony genetic algorithm (DH_ACGA) algorithm has improved the communication performance, which solved the QoS routing problems of power communication to some extent.
基金National Natural Science Foundation of China(No.61271213)
文摘The orthogonality between the subcarriers of multipleinput multiple-output orthogonal frequency division multiplexing( MIMO-OFDM) systems is destroyed due to the Doppler frequency offset,particularly in the high-speed train( HST) environment,which leads to severe inter-carrier interference( ICI). Therefore,it is necessary to analyze the mechanism and influence factor of ICI in HST environment. In this paper, by using a non-stationary geometry-based stochastic model( GBSM) for MIMO HST channels, ICI is analyzed through investigating the channel coefficients and the carrier-to-interference power ratio( CIR). It is a fact that most of signal energy spreads on itself and its several neighborhood subcarriers. By investigating the amplitude of subcarriers, CIR is used to evaluate the ICI power level. The simulation results show that the biggest impact factor for the CIR is the multipath number L and the minimum impact factor K; when the train speed υR> 400 km / h,the normalized Doppler frequency offset ε > 0. 35,the CIR tends to zero,and the communication quality will be very poor at this condition. Finally,bit error rate( BER) is investigated by simulating a specific channel environment.
