Performances of BPSK, balanced quaternary modulation, dual quaternary modulation and complex quaternary modulation in direct sequence spectrum spread (DS SS) system are discussed in this paper. Based on the crit...Performances of BPSK, balanced quaternary modulation, dual quaternary modulation and complex quaternary modulation in direct sequence spectrum spread (DS SS) system are discussed in this paper. Based on the criterion the power of original signal is the same, it is shown that complex quaternary modulation has the best performance, and dual quaternary modulation degrades 2dB. Moreover, the frequency efficient of the two modulations is 2bit/Hz. Balanced quaternary has the same performance as BPSK with frequency efficient 1bit/Hz.展开更多
Reconfigurable intelligent surface(RIS)-assisted symbiotic radio is a spectrum-and energy-efficient communication paradigm,in which an RIS performs passive beamforming to enhance active transmission,while using the el...Reconfigurable intelligent surface(RIS)-assisted symbiotic radio is a spectrum-and energy-efficient communication paradigm,in which an RIS performs passive beamforming to enhance active transmission,while using the electromagnetic waves from the active transmission for additional information transfer(i.e.,passive transmission).In this paper,a hybrid RIS-based modulation,termed hybrid phase and code modulation(HPCM),is proposed to improve the reliability of RIS-assisted symbiotic radio.In RIS-HPCM,the RIS simultaneously performs direct sequence spread spectrum and passive beamforming on incident signals.Moreover,both the spreading code and phase offset are exploited to carry the RIS’s own information.A low-complexity detector is designed,in which the receiver first detects the spreading codes and then demodulates the constellation symbols.We analyze the bit error rate(BER)performance of RIS-HPCM over Rician fading channels.BER upper bounds and approximate BER expressions are derived in closed-form for maximum-likelihood and low-complexity detectors,respectively.Simulation results in terms of BER verify the analysis and show the superiority of RIS-HPCM over the existing RIS-based modulation.展开更多
恒频直接功率控制(constant switching frequency direct power control,CSF-DPC)具有开关频率固定、动态性能好、系统采样频率较低等优点。电网电压不平衡会在脉宽调制(pulse width modulation,PWM)型整流器交流侧产生大量谐波电流,使...恒频直接功率控制(constant switching frequency direct power control,CSF-DPC)具有开关频率固定、动态性能好、系统采样频率较低等优点。电网电压不平衡会在脉宽调制(pulse width modulation,PWM)型整流器交流侧产生大量谐波电流,使系统有功功率大幅波动,恶化系统性能。针对上述情况,提出一种新型恒频直接功率控制策略。该策略首先分离出电网电压和电流正、负序分量;然后在正、负序双旋转坐标系下计算瞬时功率与参考值之间的误差,根据误差生成整流器正、负序参考电压;合成后采用空间矢量调制(spacevector modulation,SVM)算法产生整流器电压,对功率进行补偿。该策略可有效抑制交流侧电流谐波,减小系统无功功率直流分量,稳定系统输出的有功功率,改善系统稳态性能。仿真与实验结果证明了该策略的正确性和有效性。展开更多
基金ThisprojectwassupportedbytheKeyProjectoftheNaturalScienceFoundationofChina (No .6 98310 30 )
文摘Performances of BPSK, balanced quaternary modulation, dual quaternary modulation and complex quaternary modulation in direct sequence spectrum spread (DS SS) system are discussed in this paper. Based on the criterion the power of original signal is the same, it is shown that complex quaternary modulation has the best performance, and dual quaternary modulation degrades 2dB. Moreover, the frequency efficient of the two modulations is 2bit/Hz. Balanced quaternary has the same performance as BPSK with frequency efficient 1bit/Hz.
基金supported in part by the National Natural Science Foundation of China under Grant 62201228 and Grant 62001190in part by the Science and Technology Major Project of Tibetan Autonomous Region of China under Grant No.XZ202201ZD0006G02.
文摘Reconfigurable intelligent surface(RIS)-assisted symbiotic radio is a spectrum-and energy-efficient communication paradigm,in which an RIS performs passive beamforming to enhance active transmission,while using the electromagnetic waves from the active transmission for additional information transfer(i.e.,passive transmission).In this paper,a hybrid RIS-based modulation,termed hybrid phase and code modulation(HPCM),is proposed to improve the reliability of RIS-assisted symbiotic radio.In RIS-HPCM,the RIS simultaneously performs direct sequence spread spectrum and passive beamforming on incident signals.Moreover,both the spreading code and phase offset are exploited to carry the RIS’s own information.A low-complexity detector is designed,in which the receiver first detects the spreading codes and then demodulates the constellation symbols.We analyze the bit error rate(BER)performance of RIS-HPCM over Rician fading channels.BER upper bounds and approximate BER expressions are derived in closed-form for maximum-likelihood and low-complexity detectors,respectively.Simulation results in terms of BER verify the analysis and show the superiority of RIS-HPCM over the existing RIS-based modulation.
文摘恒频直接功率控制(constant switching frequency direct power control,CSF-DPC)具有开关频率固定、动态性能好、系统采样频率较低等优点。电网电压不平衡会在脉宽调制(pulse width modulation,PWM)型整流器交流侧产生大量谐波电流,使系统有功功率大幅波动,恶化系统性能。针对上述情况,提出一种新型恒频直接功率控制策略。该策略首先分离出电网电压和电流正、负序分量;然后在正、负序双旋转坐标系下计算瞬时功率与参考值之间的误差,根据误差生成整流器正、负序参考电压;合成后采用空间矢量调制(spacevector modulation,SVM)算法产生整流器电压,对功率进行补偿。该策略可有效抑制交流侧电流谐波,减小系统无功功率直流分量,稳定系统输出的有功功率,改善系统稳态性能。仿真与实验结果证明了该策略的正确性和有效性。
