Construction of two-direction tight wavelet frames

We investigate the construction of two-direction tight wavelet frames First, a sufficient condition for a two-direction refinable function generating two-direction tight wavelet frames is derived. Second, a simple constructive method of two-direction tight wavelet frames is given. Third, based on the obtained two-direction tight wavelet frames, one can construct a symmetric multiwavelet frame easily. Finally, some examples are given to illustrate the results.     

一种4.224GHz正交压控振荡器的设计

设计了一种应用于MB-OFDM UWB射频频率综合器的工作于4.224GHz的正交压控振荡器(QVCO),并采用0.18μm RF-CMOS工艺进行了设计实现.该Qvco通过改进结构能够得到更好的相位噪声.通过改变MOS变容管的接入方法实现了更好的压控增益线性度,并采用了新的低寄生电容、低导通电阻的数控电容阵列结构来补偿工艺变化带来的频率变化.测试结果表明,该QV-CO在4.224GHz附近的100kHz频偏处的相位噪声为-90.4dBc/Hz,1MHz频偏处的相位噪声为-116.7dBc/Hz,整个QVCO电路功耗为10.55mW,电源电压为1.8V.     

软件无线电中的正交解调新算法

软件无线电作为无线通信技术的又一次革命,是目前通信领域中最为重要的研究方向之一.文章基于多相滤波的数字正交变换技术,通过数学推导,提出了一种软件无线电中的数字化正交解调新算法.理论分析和仿真结果显示该解调方案的抗干扰性能有明显改善,与传统解调方法相比,省去了本地载波恢复,通用性强、简单易实现、计算量小且易于用DSP实现,适合在软件无线电接收机中使用.     

基于多相滤波原理的数字正交采样技术

针对传统正交采样方法存在运算数据量大,镜频抑制比小及硬件实现资源消耗大等方面的不足,分析了一种基于多相滤波结构的数字正交采样方法.首先对多相滤波法实现数字正交变换的原理进行了分析,然后根据多速率信号处理理论推导并给出了基于多相滤波结构的子滤波器的实现方法,最后,通过仿真验证了该方法的有效性.实验结果表明该方法较之传统的低通滤波法有很大的优越性.     

现代通信对抗系统中的直接变频技术

干扰频谱带宽是衡量现代通信对抗系统性能的一项关键指标。采用直接变频技术,有效拓宽现代通信对抗系统干扰机的瞬时干扰带宽至300MHz,同时灵活产生多个目标干扰信号,有助于提升系统综合对抗能力,也为今后可重构硬件平台的建立打下坚实基础。     

一种新的语音编码系统的设计

现有的大部分语音编码系统硬件框架复杂,软件设计难度较大.为实现低成本方案,设计了一种以SPCE061A语音单片机为基础的编码系统,压缩技术采用了基于正交滤波器的子带编码算法.系统硬件结构简洁、软件设计方便高效,具有较高的性价比.通过实验,对比了原始语音信号和重建信号的时域波形和回放质量,表明本系统具有一定的实用价值.     

积分第一中值定理中间点的一般渐近性质与求积公式

证明关于积分第一中值定理的中间点ξ的渐近性质的一般结果.而且,由此自然地推导出单节点数值积分公式.此求积公式具有高精度,还适于瑕积分的数值计算.     

Rotationally averaged linear absorption spectra beyond the electric-dipole approximation

ABSTRACT

Based on the recently developed implementation of the full semi-classical field–matter interaction operator, we present a numerically accurate yet efficient scheme to perform rotational averaging of linear absorption spectra beyond the electric-dipole approximation. This allows for a gauge-origin independent determination of UV/vis and X-ray absorption spectra for randomly oriented systems such as multilayers, liquids, and gas phase samples. The approach is illustrated by the determination of spectral intensities of electric-dipole allowed π → π* transitions and electric-dipole forbidden n → π* transitions in the UV–vis region of the spectrum as well as electric-dipole forbidden 1s → 3d transitions in the X-ray region of the spectrum. The employed Lebedev quadrature scheme shows very fast convergence with respect to the number of symmetry-independent quadrature points – in all considered cases, the oscillator strengths for the randomly oriented systems are fully converged with use of only seven quadrature points.     

Buckling analysis of nanobeams with exponentially varying stiffness by differential quadrature method

We present the application of differential quadrature(DQ) method for the buckling analysis of nanobeams with exponentially varying stiffness based on four different beam theories of Euler-Bernoulli, Timoshenko, Reddy, and Levison.The formulation is based on the nonlocal elasticity theory of Eringen. New results are presented for the guided and simply supported guided boundary conditions. Numerical results are obtained to investigate the effects of the nonlocal parameter,length-to-height ratio, boundary condition, and nonuniform parameter on the critical buckling load parameter. It is observed that the critical buckling load decreases with increase in the nonlocal parameter while the critical buckling load parameter increases with increase in the length-to-height ratio.     

Si MEMS陀螺仪的正交耦合补偿技术

为了减小正交耦合误差对硅微电子机械系统(MEMS)陀螺仪性能的影响,提高陀螺仪零偏精度,对MEMS陀螺仪正交耦合补偿技术进行研究.建立MEMS陀螺仪动力学模型,分析正交耦合产生的原因,介绍了各类正交耦合补偿机理.设计了一款可实现静电刚度补偿的MEMS陀螺仪,并利用绝缘体上硅(SOI)工艺进行制备.利用现场可编程门阵列(...