Series/Parallel Time-Multiplexed Switched-Capacitor Filters with Programmability Based on Non-Uniform Sampling

This paper presents an improved scheme for programmable time-multiplexed (TM) switched-capacitor (SC) filters. The proposed approach uses a novel sampling technique, which eliminates the need for resolution/area tradeoffs. The programmability of each processing channel is based on the use of non-uniform clock signals with noise-shaped sampling energy. No capacitor values are modified for programming frequency response parameters and, hence, the performance of the TM SC filter is not sacrificed for programmability. Such a sampling technique not only leads to an accurate frequency response control, but also allows the design procedures and the resulting SC circuit implementation to be simplified. A test-chip including a programmable second-order TM SC filter with a multiplexing order of four, which operates in series or in parallel mode, was fabricated in conventional CMOS technology. Measurement results demonstrate the effectiveness and versatility of the proposed technique.     

基于非均匀采样的信号频率和到达角联合估计

利用阵列中每个阵元有不同采样频率的非均匀采样特性,可以等效得到时变的虚拟非均匀线阵,然后采用经典的子空间法中的MUSIC测向法,通过网格搜索实现对信号频率和DOA联合估计;并且通过合理设置各阵元间的采样率,有效提高空间谱估计的分辨率和精度,还可避免测向角度模糊。该算法采用网格搜索法,明显减少了计算量。计算机仿真结果证明该方法的有效性和正确性。     

基于序贯重点采样粒子滤波的分布估计算法

 连续域分布估计算法一般假设数据服从高斯分布,而且大多采用了单峰的概率模型,但是对于一些复杂的优化问题,单峰的高斯分布模型不能有效地描述解在空间的分布.本文提出一种基于序贯重点采样粒子滤波的分布估计算法,采用带权粒子描述优选集样本服从的概率分布并从中采样得到下一代种群,不需要假设样本服从高斯分布,并且算法采用的概率模型是多峰的.仿真实验结果验证了本文方法的正确性和有效性.     

Analytical Stability Condition of the Latency Insertion Method for Nonuniform GLC Circuits

The latency insertion method (LIM) is a transient simulation technique for circuits and is based on a finite-difference formulation, like the well-known finite-difference time-domain (FDTD) method for solving Maxwells equations. The LIM, like the FDTD method, is only conditionally stable resulting in an upper bound for the time step of the transient simulation. This bound on the time step is a function of the circuit topology and the circuit element values. It is critical to know this bound analytically for a given circuit. However, stability conditions of the LIM have been proven only for 1-D, infinitelylong, distributed uniform RLC circuits, employed in transmission line modeling. For nonuniform circuits, these conditions have been predicted and have been observed experimentally as well but have not been possible to prove using the existing stability analysis techniques. Recently, analytical stability conditions of the LIM for nonuniform RLC circuits have been proven using the Lyapunovs direct method (LDM). However, when a conductance to ground (G) is added to a node of an LC or RLC circuit, the stability conditions cannot be derived using the Lyapunov function proposed. In this brief, analytical stability condition of the LIM is derived for the first time for nonuniform GLC circuits using the LDM with a new Lyapunov function.      

时空非均匀采样下双基地MIMO雷达收发角及多普勒频率联合估计方法

该文针对发射阵列、接收阵列以及多级延迟器均为非均匀配置的双基地MIMO雷达,提出基于时域和空域二次自由度扩展的发射角、接收角以及多普勒频率估计的ESPRIT (Estimating Signal Via Rotational Invariance Techniques)新方法。该方法利用双基地MIMO雷达特殊的方向矢量特点(矩阵的Khatri-Rao积形式),对接收信号进行两次行置换以及去冗余处理,实现了时域和空域孔径自由度的二次扩展。然后对新数据进行时空滑窗处理,利用ESPRIT算法分别估计出目标的收发角以及多普勒频率。理论和仿真结果表明：在相同阵元和延迟级数情况下,所提算法的估计性能优于四线性分解和多维ESPRIT算法,且能估计出更多的目标,此外,通过最小冗余配置,极大地降低了阵列和延迟器的配置需求,更利于实际工程应用。     

Widely Programmable High-Frequency Active RC Filters in CMOS Technology

We propose a circuit technique that enables the realization of widely programmable high-frequency active RC filters in CMOS technology. A fifth-order Chebyshev ladder filter having a digitally programmable 3-dB bandwidth (from 44 to 300 MHz) is used as a vehicle to validate our ideas. The opamp uses feedforward compensation for achieving high dc gain and wide bandwidth. The integrating resistors are realized as a series combination of a triode-operated MOSFET and a fixed polysilicon resistor. A charge-pump-based servo loop servoes the integrating resistor to a stable off-chip resistor. The principle of “constant capacitance scaling” is applied to the opamp and the integrating resistors so that the shape of the frequency response is maintained when the bandwidth is scaled over a 7 $times$ range. The filter core, designed in a 0.18-${rm mu}hbox{m}$ CMOS process, consumes 54 mW from 1.8-V supply and has a dynamic range of 56.6 dB.      

Estimation of Carrier Frequency Offset With I/Q Mismatch Using Pseudo-Offset Injection in OFDM Systems

This work presents a novel carrier frequency offset (CFO) estimation algorithm, based on pseudo-CFO (P-CFO), to estimate the CFO value under the conditions of I/Q mismatch for direct conversion structures with 2-dB gain error and 20-deg. phase error in frequency selective fading channels. To circumvent CFO with I/Q mismatch, the proposed P-CFO algorithm rotates three training symbols by adding extra frequency offset into the received sequence to improve CFO estimation. Simulation results indicate that the estimation error of the proposed method is about 0.3 ppm, which is lower than those of two-repeat preamble-based methods. Additionally, the proposed P-CFO algorithm is compatible with the conventional method, and is appropriate for SoC implementation. The proposed scheme is implemented as part of an orthogonal frequency-division multiplexing wireless receiver fabricated in a 0.13-mum CMOS process with 3.3 times 0.4 mm² core area and 10-mW power consumption at 54-Mbits/s data rate.     

星载SAR DPCMAB技术的方位向非均匀采样研究

在星载SAR分离相位中心方位多波束(DPCMAB)系统中,发射脉冲盲区和星下点回波盲区的存在会引起方位向非均匀采样,从而在方位向冲激响应的主瓣两侧产生不期望的尖峰。该文采用Spectral-Fit法和时域重构法在不影响图像性能的基础上,消除了非均匀采样带来的影响。最后通过对两者运算量的分析,指出时域重构法优于Spectral-Fit法。     

Ultimate Accuracy for the nand Flash Program Algorithm Due to the Electron Injection Statistics

This paper investigates the ultimate accuracy of the NAND flash program algorithm that is determined by the statistical injection of electrons from the substrate to the floating gate. The granular nature of the electron flow during a constant-current Fowler-Nordheim program operation is shown to spread the programmed threshold-voltage distribution of the array cells. The electron injection statistics displays a Poissonian behavior for low amounts of transferred charge, but a sub-Poissonian character becomes clearly evident when large charge packets are stored. This effect is expected from the reduction of the tunnel oxide field that follows each electron storage event into the floating gate, establishing a correlation among such events. Finally, the impact of the electron injection statistical spread on the accuracy of the NAND flash program algorithm is investigated as a function of the technology node feature size, drawing projections on future NAND technologies.     

微波通信中大气波导干扰的工程估算

简要地分析了微波通信系统中大气波导干扰的产生机理，介绍了一套可供工程应用的大气波导干扰电平的估算方法，根据该算法可以计算不同发生时间百分比情况下的大气波导干扰电平，最后给出一个根据该算法计算的、并经过较长时间的工作实际验证为正确的工程实例。     

一种空间非均匀噪声环境下DOA估计的改进方法

文中提出一种空间非均匀噪声环境下的信号源DOA估计的改进方法.该算法首先对阵列协方差矩阵进行平滑处理,在此基础上估计出空间非均匀噪声协方差矩阵,通过已估计的噪声协方差矩阵对平滑处理后的阵列数据协方差矩阵进行白化处理,克服了空间非均匀噪声对空间谱估计的影响,实现信号源DOA估计.相对于原方法,文中所提方法改善了DOA估计的性能,计算量小,并且能够估计强相关或相干信号源DOA.理论分析和仿真结果均表明所提方法的有效性.     

Increased Nonlinear Crosstalk in Analog Wavelength-Division-Multiplexed Links Due to the Chromatic Dispersion of Optical Filters

The effect of the chromatic dispersion of an interference filter on the nonlinear crosstalk in a wavelength-division-multiplexed microwave photonic system is investigated. For a simple two-channel pump–probe system with 200-GHz channel spacing, a crosstalk variation of greater than 30 dB is observed as the wavelength of the probe is varied across the flat-top region of the filter. The crosstalk is correlated with the dispersion of the filter and a variation of less than 7% of the filter width is observed to increase the crosstalk by 10 dB. An analytical model for calculating the crosstalk is presented.     

FIR数字滤波器的递推最小二乘设计算法

本文考虑对称系数及反对称系数的ＦＩＲ数字滤波器的设计问题,设计准则选为最小加权平方误差准则,并将这个设计问题看成一个线性系统的辨识问题,辨识系统参数所需的输入数据由一随机抽样法产生,辨识算法采用递推最小二乘法．按随机抽样法产生的数据具有很强的激励,保证了被辨识参数的收敛性,同时又自然地实现了最小加权平方误差准则．两个设计范例说明了本文提出的设计方法的有效性．     

Equivalent Circuit of Orthogonal-Loop-Coupled Magnetic Resonance Filters and Bandwidth Narrowing Due to Coupling Inductance

The equivalent circuit of an orthogonal-loop-coupled magnetic resonance filter is shown to consist of a gyrator, two ferrite-induced inductances, and two coupling loop inductances. The effects of the coupling inductances on the passband and stopband responses are shown to be significant by means of calculations based on this equivalent circuit. It is proved that the maximum passband bandwidth /spl Delta//spl conint//sub -3dB/ = /spl conint//sub 0/ (L/sub f/ / L/sub c/), where /spl conint//sub 0/, is the center frequency, and L/sub f/ and L/sub c/ the ferrite-induced and the coupling-loop inductance, respectively. Other unusual insertion-loss characteristics of this filter which differ from those of a conventional reciprocal-element bandpass filter are shown. Finally, a test circuit for determining experimentally the coupling inductance ratio L/sub c/ /L/sub f/ and the external Q, Q/sub f/ of a ferrite resonator is presented.     

小波包去噪在循环平稳信号DOA估计中的应用

基于信号循环平稳特性的到达方向(DOA)估计算法在噪声成分过大或噪声本身具有循环平稳特性的情况下,性能会迅速下降,为提高算法的估计性能,提出了利用小波包去噪与广义谱相关子空间算法相结合的方法估计信号DOA,通过仿真分析证明该方法提高了估计精度,降低了估计误差,达到了与理论分析相一致的目的.     

一种微波通信中大气散射干扰的工程估算

本文简要地分析了微波通信系统中大气散射干扰的产生机理，介绍了一套可供工作应用的大气散射干扰电平的估算方法，根据该算法可以计算不同发生时间百分比情况下的大气散射干扰电平，最后给出一个根据该算法计算的，并经过较长时间的工作实际验证为正确的工作实例。     

Fast State-Space Harmonic-Distortion Estimation in Weakly Nonlinear Gm−C Filters

A fast, one-pass harmonic-distortion estimation algorithm for G _m-C filters is introduced. It is derived using state-space modeling and can be applied directly to G_m-C filters, of any order, with MOS transconductors exhibiting any type of weak nonlinearity. The algorithm is formed out of a small number of explicit expressions involving the filter's structural matrices and the transconductors' nonlinearity. It can be easily implemented in MATLAB. For verification of the theoretical development, the algorithm was used to derive the harmonic distortion of a single-ended G_m-C filter with weakly nonlinear transconductors designed on a 0.5-mum technology. The results of the algorithm and CADENCE simulation were found to be in good agreement     

The Evolving Face of Ethics in Technical and Professional Communication: Challenger to Columbia

Our view of ethics in professional and technical communication has evolved, paralleling developments throughout society. Earlier views on ethics and values have grown into a broad perspective of complex gradations with people at many levels affecting eventual practical outcomes. This newer perspective includes not only persons but social forces and organizations. The organizational culture of NASA, for example, was specifically identified by the Columbia Accident Investigation Board (CAIB) as one of the causes of faulty communication leading to a terribly tragic event. The Challenger investigations of 20 years earlier, on the other hand, focused primarily on physical events, secondarily on professional judgments, and only little on the social and cultural context of the disaster. We learn by failures but also by self-examination. As we see how ethics and values impact technical events, we understand that technological progress is ultimately a human endeavor in which reflection and judgment is as important as measurement and observation.     

A State-Space Approach to Intermodulation Distortion Estimation in Fully Balanced Bandpass Gm– C Filters With Weak Nonlinearities

A state-space approach to estimating intermodulation distortion in bandpass G_m-C filters with fully balanced, weakly nonlinear transconductors is introduced. It results in compact analytic expressions applicable to G_m-C filters of any order. For verifying the theory, two G_m-C filters with fully balanced weakly nonlinear transconductors have been designed using Cadence. They have been simulated in SpectreS as well as modeled and simulated in Simulink. Theory and simulation results are found in good agreement     

非均匀噪声条件下的互质阵列欠定DOA估计方法

针对基于互质阵列的欠定DOA估计方法在非均匀噪声条件下性能下降的问题,该文提出一种基于协方差矩阵重构和矩阵填充的鲁棒DOA估计方法。首先,将接收数据协方差矩阵分解,得到包含非均匀噪声项的对角阵;然后,选取对角线元素中的最小值,替换其余对角线元素,进而得到重构后的数据协方差矩阵;最后,对重构后的协方差矩阵进行扩展和矩阵填充,结合子空间方法进行DOA估计。理论分析和仿真结果表明,相对于现有方法,该文方法有效地抑制了非均匀噪声的影响,有更好的DOA估计性能。