超宽带相控阵天线的低副瓣设计

探讨了在超宽带相控阵列天线上实现低副瓣的工程设计方法,提出了采用多阶量化幅相加权的方法实现发射阵和接收阵的低副瓣设计,并在一维线阵上给出了优化设计结果。结果显示该方法具有较好的低副瓣特性及工程应用参考价值。     

无先验参数条件下直扩信号时差估计研究

周期谱相关具有较强的抑制噪声和抗干扰的能力,适应于低信噪比时差估计的情况,但其抗噪声和干扰能力完全在于循环频率的选择。目前关于直扩信号时差估计的研究都是建立在循环频率已知的前提下进行的。运用直扩信号的周期谱特性,可在无先验参数条件下确定其循环频率,对时差进行估计,大大降低了谱相关时差估计算法的计算量。仿真结果表明,该方法是切实可行的。     

对通信信号的时差估计技术

以循环相关理论为基础,讨论了利用循环互相关再相关法进行通信信号时差估计的算法原理,通过仿真验证了时差估计的效果。理论分析和仿真表明该算法具有优越的信号选择能力与干扰和噪声抑制能力;并指出了该方法的优缺点,阐明了该方法适合应用于对通信源的时差估计。     

改进的通信调制信号谱相关识别方法

传统谱相关分类法利用不同信号在a截面上所表现的不同谱相关特征可对通信信号进行分类,需要提取六种特征参数。文章结合小波分析法估计信号的码元宽度Tt,利用谱相关提取的三种特征参数,可对常见八类调制信号进识别。仿真表明,该方法具有很好的识别效果。     

Hyperuniform and rigid stable matchings

We study a stable partial matching τ of the d‐dimensional lattice with a stationary determinantal point process Ψ on R^d with intensity α>1. For instance, Ψ might be a Poisson process. The matched points from Ψ form a stationary and ergodic (under lattice shifts) point process Ψ^τ with intensity 1 that very much resembles Ψ for α close to 1. On the other hand Ψ^τ is hyperuniform and number rigid, quite in contrast to a Poisson process. We deduce these properties by proving more general results for a stationary point process Ψ, whose so‐called matching flower (a stopping set determining the matching partner of a lattice point) has a certain subexponential tail behavior. For hyperuniformity, we also additionally need to assume some mixing condition on Ψ. Furthermore, if Ψ is a Poisson process then Ψ^τ has an exponentially decreasing truncated pair correlation function.     

Achievable sum‐rate analysis of correlated two‐antenna MIMO uplink channels

This paper analyzes the achievable sum‐rate of correlated two‐antenna multiple‐input multiple‐output (MIMO) uplink channels. Most of previous works have considered the case when a single user has multiple transmit antennas (i.e. multi‐antenna single‐user scenario). This paper considers the case when two‐antenna MIMO uplink channels comprise two users with a single transmit antenna (i.e. single‐antenna two‐user scenario). The analytic and simulation results show that the achievable sum‐rate of correlated single‐antenna two‐user MIMO uplink channels highly depends on the angle difference between the receive correlation coefficients of two users. It is also shown that the achievable sum‐rate of correlated single‐antenna two‐user MIMO uplink channels is larger than that of correlated two‐antenna single‐user MIMO uplink channels and can even be larger than that of independent and identically distributed Rayleigh two‐antenna MIMO uplink channels. Copyright © 2009 John Wiley & Sons, Ltd.     

Low Voltage CMOS LC VCO with Switched Self‐Biasing

This paper presents a switched self‐biasing and a tail current‐shaping technique to suppress the 1/f noise from a tail current source in differential cross‐coupled inductance‐capacitance (LC) voltage‐controlled oscillators (VCOs). The proposed LC VCO has an amplitude control characteristic due to the creation of negative feedback for the oscillation waveform amplitude. It is fabricated using a 0.13 µm CMOS process. The measured phase noise is ‐117 dBc/Hz at a 1 MHz offset from a 4.85 GHz carrier frequency, while it draws 6.5 mA from a 0.6 V supply voltage. For frequency tuning, process variation, and temperature change, the amplitude change rate of the oscillation waveform in the proposed VCO is 2.1 to 3.2 times smaller than that of an existing VCO with a fixed bias. The measured amplitude change rate of the oscillation waveform for frequency tuning from 4.55 GHz to 5.04 GHz is 131 pV/Hz.     

雷达成像中基于进退法的鸟类目标运动状态自动判别方法

利用线性调频步进体制高分辨雷达对鸟类目标进行ISAR成像是解决航空安全保障中鸟情探测问题的一个全新且重要的技术途径.为了得到鸟类目标更清晰的像,准确判断其运动状态显得至关重要.基于线性调频步进体制雷达微多普勒效应的产生原理,在距离-慢时间谱图上,针对鸟类目标特性,通过对精高分辨距离像进行分析,提出了一种利用进退法搜索相邻精高分辨距离像的互相关系数的方法来判别鸟类目标运动状态.仿真结果证明了其可行性和有效性.     

雷达相关杂波的建模与仿真研究

为了研究杂波环境下的信号处理问题,需要对雷达杂波环境进行建模与仿真。文中归纳了雷达杂波的统计模型,包括幅度分布和功率谱模型,以及杂波的相应类型,并对服从一定幅度分布和功率谱分布的相关杂波序列产生方法进行了分析,给出了每种统计模型的仿真过程,最后根据杂波仿真的两种主要方法——无记忆非线性变换法ZMNL和球不变随机过程法SIRP对相关杂波进行了仿真,解决了仿真过程中成型滤波器的设计和特殊函数求值问题。仿真结果表明,用文中所述方法进行仿真可得到较好的结果。     

Speech Enhancement Algorithm Based on MMSE Short Time Spectral Amplitude in Whispered Speech

An improved method based on minimum mean square error-short time spectral amplitude （MMSE-STSA） is proposed to cancel background noise in whispered speech. Using the acoustic character of whispered speech, the algorithm can track the change of non-stationary background noise effectively. Compared with original MMSE-STSA algorithm and method in selectable mode Vo-coder （SMV）, the improved algorithm can further suppress the residual noise for low signal-to-noise radio （SNR） and avoid the excessive suppression. Simulations show that under the non-stationary noisy environment, the proposed algorithm can not only get a better performance in enhancement, but also reduce the speech distortion.