短时傅里叶变换在线性调频信号时频滤波中的应用

将短时傅里叶变换（STFT）的时频分析方法应用到线性调频（LFM）信号的滤波中, 突破了传统匹配滤波方法基于平稳假设的限制,将信号分析空间从一维频率域扩展到二维的 时间-频率域。利用自滤波的时频滤波方法进行LFM信号的滤波,然后分别采用时域和时频域 的均方误差（MSE）标准,分析了时频滤波的性能。仿真结果表明,基于STFT的时频滤波方 法能有效实现对LFM信号的滤波。     

基于FrFT的线性调频-伪码调相复合调制雷达信号截获与特征提取

针对线性调频-伪码调相复合调制雷达信号(LFM-PRBC)的截获与特征提取问题,提出了一种基于分数阶傅里叶变换(FrFT)平面切割与相关检测相结合的新方法.理论分析和计算机仿真验证表明,该方法具有较好的有效性和准确性,能快速完成高斯白噪声背景下低信噪比复合调制雷达信号的截获与特征提取,有一定的实际应用价值.     

基于协方差匹配技术的互耦和幅相误差联合校正算法

 提出了基于协方差匹配技术的均匀线阵互耦和幅相误差联合校正算法.首先,根据协方差匹配技术中的目标函数和均匀线阵的误差模型,设计了一种交替迭代算法用以实现各种参数的优化计算.接着,为了避免该算法中的每轮循环迭代都需要进行波达方向估计这一复杂环节,利用理想条件均匀线阵协方差阵的Toeplitz性,给出了另一种改进型交替迭代算法用以减少计算复杂度.与基于子空间技术的阵列误差校正方法相比,文中的两种新算法可直接利用信源的统计特性,并且适用于不同的高斯噪声模型(例如噪声功率不一致),仿真实验验证了新算法的有效性和优越性.     

基于DSP和DDS技术相位及频率严格可调的多路同步信号发生器

基于DSP芯片TMS320f2812控制多片DDS芯片AD9833构成的信号发生器,能够产生频率和相位均严格可调的多路信号.该电路应用于是定子嵌入式电磁悬浮微马达的旋转驱动电路,实现转子的旋转驱动.通过C语言编译并采用串行方式加载芯片控制字,实现软件控制信号频率和相位差的调整.产生的信号具有频率稳定性好,低频频率准确度高及频率分辨率高,相位差精准等特点.     

Off‐grid DoA estimation method of wideband signals

In this paper, an off‐grid direction of arrival (DoA) estimation method is proposed for wideband signals. This method is based on the sparse representation (SR) of the array covariance matrix. Similar to the time domain DoA estimation methods, the correlation function of the sources was assumed to be the same and known. A new measurement vector is obtained using the lower‐left triangular elements of the covariance matrix. The DoAs are estimated by quantizing the entire range of continuous angle space into discrete grid points. However, the exact DoAs may be located between two grid points; therefore, this estimation has errors. The accuracy of DoA estimation is improved by the minimization of the difference between the new measurement vector and its estimated values. Simulation results revealed that the proposed method can enhance the DoA estimation accuracy of wideband signals.     

超宽带穿墙雷达高效的TV-MAP稀疏成像方法

现有的穿墙雷达稀疏成像方法中构建的字典矩阵占据存储空间大,而且计算复杂度高,成像时间长。为此,本文针对全变分（TV）约束的最大后验（MAP, TV-MAP）稀疏成像方法,利用超宽带窄脉冲波形的特点和冲激函数具有的抽样特性,将优化最小化（MM）框架下的交替迭代更新公式中包含字典矩阵的相关运算用线性卷积和哈希表代替,避免了字典矩阵的构造、存储与计算;同时,通过对发射序列进行变换,使所提方法可以适用于任何超宽带发射波形,而不限于对称的发射波。仿真和实验结果表明,该方法不仅减少了所需内存,降低了时间复杂度,而且有效地抑制了杂波。     

Wind turbine speed control of a contactless piezoelectric wind energy harvester

ABSTRACT

Wind turbine control is an important task to make the electricity generation secure in terms of energy demand and machine safety. It also yields to control the desired power level and optimized energy because of the assignment of turbine speed. The contactless piezoelectric wind energy harvester (CPWEH) used in this study has three piezoelectric layers located around the shaft with 120 degrees apart and they are buckled by the magnetic force without any physical contact. The superiority of this device is to generate energy for low wind speeds such as 1.5 m/s. However, for high speeds, high total harmonic distortions (THDs) govern the waveforms, thus controlling the turbine speed becomes necessary for optimizing the output power. Encouraged by this, a small low inertia dc generator is coupled with the wind turbine, and the generator terminals are connected to a resistor through a power switch to generate a braking torque that opposes to wind speed direction. By controlling the switch properly, turbine speed is ensured to remain within a certain band, which accordingly prevents the turbine from rotating very fast at damaging wind speeds. Several experiments are performed on the developed CPWEH with/without the presented control scheme which prove the existence of promising performance of our proposal.     

一种高速串行信号线性均衡电路

设计了一种高速串行信号连续时间线性均衡器。采用有源电感负载结构,结合高频与全频通路信号求和技术来实现高速串行信号均衡。电路具有面积小、功耗低、利于集成等优点。采用65 nm CMOS工艺进行设计,1.2 V电源供电,可对经过80 cm长的衰减信道、且传输速率为14 Gbit/s的信号进行补偿,实现6.24 dB@10.96 GHz的补偿。该均衡器将输出端信号眼图水平方向抖动减小至0.25UI,功耗数据率比低至0.399 mW·s/Gbit,设计版图面积为0.09 mm²。     

超宽带雷达信号产生器的设计

对雷达信号的基本数学模型、直接数字合成器（DDs）工作原理和应用做了系统的分析,介绍了一种超宽带雷达信号产生器的设计,该产生器选用直接频率合成方案,利用DDS来实现精细频率步跳,并通过和1组以高稳定度晶振为参考频率的标频源组成的粗精频率步跳的点频进行混频、滤波及放大生成各频段的信号。     

红外图像序列中不均匀背景消除新方法

从红外相机自身特性和使用角度两方面对靶场红外图像序列中不均匀(花纹)背景产生的原因进行了剖析,分析了传统红外图像非均匀校正算法在处理靶场序列红外图像上的优缺点,提出在目标跟踪过程中随着场景变化,基于实时线性标定的非线性红外图像的校正的新方法,克服了传统方法的弊端,实时确定了校正增益系数和校正因子,消除了序列红外图像中不均匀背景。通过对含有弱小目标的靶场实际序列红外图像进行仿真验证表明,新方法去除了图像固定图案噪声,消除了探测器坏元的影响,输出了理想的序列红外图像。