基于支持向量机的Morse检测算法研究

针对短波通信中Morse人工接收存在劳动强度大、实时性差的问题,提出一种Morse自动检测算法。对时频图像进行图像增强和尺度归一化预处理。提取图像的纹理特征和形状特征,并将特征组合后进行高斯归一化。最后选择不同核函数设计支持向量机分类器,基于交叉验证选取最优分类器用于Morse的检测。通过实验测试,验证了算法的有效性。     

Morse报自动译码算法研究

在现代化军事通信领域,短波电报是恶劣条件下重要的应急通信手段,但现有的自动译码方法仍没达到实用化水平,依旧采用人工译码方式。人工译码方式是在确定信号频率的同时判定信号的持续时间,因此时频分析方法非常适用于Morse报的分析。提出一种基于时频分析理论,结合数字图像处理和机器学习方法的Morse报自动译码算法,旨在提高译码准确率。在点、划、间隔的识别问题中,采用了聚类算法,智能的判定元素的种类;在码文查表转换时,提出了快速索引查表算法,提高了查表效率。仿真实验表明,提出算法可以从强噪环境下较为准确的还原码文信息,对手工码的适应性强,在时变的噪声环境下具有鲁棒性。      

宽带泄漏信号自适应对消器的性能

自适应对消器可以有效地消除雷达发射机宽带泄漏信号对雷达系统本身的影响。本文依据环路模型建立了描述自适应对消器工作过程的随机微分方程,求得了随机微分方程的瞬态解及其统计特性。最后导出了衡量对消器性能的干扰对消比的理论公式。     

宽带LFM信号瞬时频率和二维到达角联合估计

针对非平稳的宽带线性调频信号(LFM),本文利用了对称阵元 分布(WVD)将原始数据投影到时频波束空间建立了一种新颖的具有分维结构的空间时频分布数据模型,然后采用Beamspace-ESPRIT算法、子空间投影法获得了信号瞬时频率和二维到达角的联合估计.仿真实验证明算法精度较好,计算量小,具有很好的实用性.     

一种有效的宽带雷达信号压缩算法

针对宽带雷达回波信号采样数据量大、传统小波压缩算法保真度不高的特点,利用小波多层次变换系数之间的关系,提出了基于小波变换的自适应贪婪算法,并将其应用于宽带雷达回波信号数据压缩.将该算法与传统的小波多层次方法在对宽带信号的压缩性能上进行了比较,结果表明,基于小波的自适应贪婪算法对数据压缩保真效果优于传统的小波方法.     

多径传播条件下宽带线性调频信号波达方向估计方法

针对信号出现多径传播情况时现有宽带信号波达方向（direction of arrival, DOA）估计方法性能下降的问题,提出了一种多径传播条件下宽带线性调频（chirp）信号波达方向估计方法,该方法将导向有效投影（steered effective projection, STEP）技术与宽带线性调频信号的时频特性相结合,对具有不同时频特性的信号分量进行分离,逐个处理,并以时频分布矩阵代替传统的协方差矩阵,从而构造有效噪声子空间,实现时域角度估计。本方法无需进行信号聚焦操作,因此理论上不受聚焦误差的影响。仿真结果验证了所提方法的有效性。      

宽带信号模型及分辨力性能研究

讨论了宽带信号的模型及条件,在此基础上对宽线性调频信号在宽带模型下的距离、速度及速度距离联合分辨率特性进行了分析和模拟,燕对宽带模型及窄带模型下的结论进行了比较,证明了信号分辨力取决于信号频谱结构及尺度,得出了两种模型下信号分辨力特性的关系。     

宽带CDMA信号激励下的功放性能分析

根据功放的实测AM－AM、AM－PM特性,采用时域分析方法,并应用带通非线性理论和数字信号处理技术,分析了宽带数字调制信号激励下 的射频功率放大器非线性失真特性。     

海岸逆合成孔径雷达宽带信号探讨

基于在海岸警戒雷达上工程实现ISAR的重要意义，本文介绍了如何实现ISAR宽带系统，比较了各种宽带信号形式的特点，给出了线性调频信号波形和步进频率信号波形都适用于海岸逆合成孔径雷达宽带系统的结论。     

空间欠采样信号DOA估计的解模糊算法

讨论了一种主要针对机载宽段雷达侦察接收机的宽带天线阵列阵元间距配置方案及相应的空间信号到达角解模糊算法。文中以具有最小冗余度的一今天晨均匀性阵为例,给出可以实现信号到达角解模糊的天线阵元间距配置的一个必要条件,并通过一个简化的一维整数搜索算法实现了信号到达角的无模糊估计。     

Automatic detection of obstructive sleep apnea using speech signals

Obstructive sleep apnea (OSA) is a common disorder associated with anatomical abnormalities of the upper airways that affects 5% of the population. Acoustic parameters may be influenced by the vocal tract structure and soft tissue properties. We hypothesize that speech signal properties of OSA patients will be different than those of control subjects not having OSA. Using speech signal processing techniques, we explored acoustic speech features of 93 subjects who were recorded using a text-dependent speech protocol and a digital audio recorder immediately prior to polysomnography study. Following analysis of the study, subjects were divided into OSA (n=67) and non-OSA (n=26) groups. A Gaussian mixture model-based system was developed to model and classify between the groups; discriminative features such as vocal tract length and linear prediction coefficients were selected using feature selection technique. Specificity and sensitivity of 83% and 79% were achieved for the male OSA and 86% and 84% for the female OSA patients, respectively. We conclude that acoustic features from speech signals during wakefulness can detect OSA patients with good specificity and sensitivity. Such a system can be used as a basis for future development of a tool for OSA screening.     

宽带对数周期天线的优化设计

通过对ＬＰＤＡ的优化设计,研制一种适合方舱结构形式车辆运载的超宽带,高增益定向天线。在研制过程中较好地解决了ＬＰＤＡ设计中常遇到的反常共振问题,实现了天线阻抗与增益在宽频带内的均衡性,以及单边平衡架设。     

Adaptive algorithm for detection of signals in an impulsive interference environment

Impulsive interferences are frequently long relative to signal duration. This situation is observed, for example, in a telephone channel used for medium and high-speed data communication. In this paper a novel algorithm for signal detection under conditions of long impulsive interferences is proposed. The approach does not require a priori knowledge of the impulse noise statistics. It is based on the representation of the impulse noise using a linear prediction model. Performance of I he proposed algorithm is investigated using computer simulation. It is shown that the algorithm provides a greatly reduced error rate as compared with the conventional non-linear receiver. Its performance is virtually independent of the power of impulse noise.     

ADSL在宽带接入网中的应用

针对当前接入网的高速化、宽带化趋势，在非对称数字用户环路（ADSL）接入模型的基础上分析了ADSL的宽带接入方式，以及ADSL的应用发展前景。     

短波窄带莫尔斯信号自动识别技术

短波环境中存在着大量令人感兴趣的莫尔斯信号,为了降低人工侦收成本,研究了莫尔斯信号在短波环境下的窄带信号自动识别技术。针对短波信道环境,提出一种联合时频域特征的快速识别算法,并给出短波环境下莫尔斯窄带识别算法的流程设计,最后获得算法的实测结果。实验结果表明,该算法下的莫尔斯识别具有较快的速度和较好的识别率,以及较低的虚警率和漏警率。     

超宽带无线通信技术--UWB

半导体技术与网络技术的不断发展,为无线通信的应用开辟了广阔前景,诸如无线因特网、无线局域网、无线个人区域网等等的广泛应用,潜移默化地改变着人们的工作与生活,与此同时,这些应用的推广与提高又呼唤着新的技术进步.     

FM wide band panel dipole antenna

It is very common that when a broadcaster needs to install an FM transmitting antenna within a large metropolitan area he places it on the tallest structure or building available. When the rooftop is already occupied by a large number of other types of transmitting and receiving antennas, the panel dipole antenna should be chosen. This antenna is secured to the side walls of the upper floors with the panel oriented to obtain full coverage of the most desirable areas of the city. For the Buenos Aires area this orientation avoids radiating toward Uruguay and specifically toward Montevideo, some 140 miles away. A wide band antenna operation permits placing the station on the air and at the same time allows future stations to share it without the installation of new antennas. Details of model and full model impedance and radiation pattern measurements during the antenna development are presented in order to show its technical characteristics. The radiation patterns were measured on a scale model in an anechoic chamber. The full scaled model was measured in an outdoor antenna range. Both E and H plane radiation patterns were measured along the FM band in order to observe pattern variations on both planes. Practically no difference in a panel radiation beamwidth from 88 to 108 MHz was observed and at the same time good input impedance was maintained. A really wide band antenna in pattern and VSWR is obtained. Power division for the antenna system is obtained designing an eight port power divider using the microstrip line technique. In this case, however due to high power operation the ground plane and strip are contained in a sealed metallic box and are separated by high pressure dry air like into the 3" feeding coaxial line.     

毫米波宽带鳍线PIN管开关

本文介绍了3mm波宽带鳍线PIN管接收保护开关的设计和实验结果。