基于微波的粮食水分检测系统设计

针对粮食水分快速检测的特点和要求,研制了基于微波的粮食水分检测系统,采用微波无损检测方法实现了对粮食水分含量的实时、连续检测。微波发生器产生10．5GHz的微波信号,经基于自由空间传输检测技术的微波传感器,与粮食非接触作用,信号采集电路对微波信号进行放大滤波,再经A／D转换器AD7806将微波模拟信号转化为数字信号．微控制器PIC18F6527通过采集到的微波信号推算出粮食的水分含量。实验表明该系统水分检测范围为8％～20％,测量精度为0．5％。在粮食收购、储藏、加工等过程中水分含量的检测是可行有效的。     

微波致热超声信号时频特征及其影响因素

微波致热超声成像是一种兼顾了微波和超声成像两方面长处的新型生物医学成像方法。本文首先给出了一个微波致热超声（Microwave-Induced Thermo-Acoustic,MITA）实验系统,然后结合信号理论和MITA机制,讨论微波脉冲激励源和样品尺寸这两方面因素对MITA信号的时域波形和频域分布的影响。由实验数据和理论分析得出MITA信号时域波形强度与入射微波脉冲宽度和样品截面大小成正比;MITA信号的频率分布除了与激励微波脉冲频谱有关外,更主要的特性是其频谱分布中心与样品厚度所确定的超声波本振频率存在对应关系。     

A DSP-based direction finder

For many applications, existing phased arrays prove to be costly, bulky and not flexible enough to meet operational requirements. This explains the present trends towards monolithic array design; integration of microwave front end; and beam-forming by using digital signal processing (DSP) techniques. This paper discusses a phased array direction finder based on programmable digital signal processing microdevices, whereby the basic task of beam scanning is carried out by digitally processing the down-converted antenna signals.     

Microwave photonic signal processing techniques and radio-over-fiber transmission demonstration

Radio-over-fiber (RoF) utilizing microwave photonic signal processing techniques is a powerful solution for the future super-broadband wireless access. In this paper, we review our recent works on photonic processing techniques of microwave signals for RoF applications and experimental demonstration of RoF transmissions. Our works specifically focus on impulse-response ultra-wideband (IR-UWB) pulse generation for UWB-over-fiber systems, photonic vector modulation, novel analog modulation format, multi-service RoF system design and experimental demonstrations.     

Microwave Photonics

The low-loss wide bandwidth capability of opto-electronic systems makes them attractive for the transmission and processing of microwave signals, while the development of high-capacity optical communication systems has required the use of microwave techniques in optical transmitters and receivers. These two strands have led to the development of the research area of microwave photonics. This paper reviews the development status of microwave photonic devices, describes their systems applications, and suggests some likely areas for future development     

Microwave Frequency Conversion Using a Coupled Cavity Surface-Emitting Laser

Microwave signal mixing is observed when two signals of different frequencies are injected into the top and bottom cavities of a coupled cavity surface-emitting laser simultaneously. The signal amplitude at the mixed frequencies can be tailored by the dc bias or the microwave signal amplitude applied to the coupled optical cavities. Signal mixing enables the generation of microwave signals at new frequencies, which can be useful for optical signal processing or frequency conversion for a high-speed data link.     

Wavelet-based statistical signal processing using hidden Markovmodels

Wavelet-based statistical signal processing techniques such as denoising and detection typically model the wavelet coefficients as independent or jointly Gaussian. These models are unrealistic for many real-world signals. We develop a new framework for statistical signal processing based on wavelet-domain hidden Markov models (HMMs) that concisely models the statistical dependencies and non-Gaussian statistics encountered in real-world signals. Wavelet-domain HMMs are designed with the intrinsic properties of the wavelet transform in mind and provide powerful, yet tractable, probabilistic signal models. Efficient expectation maximization algorithms are developed for fitting the HMMs to observational signal data. The new framework is suitable for a wide range of applications, including signal estimation, detection, classification, prediction, and even synthesis. To demonstrate the utility of wavelet-domain HMMs, we develop novel algorithms for signal denoising, classification, and detection     

动目标检测与速度估计仿真研究

介绍了雷达信号处理技术中的脉冲压缩、动目标检测、脉冲多普勒处理和恒虚警检测技术,并对雷达发射波形、目标回波、动目标检测进行了Matlab仿真。对脉冲回波信号进行脉冲压缩与动目标显示得到动目标脉压信号。利用动目标显示和脉冲多普勒处理实现脉压信号的动目标检测,并得到脉冲多普勒数据块。在数据块的距离维上进行恒虚警检测,检测动目标的距离,然后提取对应距离门的多普勒数据,检测动目标的速度。通过仿真建立了雷达信号处理的基本框架,为雷达系统建模及其仿真的深入研究提供了仿真支持。     

基于双光学频梳的超宽带射频信号信道化合成技术研究（特邀）

随着现代通信系统的发展,宽带和高频微波射频信号在雷达,通信和信号处理等领域的应用越来越广泛。基于微波光子信道化技术,文中通过两个自由频谱范围不同的光学频梳,实现了超宽带射频信号的信道化合成。在信道化合成系统中,多个独立的窄带信号输入各个信道进行上变频,并在多外差探测中被重组成为一个具有连续频谱的宽带射频信号。在多外差探测中,干扰抑制技术的使用提高了合成射频信号可达到的最高频率。在实验中,合成了一个覆盖频率范围8.4~12.4 GHz,瞬时带宽为4 GHz的宽带射频信号。实验结果显示,干扰的抑制率达到了21 dB,表明干扰抑制技术的使用提高了输出信号的最高频率的同时有效地提高了频谱利用率。     

Pulse morphology visualization and analysis with applications in cardiovascular pressure signals

We present a new analysis and visualization method for studying the functional relationship between the pulse morphology of pressure signals and time or signal metrics such as heart rate, pulse pressure, and means of pressure signals, such as arterial blood pressure and central venous pressure. The pulse morphology is known to contain potentially useful clinical information, but it is difficult to study in the time domain without the aid of a tool such as the method we present here. The primary components of the method are established signal processing techniques, nonparametric regression, and an automatic beat detection algorithm. Some of the insights that can be gained from this are demonstrated through the analysis of intracranial pressure signals acquired from patients with traumatic brain injuries. The analysis indicates the point of transition from low-pressure morphology consisting of three distinct peaks to a high-pressure morphology consisting of a single peak. In addition, we demonstrate how the analysis can reveal distinctions in the relationship between morphology and several signal metrics for different patients.     

一种新型电子对抗通道声光微波信号处理技术

本文简要论述了一种新型电子对抗通道声光微波信号处理技术，它有别于目前常用的电子对抗技术。该技术实现了多通道声光微波信号处理，对未来战场上实施对敌多路载频信号的电子对抗，对发展雷达预和毫米波制导武器系统有着实用价值。     

一种基于模板匹配与隶属度解析的时序异常快速检测方法

传统的数据检测技术在处理大规模医疗数据时,耗时较高且抗干扰能力较弱。针对这些问题,文中应用模板匹配与隶属度解析技术,给出了一种时序数据异常状态的快速检测与分析方法。该方法采用TSTKS算法与滑动窗口理论实现时序数据多突变点快速检测,提取连续多窗口波动特征,构建时序数据的归一化波动向量,对大规模病变信号进行异常状态检测与分析。仿真数据与脑电病变信号分析等实验表明,此方法是一种较为快速、准确的大数据分析与检测方法。     

A microprocessor-based data acquisition and processing system for studying the kinematics of labor

The design, development and preliminary evaluation of a microprocessor-based data acquisition and processing system which continuously and simultaneously acquires signals of fetal heart rate, intrauterine pressure, uterine cervical dilatation and variables for calculation of spatial position or pathway of fetal descent are presented. The project consists of four phases: 1) Design and fabrication of the data acquisition system; 2) Development of signal processing and pattern recognition techniques using a PDP-11/45 based signal processing system; 3) Transfer of algorithms produced in phase 2) to the microprocessor-based data acquisition system; and 4) Long term physiological study of acquired data directed toward obtaining more conclusive diagnostic or clinical results. This paper reports the development of the first two phases.     

Multichannel Signal Processing Based on Logic Averaging

The multichannel signal processor described provides an excellent capability for the detection of any kind of signal, on-line, with a SNR of 0.1 dB at a wide frequency range. This very efficient and inexpensive approach to improving the SNR by the processor wiUl reduce the need for other signal processing techniques. The processor's reaction on an input signal and noise has been analyzed by a mathematical model. This effect is IMustrated by an in vivo noninvasive detection on a beat-by-beat basis of electrical activity of the His?Purkinje system of the heart, and the detection of a pulse-like signal from a generator.     

硅基超材料太赫兹波电光调制器

该文介绍了一种基于声光调制的微波信号多普勒移频方法。该技术基于微波光子信号处理和声光移频技术,在光学域上实现了微波信号的多普勒频移,能够用于产生雷达干扰信号。系统的工作频段为2～20 GHz,测试结果表明,速度拖引干扰信号的移频范围达到±1 MHz,最小移频量为±10 Hz。系统实现了目标速度从1 200 m/s减小到1 000 m/s情况下雷达脉冲信号的多普勒频移模拟测试。     

Optimal quadratic detection and estimation using generalized jointsignal representations

Time-frequency analysis has significant advances in two main directions: statistically optimized methods that extend the scope of time-frequency-based techniques from merely exploratory data analysis to more quantitative application and generalized joint signal representations that extend time-frequency-based methods to a richer class of nonstationary signals. This paper fuses the two advances by developing optimal detection and estimation techniques based on generalized joint signal representations. By generalizing the statistical methods developed for time-frequency representations to arbitrary joint signal representations, this paper develops a unified theory applicable to a wide variety of problems in nonstationary statistical signal processing     

Analysis of Automatic Homodyne Method Amplitude and Phase Measurements (Short Papers)

A system employing RF substitution techniques for automatic phase and intensity measurement of microwave fields is described. The system uses homodyne detection to generate error signals for servomechanisms which balance the attenuation and phase secondary standards. Accuracy and dynamic range of this method of measurement can be strongly dependent on the method of modulation employed. This paper analyzes errors from this cause and indicates what means are available to minimize them. This method of measurement is less expensive than some alternate techniques, and, at the present stage in the evolution of microwave near field measurements, its errors are less serious than uncertainties introduced by absorber reflections, probe characteristics, and mechanical positioning errors.     

基于微波光子滤波器的归零到非归零码型转换研究

从信号频域处理的角度分析并实验验证了一种基于微波光子滤波器的归零(RZ)码到非归零(NRZ)码的码型变换方案。理论上,通过对RZ和NRZ码基带信号的频谱特点以及微波光子滤波器的特性进行分析,构建一个低通滤波器并对RZ码信号进行滤波,强烈抑制RZ码信号中的时钟分量,最终实现RZ到NRZ码的码型转换。在实验中,采用一种两抽头加色散延时的微波光子滤波器对速率为10Gbit/s的RZ码信号进行了处理,成功得到了转换后的NRZ码信号。信号波形和频谱均显示了此方案的良好性能。通过简单地调节微波光子滤波器的部分参数,可对任意速率的信号进行处理,具有很好的灵活性。     

Coherent photonic processing of microwave signals using spatial light modulators: programmable amplitude filters

This paper presents a novel coherent optical signal processing approach for synthesis of programmable microwave amplitude filters over an ultrawideband. The authors' scheme relies on a programmable hyperfine optical filter implemented in a pulse-shaping geometry, which provides arbitrary, user-defined amplitude-filtering functions over a 50-GHz bandwidth with resolution better than 0.7 GHz. In contrast to previous work on discrete time optical processing of microwave signals, their approach allows direct synthesis of microwave filter functions in spectral domain without computing filter coefficients, which is needed for a discrete-time-domain approach.