共查询到20条相似文献,搜索用时 31 毫秒
1.
It is shown that the improved near-field lateral discrimination, already shown to be obtainable in a pulse radar or sonar by the use of multiplicative signal processing, can be obtained in a c.t.f.m. (continuous-transmission frequency-modulated) system. 相似文献
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Vilnrotter V.A. Rodemich E.R. Dolinar S.J. Jr. 《Communications, IEEE Transactions on》1992,40(3):604-615
A real-time digital signal combining system for use with array feeds is proposed. The combining system attempts to compensate for signal-to-noise ratio (SNR) loss resulting from antenna deformations induced by gravitational and atmospheric effects. The combining weights are obtained directly from the observed residual carrier samples in each channel using a `sliding-window' implementation of a maximum-likelihood (ML) parameter estimator. It is shown that with averaging times of about 0.1 s, combining loss for a seven-element array can be limited to about 0.1 dB in a realistic operational environment. This result suggests that the real-time combining system proposed is capable of recovering virtually all of the signal power captured by the array feed, even in the presence of severe wind gusts and similar disturbances 相似文献
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一种新的混沌同步及保密通信方式 总被引:20,自引:3,他引:17
本文提出一种新的混沌同步及保密通信方式。在发送端,将信息信号与混沌载波的和经取模运算后再嵌入混沌动力系统的迭代之中以实现调制;在接收端,用一个相应的非动力学系统从接收信号中提取混沌载波并进而恢复信息信号。研究表明,该混沌同步方式具有较强的抗干扰能力并且实现容易;该保密通信系统保密性能良好。 相似文献
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This paper provides a detailed analysis of the performance of systems recently proposed by various authors in which the received signal is Fourier transformed in real time (usually with a surface acoustic wave device) and then filtered by a multiplication of the transformed signal by an appropriate transfer function. We shall refer to this operation as transform domain filtering. General expressions for the output waveforms of the system will be derived, and a specific example illustrating the performance of the system when operating in the presence of a narrow-band interferer plus additive white Gaussian noise will be presented. It will be shown that certain filtering techniques not feasible in conventional systems, such as filtering with ideal bandpass filters, become straightforward using transform domain filtering. Finally, a receiver will be described which will eliminate that intersymbol interference between adjacent data symbols due to filtering at the receiver. 相似文献
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The resonance frequency (f/sub 0/) of a remote resonant circuit can be determined by comparing its response under different excitation signal frequencies. It is demonstrated that a sudden modification of excitation signal frequency produces a transient response which may introduce errors of the f/sub 0/ determination. Experimental results are presented. 相似文献
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Comparing spectra of a series of point events particularly for heart rate variability data 总被引:9,自引:0,他引:9
R W DeBoer J M Karemaker J Strackee 《IEEE transactions on bio-medical engineering》1984,31(4):384-387
Different methods for spectral analysis of the heart rate signal?considered as series of point events?are used in studies on heart rate variability. This paper compares these methods, focusing on the two principal ones: the interval spectrum, i.e., the spectrum of the interval series, and the spectrum of counts, which is related to the representation of the event series as a series of spikes (delta functions). Both autospectra are estimated for experimental heart rate data and are shown to produce similar results. This similarity is proven analytically, and it is shown that for small variations in interval length, the ratio of these spectra is PI(f)/PC(f) = [sin(?f?)/(?f?)]2, with PI and PC the interval spectrum and the spectrum of counts, respectively, f the frequency, and ?the mean interval length. It is concluded that both autospectra are equivalent for the considered heart rate data, but that, when relating the heart rate signal to other signals (e.g., respiration, blood pressure) by means of cross spectra, the technique to be used depends on the characteristics of the second signal. 相似文献
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该文分析了几种典型压制式宽带干扰(BPSK干扰、调频干扰)对伪码调相连续波引信相关输出的影响。分析发现当干扰强度超出伪码调相引信的抗干扰容限时,其相关输出严重恶化,因此必须在相关检测前对上述干扰进行抑制。提出了一种通过包络滤波的宽带干扰抑制新方法。接收信号经过正交解调输出I,Q两路信号,由I,Q两路分量获得解调信号的瞬时包络和瞬时相位。包络序列在变换域通过门限滤波去除有用信号和白噪声成分从而得到干扰信号包络。利用滤波后的包络和瞬时相位重构出干扰同相信号,最后将干扰信号从I路放大信号中去除即得到所需信号。仿真分析发现该方法能较好地抑制干扰,尤其是对强干扰,相关输出得到明显改善。该方法计算简单,易于理解,容易工程实现。 相似文献
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混沌信号中隐含周期信号的一种识别方法 总被引:5,自引:0,他引:5
基于周期信号所具有的自相似特性及混沌信号的广谱性,本文提出了一种识别隐含周期信号的实用方法,该方法简单易行,即使在信噪比极低的混沌信号中,也能准确地判断出周期信号的存在及其周期,为非线性系统及复杂信号中,周期信号的识别与提取提供了有效的手段。 相似文献
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For the application of undoped AlGaN/GaN HFETs to Ka-band millimetre(mm)-wave high frequency power performance, the maximum frequency of oscillation, f/sub max/, was found to be seriously limited by gate resistance and output conductance with the gate length down to 0.1 /spl mu/m. This makes it difficult for devices to achieve both high f/sub T/ and f/sub max/ at the same time. However, the technology of field-plate gate, to increase device breakdown voltage, will add extra gate capacitance. It makes the optimum gate structure design more important. The influence of gate metal thickness and gate length on f/sub max/ based on the lumped small signal circuit model analysis and the possibility to obtain high f/sub T/ and f/sub max/ simultaneously for the GaN material structure is discussed for application to the Ka-band mm-wave operating system. 相似文献
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Bayesian Compressive Sensing 总被引:12,自引:0,他引:12
The data of interest are assumed to be represented as N-dimensional real vectors, and these vectors are compressible in some linear basis B, implying that the signal can be reconstructed accurately using only a small number M Lt N of basis-function coefficients associated with B. Compressive sensing is a framework whereby one does not measure one of the aforementioned N-dimensional signals directly, but rather a set of related measurements, with the new measurements a linear combination of the original underlying N-dimensional signal. The number of required compressive-sensing measurements is typically much smaller than N, offering the potential to simplify the sensing system. Let f denote the unknown underlying N-dimensional signal, and g a vector of compressive-sensing measurements, then one may approximate f accurately by utilizing knowledge of the (under-determined) linear relationship between f and g, in addition to knowledge of the fact that f is compressible in B. In this paper we employ a Bayesian formalism for estimating the underlying signal f based on compressive-sensing measurements g. The proposed framework has the following properties: i) in addition to estimating the underlying signal f, "error bars" are also estimated, these giving a measure of confidence in the inverted signal; ii) using knowledge of the error bars, a principled means is provided for determining when a sufficient number of compressive-sensing measurements have been performed; iii) this setting lends itself naturally to a framework whereby the compressive sensing measurements are optimized adaptively and hence not determined randomly; and iv) the framework accounts for additive noise in the compressive-sensing measurements and provides an estimate of the noise variance. In this paper we present the underlying theory, an associated algorithm, example results, and provide comparisons to other compressive-sensing inversion algorithms in the literature. 相似文献
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调频步进信号是高分辨率雷达中经常采用的一种信号形式。它是线性调频信号和频率步进信号的结合,兼有两者的优点。在实际雷达系统设计中,如果频率步进值能够大于子脉冲带宽,对于以更少的子脉冲数来获得更大的带宽,从而降低目标运动对合成信号质量的影响是非常有帮助的。但此时会出现很高的栅瓣,并导致假目标的出现或者掩盖小的目标。该文利用Super-SVA超分辨方法拓展各子脉冲的频谱从而使合成频谱连续起来,解决了此情况下的栅瓣问题。再利用Super-SVA方法对合成的1维距离像进行处理,则能进一步降低旁瓣。文中给出了计算仿真结果验证了算法的有效性。 相似文献
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为了解决红外光通信存在传输方向单一和消耗功率高问题,设计基于嵌入式技术的超低功耗红外光通信系统,系统单片机使用改进型STM32,将超低功耗红外发射装置嵌入到红外光通信系统中,该装置通过固定载波频率将输入音频信号,通过发送校准模式和音频传输模式调制为高频方波信号后,采用红外光管向外发射信号,并在电路中增加功率负载电流实现限流,降低红外光发射电路功耗。红外接收装置通过共射级放大电路接收信号,采用脉冲宽度调制(PWM)调制信号,实现信号高质量、低功率传输。红外通信模块实现红外发射装置和接收装置间信号的双向传输。系统采用保护驱动模式、中断模式与用户模式的红外通信协议栈,最大程度降低系统通信能耗,提高系统通信效率。实验结果表明:该系统能够实现信号和温度信号的有效传输,在休眠和正常运行时的功耗均较低,误码率低,是一种功率消耗低、通信质量高的红外光通信系统。 相似文献
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可调谐二极管激光吸收光谱在诸多领域有广泛的应用,但因为基线获取的困难,在高压、强干扰条件下的测量存在困难。波长调制光谱的理论显示,一次谐波信号(1f)和二次谐波信号(2f)包含了初始光强和光电探测器增益两个公共项。通过一次谐波信号归一化的二次谐波(2f/1f)信号,消除了信号强度与光强的相关性,可得到吸收光谱的绝对强度及温度等信息。通过测量激光调制参数,结合已知光谱参数可通过数值仿真得到理论的2f/1f 信号。利用数值锁相算法,可以实现频分复用的免标定波长调制光谱测量,实验显示,当恒温池设定温度为600 K、700 K 和800 K 时,光谱测量温度与热电偶测量值偏差小于2%,该方法具有可靠性和更强适应性。 相似文献
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《IEEE transactions on information theory / Professional Technical Group on Information Theory》1986,32(3):410-412
For a complex-valued deterministic signal of finite energy band-limited to the normalized frequency band|w| leq pi explicit coefficients{a_{kn}} are found such that for anyT satisfying0 < T leq 1/2 ,left| f(t)-sum^{2n}_{k=1}a_{kn}f(t - kT)right| leq E_{f}cdot beta^{n} whereE_{f} is the signal energy andbeta doteq 0.6863 . Thus the estimate off(t) in terms of2n past samples taken at a rate equal to or in excess of twice the Nyquist rate converges uniformly at a geometric rate tof(t) on(- infty , infty) . The suboptimal coefficients{a_{kn}} have the desirable property of being pure numbers independent of both the particular band-limited signal and of the selected sampling rate1/T . It is also shown that these same coefficients can be used to estimate the value ofx(t) of a wide-sense stationary random process in terms of past samples. 相似文献