共查询到20条相似文献，搜索用时 593 毫秒
1.
RFID读写器工作在2.4GHz,全球开放的ISM频段,信号干扰比较严重,RFID读写器可能工作在噪声比较大和干扰比较强烈的地方,因此有必要对读写器进行一些抗干扰的措施,以加强RFID系统的可靠性。本文提出了在读写器和电子标签之间采用跳频扩频技术来达到抗干扰的目的。 相似文献
2.
Simple extensions of the polarity–coincidence correlator (PCC) for non-parametric detection of a common random signal in two-input systems are considered. The new detectors are based on conditional tests and are shown to be capable of a better performance than the PCC. For the case of Gaussian noise, substantial improvement in performance over that of the PCC is established. 相似文献
3.
Menelaos Lambiris 《Journal of The Franklin Institute》1983,316(2):175-185
The moments of the stochastic harmonic oscillator are examined, in the presence of linear damping. The procedures we follow are those described in earlier papers for stochastic linear systems and for the undamping case. The noise is approximated from the white noise process and has small but finite correlation time. The first moment is shown to be bounded and tending to zero, as time approaches infinity. The second moment is also shown to be bounded, but only if the damping factor satisfies a proper condition. Results are compared with those found in the case where there is no damping and with those obtained in other works, using different methods. 相似文献
4.
The problem of the estimation of a discrete probability density from independent observations is considered. For a wide class of noises, a method is given for estimating a probability density when the measurements are corrupted by additive noise. This method is shown to be consistent, and several bounds on the error are given. An application to the detection of a (nonparametric) random signal is discussed. Finally, the estimation of a probability density is considered where the measurements are noisy and some of the measurements are incorrect. This situation may arise when a machine collecting the data fails part of the time. 相似文献
5.
如何去除信号中的噪声．得到纯净的信号是信号处理过程中一个热点技术。本研究根据噪声与信号的小波变换模极大值点在多尺度空间上具有不同的特性，对信号进行了噪声消除。试验结果表明，使用傅里叶变换和coif2小波模极大值点法对信号去噪，都能够有效地去除信号中的噪声，且重构后的信号非常逼近原始信号．但coif2小波模极大值点法去噪效果更好。 相似文献
6.
研究了一种扩谱载波数字脉冲间隔调制SSC—DPIM(Spread spectrum carrier digital pulse interval modulation)技术并用于电力线载波扩谱通信系统．采用线性扫频SSC扩谱载波对DPIM符号进行编码，引入脉冲前导码作为传输数据块的同步信号以防止差错传播．介绍了数据传输速率及数据块传送差错率的理论分析结果．并采用单片机实现了SSC-DPIM电力线载波通信系统．实验结果表明，在同样的电力线网络环境下，其通信效果明显优于已有的电力线载波通信系统。 相似文献
7.
《Journal of The Franklin Institute》2018,355(18):9245-9270
This paper deals with noise detection and threshold free on-line denoising procedure for discrete scanning probe microscopy (SPM) surface images using wavelets. In this sense, the proposed denoising procedure works without thresholds for the localisation of noise, as well for the stop criterium of the algorithm. In particular, a proposition which states a constructive structural property of the wavelets tree with respect to a defined seminorm has been proven for a special technical case. Using orthogonal wavelets, it is possible to obtain an efficient localisation of noise and as a consequence a denoising of the measured signal. An on-line denoising algorithm, which is based upon the discrete wavelet transform (DWT), is proposed to detect unavoidable measured noise in the acquired data. With the help of a seminorm the noise of a signal is defined as an incoherent part of a measured signal and it is possible to rearrange the wavelet basis which can illuminate the differences between its coherent and incoherent part. In effect, the procedure looks for the subspaces consisting of wavelet packets characterised either by small or opposing components in the wavelet domain. Taking real measurements the effectiveness of the proposed denoising algorithm is validated and compared with Gaussian FIR- and Median filter. The proposed method was built using the free wavelet toolboxes from the WaveLab 850 library of the Stanford University (USA). 相似文献
8.
Andreas M. Maras 《Journal of The Franklin Institute》2005,342(5):565-581
In this paper, a new approach to non-parametric signal detection with independent noise sampling is presented. The present approach is based on the locally asymptotically optimum (LAO) methodology, which is valid for vanishingly small signals and very large sample sizes, and on semi-parametric statistics. Its unique feature and essential difference from other techniques is that LAO non-parametric detectors are optimum according to the Neyman-Pearson criterion by being asymptotically uniformly most powerful at false alarm level α (AUMP (α)) and adaptive in the sense that no loss in Fisher's information number is incurred when the underlying noise process is no longer parametrically defined. Accordingly, they are robust against deviations from the postulated noise model and, unlike other non-parametric detectors, are distribution-free under both hypotheses H0 (“noise only present”) and H1 (“signal and noise present”). Non-parametric LAO detectors are derived from an asymptotic stochastic expansion of the log-likelihood ratio for coherent and narrowband incoherent “on-off” signals. Moreover, under the present framework it is shown that, in direct contrast to already known results, the non-parametric sign detector is AUMP (α) and adaptive even for non-constant signal samples. 相似文献
9.
Chung-chieh Lee 《Journal of The Franklin Institute》1982,313(5):273-285
The detection of a deterministic signal in additive noise is considered. The log-likelihood ratio is studied for three cases: stationary white noise process, stationary Markov noise process, and noise process with independent increments. Procedures leading to realizable optimum detection schemes and related examples are given. An approximation to the log-likelihood ratio, which leads to the locally optimum detector, is also presented for the white noise case. 相似文献
10.
11.
The case is considered in which, during the operation of an optimal control system, the optimizer, in addition to applying his usual control, may switch structures. Necessary and sufficient conditions are derived and emphasis is placed on the special characteristics of this problem. Continuous and discrete time set-ups are considered and the separation principle is shown not to hold for the linear quadratic case in the presence of noise. 相似文献
12.
The coordinated tracking problem where a group of followers intercepts a dynamic leader is studied. It is shown in this paper that reduction of inter-agent communication is obtained and improved performance is achieved when each follower implements dynamical models of neighbors and by using an event-triggered control strategy that requires each agent to send measurement updates only when necessary. The results in this paper consider directed graphs and the possible existence of cycles. Performance bounds on the tracking error have been obtained, which are functions of the communication topology and the event thresholds. This approach is extended to consider measurement noise and similar bounds are presented for this case. 相似文献
13.
本文把三重相关技术应用于电磁检测中的磁信号分析处理,通过试验研究表明,三重相关技术可以有效地从噪声中恢复磁信号波形,特别是在低信噪比的情况下尤其明显,为电磁检测实际磁信号分析提供一种可供选择的方法。 相似文献
14.
Droplet-based microfluidics has gained extensive research interest as it overcomes several challenges confronted by conventional single-phase microfluidics. The mixing performance inside droplets/slugs is critical in many applications such as advanced material syntheses and in situ kinetic measurements. In order to understand the effects of operating conditions on the mixing performance inside liquid slugs generated by a microfluidic T-junction, we have adopted the volume of fluid method coupled with the species transport model to study and quantify the mixing efficiencies inside slugs. Our simulation results demonstrate that an efficient mixing process is achieved by the intimate collaboration of the twirling effect and the recirculating flow. Only if the reagents are distributed transversely by the twirling effect, the recirculating flow can bring in convection mechanism thus facilitating mixing. By comparing the mixing performance inside slugs at various operating conditions, we find that slug size plays the key role in influencing the mixing performance as it determines the amount of fluid to be distributed by the twirling effect. For the cases where short slugs are generated, the mixing process is governed by the fast convection mechanism because the twirling effect can distribute the fluid to the flow path of the recirculating flow effectively. For cases with long slugs, the mixing process is dominated by the slow diffusion mechanism since the twirling effect is insufficient to distribute the large amount of fluid. In addition, our results show that increasing the operating velocity has limited effects on improving the mixing performance. This study provides the insight of the mixing process and may benefit the design and operations of droplet-based microfluidics. 相似文献
15.
Chien-Hua Lee 《Journal of The Franklin Institute》2005,342(2):161-174
This paper addresses the estimation problem for the steady state and error covariances of continuous systems subjected to additive and multiplicative noise. Several upper and lower matrix bounds of these covariances are developed. Comparing to existing results, these obtained bounds are more general. Furthermore, it is also shown that they are sharper for some case(s). 相似文献
16.
利用导线、电阻和分布电容组成信号衰减电路,模拟采集器现场运行环境下信号衰减变化,对现场有抄收故障的采集器与未使用的新采集器作对比测试,结果表明:信号强、抗干扰的能力大,信息指令在转送过程中丢失少,信号强度与抄见率呈极显着相关。返回的采集器与新采集器的抄见率无明显的区别。线路对信号的衰减不是主要原因,要检测运用场地电能质量、噪音和信号强度等,分析现场的信号故障原因。 相似文献
17.
D. Wulich 《Journal of The Franklin Institute》1984,317(3):135-145
A novel method of noise variance measurement in the presence of strong sine burst interference with unknown parameters is presented. The measurement system is based on the Adaptive Sine Pulse Shortener (ASPS) which shorts each sine pulse from which the interfering burst is composed. After this a conventional noise variance measurement method is applied. A measurement accuracy is satisfactory when the interfering signal is strong and the number of periods of interfering sine-wave in each sine pulse is great. While a practical implementation of the proposed procedure is not simple in hardware, the microprocessor implementation is quite realizable. 相似文献
18.
We present numerical simulations of DNA-chip hybridization, both in the “static” and “dynamical” cases. In the static case, transport of free targets is limited by molecular diffusion; in the dynamical case, an efficient mixing is achieved by chaotic advection, with a periodic protocol using pumps in a rectangular chamber. This protocol has been shown to achieve rapid and homogeneous mixing. We suppose in our model that all free targets are identical; the chip has different spots on which the probes are fixed, also all identical, and complementary to the targets. The reaction model is an infinite sink potential of width dh, i.e., a target is captured as soon as it comes close enough to a probe, at a distance lower than dh. Our results prove that mixing with chaotic advection enables much more rapid hybridization than the static case. We show and explain why the potential width dh does not play an important role in the final results, and we discuss the role of molecular diffusion. We also recover realistic reaction rates in the static case. 相似文献
19.
The problem of designing robust systems for the detection of stochastic signals in noise is considered for the large-sample-size, small-signal case. By applying two previously-established models for the detection of stochastic signals, known results for the robust detection of deterministic signals are extended on a limited basis to the stochastic- signal case. The proposed detectors are seen to be robust over a class of possible noise statistics, based on a Huber-Tukey mixture model, which contains noises characterized by heavy-tailed probability density functions. In addition, numerical results are presented which verify the robustness property of the proposed detectors over wider classes of noise mixtures. 相似文献
20.
Mohamed B. El Mashade 《Journal of The Franklin Institute》2011,348(6):941-972
In this article, we provide a complete detection analysis, in its exact form, of what is known as moderately fluctuating radar targets when the background environment contains a number of interfering targets along with the target under test. The illumination of this class of radar targets by a coherent pulse train, return a train of correlated pulses with a correlation coefficient in the range 0<ρ<1 (intermediate between SWII and SWI models). Since the adaptive detection is one of the desirable features for modern radar receivers, it becomes of importance to adaptively detect this class of targets. The attractive class of adaptive detectors is that based on order-statistics (OS) technique. The more advanced version of the OS algorithm, known as the generalized trimmed-mean (GTM) scheme, is chosen here to carry out this task. It implements trimmed averaging of a weighted ordered range samples. This processor is analyzed for the case where the radar receiver incorporates a postdetection integrator amongst its contents and where the operating environment is multitarget. The primary and the secondary interfering targets are assumed to be fluctuating in accordance with partially correlated χ2 fluctuation model. SWI and SWII well-known models represent the cases where the signal is completely correlated and completely decorrelated, respectively, from pulse to pulse. It is shown that the processor performance improves, for weak SNR of the primary target, as the correlation coefficient ρs increases and this occurs either in the absence or in the presence of spurious targets. For strong SNR, on the other hand, the processor performance degrades as ρs increases and the SWI and SWII models enclose the correlated target case and this behavior is common for all GTM based schemes. 相似文献