共查询到19条相似文献，搜索用时 80 毫秒
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GPS输出的NMEA 0183信号的时间特性分析 总被引：4，自引：3，他引：4
为判断GPS接收机输出的NMEA0183信号是否可作为水下地形测量的同步信号，对多种CPS接收机输出的NMEA0183信号的时间特性进行了测试与分析。 相似文献
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利用GPS导航信号进行水下地形测量的时间同步 总被引：4，自引：1，他引：4
介绍了应用GPS接收机输出的导航信号用于水下地形测量时间同步的原理，并分别讨论了用于模拟测深仪、数字化／模拟测深仪和数字测深仪的同步方法。 相似文献
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本文研究了廉价GPS接收机用于海洋测绘的可行性,分析并改进了伪距平滑的方法,对Navsymm接收机的测试结果表明,98％的时间里可达到3m的差分定位精度,可以应用于小比例尺的海底地形测量、管线测量等。 相似文献
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GPS测波技术分析与初步实验研究 总被引：1，自引：0，他引：1
测波浮标是一种方便可行的波浪测量方法,首先分析了单点GPS接收机测波浮标的测量原理,然后做了单点GPS接收机测速实验和单点GPS接收机模拟测波实验,并对这两个实验的数据进行了分析处理,最后提出了单点GPS接收机测波浮标的初步设计方案,为进一步推动这项测波技术的国产化打下了基础。 相似文献
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This is the last of a series of three papers studying the theory of passive systems. The model assumes that i) the narrow-band signals are transmitted through a Rayleigh channel, ii) the observing array is geometrically linear, and iii) the source motion is deterministic. Ranging techniques based on synchronized measurements of the travel time delay are precluded by the incoherent phase model considered. The paper explores alternative methods that process the phase modulations induced on the signal by the extended geometry and relative dynamics. The present work applies maximum likelihood theory to design the receiver, being concerned with the global identifiability of all parameters defining the relative source/receiver geometry and dynamics. The emphasis is placed on the passive range global acquisition. In contradistinction with the previous papers, where the time stationarity (Part I) or the space homogeneity (Part II) lead to a one-dimensional processor, here the receiver involves processing over both domains. The paper considers the issues of space/time factorability and coupling arising in nonhomogeneous passive tracking. The cross coupling, resulting in more complex filters, improves the receiver acquisition capability. Resorting to Taylor's series type studies, the paper quantifies these improvements, as well as the receiver's mean square error performance, in terms of intuitively satisfying analytical expressions. 相似文献
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A. G. Luchinin 《Izvestiya Atmospheric and Oceanic Physics》2010,46(4):492-498
We have studied the influence of a roughed sea surface and the dispersion of photons over pathlengths on the time characteristics
of a pulsed oceanologic airborne lidar. We have derived equations describing the first two temporal moments of a return signal
for two types of lidar (a lidar with an isotropic receiver directional pattern and a lidar with an extremely narrow receiver
pattern). It is shown that the delay of the return signal and its effective width depend substantially on both the characteristics
of the lidar itself and on the parameters of the sea-surface roughness and inherent optical properties. 相似文献
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Effective communication and echolocation depends strongly upon the coherence of the channel through which the signal is propagated. Under certain conditions, the average coherence or equivalently, the spreading of a random channel may be described by a scattering function (SF). This represents a second order (energy) measure of the average delay, Doppler, and more generally, the spatial (azimuthal) spread that the signal experiences. The SF is analogous to the point spread function (PSF) discussed in the image processing literature and likewise describes the amount of “blurring” imposed upon the signal or scene transmitted. The SF will be briefly reviewed and its measurement by both direct (high resolution channel probing) and indirect (deconvolution) methods will be discussed. A new direct method using specially designed waveform pairs and a twin or uncertainty product (UP) receiver structure is introduced. Unlike high resolution matched filter implementations for direct probing that are limited by the fixed volume constraint of ambiguity functions, the UP receiver produces vanishing sidelobes and hence more nearly approximates a desirable two-dimensional delta characteristic. The improvement gained in SF measurement is illustrated by the results of an experiment in which the UP receiver and traditional matched filter implementations were used to directly probe an ocean multipath channel 相似文献
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The life duration of underwater cooperative network has been the hot topic in recent years. And the problem of node energy consuming is the key technology to maintain the energy balance among all nodes. To ensure energy efficiency of some special nodes and obtain a longer lifetime of the underwater cooperative network, this paper focuses on adopting precoding strategy to preprocess the signal at the transmitter and simplify the receiver structure. Meanwhile, it takes into account the presence of Doppler shifts and long feedback transmission delay in an underwater acoustic communication system. Precoding technique is applied based on channel prediction to realize energy saving and improve system performance. Different precoding methods are compared. Simulated results and experimental results show that the proposed scheme has a better performance, and it can provide a simple receiver and realize energy saving for some special nodes in a cooperative communication. 相似文献
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Two adaptive algorithms for multipath time delay estimation 总被引：1，自引：0，他引：1
The problem of time delay estimation (TDE) with multipath transmissions arises often in many sonar and radar systems. Two adaptive algorithms based on a parameter estimation approach are proposed to estimate the difference in arrival times of a signal at two separated sensors in the presence of multipath propagation. The first method uses an adaptive IIR filter to eliminate the multipath signal in each transmission channel prior to applying a constrained delay estimation algorithm to extract the time difference between the two received outputs. The second employs two constrained adaptive FIR filters to perform equalization of the multipath arrivals, and time delay is then derived using a constrained delay estimator similar to that in the first method. Computer simulations are presented to compare and contrast the tracing capability and convergence behavior of these multipath TDE methods 相似文献
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An underwater acoustic local area network (ALAN) provides multipoint-to-point telemetry between many high-rate, ocean-bottom sensors and a central, surface-deployed receiver in the 10-30 kHz vertical acoustical channel. Ocean-bottom modems initiate the transmission process by requesting data channel time slots via a common narrow-band request channel. Request packets overlap in time and frequency in this channel, and the throughput and average transmission delay rely heavily on the successful resolution of the request packet collisions. This paper presents the design, analysis, and experimental demonstration of a request channel receiver capable of resolving collisions between several asynchronous and cochannel packets. The receiver algorithm differs from standard capture schemes (by demodulating the data from both strong and weak transmitters), conventional spread-spectrum receivers (by overcoming the near-far problem), and existing multiple-access demodulation techniques (by adapting to the number of interfering signals, and the unknown phase, Doppler, amplitude, and timing of each signal in the collision). The receiver demodulates the collided packets by decision-directed techniques through a novel method of estimating the interference for each user which minimizes error propagation due to inaccurate tentative decisions. An inwater experiment illustrates that this technique is extremely desirable for collision resolution in underwater acoustic local area networks, and also for underwater autonomous vehicles with both sidescan sonar as well as acoustic telemetry links 相似文献
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In active sonar and in passive sonar localization, time delay is a fundamental parameter whose extraction is vital to the sonar function. The underlying time delay parameter (or parameter vector) contains information about the acoustic source (or reflector) as seen through the ocean at a receiver. The ocean effects require sonar adaptation. A tutorial review of ocean effects in time delay estimation is provided, with references to benchmark work. It covers coherence, time-delay estimation, localization, time-varying time delay estimation, the complexity of the ocean environment, and depth estimation using mode matching 相似文献
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This paper comprehensively investigates the properties of self phase modulation based optical delay systems consisting of dispersion compensation fibre and highly nonlinear fibres. It researches into the impacts of power level launched into highly nonlinear fibres, conversion wavelength, dispersion slope, modulation format and optical filter bandwidth on the overall performance of optical delay systems. The results reveal that, if the power launched into highly nonlinear fibres is fixed, the time delay generally varies linearly with the conversion wavelength, but jumps intermittently at some conversion wavelengths. However, the time delay varies semi-periodically with the power launched into highly nonlinear fibres. The dispersion slope of highly nonlinear fibres has significant influence on the time delay, especially for the negative dispersion slope. The time delay differs with modulation formats due to the different combined interaction of nonlinearity and dispersion in fibres. The bandwidth of the optical filters also greatly affects the time delay because it determines the bandwidth of the passed signal in the self phase modulation based time delay systems. The output signal quality of the overall time delay systems depends on the conversion wavelength and input power level. The optimisation of the power level and conversion wavelength to provide the best output signal quality is made at the end of this paper. 相似文献