Propagation Of Broadband Signals Research Articles

A recognition algorithm for NLOS-anchors in wireless location applications

In recent years, China's technological level has undergone rapid development, and technologies such as wireless local area networks and wireless sensor networks have also undergone rapid development in this situation. Under the influence of developed networks, many high-tech items are applied in our daily lives, such as intelligent transportation, remote control and monitoring, intelligent household appliances, and so on. In this environment, internet technology is rapidly developing and widely applied in various fields, making huge contributions to positioning technology and monitoring technology. The demand for high-precision, low-cost, strong applicability, and simple operation scientific technology in various industries is constantly increasing. Ultra wideband technology has played a significant role in the field of indoor positioning due to its unique advantages. However, in complex environments, the propagation of broadband signals is easily affected by obstacles, which weakens the signal received and seriously affects indoor positioning accuracy. As people gradually move into cities, the increase in population has caused increasingly serious traffic congestion. In order to solve the positioning problem of urban people, positioning industries that serve people have gradually emerged in the public's career, which has led to an increasing demand for accurate positioning. The complex environment of cities and the complex environment where people live can have a serious impact on positioning technology, leading to continuous deterioration of positioning accuracy. Non-Line of Sight (NLOS) is an important factor affecting positioning accuracy. So, this article conducts a thorough study on wireless local area networks and wireless sensor networks, fully improving the development of wireless positioning, and conducting a thorough study on the algorithm of NLOS- anchor.

Measured acoustic intensity fluctuations on the Chukchi continental shelf during Canada Basin Acoustic Propagation Experiment 2017

One of the main objectives of the Shallow Water (SW) CANAPE experiment was to gain a thorough understanding of a yearlong propagation of broadband signals from deep to shallow water with simultaneous oceanographic and acoustic measurements together along the and across the shelf break region. Using more than eleven acoustic arrays and seven oceanographic moorings in a 30 km2 region on the Chukchi shelf this task is being done by assessing both deep water sound signatures and shallow water source transmissions. In this paper with present analysis of acoustic signals from both shallow and deep water sources on the Chukchi continental shelf for a specific time period between June and August 2017 where a 20 dB intensity drop from along-the-shelf source (S2) at 150 m water depth was observed for more than few weeks. This intensity drop is strongly correlated with occurrence of a large oceanographic event spanning the top 150 m water column due to Pacific Water outflow from Bering sea and retreat of Marginal Ice Zone (MIZ). During the same period, cross-the-shelf source (S1) was not transmitting signal but the reception from the deep water acoustic transmitters also show variability that could be correlated with the basin scale water column variability and the ice coverage. [Work supported by ONR.]

Propagation of broad-band signals in shallow water in the presence of horizontal stratification

Horizontal stratification in shelf zone of the ocean is provided by existence of coastal wedge, temperature fronts, nonlinear internal waves, slopes, and canyons, where typical scales are up to tenths of kilometer in range and up to tenths minutes in time, for some perturbations spatial scales are essentially different in different directions in horizontal plane. In this case, there is remarkable horizontal refraction in sound propagation and frequency dependence of horizontal ray trajectories. It means that Fourier components of wideband signal propagate along different paths joining source and receiver in the horizontal plane. Distribution of spectral components in horizontal plane has crescent-like shape and restricted by rays, corresponding to boundary frequencies in spectrum. Propagating wide-band signal has additional spectral distortion as a result of different phase shift for spectral components, propagating along different paths. Also there is difference in directions of wave vectors for difference spectral components (tangents to horizontal rays), leading to phenomena similar to spatial dispersion: different directions of phase and group velocities, compression and decompression of pulses, additional time delay of signal, etc. Mentioned phenomena are considered for models of coastal wedge and temperature fronts. Analytical estimations are presented, as well as results of numerical modeling.

Horizontal refraction of sound in a shallow water and its experimental observations

Basic results of theoretical and experimental studies of acoustic effects caused by horizontal refraction in a shallow water are reviewed with special emphasis on the effect produced by intense internal waves on the propagation of broadband signals. Theoretical calculations and experimental data testifying to the manifestation of three-dimensional acoustic effects in the SWARM’95 experiment are presented.

Propagation of Broad-Band Signals in a Random Medium

The propagation of a monochromatic wave in a medium containing random inhomogeneities is generally described in terms of amplitude and phase fluctuations. Is is shown in this paper that the method can be extended to broadband waves by considering the correlation of the fluctuations between elementary frequency bands. The relation between the correlation function of the fluctuations in the frequency domain and the waveform distortion of a broad-band signal is established. The method is applied to a medium where the fluctuations in refractive index are small and have a Gaussian correlation function in space. Waveform distortion of short pulses propagating in such a medium is studied.