High Resolution In Time Domain Research Articles

A UWB-Based Indoor Positioning System Employing Neural Networks

Because of its high time-domain resolution, ultra-wideband (UWB) technology is capable of precise range measurement and has been applied in many accurate indoor positioning systems. This paper presents a practical indoor positioning and navigation system using the UWB modules we developed based on Decawave UWB chipset. In order to enhance the performance of the system in NLOS scenarios, a neural network approach is integrated. The feasibility of the combined approach is analysed and its accuracy is evaluated. The experiment results indicate that the neural network can maintain a stable accuracy no matter whether it is in an NLOS scenario and it is capable to identify the locations on two trajectories which are next to each other with very high confidence.

A UWB-Based Sensor-to-Time Transmitter for RF-Powered Sensing Applications

An ultrawideband (UWB)-based sensor-to-time transmitter consisting of a remote control ( $RC$ ) time-constant interface and an ultralow-power pulse generator is presented. The sensing information is directly extracted and transmitted in the time domain, exploiting UWB pulses with a high time-domain resolution. This approach eliminates the need for an analog-to-digital converter and baseband blocks of sensor tags; meanwhile, it reduces the number of bits to be transmitted for energy saving. The sensor interface measures the discharging time of the $RC$ time constant proportional to the sensor variation. The UWB pulses are triggered with intervals of the $RC$ discharging time, without any digitizing or modulations. The circuit prototype is implemented in the standard 0.18- $\mu\mbox{m}$ CMOS process. Resistance measurement results show that the proposed system exhibits an effective number of resolution bits (ENOB) of 7.7 bits with an average relative error of 0.42% in the range of 200–1500 $\Omega$ . The overall energy consumption of conversion and transmission per sample is measured to be 0.58 nJ with a 1.27-Vp-p pulse amplitude, which is favorable to radio-frequency-powered wireless sensing applications.

K-space use for MRI intra-voxel analysis: advantage in neuroimaging

Analyzing signals inside MRI K-space with the use of compressed sensing algorithms we want to separate, inside single voxel, the different kind of tissues eventually present inside it. The use of compressed sensing is well known in many other fields for image analysis (i.e. remote sensing) related to separation of random intra-voxel contributes so is specifically suitable also in MRI acquisitions having them same kind of characteristics. So using it for clustering single contributions inside a single voxel can be a big step forward in MRI imaging. Using Spin-Echo sequences we find that different materials evidence the different response in terms of TE signaling so to compose the 100% inside the examinated single voxel. Analyzing relaxation time due to spin-spin interaction of considered materials we can put in evidence the different nature of signals sources therefore also the different tissues composing the single voxel. While with the above described use of compressed sensing k-space analysis our goal is to improve the spatial resolution obtained with the actual MRI imaging techniques we can reach another target considering the intrinsic characteristics of compressed sensing k-space processing. We can insulate single contributions coming from random signal analysis in not completely defined k-spaces (under-sampled) so we can moreover use these algorithms for faster than actual time acquisition imaging. In this way we obtain an improved temporal resolution compared with same time acquisition as actual. This kind of advantage can be immediately used for such sampling as fMRI where an high temporal resolution is suitable for image analysis where an high time domain resolution shows clear advantages when is maintained an affordable spatial domain one getting affordable acquisition times. Having such possibility to separate different intra-voxel contributes, something in some way similar to what is done with MRS techniques, but with much less complications and with not so high fields involved, permits to give an important contribution to understanding and reading MRI results expanding the possibility related to their use.

Fast changes of the solar irradiance

The results of special measurements of solar irradiance with high resolution in time domain are compared with results of traditional measurements. Three possible characteristic parameters are studied to describe the dynamic quality of the recorded dataset: standard deviation, frequency density distribution law of increments and the number of fronts of the solar radiation per time unit. Recording traditionally one-minute average values of the solar irradiance, most of the changes cannot be registered in the condition of clouds cumulus humilis.

Partial discharge current pulses in SF6 and the effect of superposition of their radiometric measurement

The practical advantages of employing non-contact radio frequency (RF) methods for detecting partial discharges (PDs) in high voltage equipment have led to significant effort being focused on the diagnosis of electrical plants using RF techniques. This has particularly been the case for gas insulated substations, which use sulphur hexafluoride (SF6) as an insulating medium. One of the most important challenges facing RF diagnostics is the problem of relating the RF emissions to some measure of severity of the PD. Previous work has established that the amplitude or energy of RF signals radiated from a PD source is strongly dependent on the rate of change of current in the PD pulse. In this paper, measurements of PD current pulses in SF6 are presented for a point-plane configuration using an extremely wide bandwidth (13 GHz) measurement system. By this means, PD pulse shapes have been recorded with better resolution than has previously been possible and rise times have been measured with a high degree of accuracy. The results show a considerable variation in pulse shape, with the minimum rise time measured being 35 ps. With this high time-domain resolution, we have been able to distinguish features within the PD pulses that will affect the energy of the radiated RF signal. In particular, the current pulses tend to occur in bursts of up to ten individual pulses in as little as 1 ns, which will excite multiple RF signals in rapid succession. The effect of superposition of RF waveforms has been investigated by studying the variation in detected RF energy with respect to the time delay between PD pulses. It was found that when two PDs occur within a short period (< 150 ns) the combined energy of the resulting RF pulse has the potential to vary by ±30% of that resulting from two equivalent PD pulses with a wider pulse spacing (≫ 150 ns). In terms of a practical monitoring system concerned with order-of-magnitude variations; this is not considered to pose a major problem for the RF technique.

Asymptotically linear velocity analysis with high resolution in time domain

A new method of velocity analysis based on the joint use of a linear velocity analysis technique and a nonlinear penalty function is described. The penalty function is defined as a monotonic continuous function of the signal‐to‐noise ratio estimate, tending to a constant or to zero with this estimate converging respectively to infinity or to zero. The signal‐to‐noise ratio estimate is obtained as the ratio of the estimates of the energy of the signal with given velocity and the energy of the residual field. The resulting velocity analysis technique is characterized by higher noise suppression and higher resolution in the velocity and the time domain compared to the semblance based velocity analysis or the velocity analysis based on the slant stacking of input data.

Prospect of Ultrafast Electronics Using Integrated Optics.

One of the intrinsic advantages of optical information technology is the high resolution in time domain, leading to the potential of high density information transmission and processing. Especially using integrated optical technology it should be possible to implement ultarafast optoelectronic circuits by integrated circuit fabrication procedure, In this review, based on the recent progress in integrated optics, some comments will be given on the easibility of integrated optics for ultarafast electronic circuits.