TOA Techniques Research Articles

Effect of Number and Configuration of Participating Stations on Lightning Location outside the Network

The effect of the number and configuration of participating stations on lightning location outside the network is herein studied by evaluating the deviation distance between the reference location and the locations determined by the ToA technique, using recorded data from the location network in Fujian. It was found that the deviation distance decreases with the increase of number of stations, changing from 0.07 to 424.7 km with an average of 35 km for five stations while being 0.03~21.6 km and 2.2 km, respectively, for eight stations. The spatial distribution of those locations outside the network seems to be on a straight line. When the number of stations was five, the station linear configuration led to a narrow and long intersection region, resulting in a large deviation distance. The more dispersed distribution of stations leads to the minimum deviation distance. The percentage of deviation distance less than specific location accuracy (LA) can provide references on network design. 7 stations are sufficient to locate the lightning near and inside the network. 8–9 stations are necessary for an LA of 1 km when the lightning is 200 to 300 km away from the center of the network. The network is not suitable for locating the lightning from each station more than 400 km on average.

Effect of Real Terrain on the Lightning Magnetic Fields and Location Accuracy in Yunnan, China

The effects of real terrain on the lightning magnetic fields and location accuracy are studied by using two-dimensional finite difference time-domain method. Two estimation methods of wave arrival time (using the time corresponding to the peak field and 10% threshold of the peak field) are applied to the arrival time delay, and then using the ToA technique with three approaches of arrival time differences to evaluate the location accuracy. It is found that the effect of real terrain on the lightning magnetic fields is due to the enhancement of reflection wave and propagation attenuation of terrain topography. The arrival time of peak value method is delayed from 0.15 to 2.3 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> s, while that of 10% threshold method varied from −0.11 to 0.92 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> s. The lightning location accuracy using the 10% threshold method is least, about tens of meters. Furthermore, considering the specific frequency bandwidth of detection sensors, three-order 10- to 500 kHz Butterworth filter was applied. After filtering, the effect of real terrain on the lightning magnetic fields becomes more obvious. The 10% threshold method is still the best way for lightning location, and the frequency bandwidth of different sensors on the effect of the location accuracy cannot be ignored.

Analysis of acoustic sensor placement for PD location in power transformer

Partial discharge PD is an abnormal activity that occurs in high-voltage components, such as power cables, switchgear, machines, and power transformers. Such activity needs to be diagnosed for the equipment to last longer as PD could harm the insulation and potentially lead to asset destruction from time to time. Moving one or more externally mounted acoustic sensors to different locations on the transformer tank is commonly used in order to detect and locate PD signal occurring in the power transformer. However, this procedure may lead to less accuracy in PD identification. Therefore, this research paper presents an analysis of acoustic sensor placement based on time of arrival TOA technique for PD location in a power transformer. The detection and location can be determined by permanently installing the acoustic sensor to provide valuable data in an early stage of occurrence for online condition PD monitoring. Several methods are available for the detection of PD signal, whereby one of the best choices is via acoustic emission AE . PD creates an ultrasonic signal used for PD detection. This paper proposes the possible placement of AE sensors to be mounted on the power transformer wall based on ideal and static PD signals. The sensors were placed in order to capture the PD signal without any disturbance signal from inside or outside the tank. The time for the signal for the first approach for each sensor is recorded to estimate the PD location using the TOA technique. A comparison between the least square method LSM and Gauss--Jordan elimination GJE for the TOA technique was analyzed to differentiate the resulting performance. This research utilized three different PD sources to apply the performance analysis on PD locations, while five cases were proposed to represent the five different placements of four sensors for the analysis. This research ultimately suggests that sensors be placed and randomly mounted on the four sides of the transformer tank, with one sensor allocated to one side. Among all five cases, Case 1 and Case 5 yielded a displacement error DE less than others, while between these two cases, Case 5 gave the lowest DE. The findings were recorded based on LSM and GJE methods used to differentiate the resulting performance.

Localization of Compact Circularly Polarized RFID Tag Using ToA Technique

A compact, flexible crossed-dipole circularly polarized antenna using commercially available paper substrate is presented which caters North American frequency band. The crossed-dipoles have meande ...

SKIROC2_CMS an ASIC for testing CMS HGCAL

SKIROC2_CMS is a chip derived from CALICE SKIROC2 that provides 64 channels of low noise charge preamplifiers optimized for 50 pF pin diodes and 10 pC dynamic range. They are followed by high gain and low gain 25 ns shapers, a 13-deep 40 MHz analog memory used as a waveform sampler at 40 MHz. and 12-bit ADCs. A fast shaper followed by discriminator and TDC provide timing information to an accuracy of 50 ps, in order to test TOT and TOA techniques at system level and in test-beam. The chip was sent to fabrication in January 2016 in AMS SiGe 0,35 μm and was received in May. It was tested in the lab during the summer and will be mounted on sensors for beam-tests in the fall.

A statistical approach for site error correction in lightning location networks with DF/TOA technique and its application results

Lightning location network (LLN) with DF/TOA (direction-finder/time-of-arrival) combined technique has been widely used in the world. However, the accuracy of the lightning data from such LLNs has still been restricted by “site error”, especially for those detected only by two DF/TOA sensors. In this paper we practice a statistical approach for evaluation and correction of “site error” for DF/TOA type LLN based on its lightning data. By comparing lightning locations recorded by at least 4 sensors between DF and TOA techniques, the spatial characteristics of “site error” for each sensor in the network can be obtained. The obtained “site error” then can be used to improve the accuracy of lightning locations especially those recorded by only 2 sensors. With this approach, the “site error” patterns for 23 sensors in Yunnan LLN are obtained. The features of these site error patterns are in good consistency with those in literature. Significant differences in lightning locations before and after “site error” corrections indicate that the proposed approach works effectively.

Analytic equivalence of iterated TOA and TDOA techniques under structured measurement characteristics

This paper compares the iterated time-of-arrival and the time-difference-of arrival techniques analytically under the assumption of structured measurement error characteristics. The assumed measurement error characteristics consider different channel qualities and correlations. To compare the two popular localization techniques dealing with different number of states, information preserving matrices are introduced to transform original measurement vectors to modified measurement vectors. After the information preserving transformations, it is proved that the location estimates produced by both techniques are exactly the same under structured measurement error characteristics. A Monte-Carlo simulation result verifies the analysis result.

A robust to multi-path ranging technique over IEEE 802.11 networks

In this paper, we present a two-way TOA technique for distance estimation (i.e., ranging) over IEEE 802.11 networks. It is based on repetitively measuring the Round Trip Time (RTT) of IEEE 802.11 MAC frames and carrying out statistical processing in order to identify the multi-path condition of the channel and to improve accuracy. The study demonstrates that a multi-path condition has a negative impact on the ranging accuracy in Non-Dominant Direct Path (NDDP) and Undetectable Direct Path (UDP) situations. In this paper, an approach is presented to detect and overcome this impact. The proposed approach identifies the channel profile (i.e., the multi-path condition) from the statistical features of a set of RTT measurements and uses a ranging algorithm that is sensitive to multi-path. Results demonstrate the feasibility of channel profile identification in real time and a ranging accuracy of around one meter in all possible multi-path situations.

A 3D node localization scheme for wireless sensor networks

A 3D node localization scheme for WSNs is developed in this paper. In the scheme, a single mobile beacon submits UWB signals to the sensor nodes to help the whole network localize. Each sensor node receives the UWB signals and adopts TOA technique to measure the distances to the mobile beacon. SDI is proposed as the 3D positioning algorithm executed locally on each sensor node, and simulation is provided to compare it with two representative positioning algorithms, Min-max and Lateration, in terms of some evaluation parameters. The analysis in theory and the simulation show that our scheme can be a utilitarian 3D node localization scheme for WSNs.

Synthesis and characterization of copolymers containing biphenylyl rings linked to the main chain through spacers of various lengths

Copolymers between 1-(4-biphenylyloxy carbonyl)ethylene (I), 1-[2-(4-biphenylyloxy)ethyloxy carbonyl]ethylene (II) and 1-[6-(4-biphenylyloxy carbonyl)]ethylene (III) were synthesized by radical polymerization. They were characterized by DSC, TOA, RX and viscosity techniques. The smectic order of poly(I) and the crystalline order of poly(III) depend on the amounts of comonomers incorporated. The obtained data demonstrate that the presence of quantities of comonomers exceeding 10% leads to complete destruction of smectic and crystalline order in poly(I) and poly(III) respectively.