Time Domain Reflectometry Approach Research Articles

The Extraction Methodic for GaN Field Transistor input Gate Capacitance in GHz Band

Authors propose new methodic for GaN field transistor input gate capacitance extraction based high-frequency S-parameters measurement and transmission line theory. Input gate capacitance was determined for GaN device (Lg = 0.25 mkm, W = 160 mkm) using proposed methodic for different operating modes at GHz band. This paper contains the dependences of the input capacitance as function of drain voltage (1.0—20.0 V) at 15.0 GHz for Vgs = —3.0 V. It was pointed that input capacitance is decreasing: 460 fF to 340 fF. This capacitance was measured using time-domain reflectometry approach in the same operating modes. Measured results were compared.

Experimental location of damage in microelectronic solder joints after a board level reliability evaluation

Abstract Reliability evaluation of integrated circuit (IC) packages to assess drop impact is critical, especially in the case of handheld electronic products. The objective of this study is to experimentally identify the location of damage in solder joints in electronic packaging after a board level reliability (BLR) evaluation. The BLR drop test is a useful way to characterize the drop durability of different soldered assemblies onto a printed circuit board (PCB). It is also of great importance when there is a need to evaluate the solder joint between the chip package and PCB through a daisy-chained structure during the evaluation period. However, there is no detailed information available on a pattern ground with a hatched copper PCB layout for high speed responses that are closely related to actual working conditions. In this paper, a fault location on a daisy-chained structure with a pattern ground is shown through a non-destructive analysis using a time-domain reflectometry (TDR) approach. The results obtained in this project indicate that the TDR approach can be used to detect the location of a crack in the string based on changes in the waveform response. The fault location in critical solder balls as predicted by TDR correlate well with experimental observation by cross-section.

Optical fiber fuel level sensor for aeronautical applications

An optical fiber fuel level sensor for aeronautical applications is developed and tested. The sensor is based on an array of total internal reflection point sensors multiplexed on a single fiber by optical couplers and simultaneously interrogated by an Optical Time Domain Reflectometry approach. Unlike conventional sensors based on total internal reflection, the new design permits to be sensitive to common jet fuels (JetA-1, JP4, JP5, JP7), and also to correctly operate when the sensor is partially or totally exposed to condensed water on the sensor surface. The sensor does not require aircraft calibration or temperature compensation.Experimental results show that an accuracy of±1.5mm could be achieved. The sensor is also able to measure the free water level in the fuel tank.

Relaxation dynamics and thermophysical properties of vegetable oils using time-domain reflectometry

Dielectric relaxation studies of vegetable oils are important for insights into their hydrogen bonding and intermolecular dynamics. The dielectric relaxation and thermo physical properties of triglycerides present in some vegetable oils have been measured over the frequency range of 10MHz to 7GHz in the temperature region 25 to 10°C using a time-domain reflectometry approach. The frequency and temperature dependence of dielectric constants and dielectric loss factors were determined for coconut, peanut, soya bean, sunflower, palm, and olive oils. The dielectric permittivity spectra for each of the studied vegetable oils are explained using the Debye model with their complex dielectric permittivity analyzed using the Havriliak-Negami equation. The dielectric parameters static permittivity (ε 0), high-frequency limiting static permittivity (ε ∞), average relaxation time (τ 0), and thermodynamic parameters such as free energy (∆F τ), enthalpy (∆H τ), and entropy of activation (∆S τ) were also measured. Calculation and analysis of these thermodynamic parameters agrees with the determined dielectric parameters, giving insights into the temperature dependence of the molecular dynamics of these systems.

Field measurements of topsoil moisture profiles by vertical TDR probes

A recently developed inverse method for the estimation of water content profiles from single time domain reflectometry (TDR) waveforms in laboratory has been adapted and applied to field measurements of topsoil moisture profiles in a pyroclastic sandy loam. Three metallic probes of the lengths of 30 cm, 45 cm and 60 cm were vertically installed in an experimental field for the measurement of vertical water content profiles. One 15 cm long probe was inserted vertically into soil surface and five 10.5 cm long probes were buried horizontally at various depths for the measurement of local values of mean water content by means of the classical TDR approach. The experimental campaign lasted 28 days, during which daily rainfall heights and daily maximum and minimum temperatures were measured at the experimental field. TDR waveforms acquisition was carried out twice a day. The agreement between local volumetric water content measurements and vertical profiles was in general satisfactory, although some of the vertical profiles failed in detecting a layer with systematically smaller water content values indicated by the horizontal probe buried at the depth of 30 cm below soil surface. Such small water content values could be probably ascribed to the presence of a large amount of pumice stones in the soil around that depth, affecting the water content measured by TDR probes and thus increasing estimated moisture spatial variability.

TDR application for automated water level measurement from Mariotte reservoirs in tension disc infiltrometers

This paper describes the use of an automated method of measuring water level changes in Mariotte-type reservoirs via time domain reflectometry (TDR) and demonstrates its field application for measurements of soil hydraulic properties. The method is based on the assumption that the travel time of a TDR pulse propagating along a transmission line immersed in an air–water medium is the summation of the pulse travel times in the air and water phases. A TDR cable tester generates a pulse that propagates through a three-rod probe traversing the centre of the Mariotte reservoir from top to bottom. The reflection of the pulse is automatically transferred to a computer for waveform analysis with the water level being a simple function of probe length and the air, water, and air–water medium dielectric constants as measured by the cable tester. Water level measurements obtained with the TDR technique showed close agreement with those obtained using visual and pressure transducer procedures. The application of this TDR method as an alternative to more traditional methods was demonstrated in a field experiment using a tension disc infiltrometer. The TDR approach allows for automated water level measurements and is simple, accurate and easy to implement. Moreover, it allows for simultaneous TDR measurements of both water flow and volumetric water content of soil below the infiltrometer disc.

Characterization and modelling of packages by a time-domain reflectometry approach : Luc van Hauwermeirenet al. IEEE Transactions on Components, Hybrids, and Manufacturing Technology, 15(4), 478 (1992)

Characterization and modelling of packages by a time-domain reflectometry approach : Luc van Hauwermeirenet al. IEEE Transactions on Components, Hybrids, and Manufacturing Technology, 15(4), 478 (1992)

Characterization and modeling of packages by a time-domain reflectometry approach

An approach that offers the possibility of characterizing different types of packages is presented. The types that will be discussed are plastic leadless chip carrier (PLLCC), ceramic leadless chip carrier (CLLCC), pin grid array (PGA), and flat pack all of which have a high input-output (I/O) lead count. The characteristics of a signal pin (track inside the package) and the coupling between neighboring pins for different configurations is determined in the time domain by a time-domain reflectometry approach. >