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One of the most common applications of time-domain reflectometry (TDR) is the localization of dielectric permittivity variations (DPVs) along cable systems. However, signal attenuation and dispersion phenomena limit the usability of TDR when used on long cable systems. Some TDR measuring instruments offer the possibility of modifying the amplitude and the width of the TDR test pulse signal, along with the gain of the input stage amplifier. Increasing these parameters generally allows to investigate longer distances; nevertheless, increasing the gain may saturate the instrument analog to digital converter (ADC) and increasing the pulse width leads to worse spatial resolution. For this reason, it is customary for the operator to repeat TDR measurements several times, with different settings, and proceed by focusing each time on a different TDR reflectogram; however, this procedure is time-consuming and, eventually, it does not guarantee optimal performance. Starting from these considerations, in this work, a new measurement algorithm for facilitating and making more effective the TDR-based localization of large DPVs on long cable systems is proposed. The algorithm automatically acquires several TDR reflectograms obtained by setting different values of the gain of the input stage amplifier and the values of the pulse width of the test signal. The reflectograms are then automatically processed, in an effort to balance the short-distance resolution and long-distance gain in a single composite reflectogram (CR), which can be conveniently used also by non-skilled operators. The developed algorithm was implemented and validated through experiments on a practical case study to localize DPVs on a 300 m-long cable system.

Most sensing networks rely on punctual/local sensors, thus lacking the ability to spatially resolve the quantity-To-be-monitored (e.g., a temperature profile, a humidity profile, etc.) without relying on the deployment of numerous inline sensors. At the state of the art, most quasi-distributed or distributed sensing technologies rely on the use of optical fiber systems; however, these are generally expensive and this limits their large-scale adoption. On the other hand, recently, elongated sensing elements have been successfully used with time-domain reflectometry (TDR) for implementing diffused monitoring solutions. The advantage of TDR is that this is a relatively low-cost technology, with adequate measurement accuracy and the potential to be customized to suit the specific needs of different application contexts of the 4.0 Era. Starting from these considerations, this paper addresses the design, implementation and experimental validation of a novel generation of elongated sensing element networks (SENs) that can be permanently installed in the systems to be monitored and used for obtaining the diffused profile of the quantity-To-be-monitored. In particular, as case studies, three applications are considered: monitoring irrigation process in agriculture (SEN-A, agriculture); leak detection in underground pipes (SEN-W, water); and monitoring of building structures (SEN-B, building).

In this paper, a time domain reflectometry (TDR)-based system for measuring water content of raw construction materials is presented. The proposed system relies on the fact that the presence of water leads to an increase of the dielectric permittivity of materials; therefore, from TDR-based permittivity measurements, it is possible to infer the water content value. In practical applications, the proposed system could be used for assessing the intrinsic water content of construction materials before they are poured into the concrete mixture. Knowing the intrinsic water content of the raw materials, in fact, would allow to evaluate the optimal amount of water that should be added to the mixture in order to achieve the desired waterto- cement ratio. This, in turn, would permit to fine-tune and control the mechanical properties of the final concrete structures. For assessing the feasibility of using the proposed system for the intended purpose, water content measurements were carried out on three construction materials, namely, sand, gray cement, and white portland cement. For each of these materials, a calibration curve relating water content to the apparent dielectric permittivity was derived; additionally, through repeated measurements, also a confidence interval was associated with the calibration curves.

The authors have recently developed a time-domain reflectometry (TDR)-based leak-localisation system which, being based on an electromagnetic technique, overcomes the well-known downsides (sensitivity to environmental noise, to pipe material and geometry etc.) of traditional, electro-acoustic leak-localisation techniques. Starting from the positive results obtained so far, in this work, the authors investigate the possibility of implementing an integrated TDR/ground penetrating radar (TDR/GPR) approach. The TDR would allow the preliminary leak localisation, while the GPR technique would be used to have a countercheck for possible false positives. Also, GPR would allow to assess the quantity of the leaked water (thus scheduling a priority order for repair) and to obtain a three-dimensional view of the subsurface soil around the pipes, so as to assess their health status. In this work, the combined TDR/GPR approach is tested on a pipe section in the presence of two leaks. In addition to this, in this study, also a different configuration of the TDR sensing element (SE) is experimented. As described in what follows, this new SE configuration is expected to expedite considerably the implementation and the use of the TDR-based leak detection system.

It is known that bi-wires can be employed as passive distributed sensing elements (SEs), to accurately locate water infiltrations in soil, concrete materials, and so on, using the standard time-domain reflectometry instrumentation and proper signal processing. This paper examines the possibility of using the same kind of SEs with simpler techniques and cheaper hardware, in order to trigger an alert in the case of water infiltrations. Two techniques are examined: the first measures the SE capacitance, and the second measures the time-of-flight of electromagnetic waves in the SE. The performance of the techniques is comparatively evaluated, in terms of sensitivity to the presence of water and the influence of temperature variations. The capacitance-based technique is found to be more sensitive to the presence of water, but also more prone to the influence of temperature, as long as the temperature variations are of modest entity (below 10 °C). For higher temperature variations, the capacimetric method appears to be advantageous. The results of this paper are useful to practically implement the monitoring of water leaks in a large set of buried pipes, water infiltrations in a large concrete structure, and so on.

In this paper, the most recent advances in the time-domain reflectometry (TDR)-based system for leak-localization in underground pipes are described in detail. More specifically, a new design of sensing element and the use of a new connection modality are proposed. Thanks to these new features, the practical implementation of the system becomes much quicker and its use more effective. Additionally, the present work also describes all the practical aspects and technical details (from installation to functional tests), related to the practical implementation of the system. Finally, to assess the possibility of further increasing the cost-effectiveness of the TDR-based leak localization system, experimental tests were carried out by comparatively using two TDR instruments, differing in specifications and costs, to identify the position of a leak.

In this work, a time domain reflectometry (TDR)-based system for measuring water content of construction materials is presented. The proposed system relies on the fact that the presence of water leads to an increase of the effective dielectric permittivity of materials (being the relative dielectric permittivity of construction materials in the order of 3–7, and that of water approximately 78). Therefore, through TDR measurements of the apparent permittivity of the material, it is possible to obtain calibration curves that allow retrieving the water content. Starting from these considerations, in this paper, the results related to moisture content measurements of three construction materials (namely, plaster mortar, portland cement and pozzolan cement) are reported. The advantage of the proposed system is that it can allow to monitor in real time the water content of construction materials inline, so as to assess their quality throughout the production process.

In this work, the validation and the practical implementation of a methodology exploiting a time domain reflectometry (TDR)-system for monitoring rising damp in building structures are described in detail. The proposed system employs wire-like, passive, diffused sensing elements (SEs) that are embedded, at the time of construction or renovation, inside the walls of the building to be monitored. The SEs remain permanently inside the wall, ready to be interrogated when necessary. Experimental and simulation results are reported, which demonstrate the possibility of practical implementation and the associated performance in terms of sensitivity.

In this work, the performance of three time domain reflectometry (TDR) instruments (with different hardware architectures, specifications and costs) is comparatively assessed. The goal is to evaluate the performance of low-cost TDR instrumentation, in view of the development of a completely permanent TDR-based monitoring solution, wherein the costs of the instrument is so low, that it can be left on-site, even unguarded, and controlled remotely. Without losing generality, the applications considered for the comparative experiments are the TDR-based detection of leaks in underground pipes and, more in general, of soil water content variations. For this reason, both laboratory and in-the-field experiments are carried out by comparatively using three TDR instruments, in conjunction with wire-like sensing elements (SEs).

In this work, time domain reflectometry (TDR) is used in conjunction with an innovative type of low-cost, wirelike diffused sensor for diffused soil water content monitoring in agriculture. Thanks to its wire-like configuration, these passive, maintenance-free sensors can be rolled out and buried along the perimeter/path to be monitored (for example, along a row of plants/trees). A single sensor can be long up to 150 meters, and several sensors can be simultaneously installed in a large area, thus creating a diffused sensor network which can be controlled through a single measurement instrument. To assess the practical feasibility of the proposed TDR-based system, a practical experiment was carried out by employing a bifilar, wire-like sensing element (SE) for monitoring soil water content in a watermelon cultivation. For comparative purposes, also in view of continuous remote monitoring, measurements were carried out through three TDR instruments with different specifications and costs.

Olive oil production represents a big part of the Mediterranean economy, and as such it must be protected from frauds. For this reason, it is necessary to develop alternative low-cost techniques, applicable on large scale, for checking the quality of the product and for detecting adulteration. On such bases, the present work deals with the possibility of adopting microwave reflectometry for obtaining a 'spectral signature' of vegetable oils. For this purpose, time domain reflectometry (TDR) measurements, in combination with specific data processing, are first used for the dielectric characterization of several oil types. Successively, the acquired data are processed through the principal component analysis (for identifying clusters of oil types that exhibit common features) and through the partial least square analysis (for identifying a predictive model for detecting oil adulteration). Results confirm that the proposed procedure holds considerable potential for quality and anti-adulteration control purposes, especially in view of practical applications. © 2012 Elsevier Ltd. All rights reserved.

The monitoring of moisture levels and the investigation of the dielectric properties of materials are tasks that can be suitably performed through Time Domain Reflectometry (TDR) techniques. In particular, moisture monitoring of granular agro-foods is a major interest for several industrial applications. Despite the extensive literature regarding the use of TDR technology, the state of the art is lacking in a rigorous metrological characterization of the results achieved, especially for the agro-foods area. To fill this gap, in this paper the Authors carry out a comparative analysis between moisture content measurements obtained through two different TDR instruments on various granular materials. First, the major error contributions affecting the overall performance of the TDR-based method are discussed; in particular, the error contributions that are intrinsic in the method are discriminated from those related to the specific experimental conditions. Successively, systematic errors effects are minimized through a preliminary calibration procedure of the experimental set-up. Finally, results are compared and analyzed through a statistical approach, providing both an assessment of the repeatability of measurements and a rigorous metrological characterization. This ultimately leads to a performance characterization, particularly useful for practical industrial applications. © 2008 Elsevier Ltd. All rights reserved.

In this work, an accuracy analysis of the estimation of the time of flight (ToF) for time domain reflectometry (TDR) signals is carried out. For this purpose, three different criteria (referred to as ‘maximum derivative’, ‘zero derivative’, and ‘tangents crossing’) were comparatively applied for the evaluation of the ToF of a TDR signal propagating along a set of RG-58 coaxial cables (with different known length and with known electric parameters). Successively, as a further experimental test, the same criteria were applied on bi-wire cables with unknown electric parameters. Results show that, among the tested criteria, the ‘zero derivative’ criterion provided the best accuracy in the estimation of the ToF.

In this paper, a performance analysis, in terms of accuracy, linearity, and repeatability, of three criteria to estimate the time of flight in time-domain reflectometry (TDR) signals is carried out. In a first set of experiments, the three criteria [referred to as maximum derivative (MD), zero derivative, and tangent crossing (TC)] are applied to TDR signals propagating along a set of coaxial cables, with different known lengths and known electrical parameters. In a second set of experiments, the same criteria are applied to biwire cables in air, with different known lengths and unknown electrical parameters. Finally, in the last set of experiments, the criteria are applied in a more complex situation, i.e., on a biwire used as a sensing element for water-level measurement. The results show that, among the tested criteria, TC appears to provide a very good performance in terms of systematic errors and superior performance in terms of repeatability. The popular MD criterion appears to be more prone to random errors due to noise and TDR artifacts. The results of this paper are relevant to many practical applications of TDR, ranging from fault location in cables to media interface sensing.

In this paper, a time-domain reflectometry (TDR) based system for monitoring liquid level inside tanks is presented. The proposed system resorts to a flexible, two-wire probe, which can be attached to the walls of containers and adapted to their shape. The proposed system is particularly useful for industrial applications; in fact, after a preliminary calibration, it can measure automatically and in real time the level of liquids inside containers (even tens of meters tall). The proposed system was tested on metallic and on nonmetallic containers. In the latter case, as the probe is positioned on the outside wall of the container, a totally noninvasive monitoring of liquids is achieved. The obtained results show that the system has considerable potential for being easily and effectively employed in practical, industrial applications. Finally, simulations were carried out, thus providing useful information for optimizing the system performance and for predicting its limitations.

This work aims at assessing the practical applicability of an innovative time domain reflectometry (TDR)-based system for leak localization in underground pipes. For this purpose, two laboratory experiments were carried out. The first experiment (E1) allowed assessing the reliability of the TDR system in presence of two simultaneous leakage-like conditions. The second experiment (E2), which was also carried out in presence of two leaks, allowed assessing the possible effect of the type of soil on the performance of the leak-detection system. Results show that, differently from traditional leak detection methods, the TDR-based system can correctly localize the presence of two simultaneous, closely-spaced leaks and that the type of soil has very little influence on the performance of the system. Finally, in this work, the practical implementation of the system in urban areas is also addressed, thus highlighting the steps to maximize the effectiveness of the system. © 2013 Elsevier Ltd. All rights reserved.

In this work, three different techniques, namely time domain reflectometry (TDR), ground penetrating radar (GPR) and electrical resistivity tomography (ERT) were experimentally tested for water leak detection in underground pipes. Each technique was employed in three experimental conditions (one laboratory or two field experiments), thus covering a limited but significant set of possible practical scenarios. Results show that each of these techniques may represent a useful alternative/addition to the others. Starting from considerations on the obtained experimental results, a thorough analysis on the advantages and drawbacks of the possible adoption of these techniques for leak detection in underground pipes is provided. © 2013 Elsevier Ltd.

In the present work, an alternative probe configuration to be used for time domain reflectometry (TDR)-based monitoring of liquid level inside tanks is presented. The proposed probe, which resorts to a bifilar transmission line configuration, is flexible and adaptable to the surface of the containers to be monitored. This feature, along with the other advantageous characteristics of TDR, makes this probe configuration particularly attractive for industrial applications. In this paper, to test the applicability of the method, two different scenarios are considered: monitoring of liquids contained in metallic tanks and non-invasive monitoring of liquids in non-metallic tanks. Results show that, in both cases, the proposed system has considerable potential for being easily and effectively employed in practical, industrial applications.

In this paper, different customized systems for microwave permittivity measurements on liquid samples, based on reflectometric measurements, are presented and analyzed. Their performance is compared against the one deriving from the most widely adopted commercial measurement setup. The systems are designed with the aim of providing less expensive solutions without compromising measurement accuracy. The purpose of the first proposed solution is to replace the commercial measurement software exploiting a reformulation of the classical theory. Based on this alternative formulation, a 'homemade' probe is built by properly modifying an N-type coaxial connector, thus providing a system requiring a lower quantity of liquid under test. Moreover, a different experimental approach which uses time-domain reflectometry (TDR) instrumentation is presented. Such solution is by far the least expensive, as it allows avoiding the use of costly instrumentation (such as a vector network analyzer). In order to metrologically characterize the proposed solutions, a series of repeated measurements is performed on a set of well-referenced liquids. After extracting the Cole-Cole parameters through each of the considered measurement methods, the resulting type A uncertainty is evaluated. Finally, comparison with literature data allows the estimation of measurement bias. The analysis evidences that custom solutions generally exhibit an accuracy comparable to the one of the commercial solution, with a slight degradation of performance for the TDR-based setup, which, however, compensates for this drawback with its appealing low cost. © 1963-2012 IEEE.

In this paper, a time domain reflectometry (TOR)based system for the non-invasive localization of leaks in underground pipes is described and experimentally validated. The proposed system simply relies on TOR measurements performed on a two-wire cable (biwire) that is rolled out on the underground pipe at the time of installation of the pipe (but made accessible from the road surface through an inspection well); the biwire on the pipe acts as a permanent, distributed sensing element and can be connected to the TOR instrument whenever it is necessary to perform a check. Two of the major advantages of the proposed system are that it can be employed with pipes made of any material and that it strongly reduces the inspection time typically required by traditional leak detection methods. To validate the system and to assess its performance, a new pipe was installed and a leak condition was intentionally provoked at a reference position. The TOR system was then used to evaluate the position of the leak as if had been unknown. The results of this experimental test are reported and thoroughly discussed.

In this paper, a time domain reflectometry (TDR)-based solution for detecting water leaks in underground pipes is described and experimentally validated. The proposed method strongly reduces the inspection time that is typically required by traditional leak detection methods. In fact, it can successfully inspect pipes that are hundreds of meters long. In this work, two different configurations of the system are described: one can be used for detecting leaks in 'already-installed' metal pipes; whereas the other is suitable to be employed for detecting leaks in 'newly-installed' pipes made of any material. The performance of both these system configurations was assessed through an extensive, on-site experimental campaign, carried out with the collaboration of one of the largest European water operators, Acquedotto Pugliese S.p.A. (AQP). Representative results, related to both configurations, of three experimental cases (ECs) are reported and commented on. Finally, some practical considerations on the applicability of the system are provided. © IWA Publishing 2013.

Antenna characterization measurements are traditionally performed in the frequency domain (FD) through vector network analyzers (VNAs) in anechoic chambers. Nevertheless, the expensiveness of these facilities limits the possibility of using this approach for routine measurements. In this chapter, the strategies for the accurate evaluation of the reflection scattering parameter (S 11(f)) of antennas, starting from simple time domain reflectometry (TDR) measurements, are described. As a matter of fact, not only are instruments operating in time domain (TD) usually less expensive than VNAs; but they allow performing time windowing, which is the key for excluding the unwanted spurious reflection from the environment, thus avoiding the use of anechoic chamber. © 2011 Springer-Verlag Berlin Heidelberg.

In this chapter, the basic approaches of broadband microwave reflectometry are described in detail. More specifically, time domain reflectometry (TDR) and frequency domain reflectometry (FDR) are presented and the involved instrumentation is fully described. Successively, the FDR/TDR combined approach is described in detail: this approach can help exploit the benefits of both TDR and FDR, without necessarily employing two different measurement setups. Additionally, since the sensing element (or probe) plays a major role in all the aforementioned approaches, a comprehensive description of its design and of the corresponding performance is given. Finally, the basic principles leading to the possibilities of enhancing accuracy in BMR measurements are presented. © 2011 Springer-Verlag Berlin Heidelberg.

Accurate measurement of the static electrical conductivity provides a great insight into the characteristics and quality status of various materials. To overcome some limitations of the traditional measurement methods, there has been a growing interest toward the investigation of enhanced techniques for measuring electrical conductivity. In this regard, time-domain reflectometry (TDR) has attracted considerable attention, also due to the possibility of simultaneously monitoring different physical parameters. Although initially introduced for monitoring soil properties, the application of the TDR-based technique might be an interesting and cost-effective means in many other fields. However, the accuracy of traditional TDR-based electrical conductivity measurements is strongly influenced by the preliminary calibration technique. On such basis, in this paper, two innovative approaches for a more straightforward and accurate evaluation of the electrical conductivity are presented. The first method relies on the combination of the TDR measurement with transmission-line modeling (TLM); the second method simply relies on a couple of independent capacitance measurements (ICMs) performed through an LCR meter. As a further goal, the metrological performance of this last method is compared with that of the traditional method, thus validating its applicability. Experimental results and related uncertainty analysis on various samples demonstrate that the proposed alternative method is definitely suitable for a simpler and accurate estimation of the static electrical conductivity, also when dealing with moistened soils. © 2006 IEEE.

Time-domain reflectometry (TDR) techniques have become increasingly attractive for soil moisture evaluation thanks to their adaptability, low cost, and measurement accuracy. Many different TDR-based approaches are currently available for deriving moisture content: empirical calibration curve, empirical dielectric models, frequency-dependent dielectric mixing models, etc. Generally, TDR soil moisture measurements resort to multiple-rod probes, which provide good adhesion to the soil and ease of insertion. However, the typical configuration of such probes does not allow performing a short-open-load (SOL) calibration procedure, which is definitely necessary for retrieving accurate dielectric characterization from TDR waveforms. To overcome the impracticability of the traditional SOL calibration, in this paper, an innovative triple-short calibration (TSC) procedure for commercially available three-rod probes is proposed. First, the robustness of the TSC procedure is validated on well-referenced liquids, demonstrating that its application to TDR measurements leads to a substantial enhancement of the final accuracy in the evaluation of the frequency-dependent reflection coefficient. Successively, the TSC procedure is applied to TDR measurements performed on moistened sand samples. In particular, it is demonstrated that the proposed TSC method, applied to traditional TDR measurements in combination with a dielectric mixing model, leads to an accurate and effective moisture evaluation procedure. This goal is reached through an efficient optimization algorithm that minimizes the difference between experimental and theoretical reflection coefficients. Results show that the proposed strategy is a suitable candidate for low-cost, highly accurate, and easy-to-perform moisture content estimation of soils. © 2010 IEEE.

Monitoring soil moisture is a major interest for several practical applications. This task can be suitably performed through various methods; however, at the state of the art, there is not a single method that successfully combines ease of use, low cost, customization, possibility of measuring large volumes, and, most importantly, measurement accuracy. In this regard, seismic wave propagation (SWP)-based methods, which rely on the evaluation of the propagation velocity of a seismic wave vc through the soil sample under investigation, hold considerable potential for practical implementation. On such bases, in this work, first the authors propose an enhanced version of a previously developed SWP-based system for soil moisture measurement. Successively, to provide an exhaustive performance characterization of the system, a specific comparative methodology, based on reference time-domain reflectometry (TDR)-based measurements, is addressed. More specifically, SWP- and TDR-based measurements are simultaneously performed on river sand for increasing levels of water content. The TDR-measured moisture levels are taken as reference values and are used to infer the theoretical propagation velocity values vc,REF. Then, these reference values are suitably compared with those directly measured through the SWP-based system (vc,REF), thus allowing a consistent metrological assessment. The ultimate goal of this work is to validate and characterize the performance of the proposed SWP-based system in view of practical implementation for soil moisture evaluation. © 2006 IEEE.

Time domain reflectometry (TDR) is a robust approach for measuring static electrical conductivity of moistened granular materials. Although initially introduced for monitoring soil salinity, its application to granular materials might be an interesting and cost-effective means for monitoring the quality-status of various materials. However, the traditional approach requires tedious and time-consuming preliminary calibration measurements on reference liquids. In this paper, an innovative approach for the direct estimation of the electrical conductivity is presented. In fact, it is demonstrated that the suitable combination of the TDR measurement with a transmission-line modeling of the measurement setup, successfully leads to the avoidance of the preliminary calibration procedure. Investigations carried out on water and on moistened sand samples demonstrate that the performance of the proposed method in estimating the static conductivity is comparable with that achievable through the traditional approach. © 2009 IEEE.

Antenna-characterization measurements are traditionally performed in the frequency domain (FD) through a vector network analyzer (VNA) in an anechoic chamber. Nevertheless, the high cost of the required setup strongly limits the possibility of using this approach. Starting from these considerations, a time-domain (TD)-based approach for characterizing antennas without using an anechoic chamber is assessed. As a matter of fact, instruments operating in TD are usually less expensive than VNAs; nevertheless, with appropriate data processing, they provide as much information. Particularly, it is demonstrated that the selection of an optimal time windowing is the main factor that guarantees a high accuracy level in the corresponding FD. The proposed approach leads to the accurate evaluation of the reflection scattering parameter S 11 (f) from time-domain reflectometry (TDR) data. The experimental validation is tested on a commercial radio-frequency identification (RFID) reader antenna, and the results are compared with reference VNA measurements performed in an anechoic chamber. The ultimate goal of this paper is to demonstrate that, through calibrated TDR measurements, along with an optimal time windowing, an accurate antenna characterization can be achieved. © 2008 IEEE.

Monitoring soil moisture is a major interest for several practical applications, and this task can be suitably performed through various methods. Although extensive literature deals with the adoptions of standard systems (many of which are commercially available), the state of the art is lacking in a rigorous validation of specific systems, such as those based on the seismic wave propagation (SWP) method. Such methods have attracted a growing interest thanks to the simultaneous combination of reliability, ease of use, low cost and, most importantly, customization possibility. In this regard, in this paper the Authors propose an experimental comparative approach for fully validating a SWP-based system through reference time domain reflectometry (TDR) measurements. To this purpose, reference TDR measurements are performed for different moisture levels, and the corresponding reference propagation velocities are compared with those directly measured through the SWP-based system. This approach provides a comprehensive assessment of the SWP-based method, from both an experimental and a metrological point of view. The ultimate goal is to provide an exhaustive performance characterization of the system, in view of practical implementation for soil moisture evaluation. © 2009 IEEE.

Several techniques for measuring the moisture levels of materials, particularly in the soil science area, are available. Nevertheless, the state of the art is rather lacking in moisture-sensing methods that are both inexpensive and noninvasive. The time-domain reflectometry (TDR)-based method, despite being a well-established low-cost technique for sensing moisture content, is intrinsically invasive due to the configuration of the probes that are commonly used. These considerations motivated the authors to investigate the adoption of simple inexpensive microstrip antennas as sensing elements for TDR-based moisture content measurements. For this purpose, the water content of the monitored material is sensed through the changes in the reflection scattering parameter S 11 (f) of the antenna. In particular, the change in the resonant frequency of the antenna, which is evaluated through an appropriate processing of the TDR waveforms, is correlated with the water content of the material under investigation. The ultimate goal is to assess a sensing method that can be implemented for inexpensive real-time noninvasive monitoring applications. © 2009 IEEE.

Different approaches and techniques are commonly available for the continuous monitoring of moisture levels and dielectric properties of materials; typically, related applications, are largely used in soil science area. Nevertheless, the state of the art is actually rather lacking in specific sensing methods that combine the low cost and the non-invasive approach of the involved instrumentation. To fill this gap, in this paper the authors study the feasibility of the adoption of the time-domain reflectometry analysis for such purposes, using a patch antenna as sensing element. This way, the extrapolation of the scattering parameters is suitably correlated to the water content levels of the materials under test. Furthermore, the adopted methodology is assessed through full-wave simulations, thus corroborating the experimental measurements. ©2008 IEEE.

Traditionally, antenna characterization measurements are performed in the frequency-domain through a Vector Network Analyzer (VNA) in anechoic chamber. Nevertheless, the expensiveness of this set-up prevents itfrom becoming widespread in laboratories. On such bases, in this paper a time-domain-based approach is comparatively investigated; such a method virtually makes the anechoic chamber unnecessary, thus dramatically reducing the related costs. The proposed approach, based on the evaluation of the scattering parameter (S 11) from Time Domain Reflectometry (TDR) data, has been tested for the characterization of a commercial Radio Frequency Identification (RFID) reader antenna. Data acquired in the time-domain are processed in the frequency-domain through a dedicated algorithm, thus allowing the S11 extrapolation. Furthermore, results are compared to VNA measurements performed in an anechoic chamber. In order to assess the investigated method, from a metrological point of view, the root mean square error between the results is reported as a figure of merit. This way, it is demonstrated that calibrated time-domain measurements represent an alternative, inexpensive and accurate method for characterizing antennas. © 2008 IEEE.

A time domain reflectometry (TDR)-based system for the localization of water leaks has been recently developed by the authors. This system, which employs wire-like sensing elements to be installed along the underground pipes, has proven immune to the limitations that affect the traditional, acoustic leak-detection systems.Starting from the positive results obtained thus far, in this work, an improvement of this TDR-based system is proposed. More specifically, the possibility of employing a low-cost, water-absorbing sponge to be placed around the sensing element for enhancing the accuracy in the localization of the leak is addressed.To this purpose, laboratory experiments were carried out mimicking a water leakage condition, and two sensing elements (one embedded in a sponge and one without sponge) were comparatively used to identify the position of the leak through TDR measurements. Results showed that, thanks to the water retention capability of the sponge (which maintains the leaked water more localized), the sensing element embedded in the sponge leads to a higher accuracy in the evaluation of the position of the leak. Keywords: Leak localization, TDR, Time domain reflectometry, Water leaks, Underground water pipes