MHz Antenna Research Articles

Ground-Penetrating Radar for Studies of Peatlands in Permafrost

Abstract —Ground-penetrating radar (GPR) profiling is applicable to study peatlands and swampy areas in permafrost but have some limitations in summer time. Theoretical calculations and field experiments show that estimating attenuation of electromagnetic waves is required for planning GPR survey. GPR data acquired with a 300 MHz antenna fail to resolve reflections from below the permafrost if the thaw/permafrost boundary is deeper than 1.5 m and the attenuation coefficient is 0.7, as in water-saturated peat. GPR data allow high-resolution lithological division of permafrost and provide reliable constraints on the depths to interfaces and physical properties of the ground. Thus, GPR can fully or partly substitute for the time- and labor-consuming direct measurements. The inferences have been confirmed by field results.

GPR Study of a Thrust-Fault in an Active Limestone Quarry (SW Slovenia)

After conducting a successful GPR pilot study in a tectonically complex area of the Karst Thrust Edge, a follow-up study was carried out. In the pilot study, the geometry and spatial extent of the Socerb thrust-fault, which separates limestone above from flysch below, were investigated using a 50 MHz antenna in the Črnotiče quarry. After one part of the quarry was deepened and widened, new flysch outcrops were exposed and GPR profiling was made possible in areas where the thrust contact could not be reached before. By comparing the first GPR results with the locations of new flysch outcrops, we found it reached the surface almost exactly where we had predicted. In order to gain new information about the location of the thrust contact, nine new profiles were recorded. In this newly deepened area, the thrust contact runs close to the surface, therefore a 250 MHz antenna was used in addition to the 50 MHz antenna in order to ensure an adequate level of resolution. This combination of antennas provided the depth penetration of 34 m as well as resolution high enough to obtain accurate information from the shallowest parts. GPR profiles were used to create a 3D model of the thrust-fault plane, providing information about the spatial position and lateral undulations of the thrust contact. The results provided new data about the geometry of the Socerb thrust-fault and correlated well with existing borehole data. The results also showed the importance of using appropriate antenna frequencies as other features capable of becoming hazardous during excavation (air-filled and sediment-filled karst caves) could otherwise be misinterpreted or overlooked. The follow-up research not only provides new data important for understanding the tectonic setting of the area, but also information needed for calculating exploitable material quantities and for planning safe excavation processes.

Investigating the peat deposits of the Great Vasyugan Mire margin using ground-penetrating radar

The objectives of this study are to discuss some algorithms for the interpretation of GPR data in conditions of wetlands, estimate the peat layer thickness, and assess the surface transformation due to peat accumulation in the Great Vasyugan Mire. The study area is located in the southeastern part of the West Siberian plain (Middle Ob River watershed) and consists of typical Western Siberia pine-shrub-sphagnum, pine-shrub sedge-sphagnum ombrotrophic mires and swamp forest with birch, aspen, Siberian cedar, and spruce. Four separate georadar complexes corresponding to snow, fibric peat, hemic and sapric peat, and mineral subsoil were revealed with a 250 MHz antenna. An isolated area of peatland in depression within the swamp forest is identified. At the same time, a distribution of peat accumulation processes outside the original depressions was observed. The study has shown surface leveling where the surface slope decreases from 5 to 0.1 % in the process of peat accumulation within the border of the swamp and mire. An inversion of the surface slopes is observed in areas corresponding to intensive accumulation of sphagnum peat within the pine-shrub-sphagnum bog.

Delineation of Agricultural Drainage Pipe Patterns Using Ground Penetrating Radar Integrated with a Real-Time Kinematic Global Navigation Satellite System

Better methods are needed for mapping agricultural drainage pipe systems. Prior research on small test plots indicates that ground penetrating radar (GPR) is oftentimes capable of detecting buried drainage pipes; however, the feasibility of employing this geophysical technique in larger field areas has not been adequately evaluated. Ground penetrating radar integrated with a Real-Time Kinematic (RTK) Global Navigation Satellite System (GNSS) may be an effective and efficient means of mapping drain lines within agricultural fields. Therefore, GPR-RTK/GNSS was tested in three agricultural settings; with Site 1 and Site 2 located in Beltsville, MD, USA and Site 3 near Columbus, OH, USA. Soils at the three sites ranged from silty clay loam to loamy sand. A GPR unit with 250 MHz antennas was used to detect drainage pipes, and at Sites 1 and 2, a physical GNSS base station was utilized, while a virtual base station was employed at Site 3. The GPR-RTK/GNSS configurations used in this study delineated a complex rectangular drainage pipe system at Site 1, with one set of drainage pipes oriented southwest-northeast and a second oriented southeast-northwest. At Site 2, a herringbone drain line pattern was outlined, and at Site 3, random drain lines were found. When integrated with RTK/GNSS, spiral or serpentine GPR transects (or spiral/serpentine segments of a GPR transects) were utilized to provide insight on drain line directional trends. Consequently, given suitable field conditions, GPR integrated with RTK/GNSS can be a valuable tool for farmers and drainage contractors needing to map subsurface drainage systems.

Erosional features identification along a recently prograding coastal barrier by ground penetrating radar facies analysis: Paradeep, Odisha, India

Coastal barrier dynamics is a complicated system which mainly involves shoreline changes due to accretion and erosion of the coast. Erosional activity in the coastal area of Paradeep, Odisha is risking the lives of the people and the community/factory infrastructures of this major port city, adjoining to the Bay of Bengal. So, understanding of the complex barrier dynamics is more important in this study area. The purpose of this study was to identify several erosional features within sedimentary beddings by Ground Penetrating Radar (GPR) survey and to understand the processes involved in this microtidal barrier from obtained GPR facies/radar facies. GPR reflection survey, with 200 MHz antenna, along (17 profiles) and across (21 profiles) the barrier was done to delineate shapes and sizes of the sedimentary features, erosional surfaces, channels, scour-and-fill structures, progradational beddings and internal geometry of the beach ridge deposits. GPR facies analyses of the beach ridge have established the longshore drift of sediments from nearby river mouths e.g. Mahanadi and Devi river mouths. This interpretation technique has also characterized the palaeo-tidal channels of the study area into two types – (a) larger channels which are perpendicular to the shoreline having channel width of about 400 m with maximum depth of 3.4 m from the surface and (b) smaller channels (width up to 60 m) flow parallel to the shoreline. Here, seaward-dipping beach progradational facies is positioned within oblique erosional surfaces below the facies boundary. This describes the cyclicity of erosion and accretion activity at Paradeep coastal barrier.

Ground Penetrating Radar digital imaging and modeling of microbialites from the Salitre Formation, Northeast Brazil

Thanks to the discovery of new giant oil fields in the South Hemisphere in the last decades, named Pre-salt, there has been a considerable interest in the geometrical and sedimentological characterization of microbial deposits, coquinas, and collapsed caves, which represent a considerable part of these reservoirs. It is known that exposures analogous to oil reservoirs are an important source of information at the sub-seismic scale, as this information is helpful in parametrizing and modeling reservoirs, especially microbial reservoirs. This scenario is more favorable when the Ground Penetrating Radar (GPR) method is used in analogous exposures located in arid regions with scarce or no soil, such as the Fazenda Arrecife, in the Chapada Diamantina (Salitre Formation), Northeastern Brazil. Although rarely mentioned in the literature on microbialite geophysical imaging, GPR has been used in microbial deposits associated with the Neoproterozoic storm deposits of the Salitre Formation. The results of 3D imaging of a microbial colony, using the 200 MHz antenna, with both conventional processing and processing using geophysical attributes, are presented in this study. The conventional processing produced a 3D digital model that allowed the geometrical characterization and parametrization of the imaged microbial colony. The use of four geophysical attributes yielded good results, establishing the contact between the microbial colony and tempestite deposits, and determining the internal geometry of microbial deposits. The processing with “instantaneous amplitude” and “Hilbert trace with energy” highlighted the contact between the microbialite colony (low amplitude) and tempestite deposits (high amplitude), whereas the processing with the “energy” attribute provided a better visualization of the internal lamination of columnar microbialites, result similar to that obtained in the processing with “Hilbert trace with similarity”. GPR obtained images of up to 10 m in depth, with excellent resolution for microbial deposits and tempestites associated with them. The processing using geophysical attributes achieved considerably better results when compared to conventional processing, allowing a better visualization of the internal and external geometry of the imaged colony.

Ground‐penetrating radar and electrical resistivity tomography studies in the biblical Pisidian Antioch city, southwest Anatolia

AbstractPisidian Antioch was founded as a military base in the Hellenistic period around 300 bc. A consecutive archaeological structure, extending 55 m long, mainly includes two adjacent abscissas and a wall remain thought to be a watchtower. An integrated geophysical survey including ground‐penetrating radar (GPR) and electrical resistivity tomography (ERT) techniques was conducted to determine the existence of counterparts of this structure in a small‐scale area. GPR scans acquired via zigzag mode using 500 MHz antenna along 45 parallel lines were evaluated by a series of basic data processing steps. Considering the results obtained, two‐dimensional (2D) ERT data collected in a restricted area using Wenner‐alpha array along 41 parallel lines were inverted using 2D and three‐dimensional (3D) tomographic inversion schemes. On the basis of the findings obtained from various GPR and ERT imaging techniques, the existence of one of the abscissa, displaying dimensional parameters being in good accordance with those of ones still standing on the west side of the survey area was clearly revealed. Moreover, some regular anomalies, which can be attributed to the remains of the watchtower in question and various wall ruins, were successfully traced from the GPR depth slices. The existence of an antisymmetric geometry for the consecutive archaeological structure under investigation was also determined in the survey area. Combining all of that information, a possible 3D virtual image of the military headquarters was then created, and this pointed out a small square quadriburgia characteristic of the structure investigated. Thus, we can conclude that the integration of GPR and ERT and imaging techniques used in the evaluation were quite effective to provide useful prior information for the subterranean targets in the non‐excavated parts of the ancient city. An archaeological evaluation by trial trenching is therefore required to confirm the results of the archaeo‐geophysical survey in the investigation area.

Double-frequency ground penetrating radar for measurement of ice thickness and water depth in rivers and canals: Development, verification and application

In situ measurement of the ice thickness and water depth distributions in a river, canal, or lake is one of the most important means of measuring and responding to an ice flood. In view of the shortcomings of the use of single-frequency ground penetrating radar (GPR) for simultaneous measurement of ice thickness and water depth, a double-frequency GPR with 100 and 1500 MHz antennas was developed in the present study. To avoid interference between the two antennas with different frequencies, there is a 15-ms time-sharing operation. Similarity analysis of neighboring GPR signals was used to obtain the accuracy value of two-way travel time. The proposed GPR system also enables the real-time determination of the longitude and latitude coordinates of the measurement site using a real-time kinematic (RTK) system. The system measured the ice thickness and water depth at 97 and 99 sites, respectively, in the Mohe section of the Heilongjiang River, and the Togtoh, Inner Mongolia section of the Yellow River; both in China. Comparison of the measurements to those obtained by traditional drill-hole methods, yielded a mean value of absolute errors of 0.12 m and 0.04 m for water depth and ice thickness, respectively. The system was further used to measure the distribution of the ice thickness and water depth over a distance of 0.5 km in the Longdao Wharf section of the Heilongjiang River, and over a distance of 67 km in the Mohe section of the river,between the entrance of the Luogu River and Beiji village. The measurement results indicate that the developed double-frequency GPR is suitable for in situ measurement of ice thickness and water depth in rivers during ice periods.

Factors influencing the reliability of grounded and floating ice distinguishing based on ground penetrating radar reflection amplitude

Existing grounded ice or floating ice in late winter represents the distinct thermal state of the lake bottom, which regulates the evolution processes of thermokarst lakes. The aim of this study was to identify either grounded ice or floating ice using ground penetrating radar (GPR) and analyze the factors that influence identification. Densely spaced GPR measurements were collected using a pair of 900 MHz antennas in a thermokarst lake on the northeast Qinghai–Tibet Plateau. Numerical simulations were used to evaluate the factors that influence the accuracy and reliability of the GPR detection. Results show that the ice thickness was less than 1.0 m and indicated a spatial difference on the lake. The normalized amplitudes of reflected waves (NAR) were used for discriminating the grounded ice and floating ice. The floating ice was identified by high NAR (higher than 0.3), and the grounded ice was discriminated by low NAR (lower than 0.2). Numerical simulations showed that the sandwiched thin water and frozen sediment layer beneath the lake ice can smooth the amplitude contrasts between the grounded ice and floating ice. The air/water bubbles in ice and undulating ice bottom interfaces scatter the reflection amplitudes significantly. The factors that influence the GPR reflection amplitudes apart from the permittivity contrasts, can lead to notable uncertainties in identifying grounded and floating ice based on NAR.

SEA ICE THICKNESS MEASUREMENT BY GROUND PENETRATING RADAR FOR GROUND TRUTH OF MICROWAVE REMOTE SENSING DATA

Abstract. Observation of sea ice thickness is one of key issues to understand regional effect of global warming. One of approaches to monitor sea ice in large area is microwave remote sensing data analysis. However, ground truth must be necessary to discuss the effectivity of this kind of approach. The conventional method to acquire ground truth of ice thickness is drilling ice layer and directly measuring the thickness by a ruler. However, this method is destructive, time-consuming and limited spatial resolution. Although there are several methods to acquire ice thickness in non-destructive way, ground penetrating radar (GPR) can be effective solution because it can discriminate snow-ice and ice-sea water interface. In this paper, we carried out GPR measurement in Lake Saroma for relatively large area (200 m by 300 m, approximately) aiming to obtain grand truth for remote sensing data. GPR survey was conducted at 5 locations in the area. The direct measurement was also conducted simultaneously in order to calibrate GPR data for thickness estimation and to validate the result. Although GPR Bscan image obtained from 600MHz contains the reflection which may come from a structure under snow, the origin of the reflection is not obvious. Therefore, further analysis and interpretation of the GPR image, such as numerical simulation, additional signal processing and use of 200 MHz antenna, are required to move on thickness estimation.

Underwater archaeological investigation using ground penetrating radar: A case analysis of Shanglinhu Yue Kiln sites (China)

In this study we explored the possibility and effectiveness of applying ground penetrating radar (GPR) to investigate underwater cultural relics. Using this innovative technique, the remains of Yue kiln and anomalous objects buried beneath the lake or suspended in the water can now be fully studied. Although GPR has been widely used for imaging archaeological sites, skepticism remains over its use in underwater archaeology. Nevertheless, some scholars suggest that it is possible to use GPR to detect underwater remains, which has been further confirmed by the use of electrical parameter measurement (EPM) in Shanglinhu Lake. An experiment was performed by our team using antennas of different frequencies in a particular area of the lake. The results showed that the penetrability of the 100 MHz antenna was enough to examine the targets, while the 400 MHz antenna performed well in shallow water (depth <4 m) due to higher resolution. Hence, for our underwater investigation, we used both antennas for maximum coverage. We used a radargram as a topographic map which shows cross sections of the lake. Analysis of the Shanglinhu Lake data indicated that GPR is a superior tool for underwater archaeological investigation. Traditional methods including sonar, underwater cameras and salvage dives were used as supporting techniques in the study.

Application of Ground Penetrating Radar Supported by Mineralogical-Geochemical Methods for Mapping Unroofed Cave Sediments

Ground penetrating radar (GPR) using a special unshielded 50 MHz Rough Terrain Antenna (RTA) in combination with a shielded 250 MHz antenna was used to study the capability of this geophysical method for detecting cave sediments. Allochthonous cave sediments found in the study area of Lanski vrh (W Slovenia) are now exposed on the karst surface in the so-called “unroofed caves” due to a general lowering of the surface (denudation of carbonate rocks) and can provide valuable evidence of the karst development. In the first phase, GPR profiles were measured at three test locations, where cave sediments are clearly evident on the surface and appear with flowstone. It turned out that cave sediments are clearly visible on GPR radargrams as areas of strong signal attenuation. Based on this finding, GPR profiling was used in several other places where direct indicators of unroofed caves or other indicators for speleogenesis are not present due to strong surface reshaping. The influence of various field conditions, especially water content, on GPR measurements was also analysed by comparing radargrams measured in various field conditions. Further mineralogical-geochemical analyses were conducted to better understand the factors that influence the attenuation in the area of cave sediments. Samples of cave sediments and soils on carbonate rocks (rendzina) were taken for X-ray diffraction (XRD) and X-ray fluorescence (XRF) analyses to compare the mineral and geochemical compositions of both sediments. Results show that cave sediments contain higher amounts of clay minerals and iron/aluminium oxides/hydroxides which, in addition to the thickness of cave sediments, can play an important role in the depth of penetration. Differences in the mineral composition also lead to water retention in cave sediments even through dry periods which additionally contribute to increased attenuation with respect to surrounding soils. The GPR method has proven to be reliable for locating areas of cave sediments at the surface and to determine their spatial extent, which is very important in delineating the geometry of unroofed cave systems. GPR thus proved to be a very valuable method in supporting geological and geomorphological mapping for a more comprehensive recognition of unroofed cave systems. These are important for understanding karstification and speleogenetic processes that influenced the formation of former underground caves and can help us reconstruct the direction of former underground water flows.

Characterization of the Capibaribe River Dry Bed with Ground Penetrating Radar (GPR)

ABSTRACT For an adequate hydrogeological study of alluvial layers in the semi-arid zone, it is important to know well its geometry and its hydraulics characteristics. Alluvial formations are generally constituted by erosion, transport and sedimentation processes, causing considerable heterogeneity in soil hydraulic parameters and water flow. The present research had as objective to perform a geophysical characterization using the Ground Penetrating Radar – GPR in the dry bed of the Capibaribe river. To the extent that depositional layers exhibit changes in water content, granularity, sediment type and layer orientation, the water table as well as sedimentary structures and lithological contacts tend to be identified, making the method effective for hydrogeology research. The study area comprises alluvial dry river bed of upper Capibaribe river in the municipality of Santa Cruz do Capibaribe. The results showed that GPR was efficient in the imaging of the subsurface contributing to the knowledge of the geometry and the stratigraphy of the aquifer of the dry bed of the river. In the dry bed of the river, with 400 MHz antenna the signal reached a depth of 2.65 m, and with the antenna of 200 MHz, the signal reached a depth of 6.00 m. The capillary fringe was identified at a depth of 3.0m with the use of 200MHz and 400MHz antennas.

Subsurface Investigation using 2D Resistivity and Ground Penetrating Radar at Teluk Kumbar, Penang

The objective of this study is to determine the structure and condition of the subsurface by using 2D resistivity and Ground Penetrating Radar (GPR) methods. The study was conducted at SK Sungai Batu, Teluk Kumbar, Penang Island. For 2D resistivity method, Wenner-Schlumberger array was used while for GPR, 250 MHz antenna was used at the site. The survey consists of 200m length survey line. GPR result shows that there is high intensity of EM. 2D resistivity result shows that the low resistivity region (200 Ωm to 340 Ωm) appears to be at the centre of the survey line from depth 7 m to 13 m. Meanwhile, the higher resistivity region (4000 Ωm to 6000 Ωm) may indicate the bedrock structure of the subsurface, which is the granitic rock. This region is bedrock which rested at depth 14 m and below. In conclusion, data obtained from GPR and 2D resistivity methods can be easily correlated to determine the features of the subsurface.

Introduction of a Ground Penetrating Radar System for Subsurface Investigation in Balik Pulau, Penang Island

Ground penetrating radar (GPR) are non-invasive geophysical techniques that enhance studies of the shallow subsurface. The purposes of this work are to study the subsurface composition of Balik Pulau area in Penang Island and to identify shallow subsurface geology features. Data acquisition for GPR is by using 250 MHz antenna to cover 200m survey line at Jalan Tun Sardon, Balik Pulau. GPR survey was divided into ten sections at 20 m each. Results from GPR shows that there is low EM reflection along the first 40 m of the survey line. Intense EM reflections were recorded along the distance 40 m to 100 m. Less noticeable radar reflections recorded along 100 m to 200 m distance of the survey line. As a conclusion, clear signal of radar wave reflection indicates dry region of the subsurface. Meanwhile, low signal of radar wave reflection indicates highly weathered granitic soil or clay of the subsurface.

Microwave ablation of ex vivo human undifferentiated pleomorphic sarcoma

Background: Many undifferentiated pleomorphic sarcoma (UPS) patients had lost the opportunity of surgical therapy. Microwave (MW) ablation of UPS can be an effective method for achieving local tumor control while preserving the relative function. We report for the first time the size of the ablation zone and temperature distribution of MW ablation on ex vivo human UPS specimens. Methods: Twenty UPS patients’ specimens were recruited into present experimental study (11 men, 9 women, average age 52±14.7 years). A commercial 2,450 MHz MW ablation apparatus was used throughout this experiment. MW ablations were performed immediately after resection of tissue specimens by using powers of 40, 60, 80 and 100 W for 10 min, and each power setting was performed in five specimens. Coagulation shape, lesion size, and temperature distributions were recorded. Histological examination was performed to assess the pathological changes of the ablation issue. Results: All coagulation geometries were ellipsoidal under the four power settings (40, 60, 80 and 100 W for 10 min) with a ratio of short-axis/long-axis range from 0.80 to 0.88. The short-axis diameters of the coagulation at 40, 60, 80 and 100 W groups were 28.2±1.1, 35.6±1.3, 40.6±1.6, and 46.4±1.7 mm, respectively; and the corresponding long-axis were 33.4±1.5, 41.4±1.7, 47.6±1.8, and 54.2±2.1 mm, respectively. Overall, temperatures at 3 points of distance 10, 20, and 30 mm from antenna increased along with ablation time. Routine histological analysis using haematoxylin-eosin (H&E) showed tissue fixation within the ablation area. Conclusions: The present ex vivo experiment showed that MW ablation by single 2,450 MHz antennae could generate an ellipsoidal coagulation geometry and large ablation zone, which increases with increasing power and time. This initial study provides experimental evidence for clinical MW ablation of UPS.

Applying of High-Resolution Geophysical Techniques for Drainage Investigations at El-Basateen Cemetery Area, Cairo, Egypt

Due to the collapse of some cemetery in Basateen area, South of Cairo, this paper presents the application of geoelectrical resistivity sounding and imaging, as well as ground penetrating radar techniques for outlining the reasons and the presence of draining water and groundwater at the investigated area. A Vertical Electrical Sounding (VES) survey was performed at 3 points through the studied site to investigate the vertical extent of the subsurface sequence and the saturation levels. A total of 9 Dipole-Dipole imaging profiles were surveyed to determine the lateral distribution of saturation of drain water and infiltrated groundwater, and a total of 6 GPR profiles with 100- and 200- MHz antennae were surveyed to evaluate and determine the depth and the degree of saturation of the subsurface layer/s. The qualitative and quantitative interpretation of the acquired VES's and dipole-dipole imaging profiles showing easily the levels of saturations at the studied site. From the interpretation of GPR profiles, it was possible to locate and determine the saturated zones and the level of the groundwater through the area. The radar signals are penetrated enough and enabled the identification of the subsurface reflectors. The results of GPR, VES's and Resistivity imaging showed a good agreement. The integrated interpretations were verified by local geology and information from several bores. Also, the study was supported by a chemical analysis from the drain water and Ein El-Seera spring (close to studied site), to determine the main source of the drain and infiltrated water at the studied site.

Monitoring underground water leakage pattern by ground penetrating radar (GPR) using 800 MHz antenna frequency

Water is the most treasure natural resources, however, a huge amount of water are lost during its distribution that leads to water leakage problem. The leaks meant the waste of money and created more economic loss to treat and fix the damaged pipe. Researchers and engineers have put tremendous attempts and effort, to solve the water leakage problem especially in water leakage of buried pipeline. An advanced technology of ground penetrating radar (GPR) has been established as one of the non-destructive testing (NDT) method to detect the underground water pipe leaking. This paper focuses on the ability of GPR in water utility field especially on detection of water leaks in the underground pipeline distribution. A series of laboratory experiments were carried out using 800-MHz antenna, where the performance of GPR on detecting underground pipeline and locating water leakage was investigated and validated. A prototype to recreate water-leaking system was constructed using a 4-inch PVC pipe. Different diameter of holes, i.e. ¼ inch, ½ inch, and ¾ inch, were drilled into the pipe to simulate the water leaking. The PVC pipe was buried at the depth of 60 cm into the test bed that was filled with dry sand. 15 litres of water was injected into the PVC pipe. The water leakage patterns in term of radargram data were gathered. The effectiveness of the GPR in locating the underground water leakage was ascertained, after the results were collected and verified.

Ground-penetrating radar studies of permafrost, periglacial, and near-surface geology at McMurdo Station, Antarctica

Installations built on ice, permafrost, or seasonal frozen ground require careful design to avoid melting issues. Therefore, efforts to rebuild McMurdo Station, Antarctica, to improve operational efficiency and consolidate energy resources require knowledge of near-surface geology. Both 200 and 400MHz ground-penetrating radar (GPR) data were collected in McMurdo during January, October, and November of 2015 to detect the active layer, permafrost, excess ice, fill thickness, solid bedrock depth, and buried utilities or construction and waste debris. Our goal was to ultimately improve surficial geology knowledge from a geotechnical perspective. Radar penetration ranged between approximately 3 and 10m depth for the 400 and 200MHz antennas, respectively. Both antennas successfully detect buried utilities and near-surface stratified material to ~0.5–3.0m whereas 200MHz profiles were more useful for mapping deeper stratified and un-stratified fill over bedrock. Artificially generated excess ice which appears to have been created from runoff, water pooling and refreezing, aspect shading from buildings, and snowpack buried under fill, are prevalent. Results show that McMurdo Station has a complex myriad of ice-rich fill, scoria, fractured volcanic bedrock, permafrost, excess ice, and buried anthropogenically generated debris, each of which must be considered during future construction.

Potential of Sub-GHz Wireless for Future IoT Wearables and Design of Compact 915 MHz Antenna.

Internet of Things (IoT) technology is rapidly emerging in medical applications as it offers the possibility of lower-cost personalized healthcare monitoring. At the present time, the 2.45 GHz band is in widespread use for these applications but in this paper, the authors investigate the potential of the 915 MHz ISM band in implementing future, wearable IoT devices. The target sensor is a wrist-worn wireless heart rate and arterial oxygen saturation (SpO2) monitor with the goal of providing efficient wireless functionality and long battery lifetime using a commercial Sub-GHz low-power radio transceiver. A detailed analysis of current consumption for various wireless protocols is also presented and analyzed. A novel 915 MHz antenna design of compact size is reported that has good resilience to detuning by the human body. The antenna also incorporates a matching network to meet the challenging bandwidth requirements and is fabricated using standard, low-cost FR-4 material. Full-Wave EM simulations are presented for the antenna placed in both free-space and on-body cases. A prototype antenna is demonstrated and has dimensions of 44 mm × 28 mm × 1.6 mm. The measured results at 915 MHz show a 10 dB return loss bandwidth of 55 MHz, a peak realized gain of 2.37 dBi in free-space and 6.1 dBi on-body. The paper concludes by highlighting the potential benefits of 915 MHz operation for future IoT devices.