Underground Antenna Research Articles

Deployment of Underground Wireless Sensor Network Based on Magnetic Core Antennas and Multiple Surface Acoustic Wave Sensor Modules

For the first time, a 3less (batteryless, chipless, wireless) underground sensor system was developed for real time monitoring of variations in temperature, humidity, and hydrogen gas concentrations around underground utility burials. The completed sensor system consists of several magnetic core antennas, surface acoustic wave (SAW) sensors, and a measurement system. Each SAW sensor was activated by pure magnetic energy, and showed high sensor performances in sensitivity and linearity. A long readout distance was observed between the upper and underground antennas, and wireless magnetic communication was analyzed in terms of the interdistances, the angles between antennas, and the underground constituent mediums. A circulator was employed to discern magnetic signals emitting and receiving in between the upper and underground systems. A COMSOL simulation and coupling of mode (COM) modeling were also conducted to determine optimal design parameters for the sensor modules, and to predict the experimental results in advance.

ВЛИЯНИЕ СЕЗОННЫХ ВАРИАЦИЙ ПАРАМЕТРОВ ГРУНТА НА ЧУВСТВИТЕЛЬНОСТЬ ЭЛЕМЕНТА АКТИВНОЙ ФАЗИРОВАННОЙ АНТЕННОЙ РЕШЕТКИ РАДИОТЕЛЕСКОПА ГУРТ

ВЛИЯНИЕ СЕЗОННЫХ ВАРИАЦИЙ ПАРАМЕТРОВ ГРУНТА НА ЧУВСТВИТЕЛЬНОСТЬ ЭЛЕМЕНТА АКТИВНОЙ ФАЗИРОВАННОЙ АНТЕННОЙ РЕШЕТКИ РАДИОТЕЛЕСКОПА ГУРТ

A Theoretical Model of Underground Dipole Antennas for Communications in Internet of Underground Things

The realization of Internet of underground things (IOUT) relies on the establishment of reliable communication links, where the antenna becomes a major design component due to the significant impacts of soil. In this paper, a theoretical model is developed to capture the impacts of the change of soil moisture on the return loss, resonant frequency, and bandwidth (BW) of a buried dipole antenna. Experiments are conducted in silty clay loam, sandy, and silt loam soil, to characterize the effects of soil, in an indoor testbed and field testbeds. It is shown that at subsurface burial depths (0.1–0.4 m), the change in soil moisture impacts communication by resulting in a shift in the resonant frequency of the antenna. Simulations are done to validate the theoretical and measured results. This model allows system engineers to predict the underground antenna resonance and also helps to design an efficient communication system in IOUT. Accordingly, a wideband planar antenna is designed for an agricultural IOUT application. Empirical evaluations show that an antenna designed considering both the dispersion of soil and the reflection from the soil–air interface can improve communication distances by up to five times compared to antennas that are designed based on only the wavelength change in soil.

Multiscale Modeling of Electromagnetic Telemetry in Layered Transverse Isotropic Formation

Electromagnetic telemetry (EMT) systems are utilized for measurement while drilling to transmit data from borehole to the ground surface during drilling or vice versa. To help predict the successful deployment of the EMT system within complex formation and environmental noise, a reliable numerical algorithm is developed and applied to model the EMT system for directional drilling in layered transverse isotropic (TI) formation. In the telemetry system, the long and thin drill string having three-dimensional trajectory acts as an underground antenna that can be modeled as a thin wire excited by a delta gap voltage/current source near the drill bit. Using the thin wire assumption, the developed algorithm calculates the thin wire kernel in homogeneous uniaxial media with high accuracy to reduce the dimension and complexity of the problem. The mixed-potential form of layered media Green's function and electric field integral equation are used to model the electromagnetic interaction of the drill string and layered TI media. The effect of drilling fluid outside the pipe is modeled using the volumetric equivalence principle. The accuracy and efficiency of the new algorithm are demonstrated by several numerical examples.

Soil Effects on the Underground-to-Aboveground Communication Link in Ultrawideband Wireless Underground Sensor Networks

Wireless underground sensor networks (WUSNs) is an emerging area of research. They are used in many applications from intelligent irrigation to security and assisted navigation. WUSNs mainly use narrowband systems working in the frequency range below 1 GHz and, therefore, suffer from a poor localization capability and large-sized antennas. The use of impulse radio ultrawideband (UWB) technique allows alleviating these drawbacks. In this letter, the impact of soil on UWB underground-to-aboveground communication link is studied experimentally. More specifically, the effects of the orientation of the buried antenna and burial depth and soil moisture are investigated. The experimental results show that, at 7 GHz, additional attenuations of 10, 34, and 40 dB are noted for depointing the underground antenna by 90°, increasing the depth from 0 to 30 cm and raising the soil moisture from 0% to 20%, respectively. Burial depth lower than 30 cm or soil moisture lower than 20% allow getting acceptable received signal strength (superior to –100 dBm) for communication and localization, particularly in the UWB low band (3.1–5 GHz). The obtained results bring out the feasibility of UWB WUSN.

Autonomous precision agriculture through integration of wireless underground sensor networks with center pivot irrigation systems

Precision agriculture (PA) refers to a series of practices and tools necessary to correctly evaluate farming needs. The accuracy and effectiveness of PA solutions are highly dependent on accurate and timely analysis of the soil conditions. In this paper, a proof-of-concept towards an autonomous precision irrigation system is provided through the integration of a center pivot (CP) irrigation system with wireless underground sensor networks (WUSNs). This Wireless Underground Sensor-Aided Center Pivot (WUSA-CP) system will provide autonomous irrigation management capabilities by monitoring the soil conditions in real time using wireless underground sensors. To this end, field experiments with a hydraulic drive and continuous-move center pivot irrigation system are conducted. The results are used to evaluate empirical channel models for soil-air communications. The experiment results show that the concept of WUSA-CP is feasible. Through the design of an underground antenna, communication ranges can be improved by up to 400% compared to conventional antenna designs. The results also highlight that the wireless communication channel between soil and air is significantly affected by many spatio-temporal aspects, such as the location and burial depth of the sensors, soil texture and physical properties, soil moisture, and the vegetation canopy height. To the best of our knowledge, this is the first work on the development of an autonomous precision irrigation system with WUSNs.

Validation and results of the Soil Scout radio signal attenuation model

Real-time and wireless monitoring of soil properties would give important information for the decision-making process. Autonomous underground Soil Scouts for monitoring soil properties like moisture, temperature, nutrient level and pH can be produced with present radio electronics. A model has been developed to estimate the signal strength in varying conditions. The model includes three different mechanisms of signal power loss: (1) attenuation; (2) reflection; and (3) angular defocusing. Complex dielectric permittivity is the main soil parameter concerning radio wave attenuation. In field tests, a radio wave was generated at 869.5 MHz and conducted to an underground antenna. Signal strength was 10 1.4 mW (equals to 14 dB/mW). The signal was received at the soil surface with a dipole antenna and the amplitude was measured. Measurements were carried out in sandy and loamy soils. The model succeeded in estimating the signal strength and both the moisture and angle dependencies of the attenuation and in estimating heavy moisture alterations. Signal power requirements for transmitting from 25 cm depth were simulated. The results suggested that a 1 km working distance can be achieved with commercial single-chip radio components and thereby instrumentation issues are solvable.

Wideband Antenna for Underground Soil Scout Transmission

The underground soil scout system introduces a need for a small-size antenna capable of adequate radiation efficiency in soils of different moisture contents at the frequency 0.869 GHz. Such an underground antenna is created for the first time. The high permittivity of soil is utilized to downsize the instrument. A prototype design of an underground single-ended elliptical monopole antenna (USEMA) is presented and the performance measured in different soil moisture contents in a soil container. The suggested antenna has good radiation efficiency in a wide soil moisture range

Effect of a dielectric coating on currents in an underground antenna

Effect of a dielectric coating on currents in an underground antenna

Useful radiation from an underground antenna

Useful radiation from an underground antenna

The Use of Ground Wires at Remote Control Stations

By utilizing the directional selectivity of subterranean receiving antennas, it has proven possible to install receiving stations in the immediate vicinity of transmitting stations. The proper design of the underground antennas, the construction of the shielded rooms for the receiving sets, and the mode of "remotely" controlling the nearby transmitting station are described in detail. The complete design, layout, and installation of several such Naval "remote" control stations is then given. Their proper mode of use and advantages are considered.