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Microwave sensor array (a) front surface and (b) back surface with Sensor 1 to Sensor 5 shown from left to right, respectively, each of which corresponds to an increasing resonance frequency.
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Fine-grained water quality data can facilitate the optimized management of water resources, which have become increasingly scarce due to population growth, increased demand for safe sources of water, environmental pollutions, etc. There is a pressing need for cost-effective, reliable, re-useable, and autonomous water sensing technologies that can p...
Contexts in source publication
Context 1
... the real and imaginary parts of the permittivity are measured within the frequency range of 1 GHz to 10 GHz. FIGURE 11 to FIGURE 13 show the results. A table that summarizes the permittivity of samples under test is presented in the Appendix for easier reference. ...
Context 2
... it is still possible to detect them and distinguish this category of samples from distilled water. FIGURE 12 shows the variation of ε r and ε i for water solutions with pH levels of 4, 7, and 10. It is observed that ε r values differ from distilled water at higher frequencies (around 6 GHz) while ε i values have larger differences with distilled water at lower frequencies (around 4 GHz). ...
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... A values, Sensors 1 to 4 show robust responses with A larger than 1 dB. FIGURE 18 shows the variations of f and A for three pH levels of the water: 4, 7, and 10. It is observed that almost all sensors show measurable responses with f values larger than 1 MHz. ...
Context 4
... Sensor 1 and Sensor 3 show decrease of f with the increase of pH level, Sensors 4 and 5 show increase of f with respect to the increase in pH level. In general, the largest f responses are observed for Sensor 5 which is consistent with ε r measurement in FIGURE 12(b), showing the largest variation of ε r for pH solutions at higher frequencies. For A, also almost all sensors show measurable values with A larger than 1 dB. ...
Context 5
... 3 and 4 show the largest A values. FIGURE 19 shows the variation of f and A for two concentration levels of NaCl: 6440 ug/mL and 40000 ug/mL. It is observed that, in general, the values of f and A increase with the increase of the concentration level for all the sensor VOLUME 7, 2019 FIGURE 18. Response changes due to water solutions with three pH levels with respect to distilled water: (a) f and (b) A. elements. ...
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Citations
... The reader detects this frequency shift and then it can process the respiration rate [8]. For the environment monitoring application, one method is to put a small antenna tag inside a lake water sample as a probe and detect the ions dissolved in the water by measuring the change in the antenna reflection coefficient, S11 [9]. ...
This article presents two monopole antennas with an endfire radiation pattern in the UHF band that can be installed on dry walls or metallic cabinets as a part of wireless sensor nodes, making them a suitable choice for smart home applications, such as the wireless remote control of house appliances. Two different antennas are proposed to cover the RFID bands of North America (902–928 MHz) and worldwide (860–960 MHz). The antennas have wide horizontal radiation patterns that provide great reading coverage in their communication with a base station placed at a certain distance from the antennas. The structures have two ground planes, one in-plane and the other vertical. The vertical ground helps the antenna to have a directive radiation and also makes it easily installed on walls. The antenna feeding line lies over the vertical ground substrate. The maximum dimensions of the narrow-band antenna are L × W = 0.3λ× 0.14λ, and those for the wide-band antenna are L × W = 0.39λ× 0.14λ. The measured results show that the bandwidth of the proposed antennas for the North America and worldwide RFID bands are from 902 MHz to 939 MHz and 822 MHz to 961 MHz, with maximum gains of 4.2 dBi and 4.9 dBi, respectively.
... There are a few examples of microwave sensor design that has been proposed in past research such as ring resonator which can be used for water content detection [14] and gas sensor [15]. There were a variety of microwave sensor designs available, like the splitring resonator (SRR), which is able to be used as a health monitoring application [16], liquid sensor [17], [18], [19] and displacement sensor [20] or the complementary split-ring resonator design which is also used as a water quality monitoring system [21], [22], [23]. ...
... An application as a microwave sensor for water quality has been proposed by Zhang et. al., where an array of CSRRs is used, where the author placed an array of CSRRs on a single board, with each CSRR having a different resonant frequency ranging from 1.36 GHz to 8.91 GHz [21]. As the paper discusses water quality measurement, the author has used the sample based on the real content of contaminated water. ...
This study describes a complementary split-ring resonator (CSRR)-based planar microwave sensor. Its capability in detecting several samples which are based on the usual water contaminant in Malaysia was investigated. The CSRR sensor was designed with an unloaded resonant frequency of 2.0 GHz, and it was fabricated on an FR-4 substrate with a thickness of 1.6 mm and a dielectric constant of 4.3. The S-parameter responses of the sensor were measured under two conditions; i) unloaded and ii) loaded. For the latter, samples of tap water, salt water, isopropyl alcohol, filtered water and cooking oil were used to load the resonant element of the CSRR. The measurement result of unloaded CSRR shows that the designed sensor resonates at 1.99 GHz, which is in line with the simulation. The measurement results also showed that the presence of all samples caused the resonant frequency of the CSRR to shift, with filtered water and cooking oil showing the biggest frequency shifts (0.84 GHz and 0.96 GHz, respectively). A sensitivity analysis of the CSRR was carried out and it shows that it achieves 0.25% sensitivity. The proposed sensor may be a useful substitute for pricey commercial sensors for applications involving water quality because of the inexpensive materials and ease of fabrication.
... Increased TDS, TSS, and water temperature of the lake and the associated effects in the lake, including eutrophication and algae growth, have the potential to reduce the DO in the water, thereby impacting the lake's ecosystem [51,56,57,[65][66][67]. ...
Lake Mead located in the Arizona–Nevada region of the Mohave Dessert is a unique and complex water system whose flow follows that of a warm monomictic lake. Although monomictic lakes experience thermal stratification for almost the entire year with a period of complete mixing, the lake on occasion deviates from this phenomenon, undergoing incomplete turnovers categorized with light stratifications every other year. The prolonged drought and growing anthropogenic activities have the potential to considerably impact the quality of the lake. Lake Mead and by extension the Boulder Basin receive cooler flow from the Colorado River and flow with varying temperatures from the Las Vegas Wash (LVW), which impacts its stratification and complete turnovers. This study analyzes four key water quality parameters (WQPs), namely, total dissolved solids (TDS), total suspended solids (TSS), temperature, and dissolved oxygen (DO), using statistical and spatial analyses to understand their variations in light of the lake stratifications and turnovers to further maintain its overall quality and sustainability. The study also evaluates the impacts of hydrological variables including in and out flows, storage, evaporation, and water surface elevation on the WQPs. The results produced from the analysis show significant levels of TDS, TSS, and temperature from the LVW and Las Vegas Bay regions compared with the Boulder Basin. LVW is the main channel for conveying effluents from several wastewater treatment facilities into the lake. We observed an increase in the levels of TDS, TSS, and temperature water quality in the epilimnion compared with the other layers of the lake. The metalimnion and the hypolimnion layer, however, showed reduced DO due to depletion by algal blooms. We observed statistically significant differences in the WQPs throughout various months, but not in the case for season and year, an indication of relatively consistent variability throughout each season and year. We also observed a no clear trend of influence of outflows and inflows on TDS, temperature, and DO. TSS concentrations in the lake, however, remained constant, irrespective of the inflows and outflows, possibly due to the settling of the sediments and the reservoir capacity.
... On the other hand, TL-based sensing can offer a solution to this problem but it suffers low sensitivity, as mentioned earlier. To bridge this gap, preliminary results were shown in [11] related to the use of a non-uniform array of microwave sensors for water quality testing. There, array elements resonate at different frequencies over the broad range of 1 GHz to 10 GHz. ...
... It was shown that the dielectric properties of polluted water (PW) samples (obtained with a dielectric probe kit) are different from those of the distilled water (DW) samples over the abovementioned frequency band. Also, in [11], measurements of PW samples were conducted with a nonuniform array of microwave sensors made of complementary split ring resonators (CSRRs). It was observed that the resonant parameters (frequency, quality factor, and level) of the measured transmission S-parameter, |S21|, change for the PW samples compared to the DW samples. ...
... From those early observations, it was deduced that using a nonuniform microwave sensor array is very beneficial since a response pattern is obtained for each tested PW sample as compared to a single-valued response when using a single sensor. Such response patterns can be utilized for the identification of various pollutants with various concentration levels in water if processed well by MLAs (not applied in [11]). ...
Detection of pollutants in water is conventionally performed in wet chemistry labs for samples that are collected manually. This task is time-consuming, costly, and difficult to expand to large water bodies and perform frequently. Thus, to facilitate water quality testing, a new methodology is presented based on the use of a non-uniform array of microwave sensors and applying machine learning to the collected data. The sensor elements resonate at different frequencies which cover a broad bandwidth, providing sufficient information for machine learning algorithms to determine the type of pollutant. Here, as a proof-of-concept, the proposed methodology is tested with water samples including Phosphate (PO
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), Lead (Pb), Mercury (Hg), and Chromium
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(Cr
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) with various concentrations. The proposed technology is fast, cost-effective, repeatable, and expandable for detecting a larger number of pollutants.
... In this paper, we propose the utilization of an array of sensors resonating at multiple frequencies ranging from 1 GHz to 10 GHz for assessing the shape features in the dielectric media. For the first time, the responses obtained from a near-field microwave sensor array (we employ the sensor array in [18]) are postprocessed through a robust near-field holographic imaging method. This is in contrast to the previous works which normally plot the raw data measured by the near-field microwave sensors to produce images. ...
... In this section, the simulation studies for the proposed imaging technique are performed and demonstrated using FEKO software [21]. We utilize a multifrequency near-field sensor, first introduced in [18]. Shown in Figure 2, it is composed of five nonuniform CSRRs with the elements resonating at five frequencies at 1.234 GHz, 3.074 GHz, 4.949 GHz, 6.699 GHz, and 8.3768 GHz. ...
... The substrate for the sensor is Rogers RO4350 and it has a width W s of 20 mm, length of L s of 56 mm, and microstrip line width W m of 1.68 mm. For other dimensions, please refer to [18]. The sensor has been fabricated by a commercial company using standard PCB fabrication technology. ...
Microwave imaging is a high-resolution, noninvasive, and noncontact method for detecting hidden defects, cracks, and objects with applications for testing nonmetallic components such as printed circuit boards, biomedical diagnosis, aerospace components inspection, etc. In this paper, an array of microwave sensors designed based on complementary split ring resonators (CSRR) are used to evaluate the hidden features in dielectric media with applications in nondestructive testing and biomedical diagnosis. In this array, each element resonates at a different frequency in the range of 1 GHz to 10 GHz. Even though the operating frequencies are not that high, the acquisition of evanescent waves in extreme proximity to the imaged object and processing them using near-field holographic imaging allows for obtaining high-resolution images. The performance of the proposed method is demonstrated through simulation and experimental results.
... After the incident wave (a1) passes through the two-port network, part of the signal is reflected to (b1), and part of the signal passes through the network and becomes the outgoing wave (a2). Similarly, when considered from the right side, the matrix equation of S parameter is shown in Equation (12). So, the reflection coefficient S11 is used to characterize the reflection signal in a two-port network. ...
Far-field detection has been widely used in biomedical diagnosis, security inspection, such as MRI, ultrasonic, SPECT, X-ray, etc. However, the near-field detection has yet to be well established. This paper proposed a sensor structure with series inductance and capacitor. The inductance is a differential-transformer-type inductor formed by winding two spiral inductors. The interdigital capacitor is redesigned and placed inside the inductor to reduce its overall size. With the presence of the digital capacitor, the resonance shifts to the lower frequency, and the amplitude of return loss is increased. The micro-fabricated resonator was realized through integrated passive device technology for sensitive detection and characterization of glucose. The experimental results verified the performance of the proposed biosensor as the radio frequency multi-parameter bio-detector, such as the resonance frequency and the reflection coefficient. The detection results vary in response to deionized water, following by the iterative measurements of the changing glucose concentrations (from 50 to 150 mg·dL
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). The concentration of glucose solution changes from 50 mg·dL
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to 150 mg·dL
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. The experimental results show that the amplitude changes 32.1 dB, and the phase changes 60.88° at 1 GHz. The results indicate the proposed microwave sensor has an excellent biosensing performance.
... With the development of industry and agriculture, large amounts of wastewater are discharged, and the ecological environment of watersheds is seriously damaged. Floating objects on the water [1], water pollution [2], and water eutrophication [3] are all important causes of water pollution, which not only pollute and damage water resources but also threaten human safety and health. The traditional monitoring method is to deploy devices in the water that make use of sensors to monitor and analyze the water quality. ...
Water environment monitoring has always been an important method of water resource environmental protection. In practical applications, there are problems such as large water bodies, long monitoring periods, and large transmission and processing delays. Aiming at these problems, this paper proposes a framework and method for detecting floating objects on water based on the sixth-generation mobile network (6G). Using satellite remote sensing monitoring combined with ground-truth data, a regression model is established to invert various water parameters. Then, using chlorophyll as the main reference indicator, anomalies are detected, early warnings are given in a timely manner, and unmanned aerial vehicles (UAVs) are notified through 6G to detect targets in abnormal waters. The target detection method in this paper uses MobileNetV3 to replace the VGG16 network in the single-shot multi-box detector (SSD) to reduce the computational cost of the model and adapt to the computing resources of the UAV. The convolutional block attention module (CBAM) is adopted to enhance feature fusion. A small target data enhancement module is used to enhance the network identification capability in the training process, and the key-frame extraction module is applied to simplify the detection process. The network model is deployed in system-on-a-chip (SOC) using edge computing, the processing flow is optimized, and the image preprocessing module is added. Tested in an edge environment, the improved model has a 2.9% increase in detection accuracy and is 55% higher in detection speed compared with SSD. The experimental results show that this method can meet the real-time requirements of video surveillance target detection.
... Besides, the implementation of teeth gear (TG) at the center of the CSIW structure gives an effect to increase the electric fields of the microstrip line and increases the Q-factor [7]. The previous research indicates the SUT handling process for liquid glass tubes [32], immerse, reservoir/container [33], [34], pipet [17] and [5], [19], [20], [35], which are primarily used. This approach makes it difficult to work mainly in different SUT transformations and leads to waste because of the large amount of SUT needed but also delays the repeat of the measurements. ...
A new design of teeth gear-circular substrate integrated waveguide (TG-CSIW) sensor to extract complex permittivity of liquids is suggested in this study. The proposed sensor size is decreased up to 20% after the Angle Between Input and Output Ports (ABIOP) was introduced. As the outcome, there was a very excellent quality factor of 700 unloaded. The sensor operated at2.45GHz resonant frequency, and it is progressively designed by the ANSYS program HFSS. The sensor’s simulated response was evaluated by different permittivity of liquid under test (LUT) with an amount of 0.11mLaqueous. A strong correlation is obtained between the simulated and experimental findings of complex permittivity of LUTs with a minimal error of less than 0.4%. In addition, the modelled sensor was employed to estimate the complex permittivity of unknown specimens. It has contributed to a miniaturized, low-cost, secure, non-contact, fast-detection system utilizing limited liquid volumes filled into Polypropylene tubes. The proposed sensor is practically useful for food or beverage products, fluids/tissues of organic and natural herbs industry applications.
... Microwave sensing technology is relatively recent compared with other transduction methods such as electrochemistry, piezoelectric, thermocouple and optical transduction. Microwave sensors have found application in several fields such as medicine [8], environment [9], industry [10], food and agriculture [11]. ...
Molecularly imprinted sol–gel silica (MIS) coupled to a microwave sensor was designed and used to detect phenylacetaldehyde (PAA), a chemical tracer of wine oxidation. The developed method is fast, cheap and could replace the classical chromatographic methods, which require a tedious sample preparation and are expensive. To reach our objective, five MIS and their control non-imprinted silica (NIS) were synthesized and their extraction capacity toward PAA was studied in hydro alcoholic medium. The selected polymers, based on this first step, were subjected to a selectivity study in the presence of PAA and three other competing molecules. The best polymer was integrated in a microwave sensor and was used to assess PAA in red wine. The developed sensor was able to detect PAA at the µg·L−1 level, which is below the off-flavour threshold.
... Gadani et al. [20] conduct studies on effect of salinity on the dielectric properties of water with microwaves (200MHz-1.4GHz). Zhang et al. [21] present a microwave sensor array operating at different frequencies (1.0GHz-10GHz) for measuring different contaminants in water. However, microwave sensors normally employ a Vector Network Analyzer (VNA) for high-frequency signal generation and analysis, which is too bulky and expensive for household use. ...
The recent advances in energy-efficient electronics and sensor fabrication techniques have reshaped the way of sensing and communication, which have nurtured many novel applications. Among the emerging sensing techniques, wirelessly powered sensing and communication enhanced by Radio Frequency Identification (RFID) has gained increasing popularity. In this investigation, we propose a novel flexible RFID sensor tag powered and interrogated by a smartphone with its in-built High-Frequency (HF) RFID module, which can be applied for convenient non-contact analysis of liquids. In this work, the evaluation of total minerals in drinking water is conducted as a proof-of-concept demonstration. The main contributions include: (1) modeling and theoretical analysis of a planar capacitive sensor for liquids analysis by sensing the dielectric properties; (2) design of a flexible capacitive sensor tag that can be conformally mounted on the sidewall of containers for the liquid analysis; (3) a power-efficient hardware scheme for HF RFID powered battery-less sensing via smartphone tapping; (4) a Near Field Communication (NFC) data transmission method for convenient measurement without added software in smartphone devices. Finally, the developed sensor tag is calibrated by multi-piece linear function fitting. Experimental results and quantitative analysis demonstrate the feasibility of the proposed methodology.
