Search

Glyphosate‐based herbicides are the most used worldwide despite the fact that studies have shown their possible adverse effects on human health and the environment. Since the residues of these herbicides reach water bodies, their detection is considered an emergent research topic. In this work, the use of the intrinsic resonance of a microwave interdigitated capacitor fabricated on microstrip technology, is proposed for detecting the presence of glyphosate‐based herbicide in water. In addition, a sample holder is proposed to avoid the possible oxidation of the metal electrodes due to the direct contact with liquids. The proposed structure was designed to present its first intrinsic resonance at 1.95 GHz so that this resonance is shifted to 1.58 GHz when pure deionized water is used as sample. The sensor device was tested against 18 mixtures prepared with concentrations between 0% and 100% v/v of herbicide diluted in deionized water. Experimental measurements confirm that by using the intrinsic resonance parameters of the proposed structure, is possible to detect the presence of a glyphosate‐based herbicide. Finally, the results confirm the potential of the proposal as an alternative for real‐time, label‐free, and sensitive detection of glyphosate in water and they open the possibility of exploiting its use for the detection of other contaminants. [ABSTRACT FROM AUTHOR]

In recent years, several efforts have been dedicated to the development of portable and versatile microwave technologies for contact‐less liquid sensing and characterization. With respect to existing electrochemical and optical approaches, microwave liquid sensors enable high‐sensitivity and label‐free sensing with increased operation stability and robustness, and in relatively simple and inexpensive device formats. Nonetheless, current microwave solution sensing systems are still limited by either their reliance on wired connections to external electronics or by their widespread implementation on conventional rigid substrates. These limitations hinder the seamless integration of such sensors within conventional (micro)fluidic systems for real‐time solution monitoring, particularly when near‐field coupling between the sensors and the liquid under test needs to be established for operation. By leveraging the versatile material deposition capabilities granted by solution‐phase processing, a fully printed and mechanically flexible microwave resonator design is introduced that allows untethered solution sensing whether immersed in or in proximity to the liquid under test. The mechanical properties of this device facilitate the noninvasive/nondestructive integration of the device on commercial tubing. These characteristics, along with its cost‐effectiveness and its ease of fabrication, favor the seamless integration of this device into fluidic and microfluidic systems, for real‐life applications. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a microwave sensor is designed and built to measure the permittivity of aqueous solutions. The samples used in this experiment are different purities of ethanol mixed with water. Ethanol solution with different purities is a widely used material in industry. Structures of meander, ladder, and T‐structure were used to design the sensor. Then the designed sensor is simulated in CST software in range of relative dielectric from 10 to 80. After obtaining the desired answer in the simulation, the proposed sensor is built on the Rogers 4003 substrate, the built‐in sensor measured ethanol solution with a purity of 5% to 35% (equivalent to permittivity of 76 to 58), and is showed a sensitivity of 4% and a Q‐factor of 3500. The results of simulation and measurement are consistent with each other, and they indicated that the proposed sensor beyond the fluids can be supported and determine their relative dielectrics. [ABSTRACT FROM AUTHOR]

Fine‐powdered bulk materials exhibit high compressibility even under low pressure. The dosing error in volumetric dosing devices increases fundamentally with increasing product compressibility. In order to increase the dosing accuracy of a volumetric dosing of powdered bulk solids, the dosing process must be adapted to the product parameters. The most important parameter is the time‐variable product density. With a pure volumetric dosage, it has a direct influence on the actually filled product quantity. Attempts are often made to obtain feedback by means of a scale in order to continuously adjust the volume. However, this is often associated with a delay. In this article, the approach is to measure the product mass flow directly by means of a microwave sensor and to regulate it to a predetermined mass flow. The experimental investigations were carried out with a screw dosing device FVS 3111. Two scenarios were tested: on the one hand, the integration of the sensor directly at the product delivery point, whereby the difference of the average value of the dosed quantity to the target weight could be improved with the sample product coffee; on the other, the sensor was integrated directly at the beginning of the screw and the remaining product flow was simulated. A reduction of the standard deviation compared with the conventional control could also be achieved, but here, the difference between the average of the dosed quantity and the nominal quantity is greater. The cause is presumed to be the too generalized assumption of product behaviour in the case of vertical conveying by means of a screw. In summary, the dosing accuracy of a screw dosing device could be increased by measuring and regulating the mass flow and thus the costs of a manufactured packaging could be reduced. [ABSTRACT FROM AUTHOR]

As the surge for renewable and clean energy resources increases, new challenges emerge. One of the challenges related to the use of hydrogen as a clean energy source is safety. In this study, a microwave hydrogen sensor has been presented for detection of hydrogen leakage. An analytical model is developed and the performance of the sensor is investigated using numerical analysis tools. It has been shown that with optimal geometrical parameters of the sensor structure, a wide range of sensitivity levels depending on a wide range of Q‐factor can be achieved. Utilizing a palladium disk with a radius of 750 μm can detect hydrogen with a sensitivity as high as 30 MHz per % hydrogen when g=10$g=10$ μm. Average error between analytical model and numerical results is 0.23%. With reference to this work, it is believed that more compact and sensitive microwave hydrogen sensors will be produced for future uses. [ABSTRACT FROM AUTHOR]

In this paper, the human milk dielectric constant by a microwave sensor has been evaluated. The proposed sensor is result of coupling between a simple microstrip line and a split ring resonator and its resonance frequency is 6 GHz. When up to 30 μl of milk are placed on the sensing area on the sensor, it causes the resonance frequency to shift. Six samples of human milk were measured by a network analyzer, then the dielectric constant of the samples were determined, and three similar samples were measured by the built‐in sensor. The proposed microwave sensor has Q‐factor of 38 and its sensitivity is 0.17%. The implemented sensor has acceptable performance compared to previous sensors and it can be used to determine the normal behavior of human milk with a simple method and for this work, it requires to small value of sample for measurement. Key Points: The proposed sensor is able to measure of the milk sample up to a volume of 30 μlTypes of milk including human and animal can be measured by the proposed sensorThe Q‐factor and sensitivity of the sensor is acceptable compared to previous works [ABSTRACT FROM AUTHOR]

Metamaterial‐based double‐slit complementary split rectangular resonator sensor is proposed for the characterisation of dielectric properties of the materials under test (MUTs). The proposed sensor is designed and simulated on the CST microwave studio software using a low‐cost substrate FR4. An array of three identical resonators is etched in the ground plane of the sensor to achieve a single and deep notch of −58.7 dB in the transmission coefficient (S21) at the resonant frequency of 7.01 GHz, which is the novelty of the proposed sensor. A deep and single resonant frequency band has a significant role in the precise measurement of the dielectric properties of the MUTs. The effective constitutive parameters are extracted from the S‐parameters. An equivalent circuit model is suggested that describes the overall behaviour of the sensor. The sensor is fabricated on the FR4 substrate and measured through the vector network analyser (N5224B) by placing the standard materials. The parabolic equation for the proposed sensor is formulated to approximate the permittivity of the MUTs. A very small percentage of error, 0.77, is found which shows high accuracy of the sensor. This methodology is efficient, simple in fabrication, and reduces cost and computational time also. [ABSTRACT FROM AUTHOR]

This work proposes a novel method for detecting the concentration of water present in liquid‐water binary mixture in real time with a low cost, portable measurement setup. The sensing element in the proposed system is a two‐port microstrip bandstop resonator based on coupled line open‐ended quarter wavelength section. Voltage control oscillator and power detector ICs are used to generate and detect the microwave power at specific bandstop frequency. Water concentrations in commercially available liquids are monitored both in batch and continuous mode of operation using separate 3D printed liquid containing fixtures attached to the open end of the microstrip line. The measured results successfully validate the design theory. [ABSTRACT FROM AUTHOR]

The novel application of microwave directional couplers to develop angular‐displacement microwave sensors is reported. The proposed sensor approach employs as stator a branch‐line‐type coupler arranged in transversal mode by loading its direct and coupled ports with two distinct‐length open‐ended stubs. Thus, by taking the isolated port of the coupler as the stator output node, a bandpass filtering transfer function with transmission zeros (TZs) is created. Then, a rotor made up of an angularly‐moveable open‐ended stub is attached to a curved section of the longest loading stub of the stator through physical contact, so that their interconnection point varies with the angular‐displacement of the rotor. In this manner, the sensor transfer function is altered with the stub rotation through TZ reallocation, angular‐displacement sensing capabilities are achieved. The theoretical operational foundations of the conceived branch‐line‐coupler‐based microwave angular‐displacement sensor, which features single/multi‐band sensing properties in terms of inter‐TZ spacing and stop band attenuation levels, along with design examples and curves are provided. The extrapolation of this sensor principle to other classes of power‐distribution circuits, such as the rat‐race‐type directional coupler, is also demonstrated. Finally, for experimental‐validation purposes, two 920 MHz microstrip prototypes of the conceived branch‐line‐coupler‐based angular‐displacement microwave‐sensor approach are built and measured. [ABSTRACT FROM AUTHOR]

A microwave pressure sensor based on variations in the transmission zero of a microstrip circuit is proposed in this article. The structure of the sensor is consisting of a microstrip line connected in parallel to a single stub, which the stub is terminated in a reactive load. When the length of stub is around quarter‐wavelength, the frequency of the transmission zero of microstrip line can be controlled by the reactance value. Therefore, by using a simple parallel plate capacitor as a transducer in which its capacitance is changed by the pressure, a microwave pressure sensor is realized. A prototype pressure sensor by using a circular‐shape parallel plate capacitor is designed and fabricated that the measurement results show a good linear variation of transmission zero with pressure with sensitivity of −0.57 MHz/kPa when the pressure changes from 0 to 466 kPa. [ABSTRACT FROM AUTHOR]

A microwave sensor is presented in this letter for the detection of salinity and sugar concentration. The microwave sensor is used for the transmission and reception of electromagnetic wave. The sensor has a circular shaped radiating patch with semi‐circular shaped slots. The antenna sensor is prototyped on a low‐cost FR4 substrate which is 1.60 mm thick. The sensor has a small size of 26 mm × 24 mm. The high‐frequency structural simulator (HFSS) is utilized to model the microwave sensor. The sensor detects the salinity and sugar concentration by means of the reflection coefficient. The dielectric constant changes with the increased percentages of the salt and sugar which reduces the reflection coefficient. The microwave sensing device shows considerable sensitivity to determine the salinity and sugar concentration. [ABSTRACT FROM AUTHOR]

In this paper, a novel non‐invasive sensor for the measurement of the glucose concentrations in blood is presented. By using a microstrip band pass filter, a wireless sensor is achieved. In the introduced design, the thumb is placed on the structure of the filter as a superstrate. The response of the filter is dependent on the permittivity of the superstrate. A compact size, linearity and cost effectiveness are the most important advantages of the proposed sensor. The linear behaviour of the filter in terms of the frequency is investigated and for a linear behaviour, a certain frequency for operation is selected. The introduced sensor can be used by diabetics for continuous self‐monitoring of the glucose level. The structure of the proposed sensor is designed on the low‐cost substrate, FR4, by compact dimensions of 50 mm × 40 mm × 1.6 mm. A prototype of the proposed filter was fabricated and the performance of the filter was investigated, experimentally. [ABSTRACT FROM AUTHOR]

Stereo-complementary asymmetric split resonator (Stereo-CASR) perforated on a copper sheet is proposed for designing microwave resonator sensor. The effect of the degree of asymmetry on the frequency response is thoroughly studied. Compared with traditional planar ASR, stereo-CASR exhibits a nearly 100% transmission at resonate state and possesses a much higher Q factor. The performance of the stereo-CASR assisted microwaves sensor is validated by full wave simulation. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 22:545-551, 2012. [ABSTRACT FROM AUTHOR]

In this paper, the authors propose continuous-wave single-frequency (CW-SF) and multi-frequency (CW-MF) microwave techniques for measurement of large-structure vibration. Theoretical background and experimental results of tests on a vertical steel structure, subjected both to artificial solicitation through a vibrodyne and to wind, are reported. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 216–218, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10874 [ABSTRACT FROM AUTHOR]