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![Evaluation of fabricated pressure sensor. A, Measured transmission response for different values of pressure. B, Curve fitting of transmission zero (TZ) vs pressure [Color figure can be viewed at wileyonlinelibrary.com]](publication/340420678/figure/fig4/AS:11431281176582802@1690201458961/Evaluation-of-fabricated-pressure-sensor-A-Measured-transmission-response-for-different.png)
Evaluation of fabricated pressure sensor. A, Measured transmission response for different values of pressure. B, Curve fitting of transmission zero (TZ) vs pressure [Color figure can be viewed at wileyonlinelibrary.com]
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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 t...
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Citations
... This interaction results in a shift in frequency and reflection coefficient, which can be attributed to the characteristics inherent to the tested sample. The microwave sensing approach has been utilized for solution detection for several applications [22][23][24][25]. Microwave sensors have a crucial role as an important method due to their numerous advantages. ...
In this study, a planar microwave sensor was proposed and manufactured with the aim of detecting and categorizing concentrations of various organic substances, including methanol (CH3OH), ethanol (CH3CH2OH), and 1-butanol (CH3CH2CH2CH2OH), as well as inorganic substances such as sodium carbonate (Na2CO3), potassium carbonate (K2CO3), and sodium hydroxide (NaOH).
Throughout the sensor's development, a configuration incorporating a microstrip line and a rectangular patch with a central circular aperture was employed. Full-wave electromagnetic simulation software was utilized to analyze the performance of the sensor in terms of reflection coefficients. The sensor was fabricated using a PCB material with defined properties, which included a dielectric constant of 4.3, a loss tangent of 0.025, and a thickness of 1.6 mm.
The reflection coefficient (S11) was measured and analyzed using principal component analysis (PCA) to identify correlations between the classification groups and concentrations of organic and inorganic samples. Additionally, the equivalent circuit has been extracted and modeled to describe the operating mechanism of the microwave sensor. The simulation and measurement results indicate that the sensor is a suitable candidate for the detection and classification of water samples containing CH3OH, CH3CH2OH, CH3CH2CH2CH2OH, Na2CO3, K2CO3, and NaOH. The proposed microwave sensor features a surface area of 29×18 mm², leading to a noteworthy reduction in surface utilization compared to other breath biosensors designed for measurement purposes.
... Microwave technology was demonstrated for applying pressure detection [18][19][20][21]. Shamabadi et al. [18] developed a microwave pressure sensor, based on variations in the transmission zero of a microstrip circuit, which shows an excellent linear variation of transmission zero with a pressure sensitivity of 0.57 MHz/kPa when a pressure changes from 0 to 466 kPa. ...
... Microwave technology was demonstrated for applying pressure detection [18][19][20][21]. Shamabadi et al. [18] developed a microwave pressure sensor, based on variations in the transmission zero of a microstrip circuit, which shows an excellent linear variation of transmission zero with a pressure sensitivity of 0.57 MHz/kPa when a pressure changes from 0 to 466 kPa. Mrozowski et al. [20] reported a microwave pressure sensor, based on microstrip line-fed ring resonators, which can measure an applied pressure up to 40.5 kPa with an average sensitivity of 9.62 kHz/Pa. ...
A passive substrate integrated waveguide (SIW) sensor based on the complementary split ring resonator (CSRR) is presented for pressure detection in high-temperature environments. The sensor pressure sensing mechanism is described through circuit analysis and the electromagnetic coupling principle. The pressure sensor is modeled in high frequency structure simulator (HFSS), designed through parameter optimization. According to the optimized parameters, the sensor was customized and fabricated on a high temperature co-fired ceramic (HTCC) substrate using the three-dimensional co-fired technology and screen-printing technology. The pressure sensor was tested in the high-temperature pressure furnace and can work stably in the ambient environment of 25−500 °C and 10−300 kPa. The pressure sensitivity is 139.77 kHz/kPa at 25 °C, and with increasing temperature, the sensitivity increases to 191.97 kHz/kPa at 500 °C. The temperature compensation algorithm is proposed to achieve accurate acquisition of pressure signals in a high-temperature environment.
... 1 Flexible and wearable systems are utilized to monitor inflammatory skin diseases, 2 detect human body temperature, 3 analyze sweating rate, 3,4 etc. Microwave sensors based on electromagnetic (EM) resonance have become an important solution due to the virtue of low cost, high sensitivity, and robustness to harsh environments. 1 Nowadays, sensors that adopt the microwave principle have been developed quickly, including those for detecting the characterization of materials, 5,6 concentration of solution, [6][7][8][9] properties of microfluidic, 10,11 image, 12 pressure, 13 temperature, 14,15 and angular displacement. [16][17][18] In recent years, metamaterial sensors have been investigated because their designable resonances may result in novel functions and outstanding performances. ...
A metamaterial sensor is proposed to detect the random location of a sub-wavelength metallic object. The sensor is composed of a transmission line (TL), which supports the propagation of spoof surface plasmon polaritons (SSPPs) with localized electromagnetic (EM) field, and a complementary spiral resonator (CSR) that resonates strongly at designed frequencies around 0.9 and 2.7 GHz. Based on the shift of the resonance frequencies, this sensor is able to detect the location of a sub-wavelength metallic object (whose diameter is smaller than 0.6 mm) randomly attached to the CSR. A prototype of the sensor is fabricated and tested. In practice, the CSR is excited through the EM coupling of the SSPP TL, and the location of the metallic object is obtained through the transmission coefficient (S21). To improve the accuracy, a retrieval curve for locating is generated and calibrated. It is proved that the random location of the sub-wavelength object can be accurately detected inside an area of 9π mm ² with a low error of 2‰.
This article describes the development of a microwave sensor with a high Q-factor for measuring permittivity. The compact size of the sensor is deemed essential, leading to the utilization of a coupled line with two coupled split-ring resonators (SRRs) as the main section of this sensor. The coupling between the SRR and two transmission line resonators creates a trap for the electrical field, forming a hot spot and resulting in a high Q-factor sensor. To further improve the Q-factor, the electric inductive capacitive (ELC) element in the ground layer is utilized. However, losses due to the dielectric and surface wave effects are common problems faced in obtaining optimal results. To address these challenges, electromagnetic band gap (EBG) unit-cells are used as metasurfaces to enclose the main sensor element. This set-up establishes an electromagnetic shield, minimizing losses and improving the overall performance of the sensor. The sensor is specifically tuned to operate at 3.36 GHz. The study employs simulation using the finite element method (FEM) and compares the results with experimental data. The material under test (MUT) in this study is FR-4 substrates with photonic band gap (PBG) properties, having a permittivity range from 2 to 4.2. The obtained outcomes are then compared with the effective permittivity derived from the Maxwell–Garnett equation. The measured average sensitivity (
${S}_{\text {avg}}$
) of the developed sensor is determined to be 4.68%. Despite its high sensitivity, the sensor maintains a compact size, with total dimensions of
$0.4\lambda _{{0}} \times 0.4\lambda _{{0}}$
, where
$\lambda _{{0}}$
represents the free-space wavelength at the operating frequency.
Wearable technology and soft robotics have experienced significant growth in the past decade. In these applications, flexible and highly sensitive pressure and bending sensors are essential for providing feedback to control and operate devices. Despite the development of many pressure and bending sensors, the challenge remains to develop one single sensor with high sensitivity that can simultaneously measure pressure and bending, which allows for a more compact system and simplified control. In addition, wireless sensing is desirable so that the sensor and the readout system can be placed separately at convenient locations. This article presents a new wireless microwave sensor to meet the needs. The sensor uses a resonator-based design, where pressure and bending changes are reflected as resonance frequency shifts and amplitude changes in the transmission response spectrum, respectively. This “one for two” approach allows for selective sensing and easy fabrication of the sensor, with results displayed on a cost-effective handheld device. The sensor and the reader are electromagnetically coupled without the need for physical contact offering wireless sensing. With a sensitivity of 3.39 MHz kPa
$^{-1}$
, this wireless sensor design offers a promising solution for wearable devices and soft robots due to its flexibility, small size, and low fabrication cost.
A stripline transmission-line (TL)-based temperature sensor for use in harsh environments is designed to exploit the thermal coefficient of the dielectric constant (TCD) of the microwave (MW) substrate material. Rogers 3210 substrate is selected owing to its high TCD of −459 ppm/°C and a dielectric constant of 10.8. A ring resonator is designed for 2.4 GHz, with the ring selected for the simple geometric dependence of its resonant frequency on radius. TLs are gap-coupled to the ring, with widths designed for 50-
$\Omega $
impedance matching and lengths optimized for a compact form factor. Upper and lower ground planes shield the dielectric, resonator, and TLs from environmental disturbances, such as debris and moisture, which could otherwise disrupt temperature measurement. Furthermore, the electric field is completely contained within the homogeneous dielectric, providing improved sensitivity compared to similar designs using microstrip technology. The fabricated sensor requires uniform compression of layers to mitigate the effects of air pockets and thermal expansion of materials. It is found that the sensor requires temperature-conditioning, approximately 70 h cycling between 30 °C and 80 °C, before its resonant frequency reaches a steady state suitable for instantaneous temperature measurement. Subsequent 10 °C- and 2 °C-step experiments are performed in the 30 °C–80 °C and 30 °C–40 °C ranges, respectively. As a result, a linear sensitivity of
$\approx 500$
kHz/°C is identified. The duration of these experiments and time-based data are representative of applications where long-term temperature monitoring is required.
In this work, microstrip line T stub resonator is proposed as sensor for dielectric characterization of liquid material for the development of artificial tissue mimicking phantom. T stub is miniaturized using Hilbert curve geometry. The proposed sensor is modeled to sense permittivity from 1 to 80 value between 300 MHz to 900 MHz. Two configuration planar and conformal model has been analyzed. The proposed sensor utilizes two parameters: transmission coefficient and reflection coefficient independently. However, the reflection coefficient response is more sensitive than the transmission coefficient response. The sensor is quite sensitive to sense the broad range of permittivity. The proposed sensor is fabricated and tested with different concentration of sugar water mixture solution. The measured result shows very much satisfactory response of the proposed sensor design.
Most of the humidity or gas sensing researches focus on the optimization of sensitive materials, while the studies of microwave detection focus on its sensitive-field control. It is necessary to implement the cooperative study on microwave detection with different types of sensitive materials for a better understanding of the operation mechanism as well as providing a way for performance enhancement. This study presents the double split-ring resonator as the sensitive electrode, where various sensitive materials, including polymer by pure Polyimide (PI), ceramic composite by PI-TiO2, metal composite by PI-Ag composite, are respectively tested as the sensing materials. The S-parameter is tested as the humidity indicators after coating on the sensitive regions with a strong electric-magnetic field. Owing to the improved dielectric properties by doping strong-polarity TiO2 nanoparticles into PI, the higher sensitivity with the maximum of 880.0 kHz/%RH and 0.322 dB/%RH is realized. The introduction of Ag nanoparticles facilitates the water vapor adsorption and desorption showing the sensitivity of 330.0 kHz/%RH and 0.149 dB/%RH, due to the high active-site density and surface roughness. By analyzing variations in resonant frequency and return loss, the microwave sensing mechanism of different sensitive materials is fully discussed from the perspective of polarization, dielectric property, and sensitive area.
