Explore the vast range of titles available.

In this study, a high-Q circular substrate-integrated waveguide (SIW) cavity resonator is proposed as a non-contact and non-invasive radio frequency (RF) sensor for chemical sensing applications. The design of the structure utilizes SIW technology along with a circular shape to achieve a high unloaded Q factor, which is one of the important requirements for RF sensors. The resonant frequency of the proposed circular SIW cavity sensor changes when a liquid material or a chemical (microliters) is inserted in the sensitive area of the structure. The sensing of liquid materials with different permittivities is accomplished via the perturbation of the electric fields in the SIW configuration. When a microwell that is 4 mm in radius is installed vertically through the center of the bare circular SIW cavity, the operating frequency varies from 5.26 to 5.34 GHz. Similarly, when the microwell contains ethanol, the frequency shifts from 5.26 to 5.18 GHz, and the amplitude of reflection coefficient is shifted from −29 dB to −17 dB; when the microwell contains mixing deionized (DI)-water, the frequency moves from 5.26 to 4.98 GHz (which is also 0% Ethanol in our study), and the amplitude of reflection coefficient is shifted from −29 dB to −8 dB. A high unloaded Q factor is maintained throughout all experimental results. To demonstrate our idea, different concentrations of ethanol are tested and recorded. The experimental validation yields a close agreement between the simulations and the measurements.

In this study, the authors present the accurate imaging of the behavior of simultaneous operations of multiple low radar cross-section (RCS) aerial targets. Currently, the popularity of low RCS targets is increasing day by day, and detection and identification of these targets have become critical issues. Micro-Doppler signatures are key components for detecting and identifying these low RCS targets. For this, an innovative approach is proposed along with the smooth pseudo-Wigner–Ville distribution (SP-WVD) and adaptive filter bank to improve the attenuation of cross-term interferences to generate more accurate images for the micro-Doppler signatures/patterns of simultaneous multiple targets. A C-band (5.3 GHz) radio-frequency (RF) sensor is designed and used to acquire the micro-Doppler signatures of aerial rotational, flapping, and motional low RCS targets. Digital pipelined-parallel architecture is designed inside the Xilinx field-programable gate array (FPGA) for fast sensor data collection, data preprocessing, and interface to the computer (imaging algorithm). The experimental results of the proposed approach are validated with the results of the classical short-term Fourier transform (STFT), continuous wavelet transform (CWT), and smooth pseudo-Wigner Ville distribution (SP-WVD). Realistic open-field outdoor experiments are conducted covering different simultaneous postures of (i) two-/three-blade propeller/roto systems, (ii) flapping bionic bird, and (iii) kinetic warhead targets. The associated experimental results and findings are reported and analyzed in this paper. The limitations and possible future research studies are also discussed in the conclusion.

Liquid materials’ characterization using commercial probes and radio frequency techniques is expensive and complex. This study proposes a compact and cost-effective radio frequency sensor system to measure the dielectric constant using a three-material calibration. The simplified approach measures reflection coefficient magnitudes for all four materials rather than the complex values in conventional permittivity detection systems. We employ a sensor module based on a circular substrate-integrated waveguide with measured unloaded quality factor = 910 to ensure measurement reliability. Miniaturized quarter-mode substrate-integrated waveguide resonators are integrated with four microfluidic channels containing three known materials and one unknown analyte. Step-wise measurement and linearity ensures maximum 4% error for the dielectric constant compared with results obtained using a high-performance commercial product.

A device for measuring biological small volume liquid samples in real time is appealing. One way to achieve this is by using a microwave sensor based on reflection measurement. A prototype sensor was manufactured from low cost printed circuit board (PCB) combined with a microfluidic channel made of polymethylsiloxane (PDMS). Such a sensor was simulated, manufactured, and tested including a vacuum powered sample delivery system with robust fluidic ports. The sensor had a broad frequency band from 150 kHz to 6 GHz with three resonance frequencies applied in sensing. As a proof of concept, the sensor was able to detect a NaCl content of 125 to 155 mmol in water, which is the typical concentration in healthy human blood plasma.

In order to perform complex manipulation and grasp tasks, robotic hands require sensors that can handle increasingly demanding functionality and degrees of freedom. This research paper proposes a radiofrequency sensor that uses a wireless connection between a probe and a tag. A compact and low-profile antenna is mounted on the hand and functions as a probe to read a printed passive resonator on the plastic object being targeted, operating within a pre-touch sensing range. The grasping strategy consists of four stages that involve planar alignment in up-to-down and left-to-right directions between the probe and tag, the search for an appropriate distance from the object, and rotational (angular) alignment. The real and imaginary components of the probe-input impedance are analyzed for different orientation strategies and positioning between the resonator on the object and the probe. These data are used to deduce the orientation of the hand relative to the target object and to determine the optimal position for grasping.

Hydrogen combustion engines can contribute to CO 2 -free mobility. However, they produce NO x emissions, albeit only to an extremely small extent when operated very leanly. One approach to reduce these emissions even further is to use exhaust gas aftertreatment systems like NO x storage catalysts (NSC). So far, they have mainly been used in diesel or gasoline applications. This contribution shows that under conditions such as those prevailing in hydrogen engines, the NSC can achieve not only a higher storage capacity for nitrogen oxides (NO x ) but also a higher conversion. To ensure permanently high conversion rates, the amount of stored NO x has to be monitored permanently to prevent NO x breakthroughs. Conventional NO x sensors may not be accurate enough due to the very low NO x emissions. The functionality of the radio frequency (RF) sensor, which enables a direct determination of the NO x loading, is demonstrated for operation under hydrogen conditions. Furthermore, the influence of rich exhaust gas on the RF signal, which is relevant for a correct NO x loading determination during regeneration, is analyzed.

This paper presents the concept of a radiofrequency (RF) sensor designed to estimate the mass of the regolith acquired by a sampling device or excavator in planetary environments. The sensor utilizes a microstrip line with an open end as the sensing element, with the mass estimation based on measurements of the phase of the reflection coefficient (S11 of the scattering matrix) for the line immersed in the regolith. The Rotary Clamshell Excavator (RCE) was employed for the experimental evaluation of the sensor’s performance. The RCE successfully passed an environmental test campaign, demonstrating its suitability for future lunar missions. The test results indicate that the RF sensor can estimate the mass of the acquired regolith with reasonable accuracy, approximately 15%, making it a viable solution for rough mass estimation in sampling devices and excavators.

A novel compact RF sensor based on a Complementary Split Ring Resonator (CSRR) for the detection of impurities in liquid samples is designed, developed, and experimentally validated. The sensor uses changes in dielectric permittivity to measure the levels of impurities in common liquids and operates at 2.4 GHz. Two sensor configurations were designed and tested, with different dimensions. The sensor structure’s form is intended to achieve increased sensitivity. Because it makes use of the bent form configuration, the sensor structure is fairly compact. The manufactured sensor prototype has a sensitivity of 39.36, which is significantly higher than the sensors found in the literature. A case study was conducted on milk, with water and vegetable oil as impurities and changes in resonant frequency is measured. The sensor provides a 100 kHz shift in the resonant frequency for 50% adulteration. The sensor’s compact design, ease of fabrication using a low-cost FR4-Epoxy substrate, and high accuracy make it a viable alternative for non-destructive impurity detection in food safety, healthcare, and environmental monitoring applications.

Wireless, passive, and flexible strain sensors can transform structural health monitoring across various applications by eliminating the need for wired connections and active power sources. Such sensors offer the dual benefits of operational simplicity and high‐function adaptability. Herein, a novel wireless sensor is fabricated using radio frequency (RF) technology for passive, wireless measurement of mechanical strains. Previously introduced concept of coupling piezoresistive electrodes is utilized with capacitive sensors to ensure high‐sensitivity capacitive sensing. For the first time, it is implemented and demonstrated here as a fully printable, inexpensive, and ready‐to‐use device utilizing the recent advances in piezoresistive inks and screen‐printing technologies. The near‐field communication (NFC) tag features an inductor ‐ capacitor (LC) resonant circuit with a distinct resonant frequency. The sensor exhibits high sensitivity and detects substantial variations in capacitance, with a gauge factor (GF) of ≈16 at 20 MHz for strain levels below 5%. Within the wireless framework, the sensor achieves a significant shift in resonance frequency (GF of ≈2.2). It also exhibited excellent performance in wirelessly monitoring the strain in a glass fiber‐reinforced polymer (GFRP) specimen during the bending test. The results confirm the potential applicability of the sensor as an embedded sensor for monitoring various types of composite structures. This confirms the potential of the sensor for use in composite structures as an embedded sensor. Wireless, passive, and flexible strain sensors revolutionize structural health monitoring by removing wired connections and power needs. A novel radio frequency (RF)‐based wireless sensor is presented for passive strain measurement, that integrates piezoresistive electrodes with capacitive sensors for high sensitivity. This fully printable, low‐cost device using piezoresistive inks and screen‐printing, features an Near field communication (NFC) tag with an inductor‐capacitor (LC) resonant circuit. The sensor demonstrates high sensitivity and significant shifts in the resonance frequency.

In this paper, the adulteration detection in mustard oil is performed using the non-destructive (ND) novel multi-frequency resonant radio frequency (RF) sensor. The proposed sensor uses the permittivity values (calculated with the help of scattering parameter) as a parameter for quantifying the adulterated mustard oil. A diamond shaped RF sensor with microfluidic channel is proposed for monitoring mustard oil adulteration. The mustard oil is used as oil under test (OuT), whereas coconut, refined and olive oil as adulteration under test (AuT). The novelty of the proposed RF sensor is to enhance the accuracy and precision for the OuT for testing the adulteration content. The sensor resonates at multiple frequency enabling the enhanced differentiability for the different quantity of AuT mixed with OuT. The simulation is performed for optimization of the microfluidic channel and resonant frequency. The sensor is fabricated and tested for different quantity of AuT mixed with OuT and performance matrix is obtained. The sensitivity observed is 0.1 for the oil adulteration detection with the proposed device.