Passive Wireless Sensor Research Articles

A Miniaturized Wireless Passive Frequency Selective Surface Sensor for High-Temperature Applications

A passive and wireless sensor based on frequency selective surface (FSS) is presented for high-temperature applications. The sensor consists of a bent square loop array deposited in an alumina dielectric substrate. By inserting four symmetrical slots in the square loop structure, the dimension of the FSS unit cell is as compact as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.13 \lambda _{{0}}$ </tex-math></inline-formula> . The results show that the resonant frequency of the sensor decreases from 13.96 to 13.172 GHz with an average sensitivity of 0.81 MHz/°C when the temperature rises from 25 to 1000 °C. It was found that the resonant frequency shift is mainly attributed to the variations in permittivity of the substrate material. The sensor has a stable resonant frequency for both TE and TM polarizations under incident angles with a range of 0°–30°. The proposed sensor, which has the advantages of miniaturization, low profile, high sensitivity, and excellent angular stability, can be potentially applied in various harsh environments.

A Review of Radio Frequency Identification Sensing Systems for Structural Health Monitoring.

Structural health monitoring (SHM) plays a critical role in ensuring the safety of large-scale structures during their operational lifespan, such as pipelines, railways and buildings. In the last few years, radio frequency identification (RFID) combined with sensors has attracted increasing interest in SHM for the advantages of being low cost, passive and maintenance-free. Numerous scientific papers have demonstrated the great potential of RFID sensing technology in SHM, e.g., RFID vibration and crack sensing systems. Although considerable progress has been made in RFID-based SHM, there are still numerous scientific challenges to be addressed, for example, multi-parameters detection and the low sampling rate of RFID sensing systems. This paper aims to promote the application of SHM based on RFID from laboratory testing or modelling to large-scale realistic structures. First, based on the analysis of the fundamentals of the RFID sensing system, various topologies that transform RFID into passive wireless sensors are analyzed with their working mechanism and novel applications in SHM. Then, the technical challenges and solutions are summarized based on the in-depth analysis. Lastly, future directions about printable flexible sensor tags and structural health prognostics are suggested. The detailed discussion will be instructive to promote the application of RFID in SHM.

Introduction of Passive Wireless SAW Temperature Sensors and Application

Introduction of Passive Wireless SAW Temperature Sensors and Application

Range Extension in Coupling-Based Wireless Passive Displacement Sensors for Remote Structural Health Monitoring

Wireless monitoring of displacement between two points is demonstrated with an interrogation range ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${D}_{\boldsymbol {m}}$ </tex-math></inline-formula> ) which is dramatically larger compared with previous configurations based on near-field coupling. The sensing system comprises a transmitting antenna, a nested split-ring resonator (NSRR) sensor functioning as a tag, and a probe, called a “sniffer coil.” In classical configuration, the NSRR and the antenna constitute an electromagnetically coupled system which exhibits high sensitivity and resolution but is only functional within the near-field of the antenna, which in practice is much smaller than one wavelength, which limits the capabilities of the sensor. In this work, the system is separated into the TX and RX channels, which enables the transmitter antenna to be placed at a location which is several wavelengths away from the sensor. To remove the effect of clutter that disrupted the sensing signal at higher <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${D}_{\boldsymbol {m}}$ </tex-math></inline-formula> in previous works, the variation with frequency of the power level coupled to the sniffer coil is tracked instead of the variation in the scattering parameters with frequency. While extending <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${D}_{\boldsymbol {m}}$ </tex-math></inline-formula> , the high sensitivity and resolution are retained by the coupling between the NSRR and the sniffer coil. Wireless sensing of displacement is essential for several application areas, most specifically, structural health monitoring (SHM). The fact that the sensing system can work in far-field and that the NSRR is passive allows for remote and nondestructive testing (NDT) of damaged structures and buildings.

Software Analysis of the Signal Radio Profile during Passive Radio-Sensor Technical Diagnostics

Software Analysis of the Signal Radio Profile during Passive Radio-Sensor Technical Diagnostics

On-Line Temperature Monitoring System of Electrical Equipment Based on Passive Wireless Sensor

In order to solve the temperature measurement problem of fully enclosed equipment for power equipment operation inspection, the authors propose an online temperature monitoring system for electrical equipment based on passive wireless sensors. Aiming at the disadvantages of traditional temperature monitoring methods, the system adopts radio frequency technology. The scheme mainly expounds the key technologies and switchgear implementation in the monitoring system research and discusses the feasibility of the system scheme through experiments. Monitor all important components at different times, and establish a temperature monitoring network to complete monitoring and management. According to the test results, in the case of overheating, the temperature can rise to more than 75°C, and the temperature difference measured wirelessly is 0.5°C, which is sufficient to indicate the health of the change. Electrical equipment, the accuracy, and real-time performance of temperature monitoring are guaranteed.

A nanowatt noise-shaping SAR ADC for passive wireless sensor node application

A nanowatt noise-shaping SAR ADC for passive wireless sensor node application

Near Field Sensing Applications with Tunable Beam Millimeter Wave Antenna Sensors in an All-in-One Chip Design

In this paper, a single-band beam control antenna is designed with a parallel coupler to realize a microstrip patch antenna passive wireless sensor in the form of a chip. It has a phase shift characteristic of the antenna radiation direction in the positive and negative directions. The antenna includes an orthogonal direction coupler design with a 90° parallel coupler in phase using a special structure that allows the whole chip area to be miniaturized while allowing the main beam angle to have a directivity function. The coupler is designed for the 28 GHz millimeter wave band. After feeding the patch antenna at the output port of the coupler and simultaneously feeding the excitation at the input port, the beam phase changes to +45° and +135° with a phase difference of 90°. The designed antenna size is 1160 μm × 790 μm, and the overall IC size is 1.2 mm × 1.2 mm. The power density simulation shows that the maximum power density is only 0.00797 W/kg for a 1 cm2 human sampling area, which means that the antenna sensor is suitable for use on human surfaces.

Contactless Air-Filled Substrate-Integrated Waveguide (CLAF-SIW) Resonator for Wireless Passive Temperature Sensing

In this article a wireless passive temperature sensor is designed, fabricated, and tested. The sensor uses a contactless air-filled substrate-integrated waveguide (CLAF-SIW) resonator that consists of an air cavity surrounded by a low-impedance electromagnetic band gap (EBG) structure. The contactless feature of the sensor mitigates the fabrication complexity issue of air-filled SIW (AF-SIW) while it benefits from the high-quality factor of an air-filled resonator. The resonant frequency of the CLAF-SIW resonator is dependent on the permittivity of the substrate and the dimensions of the structure which are both temperature-dependent. Change in temperature results in a variation in the resonant frequency of the sensor. As such, we measure temperature by measuring the resonant frequency of the sensor. The developed CLAF-SIW sensor has a measured unloaded quality factor of 1340 that allows for long-range wireless measurements. The resonant frequency of the sensor is measured using a ringback-based wireless interrogation system. The interrogation system energizes the sensor using radio frequency (RF) pulses and determines the frequency of the ringback signals radiated by the sensor using frequency domain analysis. The sensor has a sensitivity of 300 kHz/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^\circ \text{C}$ </tex-math></inline-formula> and an interrogation-to-sensor distance of 80cm.

Design and Research of Wireless Passive High-Temperature Sensor Based on SIW Resonance

The temperature of advanced components in aviation and aerospace fields is difficult to obtain timely. In this study, we aimed to investigate microwave backscattering technology combined with the theory of substrate integrated waveguide and resonant cavity to design a wireless passive temperature sensor and explore its potential in this field. We employed silicon carbide and aluminum ceramic as the substrate to make sensors. The interrogation antenna was designed to test the sensor, which could completely cover the working frequency of the sensor and had good radiation characteristics. Based on the test results, the silicon carbide sensor was capable of bearing a temperature limit of about 1000 °C compared to the alumina sensor. From 25 °C to 500 °C, its sensitivity was 73.68 kHz/°C. Furthermore, the sensitivity was 440 kHz/°C in the range of 501 °C to 1000 °C. Moreover, we observed the surface of this sensor by using the scanning electron microscope, and the results showed that the damage to the sensor surface film structure caused by long-term high temperature is the major reason for the failure of the sensor. In conclusion, the performance of the silicon carbide sensor is superior to the alumina sensor.

A dual LC resonant circuit integrated wireless passive force and temperature sensor for harsh-environment applications

This paper proposes a dual inductor-capacitor (LC) circuit integrated wireless and passive force and temperature sensor for the simultaneous measurement of force and temperature in high-temperature environments. The sensor is fabricated by a two-step process: the preparation of the Al2O3 substrate and the fabrication of the dual LC sensor with Ag paste using screen-printing technology and metallization. The variation in ambient force and temperature can be detected wirelessly by extracting the resonant frequencies of the antenna. The sensor can work in the force range of 0–10 N and temperature range of 25–500 °C with a maximum force sensitivity of 107 kHz/N at 500 °C and temperature sensitivity of 21.7 kHz/°C. To precisely measure the force, the temperature compensation method is proposed. The sensor has the advantages of low cost, simple fabrication and test, and high stability and repeatability, which are promising for the force and temperature application on the engine turbine blade in high-temperature environments.

LC Passive Wireless Sensor System Based on Two Switches for Detection of Triple Parameters.

This paper presents the LC-type passive wireless sensing system for the simultaneous and independent detection of triple parameters, featuring three different capacitive sensors controlled by two mechanical switches. The sensor coil was connected with three different capacitors in parallel and two mechanical switches were in series between every two capacitors, which made the whole system have three resonant frequencies. The readout coil was magnetically coupled with the sensor coil to interrogate the sensor wirelessly. The circuit was simulated advanced design system (ADS) software, and the LC sensor system was mathematically analyzed by MATLAB. Results showed that the proposed LC sensing system could test three different capacitive sensors by detecting three different resonant frequencies. The sensitivity of sensors could be determined by the capacitance calculated from the detected resonant frequencies, and the resolution of capacitance was 0.1 PF and 0.2 PF when using the proposed sensor system in practical applications. To validate the proposed scheme, a PCB inductor and three variable capacitors were constructed with two mechanical switches to realize the desired system. Experimental results closely verified the simulation outputs.

All-Ceramic Passive Wireless Temperature Sensor Realized by Tin-Doped Indium Oxide (ITO) Electrodes for Harsh Environment Applications.

In this work, an all-ceramic passive wireless inductor–capacitor (LC) resonator was presented for stable temperature sensing up to 1200 °C in air. Instead of using conventional metallic electrodes, the LC resonators are modeled and fabricated with thermally stable and highly electroconductive ceramic oxide. The LC resonator was modeled in ANSYS HFSS to operate in a low-frequency region (50 MHz) within 50 × 50 mm geometry using the actual material properties of the circuit elements. The LC resonator was composed of a parallel plate capacitor coupled with a planar inductor deposited on an Al2O3 substrate using screen-printing, and the ceramic pattern was sintered at 1250 °C for 4 h in an ambient atmosphere. The sensitivity (average change in resonant frequency with respect to temperature) from 200–1200 °C was ~170 kHz/°C. The temperature-dependent electrical conductivity of the tin-doped indium oxide (ITO, 10% SnO2 doping) on the quality factor showed an increase of Qf from 36 to 43 between 200 °C and 1200 °C. The proposed ITO electrodes displayed improved sensitivity and quality factor at elevated temperatures, proving them to be an excellent candidate for temperature sensing in harsh environments. The microstructural analysis of the co-sintered LC resonator was performed using a scanning electron microscope (SEM) which showed that there are no cross-sectional and topographical defects after several thermal treatments.

Radio Frequency Resonator-Based Flexible Wireless Pressure Sensor with MWCNT-PDMS Bilayer Microstructure.

Flexible pressure sensors have been widely applied in wearable devices, e-skin, and the new generation of robots. However, most of the current sensors use connecting wires for energy supply and signal transmission, which presents an obstacle for application scenarios requiring long endurance and large movement, especially. Flexible sensors combined with wireless technology is a promising research field for realizing efficient state sensing in an active state. Here, we designed and fabricated a soft wireless passive pressure sensor, with a fully flexible Ecoflex substrate and a multi-walled carbon nanotube/polydimethylsiloxane (MWCNT/PDMS) bilayer pyramid dielectric structure. Based on the principle of the radio-frequency resonator, the device achieved pressure sensing with a changeable capacitance. Subsequently, the effect of the pyramid density was simulated by the finite element method to improve the sensitivity. With one-step embossing and spin-coating methods, the fabricated sensor had an optimized sensitivity of 14.25 MHz/kPa in the low-pressure range. The sensor exhibited the potential for application in limb bending monitoring, thus demonstrating its value for long-term wireless clinical monitoring. Moreover, the radio frequency coupling field can be affected by approaching objects, which provides a possible route for realizing non-contact sensing in applications such as pre-collision warning.

Space Tags: Ultra-Low-Power Operation and Radiation Hardness for Passive Wireless Sensor Tags

Space agencies worldwide have a long-term vision of sending human missions to Mars <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> . The next favorable launch window occurs in 2033, and plans are ongoing to realize such endeavors. An essential part of this preparation is the search for new technologies to mitigate mission performance risks. A critical further technological advancement is passive or batteryless wireless sensor technology <xref ref-type="bibr" rid="ref2" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[2]</xref> , <xref ref-type="bibr" rid="ref3" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[3]</xref> , as used in the Internet of Things (IoT) <xref ref-type="bibr" rid="ref4" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[4]</xref> , which can be favorably used to continuously monitor the physiological conditions of crew members in the space habitat and structural health of spaceflight equipment.

СХЕМОТЕХНИЧЕСКОЕ И ЭЛЕКТРОДИНАМИЧЕСКОЕ МОДЕЛИРОВАНИЕ КОЛЕБАТЕЛЬНОГО ПРОЦЕССА ПЕРЕРАСПРЕДЕЛЕНИЯ ЭНЕРГИИ В БИПОЛЯРНОМ ТРАНЗИСТОРЕ

The advantage of the promising method of passive radiosensor technical diagnostics(PRTD) over the currently existing methods for determining the technical condition (vibrometry,thermal control, JTAG-testing, optical control) are: no inertia, no processor time, no galvaniccontact with the object of study. In modern scientific literature, almost no attention is paid to numericalmodels of electronic devices, including those based on bipolar transistors (BPT), whichdescribe the process of oscillatory redistribution of energy and radiation used in PRTD. Therefore,the purpose of this study is to develop the PRTD method through the development, analysisand comparison of circuit and electrodynamic models of oscillatory energy redistribution in theBPT. The paper presents and analyzes simplified circuit and electrodynamic models of oscillatoryredistribution of energy in the BPT. The parameters of the models are calculated signal radioprofiles (SRP) are obtained for the electrical component of electromagnetic radiation created bythe radio-electronic unit itself, built on the BPT. Methods for adjusting the reference parametersdepending on the actual conditions for switching on the BPT are shown. It has been establishedthat the cross-correlation function of the SRP obtained as a result of circuit and electrodynamicmodeling is not lower than 0.93, which indicates a high similarity of the presented models. Inpractice, the use of the developed models in the analysis of SRP obtained by recording the intrinsicemissions of radio engineering components of electronic devices will allow us to determine theoperating mode of the BPT and its speed with a sufficiently high accuracy. This analysis can beused in the PRTD, indicating a malfunction of the signal circuits, or degradation of the parametersof the element itself in the early stages

High temperature effects on surface acoustic wave strain sensor

Surface acoustic wave sensors (SAW), as a wireless passive sensor, are susceptible to temperature disturbance for high-temperature strain measurements, which results in poor accuracy and repeatability of the strain sensing. This paper investigates temperature effects on SAW strain sensors. Results show that high temperature not just induces frequency drift, but also reduces strain transfer ratio due to glue softening. The resonant frequencies of the langasite (LGS) SAW sensor have a linear relationship with strain for fixed temperatures, while the strain sensitivity is greatly affected by temperature. The results also show that the difference of measured strain sensitivities between the two resonant frequencies for one device is much less affected by temperature because they suffer the same strain transfer ratio and temperature characteristics, but different strain responses. A method to eliminate temperature effects has been proposed and accurate high-temperature strain measurements with SAW sensor were conducted to extend strain range up to 380 με with high repeatability under 500 °C.

Wireless Passive Flexible Strain Sensor Based on Aluminium Nitride Film

Rolling bearings are important components of a mechanical structure; their state directly affects the operation of the whole mechanical system. To accurately and reliably evaluate the damage state of bearings, a wireless passive flexible strain sensor based on an aluminium nitride (AlN) film was proposed in this paper. The sensor was connected to the system using a plane inductor and an interdigital capacitor to form an LC loop, and the AlN film was deposited in the interdigital capacitor part to enhance the sensing performance. The structure of the sensor was optimised using a high-frequency structure simulator (HFSS), and the optimal coupling distance between the sensor and antenna was determined. The test results revealed that the resonant frequency of the sensor increases from 43.7089 to 43.735 MHz in a strain range of 0– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3000 ~\mu \varepsilon $ </tex-math></inline-formula> , and strain resolution is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$20 ~\mu \varepsilon $ </tex-math></inline-formula> . Moreover, the wireless strain sensor has a small size and high resolution. The flexible substrate can stick well to the part to be tested and can be applied to the bearing to detect micro-strain. Therefore, this sensor is applicable in fault prevention, condition monitoring, and non-destructive evaluation.

A Batteryless RFID Sensor Architecture With Distance Ambiguity Resolution for Smart Home IoT Applications

In this article, a novel batteryless wireless sensor design is proposed and demonstrated. The proposed passive wireless sensor node integrates a ultrahigh-frequency (UHF) radio-frequency identification (RFID) chip, a filter, and a reactive sensor to enable the reading of environmental conditions wirelessly, without increasing the complexity of a typical RFID chip and substantial loss of the read range. The sensor changes the phase of the reflected RFID signal based on the sensed parameter; whereas, the filter helps in resolving any phase ambiguity that may arise due to the placement of the node at different distances. The phase change is detected at the reader using a noncoherent IQ demodulator. The design can easily integrate any type of sensors, such as temperature, humidity, and water-level sensor. A flood sensor and a temperature sensor were used to demonstrate the performance of the proposed design in a home and office environment.

Degradation of Sub-Micrometer Sensitive Polymer Layers of Acoustic Sensors Exposed to Chlorpyrifos Water-Solution.

The detection of organophosphates, a wide class of pesticides, in water-solution has a huge impact in environmental monitoring. Acoustic transducers are used to design passive wireless sensors for the direct detection of pesticides in water-solution by using tailored polymers as sensitive layers. We demonstrate by combining analytical chemistry tools that organophosphate molecules strongly alter polymer layers widely used in acoustic sensors in the presence of water. This chemical degradation can limit the use of these polymers in detection of organophosphates in water-solution.