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This work addresses the theoretical and experimental investigations of a Love wave based device employing waveguide structure of SiO2/36° YX-LiTaO3 for sensing icing process. The mass loading effect induced by the icing process modulates the acoustic wave propagation, and corresponding changes in device frequency can be collected to evaluate the icing process. The waveguide structure confines the acoustic wave energy into SiO2 thin-film, which contributes well to the improvement of the mass loading sensitivity. The corresponding sensing mechanism was analyzed by solving the acoustic propagation equations in layered structure. The sensing device patterned by delay-line on 36° YX-LiTaO3 substrate with SiO2 guiding layer was photolithographically developed as the sensor element, and characterized by using the high-low temperature chamber. The icing process was simulated by dropping appropriate water on top of the device surface. Very clear and fast frequency response was observed from the proposed sensing device in the icing process, and also, the influence of SiO2 guiding layer thickness on sensor response was also investigated.

Magnetostrictive thin-film coated Surface Acoustic Wave (SAW) devices were promising for sensing magnetic field owing to their superior features as micro-size, fast response, and high sensitivity originated from the magnetostrictive effect. However, the magnetostriction nature in magnetostrictive thin-film causes significantly mechanical fatigue in service, deteriorating the sensor performances. In this work, the fatigue phenomenon in magnetostrictive coating was underlined by characterizing the prepared FeCo thin-film coated magnetic device cyclically. Obvious shedding was observed in FeCo coating after cyclic testing and the magnetic-sensitivity decreases significantly. One of the reasons is the weak adhesion of FeCo thin-film towards the substrate. As an available way allowing enhancement of adhesion, a Cr thin-film was employed as the transition-layer to weaken the mechanical fatigue. However, it accompanied by the issue of the reduced magnetostrictive coefficient and the obstruction in magnetostrain-tranfer to piezoelectric substrate. As a result, the slump in sensitivity was observed. To address such issues, a design of dotted-pattern with Cr transition layer was employed to build the SAW based magnetic-device. High magnetic-sensitivity and excellent long-term stability were achieved because of the release of coercive force in FeCo dots and enhancement of the FeCo adhesion to the substrate.

In this paper, a new TbDyFe thin-film coated Surface Acoustic Wave (SAW) sensor is proposed for sensing current. A 150 MHz SAW device with delay line pattern is fabricated photolithographically on 128° YX LiNbO 3 substrate. Then the TbDyFe thin-film is deposited into the propagation path of surface acoustic wave by magnetron sputtering to build the sensing device. The reference sensing device with TbDyFe thin-film and the naked device are collected in a dual-channel differential oscillator so as to build the current sensor. When the magnetic field excited by the current is applied, the magnetostrictive effect produced by the TbDyFe thin-film causes the change of SAW propagation speed. And then the change of the corresponding oscillator frequency is used to characterize the current. Taking advantage of the TbDyFe thin-film such as high magnetostrictive coefficient and low coercive force, high sensitivity of 16.8 kHz/A is achieved in the experiments.

Employing palladium and copper nanowires (Pd/Cu NWs) as the sensitive interface, a new surface acoustic wave (SAW) sensor with fast response and recovery was developed successfully for hydrogen gas sensing. The adsorption in Pd/Cu NWs towards hydrogen molecules modulates the SAW propagation by the induced acoustoelectric coupling effect from the changes in the resistivity of Pd, and the corresponding shifts in oscillation frequency proportional to gas concentration was collected as the sensor signal. Larger surface-to-volume of the Pd/Cu NWs contributes to improve the response speed and sensitivity. A 150 MHz SAW device with delay line pattern was fabricated photolithographically on 128° YX LiNbO3 substrate, and the Pd/Cu NWs that synthesized by optimized electrochemical deposition were dissolved in ethanol and deposited onto the SAW device surface by dropping method to build the SAW hydrogen sensors. The prepared SAW sensors were characterized by using the differential oscillation loop experimentally, excellent repeatability, fast response and recovery within 4s, and a sensitivity of 1.5 kHz/%were achieved at room temperature (25°C). Additionally, the response mechanism in hydrogen sensing was investigated experimentally.

Research has shown that SAW (surface acoustic wave) devices with an LGS/Pt (langasite La3Ga5SiO14/platinum) structure are useful in high-temperature sensor applications. Extreme high temperature brings great acoustic attenuation because of the thermal radiation loss, which requires that the sensing device offer a sufficiently high quality factor (Q) and a low loss. Therefore, it is necessary to improve the performance of the quality factor as much as possible so as to better meet the application of high-temperature sensors. Based on these reasons, the main work of this paper was to extract accurate simulation parameters to optimize the Pt/LGS device and obtain Q-value device parameters. Optimization of SAW devices with LGS/Pt structure for sensing extreme high temperature was addressed by employing a typical coupling of modes (COM) model in this work. Using the short pulse method, the reflection coefficient of Pt electrodes on LGS substrate was extracted accurately by characterizing the prepared SAW device with strategic design. Other relevant parameters for COM simulation were determined by finite element analysis. To determine the optimal design parameters, the COM simulation was conducted on the SAW sensing device with a one-port resonator pattern for sensing extreme temperature, which allows for a larger Q-value and low insertion loss. Experimental results validate the theoretical simulation. In addition, the corresponding high-temperature characteristics of the prepared sensing device were investigated.

In this paper, a novel surface acoustic wave current sensor combining SAW technology and magnetostrictive material is proposed. The typical structure of the sensor is a surface acoustic wave device surface sputtered hysteresis film based on planar lithography. The magnetic sensitive materials with high magnetostriction coefficient are a key factor. In this paper, the TbDyFe giant magnetostrictive film with better performance is used to induce the magnetostrictive strain by applying a magnetic field induced by current, which causes the SAW propagation speed to change. The applied current is evaluated using the differential oscillation frequency offset of the differential delay line oscillating loop. Current experiments show that the current sensor proposed in this paper has high sensitivity and good linearity.

a novel configuration of wireless and passive Love wave based ice sensing device employing waveguide structure of SiO 2 /36°YX LiTaO 3 with high mass sensitivity and excellent temperature stability was presented in this work. A reflective delay line consists of a transducer and three reflectors on 36° YX LiTaO 3 substrate with SiO 2 guiding layer was developed as the sensor element. Prior to sensing device development, the coupling of modes (COM) modeling was performed to device simulation. Using the typical lithography technology, the sensing device was developed at 433 MHz, and packaged with a permeable film. Using the experimental setup composed of a high-low temperature chamber, wireless transceiver module and sensing device, the response in time domain of the developed sensing device was characterized. The mass loading effect in icing process modulates the propagation of Love wave, resulting in the corresponding phase response shift. By wireless measurement, the phase change from water to ice was detected, and the measured results addressed the feasibility and effectiveness of the proposed wireless and passive Love wave ice sensor.

In this work, a surface acoustic wave device with delay line pattern with operation frequency of 200MHz was developed for sensing ice. Y-cut 35° quartz was employed as piezoelectric crystal, which exhibits excellent temperature stability. A SiO 2 thin-film was coated onto the SAW device after the photolithographic deposition of interdigital transducers (IDTs) to protect the metal electrodes in process of ice formation. The developed SAW sensing chip was characterized by using the high-low temperature chamber. When the temperature in chamber was dropped to the freezing point, a sharp change in frequency of the sensing device was observed because of the mass loading effect from the ice layer. The theoretical results obtained by solving the acoustic wave equations in layered structure oifers a clear explanation for the phenomenon observed. Obviously, fast and distinct response towards ice accretion was achieved from the developed SAW device, which indicates that it is very promising for sensing ice.

To suppress the hysteresis of the magnetostrictive thin-film coated surface acoustic wave (SAW)magnetic field sensor, dotted-design was proposed for magnetostrictive FeCo thin-film in this paper to fully release the magnetostrictive effect and reduce its coercivity. The developed sensor was composed of a sensor chip made by differential delay line-oscillators consist of two oscillation loops, the differential oscillation frequency is collected to evaluate the applied magnetic field. A FeCo dot film was deposited along the SAW propagation path of the sensing device by photolithography and overlay technologies. The size of the FeCo dot element was 3λX4λ (λ: wavelength). The patterned FeCo film produced magnetostrictive effect and ΔE effect generated by the applied magnetic field, resulting in changes in the SAW phase velocity and the corresponding oscillation frequency. Using the Helmholtz coil system, the developed SAW magnetic field sensor with 500 nm FeCo dot film were evaluated. The measured results indicated the dotted pattern design on the FeCo thin-film improved effectively its sensitivity (10.7 KHz/mT)and linearity, and also the hysteresis error reduced significantly up to 0.85%.

Fast detection and monitoring for hydrogen (H 2 )is essential in H 2 energy application. A new surface acoustic wave (SAW)H 2 sensor was proposed in this contribution employing supperlattice-structured palladium and copper nanowires(Pd/Cu NWs)depositing along the SAW propagation path and a differential oscillator structure. The adsorption in Pd/Cu NWs towards H 2 molecules modulates the SAW propagation, and the corresponding shifts in oscillation frequency proportional to gas concentration was collected as the sensor signal. The larger surface-to-volume (S/V)ratio and porous structure of the Pd/Cu NWs synthesized by wet-chemical approaches fasten the response and recovery time in H 2 -sensing behaviors, which was confirmed by characterizing the developed SAW sensors built with PdCu NWs and delay line pattern. Very fast response time and recovery time of less than 3s were achieved successfully at room temperature, also, the obtained sensitivity and detection limit are evaluated up to 1.5kHz/% and 7 ppm.

To suppress the hysteresis effect of the magnetostrictive film coated surface acoustic wave (SAW) current sensor, a patterned design on magnetostrictive FeCo coating was performed in this contribution. The developed sensor was composed of a configuration of dual-delay-line oscillators, and a strip-patterned magnetostrictive FeCo coated onto the SAW propagation path of the sensing SAW device. The patterned FeCo produced magnetostrictive strain under the electromagnetic field, generating changes in the thickness, density, and Young's modulus of the FeCo film, then the SAW propagation characteristic was modulated in the form of a linear SAW velocity shift, and the corresponding change in differential oscillation frequency was used to evaluate the applied current. The design of striped pattern with strip width of 2λ (λ: wavelength) and strip spacing of 1λ was conducted for sensing chip, and the chips were fabricated by RF magnetron sputtering deposition and overlay lithographic technique. By using the experimental setup made by the Helmholtz coil system, favorable sensitivity, excellent linearity, and lower hysteresis error were obtained from the developed SAW current sensor with strip-patterned FeCo coating in the experiments.

A magnetostrictive FeNi-coated surface acoustic wave (SAW)-based current sensor was proposed in this work. The weak remanence and hysteresis effect of the FeNi itself contributes to suppress the asymmetry in sensor response at increasing and decreasing current. The sensor response was simulated by solving the coupled electromechanical field equation in layered structure considering the magnetostrictive effect and an approach of effective dielectric constant. The effects from the aspect ratio and thickness of the FeNi film on sensor response were analyzed to determine the optimal design parameters. Differential oscillation structure was used to form the sensor, in which, the FeNi thin film was deposited along the SAW propagation of the sensor chip by using RF magnetron sputtering. The magnetostrictive effect of the FeNi coating induced by the magnetic loading generates the perturbation in SAW velocity, and corresponding oscillation frequency. High sensitivity of 10.7 KHz/A, good linearity and repeatability, lower hysteresis error of 0.97% were obtained from the developed prototype 150 MHz SAW FeNi coated current sensor.

A new surface acoustic wave (SAW) magnetic field sensor was conducted in this contribution, which was composed of a differential delay-line oscillation configuration, and a magnetostrictive FeCo film coated onto the SAW propagation path of the sensing SAW device. The FeCo coating produces magnetostrictive strain under the magnetic field, then leading to changes in the SAW propagation velocity. The corresponding differential oscillation frequency shift was used to evaluate the applied magnetic field. By theoretical analysis, the sensor response from the FeCo coated magnetic field sensor was predicted. Using the Helmholtz coil system, the developed SAW sensor was characterized, high sensitivity of 8.3 kHz/mT and good linearity were achieved from the developed 300 MHz SAW magnetic field sensor.A new surface acoustic wave (SAW) magnetic field sensor was conducted in this contribution, which was composed of a differential delay-line oscillation configuration, and a magnetostrictive FeCo film coated onto the SAW propagation path of the sensing SAW device. The FeCo coating produces magnetostrictive strain under the magnetic field, then leading to changes in the SAW propagation velocity. The corresponding differential oscillation frequency shift was used to evaluate the applied magnetic field. By theoretical analysis, the sensor response from the FeCo coated magnetic field sensor was predicted. Using the Helmholtz coil system, the developed SAW sensor was characterized, high sensitivity of 8.3 kHz/mT and good linearity were achieved from the developed 300 MHz SAW magnetic field sensor.

The magnetostrictive effect in micro-dotted FeCo film coated surface acoustic wave (SAW) devices was demonstrated by solving coupling equations using the specific coupling of modes parameters extracted by FEM analysis. Dotted-pattern on FeCo thin-film proposed in this work contributes well to suppression in hysteresis effect by fully releasing the internal coericivity of the magnetistrictive FeCo thin-film. The theoretical demonstration was confirmed well by characterizing the constructed SAW magnetic devices with FeCo dots depositing along the SAW propagation path. Significantly improvements on suppression of hysteresis phenomenon were observed by characterizing the prepared FeCo dots coated SAW magnetic devices, higher magneto-sensitivity of 21.17 kHz mT−1, and lower hysteresis error of 0.82% were achieved successfully.

This study addresses the theoretical and experimental investigations of grating-patterned magnetostrictive FeCo coated surface acoustic wave (SAW) device for sensing magnetic field. The proposed sensor is composed of a configuration of differential dual-delay-line oscillators, and a magnetostrictive FeCo grating array deposited along the SAW propagation path of the sensing device, which suppresses effectively the hysteresis effect by releasing the internal binding force in FeCo. The magnetostrictive strain and ΔE effect from the FeCo coating modulates the SAW propagation characteristic, and the corresponding shift in differential oscillation frequency was utilized to evaluate the measurant. A theoretical model is performed to investigate the wave propagation in layered structure of FeCo/LiNbO3 in the effect of magnetostrictive, and allowing determining the optimal structure. The experimental results indicate that higher sensitivity, excellent linearity, and lower hysteresis error over the typical FeCo thin-film coated sensor were achieved from the grating-patterned FeCo coated sensor successfully.

This paper developed a novel surface acoustic wave (SAW) current sensor utilizing the magnetostrictive effect. The sensor was composed of a differential delay-line oscillation configuration, and a magnetostrictive FeCo film coated onto the surface of the sensing SAW device. The FeCo coating produces magnetostrictive strain under the magnetic field induced by the applied current, then, leading to changes in the SAW propagation velocity. Hence, the corresponding differential oscillation frequency shift was used to evaluate the applied current. To realize better temperature compensation, a SiO 2 thin film was deposited onto the SAW device surface, which exhibits opposing polarity of temperature coefficient of frequency (Tcf) to the LiNbO 3 substrate used in the SAW device. Using the Helmholtz coil, the developed SAW current sensor was characterized, high sensitivity, and good linearity were observed in the current experiment.

In correlated Rician flat fading environments, we consider a single input multiple output (SIMO) system with a large-scale antenna array. We assume that the receiver only knows the channel information related to the specular component and treat the Rayleigh fading component as interference. We first present a maximum-ratio-combining (MRC) -like detection scheme only based on the specular component, and in order to analyze the reliability performance, derive receive signal to interference plus noise ratio (SINR) expressions for scenarios without and with receive spacialcorrelation. Then we extend the above SINR analysis to the scenario over frequency-selective channels as well as the one in the presence of co-channel interference. Finally, we provide some numerical results to validate the theoretical results, and show by simulation results that different from the conventional view, the strong spatial correlation can provide better reliability performance than the weak one.

A temperature-compensated surface acoustic wave (SAW)-based current sensor was proposed in this contribution, composed of a sensor chip made by SAW delay line patterns on a SiO2/128° YX LiNbO3 piezoelectric substrate, a magnetostrictive FeCo film deposited on the SAW propagation path, and a corresponding differential oscillation configuration. The FeCo coating produced magnetostrictive strain under the magnetic field generated by the applied current, leading to linearity changes in the SAW propagation in the form of velocity change. The corresponding differential oscillation frequency shift was used to evaluate the tested current. By solving the coupled electromechanical field equation in a layered structure while considering the magnetostrictive effect, the optimal FeCo film thickness, and sensor operation frequency yielding high current sensitivity, were determined, and then confirmed experimentally by evaluating the developed SAW current sensor system utilizing a Helmholtz coil. A high sensitivity of 16.6 KHz A−1 (8.3 KHz m−1 T−1), excellent linearity, and lower detection limit (~0.2 mA) were achieved with our 300 MHz SAW sensor with a 500 nm FeCo coating and aspect ratio of 2:1.