Equivalence of Open-Loop and Closed-Loop Operation of SAW Resonators and Delay Lines

Durdaut, Phillip; Höft, Michael; Friedt, Jean‐Michel; Rubiola, Enrico

doi:10.3390/s19010185

Cited by 15 publications

(10 citation statements)

References 45 publications

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“…Consequently, the ac magnetic field to be measured causes an amplitude modulation (am) and phase modulation (pm) of the current through the sensor. Detailed information on the operation and read-out can be found elsewhere [ 46 , 47 , 48 ]. The linearized change of

and

with the magnetic field can be described by the amplitude sensitivity

and the phase sensitivity

[ 49 ], respectively.…”

Section: Sensitivitymentioning

confidence: 99%

Magnetoelastic Coupling and Delta-E Effect in Magnetoelectric Torsion Mode Resonators

Spetzler

Голубева

Friedrich

et al. 2021

Sensors

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Magnetoelectric resonators have been studied for the detection of small amplitude and low frequency magnetic fields via the delta-E effect, mainly in fundamental bending or bulk resonance modes. Here, we present an experimental and theoretical investigation of magnetoelectric thin-film cantilevers that can be operated in bending modes (BMs) and torsion modes (TMs) as a magnetic field sensor. A magnetoelastic macrospin model is combined with an electromechanical finite element model and a general description of the delta-E effect of all stiffness tensor components Cij is derived. Simulations confirm quantitatively that the delta-E effect of the C66 component has the promising potential of significantly increasing the magnetic sensitivity and the maximum normalized frequency change ∆fr. However, the electrical excitation of TMs remains challenging and is found to significantly diminish the gain in sensitivity. Experiments reveal the dependency of the sensitivity and ∆fr of TMs on the mode number, which differs fundamentally from BMs and is well explained by our model. Because the contribution of C11 to the TMs increases with the mode number, the first-order TM yields the highest magnetic sensitivity. Overall, general insights are gained for the design of high-sensitivity delta-E effect sensors, as well as for frequency tunable devices based on the delta-E effect.

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and

with the magnetic field can be described by the amplitude sensitivity

and the phase sensitivity

[ 49 ], respectively.…”

Section: Sensitivitymentioning

confidence: 99%

Magnetoelastic Coupling and Delta-E Effect in Magnetoelectric Torsion Mode Resonators

Spetzler

Голубева

Friedrich

et al. 2021

Sensors

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“…When operating a SAW delay line sensor, the output signal is typically compared with its input signal to extract the desired information about the measurement signal. Although, in contrast to such open-loop systems, closed-loop or self-oscillating systems, respectively, are also common, an open-loop analysis of the sensor can be performed without any loss of generality [ 46 ].…”

Section: Saw Sensormentioning

confidence: 99%

Phase Noise of SAW Delay Line Magnetic Field Sensors

Durdaut

Müller

Kittmann

et al. 2021

Sensors

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Surface acoustic wave (SAW) sensors for the detection of magnetic fields are currently being studied scientifically in many ways, especially since both their sensitivity as well as their detectivity could be significantly improved by the utilization of shear horizontal surface acoustic waves, i.e., Love waves, instead of Rayleigh waves. By now, low-frequency limits of detection (LOD) below 100 pT/Hz can be achieved. However, the LOD can only be further improved by gaining a deep understanding of the existing sensor-intrinsic noise sources and their impact on the sensor’s overall performance. This paper reports on a comprehensive study of the inherent noise of SAW delay line magnetic field sensors. In addition to the noise, however, the sensitivity is of importance, since both quantities are equally important for the LOD. Following the necessary explanations of the electrical and magnetic sensor properties, a further focus is on the losses within the sensor, since these are closely linked to the noise. The considered parameters are in particular the ambient magnetic bias field and the input power of the sensor. Depending on the sensor’s operating point, various noise mechanisms contribute to f0 white phase noise, f−1 flicker phase noise, and f−2 random walk of phase. Flicker phase noise due to magnetic hysteresis losses, i.e. random fluctuations of the magnetization, is usually dominant under typical operating conditions. Noise characteristics are related to the overall magnetic and magnetic domain behavior. Both calculations and measurements show that the LOD cannot be further improved by increasing the sensitivity. Instead, the losses occurring in the magnetic material need to be decreased.

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“…which, in the following, is referred to as the electrical sensitivity S elec of a resonant sensor in units of rad/Hz [46].…”

Section: Mechanical Behavior and Electrical Sensitivitymentioning

confidence: 99%

“…The limit of detection (LOD) of a magnetic field sensor system denotes the frequency-dependent noise floor, i.e. an Hz [46]. Thus, the LOD is given by the ratio of the amplitude spectral density of random phase fluctuations and the phase sensitivity.…”

Section: E Limit Of Detectionmentioning

confidence: 99%

Fundamental Noise Limits and Sensitivity of Piezoelectrically Driven Magnetoelastic Cantilevers

Durdaut

Rubiola

Friedt

et al. 2020

J. Microelectromech. Syst.

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Magnetoelastic sensors for the detection of lowfrequency and low-amplitude magnetic fields are in the focus of research for more than 30 years. In order to minimize the limit of detection (LOD) of such sensor systems, it is of high importance to understand and to be able to quantify the relevant noise sources. In this contribution, cantilever-type electromechanical and magnetoelastic resonators, respectively, are comprehensively investigated and mathematically described not only with regard to their phase sensitivity but especially to the extent of the sensor-intrinsic phase noise. Both measurements and calculations reveal that the fundamental LOD is limited by additive phase noise due to thermal-mechanical noise of the resonator, i.e. by thermally induced random vibrations of the cantilever, and by thermal-electrical noise of the piezoelectric material. However, due to losses in the magnetic material parametric flicker phase noise arises, limiting the overall performance. In particular, it is shown that the LOD is virtually independent of the magnetic sensitivity but is solely determined by the magnetic losses. Instead of the sensitivity, the magnetic losses, represented by the material's effective complex permeability, should be considered as the most important parameter for the further improvement of such sensors in the future. This implication is not only valid for magnetoelastic cantilevers but also applies to any type of magnetoelastic resonator.

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Equivalence of Open-Loop and Closed-Loop Operation of SAW Resonators and Delay Lines

Cited by 15 publications

References 45 publications

Magnetoelastic Coupling and Delta-E Effect in Magnetoelectric Torsion Mode Resonators

Magnetoelastic Coupling and Delta-E Effect in Magnetoelectric Torsion Mode Resonators

Phase Noise of SAW Delay Line Magnetic Field Sensors

Fundamental Noise Limits and Sensitivity of Piezoelectrically Driven Magnetoelastic Cantilevers

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