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Item type:Publication, Access status: without files , Study of Chopping Magnetic Flux Modulation on Surface Acoustic Wave Magnetic SensorSome methods of magnetic flux modulation are used to overcome flicker phase noise, low-frequency acoustical distortions, and movement artifacts. This work proposes employing a chopping flux modulation technique controlling a high permeability toroid together with a surface acoustic wave sensor inside. In this primary proof-of-concept study, an external magnetic field is generated to estimate quantitative signal parameters and the effect of the toroid shielding factor. Finally, the limitations of this approach should be identified and how low-frequency magnetic signals are influenced. The achievable sensitivity was empirically evaluated, and a quantitative signal quality value was calculated by estimating the signal power spectrum and noise power spectrum. Thus, the study compares the signal-plus-noise to noise ratio with and without magnetic flux modulation of a reproducible excitation magnetic signal generated by a solenoid coil. The experimental results show that the noise floor of this magnetic sensor system is improved. However, the signal-plus-noise to noise ratio without the modulation is 17 dB, and with the modulation, this parameter becomes 13 dB for a given mono-frequency signal of 20 µT. In perspective, this method exhibits disadvantages in reducing the sensitivity because, with the toroid inside, the calibration factor of the solenoid is not the same anymore, and the shielding factor reduces the field strength of the alternative-current field. Furthermore, the results show that the chopping flux modulation technique requires exploring how to compensate for the losses and setup issues that affect the magnetic field to define how suitable it is for surface acoustic waves magnetic sensors.Publicationtype: Conference Paper26 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Phase noise of saw delay line magnetic field sensors(Multidisciplinary Digital Publishing Institute (MDPI), 2021-08-21); ; ; ; 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.Publicationtype: Journal ArticleScopus© Citations 12 41 144 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Frequency Response of SAW Delay Line Magnetic Field/Current SensorThis article presents the frequency response of a surface acoustic wave (SAW) sensor for current measurements. The SAW sensor exploits the Love waves of a magnetostrictively coated delay line. The focus of this article lies on the frequency response of the sensor, which shows a very wide bandwidth. The delay time τD is the time an acoustic wave needs to traverse the delay line. Since the acoustic wave is modulated during the whole duration of the delay line crossing, τD is comparable to the integration time of a sample-and-hold device. The signal measured with the SAW sensor is averaged over the delay time. Therefore, undersampling behavior occurs for signal frequencies approaching 1D. A mathematical model of their frequency response up to several megahertz was developed and compared with measurements of two SAW sensors with different delay line lengths.Publicationtype: Journal Article35