Phase Noise of SAW Delay Line Magnetic Field Sensors

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

Intangible but not intractable: the prediction of fish 'quality' variables using dielectric spectroscopy

Trabajo presentado a la Sixth Conference on "Electromagnetic Wave Interaction with Water and Moist Substances", celebrada en Alemania en junio de 2005.Peer reviewe

Active learning method for designing miniaturized waveguide filters loaded by broadside-coupled split ring resonators

This paper focuses on the design and fabrication of miniaturized rectangular waveguide bandpass filters which are loaded by broadside-coupled split ring resonators. The conventional coupling matrix approach is proposed to design these kinds of filters. Also the time consuming process of coupling factor computation which is based on full wave simulations is replaced by a very fast and accurate fuzzy based method which is named active learning method (ALM). Therefore coupling factor computation time decreases to several minutes instead of several hours in the conventional approach while keeping accuracy. Using the ALM-based extracted coupling factor surfaces two Chebychev bandpass filters were designed and fabricated. A very good agreement between simulation and measurement results shows the accuracy of the proposed method. © 2011 IEEE

Miniaturized coaxial cylindrical cavity filters based on sub-wavelength metamaterial loaded resonator

This paper presents analysis, design and simulation of a novel sub-wavelength metamaterial resonator and its application in designing miniaturized filters. The presented sub-wavelength resonator is a coaxial cylindrical cavity in which a combination of an ordinary dielectric material and a metamaterial layer has been inserted. The general dispersion relation for such a resonator is formulated. Using this general formula and considering the sub-wavelength scenario, the approximate dispersion relation is extracted. Based on this approximate dispersion relation and through the use of an anisotropic negative (MNG) layer, it is shown that this configuration may in principal exhibit an arbitrary low resonant frequency for a fixed dimension. In comparison with miniaturized rectangular cavities and also miniaturized one-dimensional resonators, the above mentioned resonator provides the possibility of selecting a distinct mode of operation and also a further degree of freedom in the approximate dispersion relation which brings more flexibility in designing miniaturized resonators. As an example design and simulation of a miniaturized coaxial cavity resonator together with the complete design of the anisotropic MNG layer are presented. The resultant cavity diameter is shortened by approximately 69% in comparison with theoretical minimum dimensions of a cylindrical cavity resonator of the same height. Finally based on the designed miniaturized resonator a miniaturized filter with the center frequency of 5.85GHz and the bandwidth of 20MHz is designed and simulated

Ultra-Wideband Radio Technologies for Communications, Localization and Sensor Applications

Ultra-Wideband Radio (UWB) earmarks a new radio access philosophy and exploits several GHz of bandwidth. It promises high data rate communication over short distances as well as innovative radar sensing and localization applications with unprecedented resolution. Fields of application may be found, among others, in industry, civil engineering, surveillance and exploration, for security and safety measures, and even for medicine. The book considers the basics and algorithms as well as hardware and application issues in the field of UWB radio technology for communications, localization and sensing based on the outcome of DFG's priority-funding program ""Ultra-Wideband Radio Technologies for Communications, Localization and Sensor Applications (UKoLoS)""

Oscillator Phase Noise Suppression in Surface Acoustic Wave Sensor Systems

Surface acoustic wave (SAW) sensors are widely used in different fields of application. In order to maximize the limit of detection of such sensor systems, it is of high importance to understand and to be able to quantify the relevant noise sources. A straightforward approach to detect the desired phase information of SAW sensors is to compare the sensor output signal with a reference signal. In this paper, the effect of decorrelation of oscillator phase noise as a function of delay time and offset frequency is discussed and analyzed. An analytical expression is derived which describes the degree of phase noise suppression in heterodyne readout systems. The model is verified by various measurement series, showing a degree of phase noise suppression of -100 dB for an offset frequency of 1 Hz and for a decorrelation time of 1500 ns which represents a typical time delay of SAW sensors. Although the effect is analyzed with respect to SAW sensors, the results are basically applicable to all kinds of phase sensitive sensors

Noise Analysis of Open-Loop and Closed-Loop Readout Systems for Phase Sensitive Magnetic Field Sensors

International audienceransmission surface acoustic wave (SAW) sensors are widely used in various fields of application. In order to maximize 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 paper, low noise readout systems for the application with a SAW delay line magnetic field sensor in an open-loop and closed-loop configuration are presented and analyzed with regard to their phase noise contribution. By applying oscillator phase noise theory to closed-loop sensor systems, it is shown that the phase noise of the SAW delay line oscillator can be predicted accurately. This allows the derivation of expressions for the limits of detection for both readout structures. Based on these equations, the equivalence between the LOD of open-loop and closed-loop SAW delay line readout can be shown analytically, assuming that the sensor contributes the dominant phase noise. This equality is verified by measurements. These results are applicable to all kinds of phase sensitive delay line sensors

Discussion and conclusions

Peer reviewe

Noise Analysis and Comparison of Phase-and Frequency-Detecting Readout Systems: Application to SAW Delay Line Magnetic Field Sensor

International audienceTransmission surface acoustic wave (SAW) sensors are widely used in various fields of application. In order to improve the limit of detection (LOD) of such sensor systems, it is essential to understand and quantify the relevant noise sources. Only then, strategies for noise reduction can be developed. In this paper, low noise readout systems for the application with SAW sensors in an open-loop and a closed-loop configuration are presented and experimentally investigated with regard to their phase noise on the example of a SAW delay line magnetic field sensor. Besides a comprehensive analysis of the phaseand frequency modulated signals, respectively, previously derived equations in a theoretic study for describing the LOD of both readout structures are utilized in the experimental context. According to the theory, the same LOD is also obtained in the experiment for all frequencies for which the noise contributions of the readout electronics are negligible. To the best of our knowledge, this is the first experimental study that directly compares both operating modes for the same sensor and in terms of the overall achievable LOD. The results are applicable to all kinds of phase-sensitive delay-line sensors