Broadband Butler Matrices with the Use of High-Pass LC Sections as Left-Handed Transmission Lines

An application of left-handed transmission line sections in Butler matrices has been investigated. It has been shown, for the first time, that the utilization of both left-handed and right-handed transmission lines allows for broadband differential phase shifters’ realization, required in the Butler matrices. A complete theoretical analysis is given, for Butler matrices incorporating ideal transmission lines of both right- and left handed types and expressions for the achievable bandwidth and differential phase deviation are derived. The presented idea has been verified by the design of a 4 x 4 Butler matrix operating in a frequency range of 2.5 – 3.5 GHz. As an artificial left-handed transmission line, an equivalent high-pass LC circuit realized in a quasi-lumped element technique, has been considered, and the resulting phase shift of such a circuit is given analytically. The obtained measurement results fully confirm the validity of the proposed idea of broadband Butler matrices’ realization

Hardware implementation of phase extraction algorithm in fringe pattern analysis

Niniejszy artykuł przedstawia opis algorytmu wyznaczania rozkładu fazy z obrazów prążkowych. Jest to jeden z kroków przetwarzania obrazów stosowanych powszechnie w profilometrii optycznej, dzięki której na podstawie zdjęcia można odtworzyć trójwymiarowy kształt obiektu. Algorytm oparty został na zespolonej transformacji falkowej i pozwala na pełną automatyzację procesu skanowania. Duży nacisk został położony na optymalizację pod kątem sprzętowej implementacji w układzie FPGA. Wykazana została dobra odporność zarówno na szumy jak i niską jakość obrazu prążkowego.This paper presents a phase extraction algorithm used in fringe pattern analysis. It is one of steps in optical profilometry process used to obtain full three-dimensional information about the measured object shape. The algorithm is based on the complex wavelet transform and allows full automation of the process. Since the fringe patterns represent non-stationary signals, application of time-frequency analysis provides better results than the commonly used Fourier transform. Six variants of the wavelet transform (one- and two-dimensional) were simulated in order to minimise the required hardware resources in FPGA and test their robustness. As a result the one-dimensional minimised transform of variable size was chosen. A further part of the paper is focused on particular blocks of implementation. The presented wavelet coefficient computational method decreases the number of necessary operations during transform computing and enables significant reducing of memory requirements. The applied arcus tangens block with logarithmic division of approximation intervals gives correct extracted phase values in the entire four-quarter interval. The solution mentioned above leads to great minimisation of the described block without any impact on the accuracy. The last part of the paper presents processing results. The emphasis was put on the noise robustness and influence of the fringe pattern poor quality on the processing error. As it is shown, the algorithm works correctly even with only three gray levels and high noise level present in the input picture

Temporal response of magnitude distribution to fluid injection rates in The Geysers geothermal field

The influence of fluid injection rates on the magnitude distribution of the seismicity which occurred in the NW part of The Geysers geothermal site is studied here. A direct comparison between injection rate changes and b value response is attempted after appropriate selection of data subsets. Due to the relatively small sample (1121 events, corresponding to an average rate of ~ 0.45 events/day), we also aggregated seismic activity into two families corresponding to increasing and decreasing injection rates, respectively. The b values were calculated as a function of time lag related to the injection activity. In agreement with previous studies, we found a statistically significant direct relation between b values and injection rate changes, which occurred at a zero or very short time lag (from 0 to ~ 15 days). However, the b value changes are related to the slope (i.e., the second derivative of injection volume), instead of the absolute values of injection rates. The increasing injection rates correspond to b = 1.18 ± 0.06, whereas the decreasing injection rates correspond to b = 1.10 ± 0.05. The corresponding values estimated by the repeated medians technique are b = 1.97 ± 0.20 and b = 1.50 ± 0.13. Both differences are significant at 0.05 level

A correlation analysis between injection rates and magnitude distribution in the geysers geothermal field

The magnitude distribution variation in the north western part of The Geysers geothermal field is studied. Various types of b-value analysis are performed in order to investigate thoroughly the impact of fluid injection to magnitude distribution. Other parameters such as distance from the open hole of the injection well are also investigated. The analysis performed in this study indicated that b-values are significantly positively correlated to injection rate fluctuations whereas no significant influence of the seismicity rates and the distance from the injection well on b-values was detected

Compact Broadband Rat-Race Coupler in Multilayer Technology Designed with the Use of Artificial Right- and Left-Handed Transmission Lines

The paper presents a compact broadband rat-race coupler for the first time designed and realized in a mul- tilayer microstrip technology. To achieve both broad operational bandwidth and a compact size the 270? transmission line of a conventional rat-race, coupler has been replaced by a -90? left-handed transmission line realized with the use of a quasi-lumped element technique. Moreover, to achieve better compactness of the resulting coupler, all 90? right-handed transmission lines have been realized with the use of the same technique. It has been also proved that simple LC approximation of a left-handed transmission line can be successfully used for the design. Moreover, it has been shown that when appropriately chosen, the multilayer dielectric structure allows for realization of structures designed with the use of this simple approximation, for both right-handed and left-handed transmission lines, without loosing too much of a performance

Time-dependent seismic hazard in Bobrek coal mine, Poland, assuming different magnitude distribution estimations

The purpose of this study is to evaluate seismic hazard parameters in connection with the evolution of mining operations and seismic activity. The time-dependent hazard parameters to be estimated are activity rate, Gutenberg–Richter b-value, mean return period and exceedance probability of a prescribed magnitude for selected time windows related with the advance of the mining front. Four magnitude distribution estimation methods are applied and the results obtained from each one are compared with each other. Those approaches are maximum likelihood using the unbounded and upper bounded Gutenberg–Richter law and the non-parametric unbounded and non-parametric upper-bounded kernel estimation of magnitude distribution. The method is applied for seismicity occurred in the longwall mining of panel 3 in coal seam 503 in Bobrek colliery in Upper Silesia Coal Basin, Poland, during 2009–2010. Applications are performed in the recently established Web-Platform for Anthropogenic Seismicity Research, available at https://tcs.ah-epos.eu/

Temporal static stress drop variations due to injection activity at The Geysers geothermal field, California

We use a high‐quality data set from the NW part of The Geysers geothermal field to determine statistical significance of temporal static stress drop variations and their relation to injection rate changes. We use a group of 322 seismic events which occurred in the proximity of Prati‐9 and Prati‐29 injection wells to examine the influence of parameters such as moment magnitude, focal mechanism, hypocentral depth, and normalized hypocentral distances from open‐hole sections of injection wells on static stress drop changes. Our results indicate that (1) static stress drop variations in time are statistically significant, (2) statistically significant static stress drop changes are inversely related to injection rate fluctuations. Therefore, it is highly expected that static stress drop of seismic events is influenced by pore pressure in underground fluid injection conditions and depends on the effective normal stress and strength of the medium