Papers by Keyword: Audio Frequency

Abstract: The architectural scheme of the designed Sigma-Delta DAC on the FPGA is considered. The place of the interpolator in Sigma-Delta DACs is briefly discussed. The summarized structure of the most common interpolators is presented. More applicable structures of interpolators were suggested and analyzed, providing the comparison with [1]. Having changed the structure of the incomplete interpolator and having optimized the stages, it was possible to improve the characteristic of amplitude frequency response with a smaller number of non-zero coefficients and much lower FPGA resources. The paper provides simulated results of the interpolator filter transmission characteristics as well as Sigma-Delta modulator quantization noise parameters. It is demonstrated that simulation of the complete converter system (interpolator + modulator + output filter) allows to identify places of the interpolator, where hardware resources could be saved, thereby reducing the chip area occupied by the converter, which is not always obvious when analyzing nodes separately. Therefore another version of the interpolator was proposed for the system ensuring larger suppression of the additional frequency band in the whole system compared with the previous interpolator. Simulated results related to occupied chip resources are also confirmed by the experiment, which was implemented in Xilinx Spartan FPGA.

Abstract: This paper discuss a simple, low-cost method I detecting wear progress of bearing within audio frequency signals; f < 20 kHz. The technique is found to be suitable since it is sensitive to the surface degradation prior to the onset of severe wear. The wear test is conducted under pin-on-disc configuration in a lubricated sliding condition. The results show that the value of I-kaz coefficient Z∞ is represented by scattered data in an I-kaz 3D spaces in which the scattered areas underwent contraction with increased sliding distance. From this statistical analysis, a clear-cut correlation with the established Taylor Tool Life Curve is noted. Here, the lower value of Z∞ indicates severe wear which lies I the failure region of Taylor’s curve. Examination of worn microstructures is carried out using a secondary electron microscopy (SEM). Based on the morphology investigation, it is found that under lubricated test, parallel grooves and craters up to 2 µm in size are present indicating an abrasive wear mechanism has occurred. The surface damages are found to scale with the increasing sliding distance. However the wear resistance behaviour of the bearings seems to improve as the sliding distance is increased.