This paper presents an in-depth treatment of mixers and polyphase filters, and how they are used in rejecting the image in transmitters and receivers. A powerful phasor-based analysis is used to ...explain all common image-reject topologies and their limitations, and it is shown how this can replace complex trigonometric equations commonly found in the literature. Practical problems in design and layout that limit the performance of image-reject upconversion and downconversion mixers are identified, and solutions are presented or limits explained. This understanding is put to work in a low-IF CMOS wideband, low-IF downconversion circuit, which repeatedly rejects the image by 60 dB over the wide band of 3.5 to 20 MHz without trimming or calibration.
Abstract
Appearance of an automobile is one of the appealing points to customers. Character ridgelines in outer panels such as hood and door panels play an important role to make automobiles ...attractive, and a sharp character ridgeline which has a ridge of a small curvature radius is much more preferred to a blunt character ridgeline. However, a skid line, a kind of appearance defect, is apt to generate along the character ridgeline in press forming of a sharp character ridgeline. Although it is well-known that skid lines are caused by inhomogeneous tension, the mechanism of skid line generation was not yet fully understood. In this study, the skid line defect is quantitatively evaluated by draw forming experiment using a newly devised die which can measure a panel shape at any time during press forming. The mechanism of skid line formation was clarified by experimental results. The results of the shape measurement suggest that the ridge shape in a panel formed on the punch ridge should move to a flat area of the punch. A wavy shape should be generated there immediately before the ridge shape is flattened at the bottom dead center of the die. Then the wavy shape should grow to a skid line through springback.
Sheet steels have more or less plastic anisotropy. It is therefore important to consider the anisotropy of a sheet steel in FE analysis of press forming. There are many anisotropic yield functions ...proposed such as Hill'48, Blart's Yld functions and Gotoh's orthotropic yield function. These yield functions have material parameters to express the anisotropy of a sheet steel, and the parameters need to be calibrated based on r-values and stresses in tension tests in various directions, and/or stresses and strains in bulge tests or in biaxial tension tests. The accuracy of a calibrated yield function should be confirmed by using the results of another material test which is not used in the calibration. However, some functions have many parameters and need many calibration tests. A new method to check parameters of yield functions was developed making use of shear strains in a uniaxial tension test. In this study, shear strains were measured by DIC in uniaxial tension tests in various directions. The results, the ratios of a share strain to the tensile strain, were compared with theoretical values from the calibrated yield functions.
PDF
