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Power Control in Passive Waveguide Circuits
Zehentner, Ján; Macháč, Jan; Zabloudil, Pavel
2006 -
A new concept of a passive waveguide reflection attenuator and a T-junction with a variable ratio of the output powers is reported here. A conductive uniform linear polarization grid of nano thickness is inserted into the standard rectangular waveguide. Rotation of the grid results in a change of the output powers. The measured scattering matrix elements compare well with the computer simulation, confirming the expected characteristics of the two circuits.
Keywords:
power dividers; power combiners; power control; variable attenuators; waveguide attenuators; waveguide T-junctions
Available in digital repository of ČVUT.
Power Control in Passive Waveguide Circuits
A new concept of a passive waveguide reflection attenuator and a T-junction with a variable ratio of the output powers is reported here. A conductive uniform linear polarization grid of nano thickness ...
Comparison of Methods for Tool Localization in Biological Tissue from 3D Ultrasound Data
Barva, Martin; Kybic, Jan; Hlaváč, Václav; Liebgott, Hervé; Cachard, Christian
2006 -
In medical applications, miniature surgical instruments such as needles, or electrodes are introduced into human body. The position of instrument in tissue can be estimated using 3D ultrasound. In previous publications, we introduced two novel algorithms for automatic electrode localization from 3D ultrasound images. The first method is based on the parallel integral projection (PIP) transform, a modification of the Radon transform. We showed that the axis of the electrode can be estimated from the maximum of PIP transformation. To accelerate search for the maximum, a hierarchical mesh-grid algorithm is implemented. In second method, the electrode axis is described by a cubic polynomial. The distribution of voxel intensities inside the electrode region is a priori estimated from acquired data. The model parameters are robustly estimated using the RANSAC estimator. In this paper, their performance in terms of accuracy is compared. A series of tests on numerical phantoms created with the FIELD II simulation program were performed to quantitatively evaluate the localization accuracy. We observed a decrease in accuracy when artificial noise was added to the input data. The algorithms were also tested on real ultrasound data of a cryogel phantom comprising metallic electrode.
Available in digital repository of ČVUT.
Comparison of Methods for Tool Localization in Biological Tissue from 3D Ultrasound Data
In medical applications, miniature surgical instruments such as needles, or electrodes are introduced into human body. The position of instrument in tissue can be estimated using 3D ultrasound. In ...
Influence of High Current Load on Electrical Properties of Adhesive Conductive Joints
Duraj, Aleš; Mach, Pavel; Radev, Radoslav; Matějec, Jan
2006 -
Isotropic and anisotropic electrically conductive adhesives (ICAs and ACAs) are alternative materials for substitution of common used tin-lead solders in electronic assembly. Electrically conductive adhesives are potential materials for the bonding of surface mounted components and for some special applications. In this research we are focused on an investigation of influence of high current load on changes of quality of adhesive joints. Monitored parameters are electrical resistance and nonlinearity of V-C characteristics. Research is divided into two types of high current load: a) direct current (DC), amplitude 1 A, b) current pulses 1:1, f= 500 Hz, amplitude 1.41 A.
Available in digital repository of ČVUT.
Influence of High Current Load on Electrical Properties of Adhesive Conductive Joints
Isotropic and anisotropic electrically conductive adhesives (ICAs and ACAs) are alternative materials for substitution of common used tin-lead solders in electronic assembly. Electrically conductive ...
Use of Nano-Grids in a Waveguide
Zehentner, Ján; Macháč, Jan; Zabloudil, Pavel
2006 -
A new concept of passive waveguide circuits is presented. It is based on a combination of the standard rectangular waveguide with a metal uniform linear polarization grid of nano thickness. The grid is deposited on a polymer foil and inserted into the waveguide, allowing it to rotate between two opposite flanges. The concept is demonstrated on a T-junction with an adjustable ratio of the output powers, and on a variable reflection attenuator. The two circuits were designed, manufactured and tested. The measured characteristics compare well with the computer simulations, and have confirmed the expected behavior of the two circuits.
Keywords:
power dividers; power combiners; power control; waveguide attenuators; waveguide T-junctions
Available in digital repository of ČVUT.
Use of Nano-Grids in a Waveguide
A new concept of passive waveguide circuits is presented. It is based on a combination of the standard rectangular waveguide with a metal uniform linear polarization grid of nano thickness. The grid ...
Frequency Dependence of Impedance of Adhesive Joints
Mach, Pavel; Papež, Václav; Duraj, Aleš
2006 -
Electrically conductive adhesives have, in comparison with solders, significantly higher non-homogeneity of the structure, and therefore stability of electrical as well as mechanical properties of adhesive joints is lower than soldered ones. The impedance of the joints has been measured in wide frequency range (20 Hz to 1 MHz and 300 MHz to 3GHz). Measurements have been carried out by two methods: impedance in the range 20 Hz to 1MHz has been measured by LCR meter HP 4284A. A special test board for assembly of 1 jumper (of the type 1206) by electrically conductive adhesive has been fabricated for this measurement. The measurements at the frequencies 300 MHz and higher have been carried out using a shielded high-Q triplate line. Specimens have been prepared on Teflon boards, a scalar analyzer Rohde Scwartz ESPI has been used for evaluation. Very low changes of impedances of the joints have been found in the range of 20 Hz to 1 MHz. Typical courses of real and imaginary components of joints impedances in the frequency range 300 MHz to 3 GHz are as follows: the real components have grown in consequence of a skin-effect and have dominated. The imaginary components have been very low. The task for the future research is to explain decrease of the resistance of the joints with growing frequency for two types of adhesives.
Available in digital repository of ČVUT.
Frequency Dependence of Impedance of Adhesive Joints
Electrically conductive adhesives have, in comparison with solders, significantly higher non-homogeneity of the structure, and therefore stability of electrical as well as mechanical properties of ...
Stability of Electrical Resistance of Isotropic Conductive Adhesives within Mechanical Stress
Duraj, Aleš; Mach, Pavel
2006 -
This work is focused on investigation of influence of dynamic mechanical load (bending of testing boards) on resistance of the adhesive joints. The load has been induced by a definite deflection of testing boards (fiberglass laminated PCB assembled with 1206 SMD resistors). There were used four different types of isotropic electrically conductive adhesives (two types of one-component, one type of two-component adhesive and one type of conductive lacquer). The frequency of one cycle per second (1 Hz) has been used for generation of the dynamic load (2000 cycles of bend have been applied). For the analysis of adhesive joint resistance has been used precision LCR meter HP 4284A with continual measuring software (WEE Pro v6.0). The dynamic load has caused changes of basic electrical parameters of the bonds The more of deflections has been applied the more changes of parameters have been found. Nevertheless increasing of joint resistance is not linear and it is not same for all tested adhesives - initial rising of resistance is in most cases higher than changes after few cycles. From our experiment it is evident that for low deflection of testing board there are both of permanent and also elastic deformations in adhesive joints (graphs of joint resistance have not continual rising trend).
Available in digital repository of ČVUT.
Stability of Electrical Resistance of Isotropic Conductive Adhesives within Mechanical Stress
This work is focused on investigation of influence of dynamic mechanical load (bending of testing boards) on resistance of the adhesive joints. The load has been induced by a definite deflection of ...
Multiview 3D Tracking with an Incrementally Constructed 3D Model
Zimmermann, Karel; Svoboda, Tomáš; Matas, Jiří
2006 -
We propose a multiview tracking method for rigid objects. Assuming that a part of the object is visible in at least two cameras, a partial 3D model is reconstructed in terms of a collection of small 3D planar patches of arbitrary topology. The 3D representation, recovered fully automatically, allows to formulate tracking as gradient minimization in pose (translation, rotation) space. As the object moves, the 3D model is incrementally updated. A virtuous circle emerges: tracking enables composition of the partial 3D model; the 3D model facilitates and robustifies the multiview tracking. We demonstrate experimentally that the interleaved track-and-reconstruct approach successfully tracks a 360 degrees turn-around and a wide range of motions. Monocular tracking is also possible after the model is constructed. Using more cameras, however, significantly increases stability in critical poses and moves. We demonstrate how to exploit the 3D model to increases stability in the presence of uneven and/or changing illumination.
Available in digital repository of ČVUT.
Multiview 3D Tracking with an Incrementally Constructed 3D Model
We propose a multiview tracking method for rigid objects. Assuming that a part of the object is visible in at least two cameras, a partial 3D model is reconstructed in terms of a collection of small ...
Bandpass Filters on a Modified Multilayer Coplanar Line
Balalem, Atallah; Hamad, Ehab K. I.; Macháč, Jan; Omar, Abbas S.
2006 -
The design of compact multilayer coplanar line bandpass filters is presented. These very compact filters make use of the two sides of the substrate of the modified coplanar line. In addition, a transmission zero has been introduced to the filter response, either by extending the metalization under the ground planes, or by employing additional capacitive coupling between the different parts of the filter structure. A good agreement between the simulated and measured responses has been achieved.
Keywords:
bandpass filter; CPW; filter; multilayer coplanar line
Available in digital repository of ČVUT.
Bandpass Filters on a Modified Multilayer Coplanar Line
The design of compact multilayer coplanar line bandpass filters is presented. These very compact filters make use of the two sides of the substrate of the modified coplanar line. In addition, a ...
Geometric Hashing with Local Af ne Frames
Chum, Ondřej; Matas, Jiří
2006 -
We propose a novel representation of local image structure and a matching scheme that are insensitive to a wide range of appearance changes. The representation is a collection of local affine frames that are constructed on outer boundaries of maximally stable extremal regions (MSERS) in an affine-covariant way. Each local affine frame is described by a relative location of other local affine frames in its neighborhood. The image is thus represented by quantities that depend only on the location of the boundaries of MSERs. Inter-image correspondences between local affine frames are formed in constant time by geometric hashing. Direct detection of local afine frames removes the requirement of a point-based hashing to establish reference frames in a combinatorial way, which has in the case of affine transform complexily that is cubic in the number of points. Local affine frames, which are also the quantities represented in the hash table, occupy a 6 0 space and hence data collisions are less likely compared with 2 0 point hashing. Experimentally, the robustness of the method and its insensitiviq to photometric changes is demonstrated on images from different spectral bands of satellite sensor; on images of a transparent object and on images of an object taken during day and night.
Available in digital repository of ČVUT.
Geometric Hashing with Local Af ne Frames
We propose a novel representation of local image structure and a matching scheme that are insensitive to a wide range of appearance changes. The representation is a collection of local affine frames ...
Low Profile Slotted Flat Waveguide Leaky Wave Antenna
Zehentner, Ján; Macháč, Jan; Zabloudil, Pavel
2006 -
This paper presents the application of a flat waveguide with a longitudinal slot in the middle of its wider wall for the design of a leaky wave antenna. The antenna radiates into one relatively narrow main beam and its gain is 14.2 dB at 4.75 GHz. The characteristics and radiation aspects of the antenna are discussed. The measured antenna characteristics are in accord with those predicted by simulation.
Keywords:
flat slotted waveguide; leaky waves; leaky wave antenna; radiation
Available in digital repository of ČVUT.
Low Profile Slotted Flat Waveguide Leaky Wave Antenna
This paper presents the application of a flat waveguide with a longitudinal slot in the middle of its wider wall for the design of a leaky wave antenna. The antenna radiates into one relatively narrow ...
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