Linearity optimizing on HBT power amplifier design

Highly linearized of HBT power amplifier (PA) was achieved for wireless digital mobile communication systems. This study investigates in detail the improvement of the linearity of HBT power amplifiers. The dependence of collector–base capacitance (C_bc) on bias is regarded initially as a trade-off between linearity and breakdown voltage. A simulation of device performed using SILVACO software reveals that at a capacitance ratio; C_bc (0/6 V) is 1.25 at a BV_ceo of 22 V. The device-level DC characteristic, load-pull power performance and power cell PAs are evaluated. A reasonably high PAE ~55% is attainable at 2.0 GHz and an adjacent channel leakage power ratio (ACPR) of over −48 dBc is achieved. The maximum achievable PAE is 54% with a maximum power density of 0.75 W/mm at 5.8 GHz. The novel HBT epitaxial structure, the layout of power cell design and the thick metal shunt process used to ensure the high linearity of the power cell are demonstrated.     

System identification of torsionally coupled buildings

In this study, an extended random decrement method, which considers the correlation among measurements, was employed to reduce the measured dynamic responses of general torsionally coupled multi-story building under random excitations. The Ibrahim time domain technique was then applied to calculate the modal frequencies and damping ratios based on only a few floor response measurements. To obtain the complete mode shapes, an interpolation method was developed to estimate the mode shape values for the locations without measurements. The seismic responses at floors with and without measurements were also calculated. Numerical results through a seven-story torsionally coupled building under ambient random excitations demonstrated that the proposed method is able to identify structural dominant modal parameters accurately even with highly coupled modes and noise contamination. A small number of response measurements, no requirement for input excitation measurements and simple on-line calculations make the proposed method favorable for implementation.     

Error analysis leading to design criteria for transmission linemodel characterization of ohmic contacts

The transmission line model (TLM) is a standard method for planar specific contact resistance measurement. Although widely used, the accuracy of a measurement is typically not stated. In addition to contributions from random errors, there can be substantial contributions from systematic errors in typical TLM measurements. In this paper, we develop an analytical model for the experimental uncertainty from the fundamental TLM expressions in order to understand and calculate the uncertainty associated with the specific contact resistance and sheet resistance derived by the TLM method. The experimental uncertainties in measured resistances, together with the pad width and pad spacing, are the dominant contributions to the total uncertainty. Analytical expressions for relative random and systematic uncertainties in contact resistance and sheet resistance are developed in terms of the error contributions and the parameters of the TLM geometry. Expressions for minimum uncertainty, with associated optimum widths and sheet resistances, serve as a basis for the design of TLM structures with minimum uncertainty. The model quantifies the increase in relative uncertainty associated with decreasing contact resistance. Simulations of uncertainty under various sheet resistance, contact resistance, and pad width are implemented and uncertainties are calculated for realistic data sets     

Intelligent molecular orientation transformation in 3D printing system

Microsystem Technologies - Proper orientation of a molecular structure in three-dimensional (3D) printing could increase successful printing rates, reduce the amount of supporting material...     

Program optimization carving for GPU computing

Contemporary many-core processors such as the GeForce 8800 GTX enable application developers to utilize various levels of parallelism to enhance the performance of their applications. However, iterative optimization for such a system may lead to a local performance maximum, due to the complexity of the system. We propose program optimization carving, a technique that begins with a complete optimization space and prunes it down to a set of configurations that is likely to contain the global maximum. The remaining configurations can then be evaluated to determine the one with the best performance. The technique can reduce the number of configurations to be evaluated by as much as 98% and is successful at finding a near-best configuration. For some applications, we show that this approach is significantly superior to random sampling of the search space.     

Blind adaptive beamforming based on generalized sidelobe canceller

The generalized sidelobe canceller (GSC) is an efficient implementation of the direction constrained adaptive array. Conventional GSC is designed according to a quiescent weight vector and a blocking matrix. The quiescent weight vector provides the array with specified array response at some direction. The blocking matrix is designed based on a priori knowledge of the direction of arrival (DOA) of the desired signal. In this paper, we propose a new GSC-based adaptive array without a priori knowledge of the DOA of the desired signal. This paper utilizes eigensubspace decomposition and statistically cyclostationary properties of the signals to design the adaptive array. A method for constructing the most efficient blocking matrix for the GSC is developed. Simulation examples illustrate the effectiveness of the proposed method.     

Complex electrophysiological characteristics in atrioventricular nodal reentrant tachycardia with continuous atrioventricular node function curves

BACKGROUND: Although typical atrioventricular nodal reentrant tachycardia (AVNRT) with discontinuous AV node function curves has been well studied, there has been a lack of any significant information about AVNRT without evidence of dual AV nodal pathway physiology during atrial extrastimulus testing or atrial pacing. METHODS AND RESULTS: Group 1 included 9 patients with continuous curves during atrial extrastimulus testing but without a jump (> or = 50 ms) of the atrial-His bundle (AH) interval during incremental atrial pacing. The maximal AH interval during atrial pacing (266 +/- 61 versus 168 +/- 27 ms, P = .007) or extrastimulus testing (290 +/- 60 versus 176 +/- 18 ms, P = .005) shortened significantly after ablation. Antegrade and retrograde AV node properties were similar before and after ablation. Group 2 included 14 patients with continuous curves and a jump of the AH interval during incremental atrial pacing. The atrial pacing cycle length with 1:1 AV conduction and effective refractory period (ERP) of the antegrade AV node increased significantly, whereas the maximal AH interval during atrial pacing (358 +/- 70 versus 203 +/- 28 ms, P = .001) or extrastimulus testing (338 +/- 75 versus 196 +/- 34 ms, P = .002) shortened significantly after ablation. Group 3 included 24 patients with discontinuous curves. The maximal AH interval during atrial pacing or extrastimulus testing and the ERP of the antegrade fast AV node shortened, whereas the ERP of the antegrade AV node increased significantly after ablation. The maximal AH interval before ablation, extent of decrease in maximal AH interval after ablation, ERP of the retrograde AV node before ablation, and tachycardia cycle length were significantly shorter in group 1 than groups 2 and 3. CONCLUSIONS: In AVNRT with continuous AV node function curves, dual AV nodal pathway physiology may or may not be demonstrated during atrial pacing. Significant shortening of the maximal AH interval during atrial pacing after radiofrequency ablation suggests successful elimination of AVNRT.     

Characterization of low right atrial isthmus as the slow conduction zone and pharmacological target in typical atrial flutter

BACKGROUND: Previous electrophysiological studies in patients with typical atrial flutter suggested that the slow conduction zone might be located in the low right atrial isthmus, which is a path formed by orifice of inferior vena cava, eustachian valve/ridge, coronary sinus ostium, and tricuspid annulus. The conduction characteristics during atrial pacing and responses to antiarrhythmic drugs of this anatomic isthmus were unknown. METHODS AND RESULTS: Forty-four patients, 20 patients with paroxysmal supraventricular tachycardia (group 1) and 24 patients with clinically documented paroxysmal typical atrial flutter (group 2), were studied. A 20-pole halo catheter was situated around the tricuspid annulus. Incremental pacing from the low right atrium and coronary sinus ostium was performed to measure the conduction time and velocity along the isthmus and lateral wall in the baseline state and after intravenous infusion of procainamide or sotalol. In both groups, conduction velocity in the isthmus during incremental pacing was significantly lower than that in the lateral wall before and after infusion of antiarrhythmic drugs. Furthermore, gradual conduction delay with unidirectional block in the isthmus was relevant to initiation of typical atrial flutter. Compared with group 1, group 2 had a lower conduction velocity in the isthmus and shorter right atrial refractory period. Procainamide significantly decreased the conduction velocity, but sotalol did not change it. In contrast, sotalol significantly prolonged the atrial refractory period with a higher extent than procainamide. After infusion of procainamide, the increase of conduction time in the isthmus accounted for 52+/-19% of the increase in flutter cycle length, and 5 of 12 patients (42%) had spontaneous termination of typical flutter. After infusion of sotalol, typical flutter was induced in only 6 of 12 patients (50%) without significant prolongation of flutter cycle length. CONCLUSIONS: The low right atrial isthmus with rate-dependent slow conduction properties is critical to initiation of typical human atrial flutter. It may be the potentially pharmacological target of antiarrhythmic drugs in the future.     

Effects of motorcycle exhaust on cytochrome P-450-dependent monooxygenases and glutathione S-transferase in rat tissues

The effects of motorcycle exhaust (ME) on cytochrome P-450 (P-450)-dependent monooxygenases were determined using rats exposed to the exhaust by either inhalation, intratracheal, or intraperitoneal administration. A 4-wk ME inhalation significantly increased benzo[a]pyrene hydroxylation, 7-ethoxyresorufin O-deethylation, and NADPH-cytochrome c reductase activities in liver, kidney, and lung microsomes. Intratracheal instillation of organic extracts of ME particulate (MEP) caused a dose- and time-dependent significant increase of monooxygenase activity. Intratracheal treatment with 0.1 g MEP extract/kg markedly elevated benzo[a]pyrene hydroxylation and 7-ethoxyresorufin O-deethylation activities in the rat tissues 24 h following treatment. Intraperitoneal treatment with 0.5 g MEP extract/kg/d for 4 d resulted in significant increases of P-450 and cytochrome b5 contents and NADPH-cytochrome c reductase activity in liver microsomes. The intraperitoneal treatment also markedly increased monooxygenases activities toward methoxyresorufin, aniline, benzphetamine, and erythromycin in liver and benzo[a]pyrene and 7-ethoxyresorufin in liver, kidney, and lung. Immunoblotting analyses of microsomal proteins using a mouse monoclonal antibody (Mab) 1-12-3 against rat P-450 1A1 revealed that ME inhalation, MEP intratracheal, or MEP intraperitoneal treatment increased a P-450 1A protein in the hepatic and extrahepatic tissues. Protein blots analyzed using antibodies to P-450 enzymes showed that MEP intraperitoneal treatment caused increases of P-450 2B, 2E, and 3A subfamily proteins in the liver. The ME inhalation, MEP intratracheal, or MEP intraperitoneal treatment resulted in significant increases in glutathione S-transferase activity in liver cytosols. The present study shows that ME and MEP extract contain substances that can induce multiple forms of P-450 and glutathione S-transferase activity in the rat.