Design of a Low-Phase-Noise Ka-Band GaAs HBT VCO

In this paper, the study of a Ka-band GaAs HBT VCO is reported with particular emphasis on achieving low-phase noise while using direct coupled varactor. A push–push cross-coupled VCO configuration is employed to achieve high oscillation frequency and low-phase noise. The measured oscillation bandwidth spans from 30.2 to 28.6[Formula: see text]GHz with a tuning range of 1.6[Formula: see text]GHz, while the phase noise at 1[Formula: see text]MHz of frequency offset from the carrier at 29.3[Formula: see text]GHz is [Formula: see text][Formula: see text]dBc/Hz. The VCO consumes 28.2[Formula: see text]mW from 3[Formula: see text]V supply and occupies an area of [Formula: see text][Formula: see text]mm. The FOM of the VCO achieves [Formula: see text][Formula: see text]dBc/Hz.

Regulation of dynamic postural control to attend manual steadiness constraints

In daily living activities, performance of spatially accurate manual movements in upright stance depends on postural stability. In the present investigation, we aimed to evaluate the effect of the required manual steadiness (task constraint) on the regulation of dynamic postural control. A single group of young participants ( n = 20) were evaluated in the performance of a dual posturo-manual task of balancing on a platform oscillating in sinusoidal translations at 0.4-Hz (low) or 1-Hz (high) frequencies while stabilizing a cylinder on a handheld tray. Manual task constraint was manipulated by comparing the conditions of keeping the cylinder stationary on its flat or round side, corresponding to low and high manual task constraints, respectively. Results showed that in the low oscillation frequency the high manual task constraint led to lower oscillation amplitudes of the head, center of mass, and tray, in addition to higher relative phase values between ankle/hip-shoulder oscillatory rotations and between center of mass/center of pressure-feet oscillations as compared with values observed in the low manual task constraint. Further analyses showed that the high manual task constraint also affected variables related to both postural (increased amplitudes of center of pressure oscillation) and manual (increased amplitude of shoulder rotations) task components in the high oscillation frequency. These results suggest that control of a dynamic posturo-manual task is modulated in distinct parameters to attend the required manual steadiness in a complex and flexible way. NEW & NOTEWORTHY We evaluated dynamic postural control on a platform oscillating in sinusoidal translations at different frequencies while performing a manual task with low or high steadiness constraints. Results showed that high manual task constraint led to modulation of metric and coordination variables associated with greater postural stability. Our findings suggest that motor control is regulated in an integrative mode at the posturo-manual task level, with reciprocal interplay between the postural and manual components.

Energy-Efficient Gain Cell and Its Applications in the Limiting Amplifier and Ring Oscillator for Gbps Communications

This paper presents a low-power, high gain-bandwidth product (GBW) gain cell for gigabits-per-second communications. Based on this gain cell, a large GBW limiting amplifier (LA) and two types of high oscillation-frequency ring oscillators (ROs) are implemented with good energy efficiencies. Fabricated in the 0.18[Formula: see text][Formula: see text]m CMOS process, the proposed LA can support 1.25[Formula: see text]Gbps data-rate with a measured GBW of 338[Formula: see text]GHz under 5[Formula: see text]mW. The proposed single- and multi-loop ROs obtain a simulated typical oscillation frequency of 5.26[Formula: see text]GHz and 6.96[Formula: see text]GHz, respectively, under 6.2 mW, which is less than one-eighth the power consumption of published ROs at similar frequencies in the same process.

Low Voltage and High Oscillation Frequency Gated Ring Oscillator Using Bootstrap Technique

In this paper, a high frequency ring oscillator with low power consumption is proposed.The proposed ring oscillator is based on GRO by applying boot strap technique. Simulation resultsindicate that the FoM(Power Consumption/Oscillation Frequency) of the proposed ring oscillator isless than that of the conventional ring oscillator.

High frequency oscillatory flows in a slightly rarefied gas according to the Boltzmann–BGK equation

The Boltzmann equation provides a rigorous theoretical framework to study dilute gas flows at arbitrary degrees of rarefaction. Asymptotic methods have been applied to steady flows, enabling the development of analytical formulae. For unsteady (oscillatory) flows, two important limits have been studied: (i) at low oscillation frequency and small mean free path, slip models have been derived; and (ii) at high oscillation frequency and large mean free path, the leading-order dynamics are free-molecular. In this article, the complementary case of small mean free path and high oscillation frequency is examined in detail. All walls are solid and of arbitrary smooth shape. We perform a matched asymptotic expansion of the unsteady linearized Boltzmann–BGK equation in the small parameter $\nu / \omega $, where $\nu $ is the collision frequency of gas particles and $\omega $ is the characteristic oscillation frequency of the flow. Critically, an algebraic expression is derived for the perturbed mass distribution function throughout the bulk of the gas away from any walls, at all orders in the frequency ratio $\nu / \omega $. This is supplemented by a boundary layer correction defined by a set of first-order differential equations. This system is solved explicitly and in complete generality. We thus provide analytical expressions up to first order in the frequency ratio, for the density, temperature, mean velocity and stress tensor of the gas, in terms of the temperature and mean velocity of the wall, and the applied body force. In stark contrast to other asymptotic regimes, these explicit formulae eliminate the need to solve a differential equation for a body of arbitrary geometry. To illustrate the utility of these results, we study the oscillatory thermal creep problem for which we find a tangential boundary layer flow arises at first order in the frequency ratio.

Characterisation of the Sound and Vibration Signal of Impact Testing on Automotive Component Materials

Dynamic response of automotive component materials which are carbon steel S50C and cast ironon its sound and vibration characteristichas been studied. This paper shows that I-kaz analysis method can be applied to characterise this dynamic behavior problem. In the present work, an excitation has been performed by an impact hammer at the center of a rectangular bar specimen instrumented with accelerometer and microphone to obtain sound and vibration time-histories. From the experimental results, it was found that the recorded sound and vibration signal has a transient characteristic with high oscillation. Frequency spectrum analysis shows that impact testing on any material will generate its own characteristic of frequency peak and constantboth for sound and vibration signal. From I-kaz analysis method, it can be concluded that I-kaz coefficient, for sound signal is proportional to the modulus of elasticity, density and Poissons ratio. It is also shown that for vibration signal is inversely proportional to these mechanical properties.Data scattering representation supported this pattern of .