1,721,070 research outputs found
Fully autonomous wireless sensor network for freight wagon monitoring
No full textThis paper presents a wireless sensor network (WSN) for onboard monitoring of railway freight wagons, in which all the network nodes are energetically autonomous. Unlike the usual energy-harvesting WSNs, here it is proposed to supply not only the sensor nodes but also the sink node by means of an energy harvester, in order to realize independent networks for each wagon. This choice allows the overcoming of several issues related to a single network for the whole train, but it requires a significant reduction of the energy consumption of the power-hungry sink node. In order to reduce the energy consumption to values sustainable by energy harvesters without penalizing the quality of service, this paper proposes a bi-periodic communication scheme for the local wireless transmission, a dynamic management of the GPS receiver, and a consumption model of the GPRS transceiver, which allows an optimized management of the sleep modes. The proposed solutions are compared with the existing ones, and the theoretical predictions are validated by measurements on a system prototype under different operating conditions
Analysis and Design of Dual-Mode CMOS LC-VCOs
No full textWe present a nonlinear analysis of the basic circuit of a dual-band voltage controlled oscillator (VCO), composed by an active one-port and by a double-tuned LC circuit. Both the frequencies and the amplitudes of the two modes of sinusoidal oscillation are calculated by closed-form expressions by which a detailed analysis of the steady-state and dynamical behavior of circuit is performed, including the stability analysis of the modes. We show the appearance of the phenomenon of the frequency hysteresis allowing us to explain the mechanism of the switching between modes and predict the VCOs performance over the whole operation range. The theoretical results, validated by Spice simulations of a VCO realized in 0.13 μm MOS technology and by measurements on a circuit prototype, provide useful design insights
Finding the Tuning Curve of a CMOS – LC VCO
No full textA nonlinear perturbation model of a complementary
LC-tuned voltage-controlled oscillator is derived, which consists
of two mutually-coupled second-order differential equations. The
first-order approximate periodic solution of the describing equations
is found, obtaining closed-form expressions for both the amplitude
and the harmonics of oscillation, as well as for the correction
of the oscillation frequency due to the nonlinear effect of varactors.
This allows us to find the tuning curve in explicit form. The
accuracy of presented formulas was validated by circuit simulations
Perturbation Analysis of Nonlinear Distortion in Analog Integrated Circuits
No full textA method for predicting the distortion in weakly
nonlinear analog circuits is presented, which relies on the classical
theory of regular perturbation. Accordingly, a nonlinear
circuit is described and analyzed as a perturbation of its linearized
model, and the response to a periodic signal is analytically
calculated through frequency-domain recurrent formulas. The
method is simple and quite straightforward to apply, as it involves
the calculation of frequency-domain transfer functions and of
Fourier coefficients only, making it easily adaptable to any circuit
topology. The method can be a valid alternative to the Volterra
series method. A relationship between the proposed method and
the Volterra series method is established, showing that they lead
to very similar approximants to the solution. The method has been
numerically tested in practical circuits wherein the devices are
modeled by polynomial and exponential nonlinearities
- …
