A long-range UHF RF identification (RFID) sensor has been designed using a 0.35-µm CMOS standard process. The power-optimized tag, combined with the ultralow-power temperature sensor, allows an ID and a temperature reading range of 2 m from a 2-W effective radiated power output power reader. The temperature sensor is based on a ring oscillator, where the temperature dependence of the oscillation frequency is used for thermal sensing. The temperature sensor exhibits a resolution of 0.035 • C and an inaccuracy value lower than 0.1 • C in the range from 35 • C to 45 • C after two-point calibration. The average power consumption of the temperature sensor is only 110 nW at ten conversions per second while keeping a high resolution and accuracy. These properties allow the use of the RFID as a batteryless sensor in a wireless human body temperature monitoring system. Index Terms-CMOS analog front end, digital core, high accuracy, low power, RF identification (RFID), temperature sensor, ultrahigh frequency (UHF).

Articles you may be interested inNoise and terahertz rectification linked by geometry in planar asymmetric nanodiodes Appl. Phys. Lett. 94, 093512 (2009); 10.1063/1.3095845Terahertz Gunn-like oscillations in InGaAs/InAlAs planar diodes

Shot-noise suppression is investigated in nondegenerate diffusive conductors by means of an ensemble Monte Carlo simulator. The universal 1͞3 suppression value is obtained when transport occurs under elastic collision regime provided the following conditions are satisfied: (i) The applied voltage is much larger than the thermal value; (ii) the length of the device is much greater than both the elastic mean free path and the Debye length. By fully suppressing carrier-number fluctuations, long-range Coulomb interaction is essential to obtain the 1͞3 value in the low-frequency limit.[ S0031-9007(98)05732-9] PACS numbers: 72.70. + m, 73.23.Ad, 73.50.Td In recent years kinetic phenomena in mesoscopic structures are offering a fascinating scenario for fundamental research [1]. One of the most up-to-date subjects is shotnoise suppression in disordered conductors. Here, the excess noise power has been predicted to comprise exactly one-third of the full shot-noise value S I 2eI. This result has been credited to different theoretical approaches as applied to several microscopic models of disordered conductors. For a phase-coherent model Beenakker and Büttiker [2] obtained the result using a bimodal distribution of transmission eigenvalues with the help of random matrix theory to calculate averages. For a semiclassical 1D model which includes Pauli principle Nagaev [3] found the same result using a Boltzmann kinetic approach within an elastic and energy independent relaxation-time approximation. For a semiclassical sequential tunneling model de Jong and Beenakker [4] obtained the 1͞3 value within a Boltzmann-Langevin approach in the limit of an infinite number of equal barriers and independently from the value of their transmission coefficient. Compatible results have been found by Liu et al.[5] from a semiclassical implementation of a Monte Carlo simulation which includes Pauli principle. For a phase-coherent model Nazarov [6] has proven the universality of this result in the diffusive limit for arbitrary shape and resistivity distribution of the conductor as long as its length is greater than the carrier mean free path. Experimental evidence of the reduced shot-noise level close to the predicted 1͞3 value in diffusive mesoscopic conductors has been provided in [7][8][9].From the above it is argued that the 1͞3 value of the suppression factor g S I ͞2eI is a universal phenomenon whose physical meaning should lay beyond classical or quantum mechanics and originate from some unifying concept. The aim of this Letter is to address this issue. We conjecture that discreteness of charge transport is at the basis of such a concept, and that a transport dominated by elastic interactions is ultimately the physical reason for the 1͞3 suppression independently from the quantum or classical approach used. Both the (apparently unrelated) coherent [2] and semiclassical [3] contexts where the reduction factor 1͞3 has appeared assume a degenerate Fermi gas, and the noise reduction comes from the regulation of electron motion by the ...

By using a semi-classical two-dimensional Monte Carlo simulation, simple devices (T-branch junctions (TBJs) and rectifying diodes) based on AlInAs/InGaAs ballistic channels are analysed. Initially, the model is validated by means of Hall-effect measurements of mobility and electron concentration in long (diffusive) channels. Then, quasi-ballistic transport at room temperature is confirmed in a 100 nm channel. Our simulations qualitatively reproduce the experimental results of electric potential measured in a TBJ appearing as a result of electron ballistic transport, and in close relation with the presence of space charge inside the structure. As examples of devices exploiting the ballistic transport of electrons, preliminary simulations of a multiplexor/demultiplexor and a rectifying diode are presented, demonstrating their capability for terahertz operation.

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By using a semi-classical two-dimensional (2-D) Monte Carlo simulation, simple ballistic devices based on AlInAs/InGaAs channels are analyzed. Our simulations qualitatively reproduce the experimental results in T-and Y-branch junctions as well as in a ballistic rectifier appearing as a result of electron ballistic transport. We show that a quantum description of electron transport is not essential for the physical explanation of these results since phase coherence plays no significant role. On the contrary, its origin can be purely classical: the presence of classical electron transport and space charge inside the structures.

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We present a microscopic analysis of shot-noise suppression due to long-range Coulomb interaction in semiconductor devices under ballistic transport conditions. An ensemble Monte Carlo simulator selfconsistently coupled with a Poisson solver is used for the calculations. A wide range of injection-rate densities leading to different degrees of suppression is investigated. A sharp tendency of noise suppression at increasing injection densities is found to scale with a dimensionless Debye length related to the importance of spacecharge effects in the structure. ͓S0163-1829͑97͒09735-X͔The phenomenon of shot noise, associated with the randomness in the flux of carriers crossing the active region of a device, has become a fundamental issue in the study of electron transport through mesoscopic devices. In particular, the possibility of shot-noise suppression has recently attracted a lot of attention, both theoretically and experimentally.1 At low frequency ͑small compared to the inverse transit time through the active region͒ the power spectral density of shot noise is given by S I ϭ␥2qI, where I is the dc current, q is the electron charge, and ␥ is the suppression factor. When the carriers crossing the active region are uncorrelated, full shot noise with ␥ϭ1 ͑Poisson statistics͒ is observed. However, correlations between carriers can reduce the shot-noise value, giving ␥Ͻ1. In real mesoscopic devices different types of mechanisms resulting in shot-noise suppression can be distinguished: ͑i͒ statistical correlations due to the Pauli exclusion principle ͑important for degenerate materials obeying Fermi statistics͒, ͑ii͒ short-range Coulomb interaction ͑electron-electron scattering͒, and ͑iii͒ long-range Coulomb interaction ͑by means of the self-consistent electric potential͒. While the first two mechanisms have been extensively discussed in solid-state literature, 1 the last one has received less attention, 2 although its role in shot-noise suppression has been known for a long time in vacuum-tube devices.3 The only exception that should be mentioned is the Coulomb blockade in resonant-tunneling devices, which can be also referred to as the last mechanism of suppression. The blockade is provided by a built-in charge inside a quantum well which redistributes the chemical potential, and prevents the incoming carriers from passing through the well, thereby resulting in carrier correlation and shot-noise suppression ͑see the experimental evidence 4 ͒. The Coulomb blockade is a consequence of long-range Coulomb interaction, and it acts under the sequential tunneling regime of carrier transport.The main objective of the present paper is to prove the importance of long-range Coulomb interaction between the carriers on the shot-noise power spectrum under the ballistic regime of electron transport. The ballistic regime is now accessible in modern mesoscopic devices like electron waveguides, quantum point contacts, etc., which have characteristic lengths of the order, or smaller, than the carrier mean free path. The current exist...