Trenched‐Sinker LDMOSFET (TS‐LDMOS) Structure for 2 GHz Power Amplifiers

This paper proposes a new LDMOSFET structure with a trenched sinker for high‐power RF amplifiers. Using a low‐temperature, deep‐trench technology, we succeeded in drastically shrinking the sinker area to one‐third the size of the conventional diffusion‐type structure. The RF performance of the proposed device with a channel width of 5 mm showed a small signal gain of 16.5 dB and a maximum peak power of 32 dBm with a power‐added efficiency of 25% at 2 GHz. Furthermore, the trench sinker, which was applied to the guard ring to suppress coupling between inductors, showed an excellent blocking performance below ?40 dB at a frequency of up to 20 GHz. These results confirm that the proposed trenched sinker should be an effective technology both as a compact sinker for RF power devices and as a guard ring against coupling.     

Data retention characteristics of sub-100 nm NAND flash memory cells

In contrast to the conventional theories, we have revealed that the most distinguished mechanism in the data retention phenomenon after Fowler-Nordheim (FN) stress in sub-100 nm NAND Flash memory cells is the annihilation of interface states. Interface state generation rate increases rapidly as the channel width of NAND flash cell decreases. Comparison of interface states and stress-induced leakage current (SILC) component during retention mode shows that the annihilation of interface states strongly affects data retention characteristics of the programmed cells.     

A new time-domain discontinuous space-vector PWM technique in overmodulation region

A new discontinuous modulation method based on space-vector control is proposed and analyzed. The proposed technique employs a pulse-dropping method and is designed in the time domain. It features a very wide modulation range while maintaining the required waveform qualities and switching numbers in the overmodulation region. Since the modulation method and modulation index equation are simple, the proposed technique can be easily implemented by software and is applicable to the overmodulation region in ac motor drives. The performance indexes are discussed and experiments have been performed.     

Electrochemical behavior of Li intercalation processes into a Li[NixLi(1/3−2x/3)Mn(2/3−x/3)]O2 cathode

Li[Ni_xLi_(1/3−2x/3)Mn_(2/3−x/3)]O₂ (X=0.17, 0.25, 0.33, 0.5) compounds are prepared by a simple combustion method. The Rietvelt analysis shows that these compounds could be classified as having the α-NaFeO₂ structure. The initial charge-discharge and irreversible capacity increases with the decrease of x in Li[Ni_xLi_(1/3−2x/3)Mn_(2/3−x/3)]O₂. Indeed, Li[Ni_0.50Mn_0.50]O₂ compound shows relatively low initial discharge capacity of 200 mAh/g and large capacity loss during cycling, with Li[Ni_0.17Li_0.22Mn_0.61]O₂ and Li[Ni_0.25Li_0.17Mn₀.₅₈]O₂ compounds exhibit high initial discharge capacity over 245 mAh/g and stable cycle performance in the voltage range of 4.8 -2.0 V. On the other hand, XANES analysis shows that the oxidation state of Ni ion reversibly changes between Ni²⁺ and about Ni³⁺, while the oxidation state of Mn ion sustains Mn⁴⁺ during charge-discharge process. This result does not agree with the previously reported ‘electrochemistry model’ of Li[Ni_xLi_(1/3−2x/3)Mn_(2/3−x/3)]O₂, in which Ni ion changes between Ni²⁺ and NI⁴⁺. Based on these results, we modified oxidation-state change of Mn and Ni ion during charge-discharge process.     

Hyers-Ulam-Rassias stability of homomorphisms in quasi-Banach algebras associated to the Pexiderized Cauchy functional equation

In this paper, we prove the Hyers-Ulam-Rassias stability of homomorphisms in quasi-Banach algebras associated to the Pexiderized Cauchy functional equation. This is applied to investigate homomorphisms between quasi-Banach algebras. The concept of Hyers-Ulam-Rassias stability originated from Th.M. Rassias' stability theorem that appeared in his paper [Th.M. Rassias, On the stability of the linear mapping in Banach spaces, Proc. Amer. Math. Soc. 72 (1978) 297-300].     

89-GHz fT room-temperature silicon MOSFETs

The authors report the implementation of deep-submicrometer Si MOSFETs that at room temperature have a unity-current-gain cutoff frequency (f_T) of 89 GHz, for a drain-to-source bias of 1.5 V, a gate-to-source bias of 1 V, a gate oxide thickness of 40 Å, and a channel length of 0.15 μm. The fabrication procedure is mostly conventional, except for the e-beam defined gates. The speed performance is achieved through an intrinsic transit time of only 1.8 ps across the active device region     

A new millimeter-wave step-frequency radar sensor for distancemeasurement

A new compact millimeter-wave distance-measurement sensor prototype has been developed. The sensor is a step-frequency radar implemented using coherent heterodyne technique. It operates in Ka-band (26.5-40 GHz) and is realized using MICs and MMICs. The sensor transmits sinusoidal signals of incremental frequencies and demodulates the received signals into base-band I/Q signals for processing. Experimental results show that the sensor is capable of measuring distance with less than 0.2 inch of absolute error and a low transmitted power of only -20±3 dBm     

An efficient implementation of surface impedance boundaryconditions for the finite-difference time-domain method

An efficient way to implement the surface impedance boundary conditions (SIBC) for the finite-difference time-domain (FDTD) method is presented in this paper. Surface impedance boundary conditions are first formulated for a lossy dielectric half-space in the frequency domain. The impedance function of a lossy medium is approximated with a series of first-order rational functions. Then, the resulting time-domain convolution integrals are computed using recursive formulas which are obtained by assuming that the fields are piecewise linear in time. Thus, the recursive formulas derived here are second-order accurate. Unlike a previously published method [7] which requires preprocessing to compute the exponential approximation prior to the FDTD simulation, the preprocessing time is eliminated by performing a rational approximation on the normalized frequency-domain impedance. This approximation is independent of material properties, and the results are tabulated for reference. The implementation of the SIBC for a PEC-backed lossy dielectric shell is also introduced     

Topology design and bridge-capacity assignment for interconnecting token ring LANs: A simulated annealing approach

We address the problem of determining the topology and bridge-capacity assignments for a network connecting a number of token rings via source-routing bridges. The objective is to minimize the cost of bridge installations while meeting the network users' performance requirements. The problem is modeled as a mixed 0–1 integer program. A comparison is given between two solution algorithms: a simulated annealing algorithm using the flow-deviation algorithm for each routing subproblem, and a drop algorithm using the simplex method for the same subproblems to provide benchmark solutions. In the former algorithm, the routing subproblem is formulated as a nonlinear program with penalty functions to model node and link capacity constraints, and in the latter as a multicommodity flow model with the same capacity constraints. Computational results show that the simulated-annealing/flow-deviation algorithm produced substantially better solutions than the LP-based drop algorithm.