Gaofeng Wang

A hybrid wavelet expansion and boundary element analysis of electromagnetic scattering from conducting objects

A new wavelet approach is presented for treating the two-dimensional electromagnetic scattering problems over curved computation domains. The wavelet expansion method, in combination with the boundary element method (BEM), is applied to solve the integral equation for the unknown surface current. The unknown surface current is expanded in terms of a basis derived from a periodic, orthogonal wavelet in interval [0, 1]. The geometrical representation of the BEM is employed to establish the map between the curved computation domain and the interval [0, 1]. This technique exhibits the advantages of both the wavelet expansion method and the boundary element method: sparse matrix system and accurately modeling of curved surfaces. Comparisons of the results from the new technique with the moment method solutions, the analytical solutions or the data in previous publications are provided. Good agreements are observed. >

Full wave analysis of microstrip floating line structures by wavelet expansion method

A full wave analysis of microstrip floating line structures by wavelet expansion method is presented. The surface integral equation developed from a dyadic Greens function is solved by Galerkins method, with the integral kernel and the unknown current expanded in terms of orthogonal wavelets. Using the orthonormal wavelets (and scaling functions) with compact support as basis functions and weighting functions, the integral equation is converted into a set of linear algebraic equations, with the matrices nearly diagonal or block-diagonal due to the localization, orthogonality, and cancellation properties of the orthogonal wavelets. Limitations inherited in the traditional orthogonal basis systems are released: The problem-dependent normal modes have been replaced by the problem-independent wavelets, preserving the orthogonality; the trade-off between orthogonality and continuity (e.g. subsectional basis functions including pulse functions, roof-top functions, piecewise sinusoidal functions, etc.) is well balanced by the orthogonal wavelets. Numerical results are compared with measurements and previous published data with good agreement. >

On-chip inductance modeling and RLC extraction of VLSI interconnects for circuit simulation

On-chip inductance modeling of VLSI interconnects is presented which captures 3D geometry from layout design and process technology information. Analytical formulae are derived for quick and accurate inductance estimation which can be used in circuit simulations and whole chip extraction screening process. Circuit simulations show critical global wire inductive effects as well as power and ground inductive noise.

Slot Antenna for Metal-Rimmed Mobile Handsets

This letter introduces a 15.5 × 56.5-mm2 planar slot antenna operated under surroundings of an unbroken metal rim in mobile handsets. The height of the slot antenna is shortened, and the bandwidth for low band is expanded to cover both GSM850 and GSM900. This antenna provides a solution for planar unbroken metal-rimmed handsets and can be operated in five wireless communication bands (i.e., GSM850, GSM900, DCS1800, PCS1900, and UMTS bands). Good performances on return loss, radiation pattern, efficiency, and gain are obtained over these five operating bands. Hand effect of this slot antenna is also studied by comparison to the conventional monopole antenna.

Modeling of Crosstalk Effects in Multiwall Carbon Nanotube Interconnects

Crosstalk effects in multiwall carbon nanotube (MWCNT) interconnects for future ICs are investigated by virtue of the equivalent single conductor model and the finite-difference time-domain solution of transmission line equations. The worst case time delay and the peak crosstalk voltage on victim wire of multiwire MWCNT interconnect configurations are derived and compared to those of the copper (Cu) wire counterparts for the intermediate and global interconnects at the 22- and 14-nm technology nodes. The numerical results illustrate that the crosstalk-induced time delays in the MWCNT interconnects are much smaller than those in the Cu interconnects, in particular, for longer wires. Nevertheless, the MWCNT interconnects exhibit little improvement on the crosstalk-induced noises in comparison with their Cu counterparts.

A hybrid wavelet expansion and boundary element analysis for multiconductor transmission lines in multilayered dielectric media

In this paper the wavelet expansion method, in conjunction with the boundary element method (BEM), is applied for the evaluation of the capacitance and inductance matrices of multiconductor transmission lines in multilayered dielectric media. The integral equations obtained by using a Greens function above a ground plane are solved by Galerkins method, with the unknown total charge expanded in terms of orthogonal wavelets in L/sup 2/([0,1]). The difficulty of using wavelets on the real line to expand unknown functions defined in finite intervals is overcome by the utilization of wavelets in L/sup 2/([0,1]). The adoption of the geometric representation of the BEM converts the two-dimensional problem into a one-dimensional problem, and provides a versatile and accurate treatment of curved conductor surfaces and dielectric interfaces. A sparse matrix equation is developed from the set of integral equations, which is extremely valuable, in particular when a large system of equations must be solved. Finally, we compare our numerical results with previously published data, and demonstrate good agreement between the two sets of results. >

Design and fabrication of PIN-PMN-PT single-crystal high-frequency ultrasound transducers

High-frequency PIN-PMN-PT single crystal ultrasound transducers at center frequencies of 35 MHz and 60 MHz were successfully fabricated using lead indium niobate-lead magnesium niobate-lead titanate (0.23PIN- 0.5PMN-0.27PT) single crystal. The new PIN-PMN-PT single crystal has higher coercivity (6.0 kV/cm) and higher Curie temperature (160°C) than PMN-PT crystal. Experimental results showed that the PIN-PMN-PT transducers have similar performance but better thermal stability compared with the PMN-PT transducers.

A Compact Multiband Open-Ended Slot Antenna for Mobile Handsets

A novel compact multiband antenna formed by two printed open-ended slots, with the first one a T-shaped slot and the second one an E-shaped slot, cut at the edge of the ground plane of mobile handsets is presented. This antenna can generate five resonant modes to cover GSM900/DCS1800/ PCS1900/UMTS and 2.4-GHz-based WLAN bands, which can be controlled almost independently by the five respective monopole slots of different lengths. Furthermore, the proposed antenna has a simple planar structure and occupies a small area of only 10 × 42.5 mm2. It is also promising to bend the antenna into a E shape, inverted-T shape and meander line to reduce its volume occupied. Details of the antenna design and experimental results are presented and discussed.

Edge effect enforced boundary element analysis of multilayered transmission lines

An improved boundary element method (BEM) for the calculation of the capacitance matrix in a multiconductor transmission line structure is presented, where the edge singularities of the charge and current near the corners of the cross-sections of the signal lines are embedded in the basis functions. The new method demonstrates improved accuracy and enhanced computational efficiency in comparison to previous methods. The results for the new algorithm are compared with those for other approaches presented in the literature. >

A Novel Barrier Controlled Tunnel FET

A novel structure of tunnel field-effect transistor (FET) is introduced with the gate composed of three segments of different work functions. The tunnel current is controlled by an in channel potential barrier as well as the source-channel tunnel junction bandgap, which combines the merits of both bandgap-controlled tunnel FET and barrier-controlled traditional MOSFET. Intuitive explanation is provided for this novel device structure. The performance enhancement is confirmed by numerical simulation with carbon nanotube as the channel material. This structure is especially suitable for bandgap tunable ballistic transport materials (e.g., carbon nanotube and graphene nanoribbon).