Jun-Fa Mao

Bio: Jun-Fa Mao is an academic researcher from Shanghai Jiao Tong University. The author has contributed to research in topics: Microstrip & Antenna (radio). The author has an hindex of 35, co-authored 552 publications receiving 4954 citations. Previous affiliations of Jun-Fa Mao include University of California, Berkeley & Nanyang Technological University.

Circuit Modeling and Performance Analysis of Multi-Walled Carbon Nanotube Interconnects

Abstract: Metallic carbon nanotubes (CNTs) have received much attention for their unique characteristics as a possible alternative to Cu interconnects in future ICs. Until this date, while almost all fabrication efforts have been directed toward multiwalled CNT (MWCNT) interconnects, there is a lack of MWCNT modeling work. This paper presents, for the first time, a detailed investigation of MWCNT-based interconnect performance. A compact equivalent circuit model of MWCNTs is presented for the first time, and the performance of MWCNT interconnects is evaluated and compared against traditional Cu interconnects, as well as Single-Walled CNT (SWCNT)-based interconnects, at different interconnect levels (local, intermediate, and global) for future technology nodes. It is shown that at the intermediate and global levels, MWCNT interconnects can achieve smaller signal delay than that of Cu interconnects, and the improvements become more significant with technology scaling and increasing wire lengths. At 1000- global or 500- intermediate level interconnects, the delay of MWCNT interconnects can reach as low as 15% of Cu interconnect delay. It is also shown that in order for SWCNT bundles to outperform MWCNT interconnects, dense and high metallic-fraction SWCNT bundles are necessary. On the other hand, since MWCNTs are easier to fabricate with less concern about the chirality and density control, they can be attractive for immediate use as horizontal wires in VLSI, including local, intermediate, and global level interconnects.

Crosstalk Prediction of Single- and Double-Walled Carbon-Nanotube (SWCNT/DWCNT) Bundle Interconnects

Abstract: The crosstalk effects in single- and double-walled carbon-nanotube (SWCNT and DWCNT) bundle-interconnect architectures are investigated in this paper. Some modified equivalent-circuit models are proposed for both SWCNT and DWCNT bundles, where capacitive couplings between adjacent bundles are incorporated. These circuit models are further used to predict the performance of SWCNT and DWCNT bundle interconnects in comparison with the Cu wire counterpart at all interconnect levels for advanced future technology generations. It is found that, compared with the SWCNT bundle, the DWCNT bundle interconnect can lead to a reduction of crosstalk-induced time delay, which will be more significant with increasing bundle length, while the peak voltage of the crosstalk-induced glitch in SWCNT and DWCNT bundle interconnects is in the same order as that of Cu wires. Due to the improvement in time delay, it is numerically confirmed that the DWCNT bundle interconnect will be more suitable for the next generation of interconnect technology as compared with the SWCNT bundle counterpart.

Harmonic suppression with photonic bandgap and defected ground structure for a microstrip patch antenna

Abstract: This letter presents a microstrip patch antenna integrated with two-dimensional photonic bandgap (PBG) and one-dimensional defected ground structure (DGS) jointly in ground plane. It is demonstrated that application of both PBG and DGS eliminates the second and third harmonics and improves the return loss level. Moreover, the combination use of PBG and DGS decreases the occupied area by 70% compared to the conventional PBG patch antenna.

Design of a Beam Reconfigurable THz Antenna With Graphene-Based Switchable High-Impedance Surface

Abstract: In this paper, a new beam reconfigurable antenna is proposed for THz application, which is based on a switchable high-impedance surface (HIS) using a single-layer graphene. The effects of impurity density and gate voltage on the conductivity of graphene are utilized, and the switchable reflection characteristic of the graphene-based HIS is observed. Then the THz antenna is designed over this switchable HIS. By applying different voltages for different rows of HIS units, the antenna beam can be reconfigurable. The performance of the antenna is analyzed with its reflection coefficient, radiation pattern, and input impedance. The radiation beam of the antenna can vary in a range of ±30° as demonstrated by the simulated results.

An improved 1D periodic defected ground structure for microstrip line

Abstract: A novel one-dimensional (1-D) periodic defected ground structure (DGS) for microstrip line is presented in this letter. Different from the periodic DGS with uniform square-patterned defects, the improved periodic DGS has a compensated microstrip line and the dimensions of the square defects are nonuniform and varied proportionally to the relative amplitudes distribution of the exponential function e/sup 1/n/ (n denotes the positive integer). A uniform periodic DGS circuit and two improved periodic DGS circuits are designed, fabricated, and measured. Measurements show that the latter exhibit more excellent performances by suppressing ripples and enlarging stopband bandwidth.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

An Overview on Defected Ground Structure

Abstract: This paper focuses on a tutorial overview of defected ground structure (DGS). The basic conceptions and transmission characteristics of DGS are introduced and the equivalent circuit models of varieties of DGS units are also presented. Finally, the main applications of DGS in microwave technology field are summarized and the evolution trend of DGS is given.