Zheng-Fan Li

An improved 1D periodic defected ground structure for microstrip line

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.

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

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.

Analysis of the time response of nonuniform multiconductor transmission lines with a method of equivalent cascaded network chain

Nonuniform multiconductor transmission lines are considered to be equivalent to a cascaded chain of many multiport subnetworks which are made of short sections of uniform lines. The ABCD matrices of the subnetworks can be obtained by the matrix series expansions of their analytic expressions. As long as the number of the subnetworks is large enough to reflect the line nonuniformity fully, the expansions will converge so fast that a few of low-order series terms will be good approximations. After the overall ABCD matrix of the cascaded network chain is evaluated from that of each subnetwork, the time of response of transmission lines can be analyzed. The lines may have frequency-dependent parameters and arbitrary nonlinear terminals. Furthermore, transmission systems with branches uniform and nonuniform transmission lines can be studied with this method conveniently. The analysis accuracy and efficiency are discussed in detail. >

Compact Lowpass Filters With Sharp and Expanded Stopband Using Stepped Impedance Hairpin Units

This letter presents a novel compact lowpass filter with two transmission zeros. By tap-connecting the stepped-impedance hairpin unit, two transmission zeros can be generated when an interdigital structure is introduced between the two low-impedance sections. Further, the two transmission zeros can be adjusted easily to obtain a larger zero separation without the need to change the stepped-impedance unit. Therefore, a sharp transition, an expanded stopband, a low insertion loss, and a compact size can be obtained simultaneously. Two filters with single and two asymmetric units are designed, fabricated, and tested. The measured results demonstrate good performance: compact size, low passband insertion loss, broad stopband, and sharp skirt characteristic.

Side-Coupled Shorted Microstrip Line for Compact Quasi-Elliptic Wideband Bandpass Filter Design

This letter presents a novel structure composed of a shorted quarter-wavelength microstrip line side-coupled to two open-ended stubs. The proposed topology exhibits a quasi-elliptic wideband response with two transmission zeros enhancing the selectivity. To verify the design concept, one filter example has been designed, fabricated and measured. Good insertion/return losses, flat group delay, sharp transition, excellent DC-choked property, simple topology, and compact size are achieved as demonstrated in both simulation and experiment.

Transient analysis of lossy interconnects by modified method of characteristics

In this paper, the modified method of characteristics (MMC) is presented to analyze lossy interconnects. The method applies lower order Taylor approximation to model the characteristic admittance, and further applies lower order Pade approximation to model propagation functions of a transmission line. However, different from the single-point or multipoint moment-matching approaches, this method does not generate a reduced-order model of a transmission line prior to constructing the system matrix. Instead, it takes a special expansion and directly incorporates the coefficients of the expansion into the modified nodal admittance (MNA) matrix. On the basis of the specific expansion, a set of time-domain recursive formulae is derived, which concerns only the quantities at the ends of transmission lines. The recursive formulae are similar to those of method of characteristics (MC), with some added modifications. Based on the formulae of MMC, an equivalent time-domain macromodel of a uniform lossy transmission line is obtained. It can be easily implemented within the framework of an existing circuit simulator such as SPICE. The examples indicate that the method gives accurate time-domain simulation of interconnects in high-speed IC systems.

Analysis of the bounces on the power/ground plane structures by planar circuit model and APA-E algorithm

In this paper, a novel effective numerical algorithm for analysis of the bounces on the power/ground-plane structure in printed circuit board (PCB) or multichip modules (MCMs) is proposed, which is based upon planar circuit model combined with APA-E algorithm. Firstly, the planar circuit model is developed to simulate the power/ground bounces when switching current is added in the structure. Secondly, on the basis of the abstract Pade approximant and the extrapolation algorithm, the APA-E algorithm is proposed. The classical multivariable rational Pade approximant is also constructed for comparison. Compared with finite difference time domain (FDTD) method, the new algorithm can provide a very accurate approximant in time domain, only requires little storage and CPU time. At last, attaching the decoupling capacitors for reducing the bounces on lossy power/ground-plane structures is also analyzed with this method.

Novel Two-Dimensional (2-D) Defected Ground Array for Planar Circuits

This paper presents a novel two-dimensional (2-D) defected ground array (DGA) for planar circuits, which has horizontal and vertical periodicities of defect structure. The defected unit cell of DGA is composed of a Sierpinski carpet structure to improve the effective inductance. Measurements show that the proposed DGA provides steeper cutoff characteristics, lower cutoff frequency, and higher slow-wave factors than the conventional periodic defected ground structure in the same occupied surface.

A new parameter-extraction method for DGS and its application to the low-pass filter

A new and simple parameter-extraction method for the equivalent circuit of defected ground structure (DGS) is presented. Using this method, circuit simulation, based on the DGS equivalent-circuit model, show excellent agreements with the electromagnetic (EM) simulation. Further, our method is applied effectively to design a low-pass filter (LPF) with DGS. Comparison between simulation and measurement confirm the validity of the LPF configuration and design procedure. Simple structure and high power handling capability are obtained from the proposed LPF.

A PEEC with a new capacitance model for circuit simulation of interconnects and packaging structures

In this paper, a modified partial-element equivalent-circuit (PEEC) model, i.e., (L/sub p/, A/spl I.oarr/, R, /spl epsiv/f)PEEC, is introduced. In such a model, no equivalent circuit, but a set of state equations for the variables representing the function of circuit, are given to model a three-dimensional structure. Unlike the original (L/sub p/, P, R, /spl epsiv/f) PEEC model, the definition of vector potential A/spl I.oarr/ with integral form and the Lorentz gauge are used in expanding the basic integral equation instead of the definition of the scalar potential /spl phi/ with integral form. This can directly lead to the state equations, and the capacitance extraction can be replaced by the calculation of the divergence of A/spl I.oarr/, which is analytical. For analysis of most interconnect and packaging problems, generally containing complex dielectric structures, the new model can save a large part of computing time. The validity of the new model is verified by the analysis in time and frequency domain with several examples of typical interconnect and packaging structures, and the results with this new method agree well with those of other papers.