Feng Xu

Bio: Feng Xu is an academic researcher from Nanjing University of Posts and Telecommunications. The author has contributed to research in topics: Band-pass filter & Resonator. The author has an hindex of 14, co-authored 96 publications receiving 2215 citations. Previous affiliations of Feng Xu include Nanjing University & École Polytechnique de Montréal.

Guided-wave and leakage characteristics of substrate integrated waveguide

Abstract: The substrate integrated waveguide (SIW) technique makes it possible that a complete circuit including planar circuitry, transitions, and rectangular waveguides are fabricated in planar form using a standard printed circuit board or other planar processing techniques. In this paper, guided wave and modes characteristics of such an SIW periodic structure are studied in detail for the first time. A numerical multimode calibration procedure is proposed and developed with a commercial software package on the basis of a full-wave finite-element method for the accurate extraction of complex propagation constants of the SIW structure. Two different lengths of the SIW are numerically simulated under multimode excitation. By means of our proposed technique, the complex propagation constant of each SIW mode can accurately be extracted and the electromagnetic bandstop phenomena of periodic structures are also investigated. Experiments are made to validate our proposed technique. Simple design rules are provided and discussed.

Finite-difference frequency-domain algorithm for modeling guided-wave properties of substrate integrated waveguide

Abstract: In multilayer microwave integrated circuits such as low-temperature co-fired ceramics or multilayered printed circuit boards, waveguide-like structures can be fabricated by using periodic metallic via-holes referred to as substrate integrated waveguide (SIW). Such SIW structures can largely preserve the advantages of conventional rectangular waveguides such as high-Q factor and high power capacity. However, they are subject to leakage due to periodic gaps, which potentially results in wave attenuation. Therefore, such a guided-wave modeling problem becomes a very complicated complex eigenvalue problem. Since the SIW are bilaterally unbounded, absorbing boundary conditions should be deployed in numerical algorithms. This often leads to a difficult complex root-extracting problem of a transcend equation. In this paper, we present a novel finite-difference frequency-domain algorithm with a perfectly matched layer and Floquet's theorem for the analysis of SIW guided-wave problems. In this scheme, the problem is converted into a generalized matrix eigenvalue problem and finally transformed to a standard matrix eigenvalue problem that can be solved with efficient subroutines available. This approach has been validated by experiment.

Periodic Leaky-Wave Antenna for Millimeter Wave Applications Based on Substrate Integrated Waveguide

Abstract: Substrate integrated waveguides (SIW) are built up of periodically arranged metallic via-holes or via-slots The leakage loss of SIW structures increases with the distance between the via-holes or via-slots An open periodic waveguide with a large via distance supports the propagation of leaky-wave modes and can thus be used for the design of a leaky-wave antenna In this paper, this leakage loss is studied in detail and used to design a periodic leaky-wave antenna The proposed concept represents an excellent choice for applications in the millimeter-wave band Due to its versatility, the finite difference frequency domain method for periodic guided-wave or leaky-wave structures is used to analyze the characteristics of the proposed periodic leaky-wave antenna Two modes (TE10 and TE20) are investigated and their different leaky-wave properties are analyzed Based on the proposed leaky-mode analysis method, a novel periodic leaky-wave antenna at 28-34 GHz is designed and fabricated

Dual-Mode Substrate Integrated Waveguide Filter With Flexible Response

Abstract: This paper proposes a novel dual-mode substrate integrated waveguide (SIW) filter technique. Based on the conventional dual-mode SIW structure, further investigation is performed. Multiple transmission zeros can be obtained at one side or both sides of the passband for an SIW cavity. Therefore, flexible design and high performance response can be available for dual-mode SIW filter. A dual-mode SIW bandpass filter with quasi-elliptic response and a dual-mode SIW diplexer with asymmetric channel response are simulated, fabricated, and measured to demonstrate and verify the novel property.

Understanding Leaky-Wave Structures: A Special Form of Guided-Wave Structure

Abstract: Guided-wave structures are the foundation for the design and development of RF and microwave circuits and systems. Whether it is planar or nonplanar, periodic or straight, a guided-wave structure, which consists of metallic and/or dielectric composite building blocks, is used to support signal propagation and processing. Except for free-space propagation, diffraction and scattering in an open medium or space, microwave energy is usually transferred by means of specially designed guided-wave structures with modal propagation behavior that are fundamentally characterized by a propagation constant and transmission loss with respect to specific guided-wave modes. Those modes are structure and frequency dependent, and satisfy the boundary conditions of a guided-wave structure. Guided-wave structures can be divided into two kinds, open and closed. The completely closed structures are known to support only the wave guided therein, while the open structure, including semi-open or partially open structures, are subject to a potential gradual wave leakage along the propagation path. Wave leakage is always related to wave guidance, which is very much dependent on a number of factors including structural geometry, fill materials, operating frequency and guided mode. Such leakage can be used positively to develop a leaky-wave structure called a leaky-wave antenna, which enjoys some distinctive properties such as beam-scanning with frequency. Leaky-wave radiating structures are easily fabricated at millimeter wave frequencies compared with other antennas. Although leaky-wave and guided-wave structures have similar characteristics and can be designed by common methods, the simulation and design of leaky-wave structures are usually much more complicated. This is because leaky-wave structures are not closed and their attenuation constant related to leakage needs to be considered. In this article, we focus on the presentation of basic operating principles and special features of positive leaky-wave structures (leaky-wave antennas) ranging from straight to periodic geometries.

Guided-wave and leakage characteristics of substrate integrated waveguide

Abstract: The substrate integrated waveguide (SIW) technique makes it possible that a complete circuit including planar circuitry, transitions, and rectangular waveguides are fabricated in planar form using a standard printed circuit board or other planar processing techniques. In this paper, guided wave and modes characteristics of such an SIW periodic structure are studied in detail for the first time. A numerical multimode calibration procedure is proposed and developed with a commercial software package on the basis of a full-wave finite-element method for the accurate extraction of complex propagation constants of the SIW structure. Two different lengths of the SIW are numerically simulated under multimode excitation. By means of our proposed technique, the complex propagation constant of each SIW mode can accurately be extracted and the electromagnetic bandstop phenomena of periodic structures are also investigated. Experiments are made to validate our proposed technique. Simple design rules are provided and discussed.

Review of substrate-integrated waveguide circuits and antennas

Abstract: Substrate-integrated waveguide (SIW) technology represents an emerging and very promising candidate for the development of circuits and components operating in the microwave and millimetre-wave region. SIW structures are generally fabricated by using two rows of conducting cylinders or slots embedded in a dielectric substrate that connects two parallel metal plates, and permit the implementation of classical rectangular waveguide components in planar form, along with printed circuitry, active devices and antennas. This study aims to provide an overview of the recent advances in the modelling, design and technological implementation of SIW structures and components.

Accurate modeling, wave mechanisms, and design considerations of a substrate integrated waveguide

Abstract: A new method of analysis is presented in this paper for the determination of complex propagation constants in substrate integrated waveguides (SIWs) This method makes use of the concept of surface impedance to model the rows of conducting cylinders, and the proposed model is then solved by combining a method of moments and a transverse resonance procedure The proposed method is further applied to extract results in terms of parametric curves and graphs which demonstrate fundamental and interesting wave guidance and leakage properties of this type of periodic waveguide Useful design rules are extracted from this analysis, suggesting that appropriate design parameters and regions should be carefully selected for practical applications In addition, comprehensive review and comparisons with published results are also presented to show the performance and accuracy of the proposed modeling technique Practical measurements of fabricated samples with different levels of loss have confirmed the accuracy of this new method and validity of design rules

Gain enhancement methods for printed circuit antennas

Abstract: Resonance conditions for a substrate-superstrate printed antenna geometry which allow for large antenna gain are presented. Asymptotic formulas for gain, beamwidth, and bandwidth are given, and the bandwidth limitation of the method is discussed. The method is extended to produce narrow patterns about the horizon, and directive patterns at two different angles.

Simulation and experiment on SIW slot array antennas

Abstract: By etching longitudinal slots on the top metallic surface of the substrate integrated waveguide (SIW), an integrated slot-array antenna is proposed in this letter. The whole antenna and feeding system are fabricated on a single substrate, which takes the advantage of small size, low profile, and low cost, etc. The design process and experimental results of a four-by-four SIW slot array antenna at X-band are presented.