N. Militaru

Aperture Couplings in Multilayer Filtering Structures

In multilayer structures apertures in metallic sheets can be used as coupling elements between resonators located on different layers, allowing very compact filter designs. In this paper, some novel types of planar microwave bandpass filters, using aperture couplings, in structures with three metallic layers, are considered. Couplings between two miniaturized resonators are investigated, by full electromagnetic field simulation. Based on the results of this study, several models of planar microwave bandpass filters, with a single or with two apertures, are designed, verified by simulation, fabricated and measured. Compared to the classical filters, these novel structures show a good compactness and can offer some technological advantages.

Backward couplers using coupled composite right/left-handed transmission lines

A new asymmetric backward coupler is obtained by edge-coupling two types of composite right/left handed (CRLH) lines. This novel coupler is analyzed in a microwave range (1–10 GHz) and the magnitude of the scattering parameters reveals tight coupling effects (even 0 dB) in a dual frequency band and also very good directivity in the working band.

Investigation on microwave signal propagation through some left-handed structures

Some aspects of microwave propagation through left-handed materials are investigated in this paper. The strong distortion of a Gaussian TEM pulse through a material with negative refraction index is studied in the time domain. Moreover, a method of extracting the constitutive parameters of a material by using the scattering parameters of a sample two-port is developed. This method is then applied to some left-handed microstrip structures.

Compact Microwave Bandpass Filter using Multilayer Resonator-Embedded Packaging

The design of a compact microwave multilayer bandpass filter with aperture couplings and with an embedded-resonator topology is shown and investigated in this paper. Different types of inter-resonator and resonator-feedline couplings, in a three metallic-layer configuration, are presented. The bandpass filter is designed using coupling coefficients extracted through a full-wave electromagnetic-field simulation. The proposed multilayer configuration demonstrates a significant size reduction (about 50% in surface area), compared to a classical microstrip filter. The designed filters were realized in both classical electro-chemical and mechanical engraving technologies, in order to verify the influence of the manufacturing process on the filter characteristics. The measured parameters of the experimental models demonstrate the validity of the design method, based on electromagnetic-field simulation.

Broadband Planar Filters with Enhanced Couplings Using Defected Ground Structures

In this paper a study of some microwave microstrip bandpass filters (BPF) using defected ground structures (DOS) is presented. This technique allows designs of tight couplings without the necessity of using very narrow coupling gaps. Based on the results of the study, four-pole cross-coupled planar microwave bandpass filters were designed, with a single or with two ground slots. Compared to similar microstrip filters without defected ground, the simulated performances of these novel structures indicate some technological advantages

Compact Wireless Devices with Defected-Ground Structures

In this paper are presented some investigations on micro- strip defected ground structures (DGS). It is shown that the presence of a slot in the ground plane can substantially enhance the electric coupling, or the electric part of a mixed coupling between resonators and its external feedings. The proposed technique can eliminate the very narrow coupling gaps needed for a tight coupling and thus can relax the fab rication tolerances.

Couplings Control in the Defected Ground Star-Geometry Dual-Mode Filter

Investigations on coupling coefficients in a star-geometry filter with defected ground are presented in this paper. The device is compact, requiring a surface area of more than 6 times smaller than the area needed for a conventional patch dual mode resonator

Microwave antenna array using new dielectric resonator antenna elements

Investigations on antenna array for 5.8 GHz frequency band applications are presented in this paper. In order to enhance the characteristics of the dielectric resonator antenna elements, a pair of resonators with different sizes and dielectric constants is used. The antenna elements are connected to four daughter-boards of Universal Software Radio Peripherals, which perform the signal processing required by the sources detection and beamforming.

Investigation of electromagnetic couplings between planar open-loop triangular-shaped resonators in microstrip and in multilayer technologies

The paper presents a study of the electromagnetic couplings between planar open-loop triangular-shaped resonators. Based on the proposed single-mode resonator, various couplings schemes are considered: between a single microstrip resonator and its 50Ω feeding line, between two identical triangular-shaped resonators designed in microstrip technology, and between pairs of synchronously-tuned resonators located on different metallization layers, in a multilayer configuration. In this last case, properly located slots, cut out in the common ground plane, ensure and control the coupling between resonators. The results shown in the paper can be used in the design of different miniature planar band-pass filters, including filters with cross-coupled resonators, in microstrip and in multilayer technologies.

Material constraints on high-speed design

Current high-speed circuit designs with signal rates up to 100Gbps and above are implying constraints for dielectric and conductive materials and their dependence of frequency, for component elements and for production processes. The purpose of this paper is to highlight through various simulation results the frequency dependence of specific parameters like insertion and return loss, eye diagrams, group delay that are part of signal integrity analyses type. In low-power environment designs become more complex as the operation frequency increases. The need for new materials with spatial uniformity for dielectric constant is a need for higher data rates circuits. The fiber weave effect (FWE) will be analyzed through the eye diagram results for various dielectric materials in a differential signaling scheme given the fact that the FWE is a phenomenon that affects randomly the performance of the circuit on balanced/differential transmission lines which are typically characterized through the above mentioned approaches. Crosstalk between traces is also of concern due to propagated signals that have tight rise and fall times or due to high density of the boards. Criteria should be considered to achieve maximum performance of the designed system requiring critical electronic properties.