Nicolae Militaru

Polytechnic University of Bucharest | UPB · Department of Telecommunications

According to the requirements imposed by the new four-level pulse amplitude modulation (PAM4) standard for high-speed data transfer and processing, electrical constraints and manufacturing tolerances in integrated electronic packages impose accurate electromagnetic simulations and new S-parameters analysis, saving time and financial resources for n...

Neuron, the anatomical unit of the nervous system, processes the information received as coded pulses and generates stereotype pulses sent to other neurons through axon buttons. Current technology does not allow in vivo evaluation of the electrical activity of a single neuron and electromagnetic field detected on scalp is determined by the activity...

This paper presents the design of novel microwave bandpass filters, composed of coupled single-mode triangular resonators, in microstrip technology. Based on the study through electromagnetic-field simulation on the couplings between pairs of such open-loop triangular resonators and between a single resonator and its 50 O feeding line, microwave ba...

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 parame...

Considering loss effects on signals in the design of a circuit or a system that works at high frequency will allow to accurately predict a realistic behavior through models that include specific parameters. Losses in dielectric materials and in conductors are simulated in time or frequency domains where different models can better estimate the mate...

A new topology for fourth-order microstrip bandpass filters is investigated in this paper. Compared to the classical quadruplet, the proposed new topology offers an extra coupling between two resonators, allowing this way the design of fourth order filters with two attenuation poles situated on the same side of the passband. A strongly asymmetric t...

Simple, compact low-cost microwave bandpass filters with strongly asymmetric characteristics, based on new topologies, are investigated, designed, fabricated and measured. A classical fourth-order filter or quadruplet, for example, has two transmission zeros located symmetrically, one on each side of the passband. A filter of the same order and, co...

New multilayer microstrip structures are investigated in microwave range. Due to the use of stepped impedance resonators (SIR), the multilayer microstrip left-handed transmission lines are more compact than the structures with conventional split ring resonators. The amplitude and phase responses are analyzed for different geometrical parameters, nu...

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.

In this paper, dispersion/attenuation diagrams are investigated for purely left-handed (PLH) and for composite right/left handed (CRLH) transmission lines. The magnitude and phase of the S parameters of these structures are analyzed in a broadband (1-7 GHz) range. The investigations on microstrip CRLH lines demonstrate the presence of the left-hand...

In this paper a band-pass filter in microstrip technology, with cross couplings and with a pair of attenuation poles, is investigated. The equi-ripple in-band response and the location of the poles on the frequency axis can be precisely controlled through a new technique which combines accurate electromagnetic-field simulation and fast linear circu...

In this paper the problem of designing simple low-cost planar microwave bandpass filters with strongly asymmetric characteristics, filters that can very efficiently attenuate one of the two adjacent channels, is investigated. In case of a fourth-order filter, the usual quadruplet structure leads to two transmission zeros located one on each side of...

In this paper the problem of designing simple low-cost planar microwave band-pass filters with strongly asymmetric characteristics, filters that can very efficiently attenuate an adjacent channel, is investigated. For a fourth-order filter, the usual quadruplet structure leads to two transmission zeros, located one on each side of the passband. For...

Microstrip structures with left-handed properties are investigated in frequency domain. A method of extracting material effective parameters from the two-port scattering parameters is developed and applied to the proposed left-handed structures.

In this paper the problem of designing simple low-cost planar microwave bandpass filters with strongly asymmetric characteristics, filters that can efficiently attenuate an adjacent channel, is investigated. The usual quadruplet structure of a fourth-order filter offers two transmission zeros, located one on each side of the passband. For one of th...

In this paper a bandpass planar filter, with cross-couplings and with a pair of attenuation poles, is investigated. The equi-ripple in-band response and the location of the poles on the frequency axis can be precisely controlled by using a new technique which combines accurate electromagnetic field simulations and fast linear circuit optimization,...

In this paper a novel configuration of microwave planar filters, with multiple cross-couplings and with a number of attenuation poles equal to the order of the filter, is investigated. The location of the poles on the frequency axis can be controlled, allowing the design of band-pass filters with improved selectivity with respect to the adjacent ch...

Microstrip structures with left-handed properties are investigated in time and frequency domain. A method of extracting material effective parameters from the two-port scattering parameters is developed and applied to the proposed 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 t...

In this paper a novel configuration of microwave planar filters, with multiple cross-couplings and with a number of poles of attenuation NZ equal to the order N of the filter, is investigated. The position of the poles on the frequency axis can be controlled, allowing the design of band-pass filters with improved selectivity with respect to the adj...

This paper is dedicated mainly to the study of couplings between planar resonators in multilayer structures with modified (defected) ground plane. 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 s...

In this paper a new type of dual-mode compact resonator for mobile communication systems, in the 900 MHz frequency band, is investigated. This compact planar resonator, developed on a 0.635 mm substrate with a 10.8 dielectric constant, has a square shape with an edge of 20.5 mm. For this dual resonator, several methods of modes coupling were consid...

A compact microstrip dual-mode resonator with slots in the ground plane is presented in this paper. Several methods for coupling between the dual modes are investigated. One of the methods involves using slots in the ground plane in order to enhance the external coupling and to introduce the necessary perturbation to the initially symmetrical struc...

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 m...

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...

In this paper some novel types of microwave bandpass filters using defected ground structures (DGS) on iar structurers with two or on three metallic layers are investigated. In the (two-layer) microstrip technology, the use of different DGS allows designs of filters with tight couplings, without the necessity of using very narrow coupling gaps. In...

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 s...

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

In this paper a study of some planar microwave bandpass filters composed of defected ground resonators is presented. Different kinds of couplings between two defected ground resonators are investigated: electric coupling, magnetic coupling and two different mixed couplings. The values of the coupling coefficients are extracted from the simulation r...

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 cou...

In this paper some novel types of microwave bandpass filters using defected ground structures are investigated. In the microstrip technology the use of defected ground structures (DGS) allows designs of filters with tight couplings, without the necessity of using very narrow coupling gaps. In multilayer filters DGS can be used as coupling elements...

Very compact planar resonators were developed for the 1950 MHz frequency band. Resonators are of the stepped-impedance (SIR) type and they are folded, in order to occupy a very small surface area. On a 0.635 mm height commercial substrate with a 10.8 dielectric constant, a resonator can be fitted into a square with an edge size of 5.8 mm. Small-siz...

A new type of dual mode filter is proposed for mobile communications systems in 900 MHz frequency bandwidth such as GSM or GPRS. The planar filters were developed on a 0.635 mm substrate with a 10.8 dielectric constant. Several methods of modes coupling were investigated. Each dual mode resonator has a square-shape with the edge 20.5 mm and contrib...

Dual-mode, meander loop filters can provide a valid solution for narrow-band, compact and cost-effective devices for mobile communications. The finite-difference time-domain (FDTD) method was employed in order to obtain an accurate filter design. For the non-reflective boundary conditions, the Bérenger perfectly-matched layer (PML) was extended to...

Investigations on compact planar devices are presented in this paper. The proposed patch dual mode filter occupies about 16% of the surface area of a conventional square patch. The six-pole filter with compact cross-coupled resonators provides an improved rejection band.

Articolul prezintă o metodă analitică de sinteză pentru filtrele trece-bandă (FTB) cuasi-eliptice cu poli de atenuare impuşi funcţiei de transfer. În general, matricea filtrelor obţinută prin această procedură presupune existenţa unor cuplaje directe între toate rezonatoarele filtrului. Prin transformări de similitudine pot fi însă obţinute alte ma...