Frequency Selective Characteristics Research Articles

Channel Estimation and Simulation of an Indoor Power-Line Network via a Recursive Time-Domain Solution

The frequency-selective characteristics of a power-line channel is a result of the tree-like structure of the power-line network and the various loads connected to its termination points. Channel modeling is important for the estimation and compensation of the degradation suffered by the signal propagating over power lines, and is also the basis for channel simulation. Based on the previously proposed time-domain models, the authors present a new method to efficiently calculate a power-line channel's frequency response. With the knowledge about the power-line network's topology and cable characteristics, this algorithm utilizes simple but effective recursive matrix operations to accurately estimate the channel response of a particular power-line network. This method can be used to estimate the frequency response of any point-to-point channel in a power-line network, and can also be exploited as a channel simulation tool which provides a remarkably realistic description of a power-line channel. The effectiveness of the proposed algorithm is demonstrated by comparing the estimated and measured responses of two example power-line networks.

Auditory Sparse Representation for Robust Speaker Recognition Based on Tensor Structure

This paper investigates the problem of speaker recognition in noisy conditions. A new approach called nonnegative tensor principal component analysis (NTPCA) with sparse constraint is proposed for speech feature extraction. We encode speech as a general higher-order tensor in order to extract discriminative features in spectrotemporal domain. Firstly, speech signals are represented by cochlear feature based on frequency selectivity characteristics at basilar membrane and inner hair cells; then, low-dimension sparse features are extracted by NTPCA for robust speaker modeling. The useful information of each subspace in the higher-order tensor can be preserved. Alternating projection algorithm is used to obtain a stable solution. Experimental results demonstrate that our method can increase the recognition accuracy specifically in noisy environments.

Scattering characteristics of a new dielectric periodic array composed of left‐handed gratings

AbstractThe scattering characteristics of a new dielectric periodic array composed of left‐handed gratings are carefully investigated by a method which combines the multimode network theory with the rigorous mode matching method. The variations of the frequency selective characteristics with the number of periodic layers are presented and comparisons of scattering properties between the left‐handed and right‐handed periodic arrays are also shown with some explanations. Guidelines for accurate design of the millimeter wave frequency selective surface are given. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 266–269, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23076

A NEW FREQUENCY SELECTIVE SURFACE COMPOSED OF LEFT-HANDED MATERIALS

The frequency selective characteristics of a new dielectric periodic structure composed of left-handed materials (LHM) are carefully studied by a method which combines the multimode network theory with the rigorous mode matching method. The variations of the frequency selective characteristics with structure parameters and dielectric loss are presented and comparisons for the frequency selective properties between RHM and LHM gratings are also shown with some explanations. Guidelines for accurate design of the LHM dielectric frequency selective surface are given.

INVESTIGATION ON EFFECTS OF LEFT-HANDED MATERIALS ON FREQUENCY SELECTIVE CHARACTERISTICS OF DIELECTRIC PERIODIC STRUCTURES

The effects of left-handed materials (LHM) on frequency selective reflection and transmission characteristics of dielectric periodic structures are carefully investigated using a method which combines the multimode network theory with the rigorous mode matching method. In addition, the effects of LHM dielectric loss on the selective properties are also given. It has been shown that the selective behavior of periodic structures can be modified by adding LHM layers above and below the periodic layer.

An ultra-small cavity resonator loaded with LHM and RHM layers

In this paper, an ultra-small cavity resonator (USCR) loaded with left-handed metamaterial (LHM) and right-handed material (RHM) layers is designed using a novel miniaturization approach. The resonant behavior is successfully observed, and the dimensions of the USCR are only 4.58 mm × 5.08 mm × 2.29 mm at the dominant resonance frequency of 10.3 GHz. Through the field distribution calculation, we confirmed that the miniaturization of the USCR arises from the left-handed property of the LHM. For a practical application, a miniaturized filter with overall length of 10.19 mm consisting of two USCRs is designed to confirm the frequency-selective characteristics. Results show that the filter has some narrow pass bands, which correspond to the resonant modes of the electromagnetic resonance in the USCR, and the insertion loss at the dominant resonance frequency of the USCR is as low as 0.65 dB. Moreover, the filtering characteristics of the filter can be controlled by changing its feeding loop positions in the USCR.

Air suspension and air damping in the context of comfort, dynamics and safety

Air springs are considered comfort increasing components. Besides the spring, elastic components effect the driving comfort. A negative impact is attributed to friction and component rigidity that is not taken into account. At Vibracoustic GmbH & Co. KG optimal driving comfort is attained by taking a close look at all elastic components and the system design. Leveling air springs provide increased driving safety. And additional optimizations are obtained by means of the frequency selective and load adaptive characteristics of an air damping system.

Frequency selective characteristics of a new dielectric periodic structure composed of left‐handed materials

AbstractThe frequency selective characteristics of a new dielectric periodic structure composed of left‐handed materials (LHM) are carefully investigated by a method, which combines the multimode network theory with the rigorous mode matching method. The variations of the frequency selective characteristics with structure parameters are presented and comparisons of propagation properties between right‐handed materials and LHM gratings are also shown with some explanations. Guidelines for accurate design of the left‐handed dielectric frequency selective surface are given. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 421–424, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22153

The effect of boundary conditions on sound loudness radiated from rectangular plates

This paper describes the effect of boundary conditions on sound loudness radiated from rectangular plates. Based on the Rayleigh integral, the Zwicker’s loudness model and the dynamic response of the plates, the sound loudness radiated from vibrating plates and the effects of simple support, clamped support and free support on sound loudness are separately studied. The effects of boundary conditions on sound intensity level, sound intensity density and critical-band level are also studied, taking the frequency selectivity of human hearing into account. The transformation from sound intensity level to sound loudness radiated from rectangular plates, due to the frequency-selectivity characteristics of human hearing, is also illustrated.

Frequency-Selective Characteristics of Two-Dimensional Random Array of Fine Silver Particles Formed on AlN and TiO2 Films

Our previous investigation showed that a random array of fine silver particles formed on sheet glass works as a frequency-selective screen that reflects near-infrared rays and transmits radio waves. In order to improve its screening efficiency, we investigated the use of AlN and TiO2 films with relative dielectric constants of 4.0 and 5.7, respectively, deposited on sheet glass. It was found that for both substrate films resonance reflection occurred at longer wavelengths and the irregular reflectance was lower than for a glass substrate. In particular, the array on the TiO2 film showed a very low value of irregular reflectance and high values of shielding effect and visible light transmittance. These results suggest that a system in which a two-dimensional random array of fine silver particles is fixed on a dielectric film deposited on sheet glass can be applied as a solar control glass, which suppresses near-infrared rays and admits radio waves into a room.

Investigation into effects of dielectric loss on frequency selective characteristics of dielectric periodic structures

The frequency selective characteristics of lossy dielectric periodic structures with arbitrary grooved profiles and any incident angle are analysed using a method which combines multimode network theory with the rigorous mode matching method. Based on this, the effects of dielectric loss on the selective behaviour are systematically studied. Some guidelines for the accurate design of the dielectric frequency selective surface are given.

On optimal ambiguity resistant precoders in ISI/multipath cancellation

Ambiguity resistant (AR) precoding has recently been proposed in intersymbol interference (ISI) and multipath cancellations, where the ISI/multipath channel may have frequency-selective fading characteristics and its knowledge is not necessarily known. With the AR precoding, no diversity is necessary at the receiver. In the precoding, the AR property for a precoder plays an important rule. In this paper, more families and properties of AR precoders are presented and characterized. In particular, all systematic AR precoders are characterized. More importantly, we introduce the concepts of precoder distance and optimal precoders, and characterize and construct all optimal systematic AR precoders, when additive channel random noise is concerned. A necessary and sufficient condition for an AR precoder to be optimal is given, which is easy to check. With the optimal precoders, numerical simulations are presented to show the improved performance over the known AR precoders in ISI cancellation applications.

Frequency Selective Properties of Two-Dimensional Dielectric Gratings: TE- and TM-Polarizations

This work analyzes the propagation characteristics of electromagnetic waves and the frequency selectivity of dielectric gratings with periodicity in two dimensions, having in mind their application as dichroic surfaces in the millimeter wave band. The moment method and the Green's functions, along with the volume equivalence theorem are used. Particular cases were analyzed to compare with results available in the specialized literature and agreement was observed. This work gives evidence that the inclusion of the periodicity along a second dimension allows an additional adjusting parameter of the frequency selective characteristics for the design requirements of dielectric gratings.

Frequency Selective Characteristics of Dielectric Periodic Structures for Millimeter Wave Application

In this paper, the frequency selective reflection characteristics of dielectric periodic structures for the oblique incidence of a plane wave are analyzed by a method which combines the multimode network theory with the rigorous mode matching method. The variations of the total reflection characteristics with the geometric dimensions of the dielectric periodic structures are systematically investigated to develop useful guidelines for the design of the dielectric frequency selective surface. Moreover, the relationship between the related wave phenomenon and the dispersion characteristics of multilayer plane dielectric structure is explained with the theory of plane dielectric waveguide.

Effect of dielectric groove profiles on reflection characteristics of millimeter wave frequency selective surface

In this paper, the frequency selective reflection characteristics of dielectric periodic structures with arbitrary groove profiles are analyzed by a method which combines the multimode network theory with the rigorous mode matching procedure. Emphasis is placed on the discussion about the effect of the different groove profiles, such as rectangle, trapezoid, increasing cosine and triangle, on the reflection characteristics of the millimeter wave (MMW) frequency selective surface (FSS). Some useful guidelines for the design of the MMW dielectric FSS are thus suggested. Moreover, the physical explanation of the related wave phenomenon is given.

Multipath impulse response modelling for indoor channel using TD-BEM

Indoor radio networks operating in the millimetre-wave frequency range may offer large information transport capacity and more sharply defined cell boundaries. The main features of the propagation in an indoor radio environment are multipath, due to reflection or diffraction from the walls and surrounding objects, and shadowing of the direct or line-of-sight propagation path by intervening obstacles. This paper presents a prediction technique for the multipath impulse response inside a confined cell/room with high resolution. The technique is based on a deterministic model developed using the Time-Domain Boundary Element Method (TD-BEM). Given the complete specifications of the structural environment (room size and shape, wall and furnishing materials), the discussed model can predict the impulse responses, the multipath spread and the frequency-selective characteristics of wireless indoor channels. Both modelled and measured results are given for a 37.2-GHz wireless system operating in two different environments, demonstrating the model's ability to predict adequate results.

MSW Signal-to-Noise Enhancers for Noise Reduction in DBS Reception

The RF performance of MSW signal- to- noise enhancers is characterized by operational power level and frequency, frequency-selectivity, and transient response in MSW saturation. The frequency selectivity and transient response characteristics are especially important for noise reduction in frequency modulated signals such as DBS reception signals. However, it is difficult to make both the characteristics good at the same time. In this paper three types of signal- to- noise enhancers with difference structures arc discussed from the viewpoint of DBS application. We show that using an MSBVW/SW hybrid mode is an effective approach to lowering the operational frequency.

Quadratic power spectrum estimation with orthogonal frequency division multiple windows

Studies a new quadratic power spectral density estimator implemented with orthogonal frequency division multiple windows. The windows are constructed from a single window shifted in frequency. The orthogonality constraint ensures that the estimator meets a minimum mean-squared error performance criterion. Solutions for the window are obtained numerically. The new estimator has good frequency selectivity characteristics, and its statistical properties are comparable to the best multiple window estimators available.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Wideband sounding of 11.6 GHz trans-horizon channel

A high speed, wideband channel probe is briefly described. The use of the probe on an experimental 158 km link across the English Channel is reported. Preliminary results depicting the time-variant and frequency-selective characteristics of the link are presented.

Finite curved frequency selective surfaces

Curved arrays of a finite number of dipoles are analysed using the vector potential equation to compute the current distribution in each dipole in the array, taking into account mutual coupling among the elements. The frequency selective characteristics of such curved arrays are compared with finite and infinite planar arrays. The effect of mutual coupling on the transmission characteristics of the arrays is also discussed.