Miloš D. Davidović

B-Spline Entire-Domain Higher Order Finite Elements for 3-D Electromagnetic Modeling

A novel entire-domain finite element technique based on curvilinear hexahedral geometrical modeling using B-splines in conjunction with higher order hierarchical polynomial curl-conforming vector basis functions for field expansions is proposed for electromagnetic analysis of microwave devices. The effectiveness of the technique is evaluated in analysis of microwave cavities and it is compared with alternative reference solutions and with HFSS. Examples demonstrate large single-element (entire-domain) models with p-refined field distributions and better accuracy in curvature modeling than with the Lagrange interpolation. Extraordinary flexibility of the B-spline hexahedral elements, combined with higher order field expansions, allows accurate modeling of complex structures with sharp edges using a single finite element.

Triple notch UWB antenna controlled by three types of resonators

This paper discusses a microstrip fed UWB monopole antenna with a triple notch characteristic. The three notches are designed to occur at the WiMAX frequency range, the WLAN and at a third frequency in the higher end of the UWB range. Each of the three notches is controlled by a different type of resonators and each and every notch can be adjusted without affecting the position or the shape of the remaining two, thus allowing for an antenna design with adjustable, agile S11 response.

UWB antenna with a WiMAX frequency notch caused by a novel stepped U shaped slot that suppresses the parasitic notches

UWB antennas with embedded stubs or slots can create a notch in the frequency range. The frequency notch and therefore the reduced radiation intensity is confined to frequencies used by other applications in order to achieve reduced interference. However the use of such resonant elements causes additional notches at the fre quencies which equal to even or odd multiples of the design frequency. While the lowest odd multiple of the WLAN frequency (5.2–5.8 GHz) lays outside the UWB range (3.1–10.6 GHz) this is not the case for the WiMAX frequency. In this paper, a stepped slot is introduced in a UWB elliptical monopole that suppresses the unwanted higher order notch, and with the use of a linearly tapered feed line return loss better than −10dB is achieved throughout the UWB range with the exception of the WiMAX range.

Derivation of the Husimi symbols without antinormal ordering, scale transformation and uncertainty relations

We propose a new method for the derivation of Husimi symbols, for operators that are given in the form of products of an arbitrary number of coordinates, and momentum operators, in an arbitrary order. For such an operator, in the standard approach, one expresses coordinate and momentum operators as a linear combination of the creation and annihilation operators, and then uses the antinormal ordering to obtain the final form of the symbol. In our method, one obtains the Husimi symbol in a much more straightforward fashion, departing directly from operator explicit form without transforming it through creation and annihilation operators. With this method the mean values of some operators are found. It is shown how the Heisenberg and the Schrodinger–Robertson uncertainty relations, for position and momentum, are transformed under scale transformation . The physical sense of some states which can be constructed with this transformation is also discussed.

Scale transformations in phase space and stretched states of a harmonic oscillator

We consider scale transformations (q, p) → (λq, λp) in phase space. They induce transformations of the Husimi functions H(q, p) defined in this space. We consider the Husimi functions for states that are arbitrary superpositions of n-particle states of a harmonic oscillator. We develop a method that allows finding so-called stretched states to which these superpositions transform under such a scale transformation. We study the properties of the stretched states and calculate their density matrices in explicit form. We establish that the density matrix structure can be described using negative binomial distributions. We find expressions for the energy and entropy of stretched states and calculate the means of the number-ofstates operator. We give the form of the Heisenberg and Robertson–Schrödinger uncertainty relations for stretched states.