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The novel microwave wideband quasi-elliptic bandpass filter, in which the initially uncoupled strip transmission lines are used is considered in the present study. The proposed filter is based on the reentrant structure in which the metallic body with a floating potential is asymmetrical. Generally speaking, the internal and external dielectric fillings must be of unequal relative permittivity. As a result, the additional symmetrical transmission zeros are reached at the lower and upper stop bands of the pass band leading to the quasi-elliptic response function that improves the bandpass filter selectivity. The general TEM circuit model for the proposed filter, in terms of the multi-port series connection, is presented and then used to predict the initial electrical and geometrical quantities. A printed circuit prototype has been manufactured using a common printed circuit board implementation. The measured results are in an acceptable agreement with the simulation-derived ones, and that improves the degree of freedom in the frequency selective unit design. [ABSTRACT FROM AUTHOR]

The modified dual-frequency printed quasi-Yagi antenna has been designed. After multi-step optimization, theS11parameter of the antenna is as low as −27 and −14 dB atf01= 1.7 andf02= 2.45 GHz, respectively. The antenna directivity is 7.1 and 5 dB atf01= 1.7 andf02= 2.45 GHz, respectively. The total length of the planar dual-frequency quasi-Yagi antenna is 158 mm. The universal algorithm of the antenna design has been proposed, and the algorithm can be applied to the creation of three-frequency printed quasi-Yagi antennas. [ABSTRACT FROM AUTHOR]

A set of ∼100 noncentrosymmetric germanates has been observed in reference to nonlinear optical properties. It has been found that, on the plane of the oxide bond lengths, the noncentrosymmetric germanate crystals are positioned into three intersected ellipses of «acentricity». The nonlinear optical properties of α-GeO2, space groupP3121, have been evaluated by powder method. The non-monotonic dependence of nonlinear optical susceptibility χ(2)on the shortest chemical bond lengthL(Ge-O) has been obtained for germanates. The suggested crystal chemistry analysis is useful for searching new noncentrosymmetric germanate crystals. [ABSTRACT FROM PUBLISHER]

A set of ∼100 noncentrosymmetric (NCS) tungstates has been observed in reference to nonlinear optical properties. It has been found that on the plane of the shortest oxide bond lengths the NCS tungstate crystals are positioned into three intersected ellipses of «acentricity». The non-monotonic dependence of nonlinear optical susceptibility χ(2)on the shortest chemical bond lengthL(W-O) obtained for tungstates shows two pronounced maximums atL(W-O) ∼173 and 187 pm. The suggested crystal chemistry analysis is useful for searching new noncentrosymmetric tungstate crystals. [ABSTRACT FROM PUBLISHER]

On the plane of oxide bond lengths the rosette with three ellipses of acentricity have been displayed for noncentrosymmetric (NCS) niobate crystals distributed over 2 groups of paraelastic and ferroelastic crystals. Two small ellipses have perpendicular main axes and main axis of one large ellipse lie on bisector of other ellipses axis. Six characteristic regions and 12 sub-regions are found inside the ellipse rosette showing different crystal structure and χ(2) levels: 1) total crossing part of three ellipses; (2) four parts of two small ellipses outside crossing part, 3) one part of large ellipse outside other ellipses. The dependence of nonlinear optical susceptibility χ(2) on the shortest niobate bond length Nb-O has been revealed. [ABSTRACT FROM AUTHOR]

It is shown that acentric silicate crystals are positioned into three intersected ellipses of «acentricity» on the plane of the oxide bond lengths plane. The dependence of nonlinear optical property of silicates on the shortest chemical bond length L(Si-O) is non-monotonous. The suggested crystal chemistry analysis is useful for searching new acentric silicate crystals. [ABSTRACT FROM AUTHOR]

The relation “composition-structure-property” for a set of >100 simple and binary noncentrosymmetric aluminate crystals is considered. These crystals are distributed on the plane of the shortest metal-oxygen chemical bond lengths over an area, covered by a rosette of three ellipses. The distribution of ferroelastic and paraelastic aluminates having measurable level of nonlinear optical susceptibility is different. It is shown that small part of trigonal and monoclinic aluminum-bearing borates and phosphates possess noticeable χ(2) level and only three polar crystals related to aluminum iodate family are characterized by pronounced χ(2) level. [ABSTRACT FROM AUTHOR]

A diagram showing the relationships between point symmetry and a set of physical properties has been created for centrosymmetric (CS) and noncentrosymmetric (NCS) crystals. The "acentric" (ferro-, pyro- and piezoelectrical, electrooptical, nonlinear optical, ferromagnetic, enantiomorphic, girotropic), ferroelastic, ferromagnetic and refractive characteristics are accounted. The distribution of crystals over symmetry classes are plotted for CS and NCS elements and their oxides. This diagram is helpful for classification and searching new materials. [ABSTRACT FROM AUTHOR]

On the plane of sulfide bond lengths the ellipses of acentricity have been displayed for noncentrosymmetric (NCS) sulfide crystals distributed over 4 groups of polar and nonpolar paraferroelastics - ferroelastics. The dependence of nonlinear optical susceptibility χ(2) on the shortest sulfide bond length has been determined. Three characteristic regions are found inside the ellipses showing three different χ(2) levels: 1) crossing part of ellipses; 2) two symmetrical parts of ellipses outside crossing part. On this basis a method has been proposed for designing new acentric crystals promising a high χ(2) value. [ABSTRACT FROM AUTHOR]

On the plane of oxide bond lengths the ellipses of acentricity have been displayed for noncentrosymmetric (NCS) oxide crystals distributed over 4 groups of polar and nonpolar paraelastics - ferroelastics. The dependence of nonlinear optical susceptibility χ (2) on the shortest oxide bond length has been revealed. Three characteristic regions are found inside the ellipses showing three different χ(2) levels: (1) crossing part of ellipses; (2) two symmetrical parts of ellipses outside crossing part. On this basis a method has been proposed for design of new acentric crystals promising a high χ (2). [ABSTRACT FROM AUTHOR]