Printed antenna with circular polarization and a Tunable elevation angle

Circularly polarized antenna with a possibility of tuning the elevation angle i.e. obtaining maximum radiation in either broadside or directions declined from the zenith is presented in the paper. The antenna consists of a pair of printed crossed dipoles, feed line and gear mechanism for adjusting the height of the antenna in regard to vehicle roof, thus enabling maximums in radiation patterns at lower elevation angles. This feature is particularly interesting in communications between mobile objects and satellites. All simulations and optimizations have been carried out using program package WIPL-D and analysis of obtained results proves the validity of presented concept. Simulated gain is between 4.3 dBi and 7.3 dBi, depending on the antenna position; axial ratio (AR) is less than 3 dB in the operational range of frequencies (2%); reflection coefficient S11 is less than -19 dB. Antenna is designed for INMARSAT frequency range

Antena solution for future communication devices in mm-wave range

Different type of printed antennas for millimeter ranges like: high gain (narrow beam) with linear and circular polarization, sector antennas with azimuth angle of 600, 900 and 1800, omnidirectional antennas are proposed. All type suitable for integration with active microwave and millimeter wave like amplifiers, down and up convectors. Also, proposed sector and omnidirectional antennas are practically applicable for lower microwave range of 5 GHz that is included in new generation of communication systems for 60 GHz range

Cylindrical-parabolic reflector with printed antenna structures

The paper presents concept of design and realization of the new class of printed antenna structures which consist of a linear axial array of dipoles, subreflector, feed network and a bal-un, all printed on a common dielectric substrate. The array is positioned on the axis focus of the cylindrical-parabolic reflector. Use of the reflector enables reducing back side radiation and shaping beamwidth in H-plane thus obtaining higher gain while the printed subreflector gives the possibility of achieving additional gain. Besides, by using dipoles with pentagonal shape that operate on the second resonance, enhanced bandwidth of the array has been accomplished. Four variants of such arrays have been realized: two of them with 8 radiating elements for the frequency range around 26 GHz - one with uniform and the other with tapered feed distribution, featuring gains of 27.5 dBi and 25.7 dBi, respectively. The latter has the side lobe suppression of 28 dB in E-plane. Two other arrays that are intended for ranges around 23 GHz and 60 GHz have 16 radiating elements, uniform feed distribution and measured gains of 33 dBi and 34 dBi, respectively. Bandwidths of all realized model for S11 less than -10 dB is around 30 %. In all cases agreement between simulated and measured results is very good

On the torque transmission by a Cardan-Hooke joint

Proučavana je kinemtika i dinamika Kardan-Hukovog zgloba. Kinematička analiza se bazira na teoriji složenog kretanja krutog tela. Dinamička analiza Kardan-Hukovog zgloba je izvršena na bazi Lagranževih jednačina druge vrste. Kardan-Hukov zglob je analiziran u uslovima promenljive ugaone brzine pogonskog (ulaznog) vratila zgloba. Razmatrane su dve varijante zgloba: (1) ravan pogonske viljuške se poklapa sa ravni vratila; (2) ravan pogonske viljuške je normalna na ravan vratila. Izveden je izraz kojim se opisuje prenos obrtnog momenta Kardan-Hukovim zglobom. Izvedeni izraz sadrži članove koji potiču od inercije ulaznog i izlaznog vratila kao i od inercije krsta Kardan-Hukovog zgloba. Teorijska razmatranja su propraćena numeričkim primerom.Kinematics and dynamics of a Cardan-Hooke joint are investigated. Kinematic analysis is based on the kinematic chain rule for angular velocity vectors. Dynamics of the Cardan-Hooke joint is analyzed by means of the Lagrange equations of the second kind. The Cardan-Hooke joint is analysed under varying operating conditions, that is, it is assumed that the input shaft has variable angular velocity. Two cases are considered: (1) the driving yoke plane coincides with the plane of the shafts; (2) the driving yoke plane is normal to the plane of the shafts. An expression for torque transmission in a Cardan-Hooke joint in varying operating conditions was developed. The expression contains terms representing inertia of the shafts and the cross of the Cardan-Hooke joint. Theoretical considerations are accompanied by a numerical example

Printed antenna with circular polarization and a Tunable elevation angle

Circularly polarized antenna with a possibility of tuning the elevation angle i.e. obtaining maximum radiation in either broadside or directions declined from the zenith is presented in the paper. The antenna consists of a pair of printed crossed dipoles, feed line and gear mechanism for adjusting the height of the antenna in regard to vehicle roof, thus enabling maximums in radiation patterns at lower elevation angles. This feature is particularly interesting in communications between mobile objects and satellites. All simulations and optimizations have been carried out using program package WIPL-D and analysis of obtained results proves the validity of presented concept. Simulated gain is between 4.3 dBi and 7.3 dBi, depending on the antenna position; axial ratio (AR) is less than 3 dB in the operational range of frequencies (2%); reflection coefficient S11 is less than -19 dB. Antenna is designed for INMARSAT frequency range

Cylindrical-parabolic reflector with printed antenna structures

The paper presents concept of design and realization of the new class of printed antenna structures which consist of a linear axial array of dipoles, subreflector, feed network and a bal-un, all printed on a common dielectric substrate. The array is positioned on the axis focus of the cylindrical-parabolic reflector. Use of the reflector enables reducing back side radiation and shaping beamwidth in H-plane thus obtaining higher gain while the printed subreflector gives the possibility of achieving additional gain. Besides, by using dipoles with pentagonal shape that operate on the second resonance, enhanced bandwidth of the array has been accomplished. Four variants of such arrays have been realized: two of them with 8 radiating elements for the frequency range around 26 GHz - one with uniform and the other with tapered feed distribution, featuring gains of 27.5 dBi and 25.7 dBi, respectively. The latter has the side lobe suppression of 28 dB in E-plane. Two other arrays that are intended for ranges around 23 GHz and 60 GHz have 16 radiating elements, uniform feed distribution and measured gains of 33 dBi and 34 dBi, respectively. Bandwidths of all realized model for S11 less than -10 dB is around 30 %. In all cases agreement between simulated and measured results is very good

Cylindrical-parabolic reflector with printed antenna structures

The paper presents concept of design and realization of the new class of printed antenna structures which consist of a linear axial array of dipoles, subreflector, feed network and a bal-un, all printed on a common dielectric substrate. The array is positioned on the axis focus of the cylindrical-parabolic reflector. Use of the reflector enables reducing back side radiation and shaping beamwidth in H-plane thus obtaining higher gain while the printed subreflector gives the possibility of achieving additional gain. Besides, by using dipoles with pentagonal shape that operate on the second resonance, enhanced bandwidth of the array has been accomplished. Four variants of such arrays have been realized: two of them with 8 radiating elements for the frequency range around 26 GHz - one with uniform and the other with tapered feed distribution, featuring gains of 27.5 dBi and 25.7 dBi, respectively. The latter has the side lobe suppression of 28 dB in E-plane. Two other arrays that are intended for ranges around 23 GHz and 60 GHz have 16 radiating elements, uniform feed distribution and measured gains of 33 dBi and 34 dBi, respectively. Bandwidths of all realized model for S11 less than -10 dB is around 30 %. In all cases agreement between simulated and measured results is very good

Nonlinear vibration of a nonlocal functionally graded beam on fractional visco-Pasternak foundation

This paper investigates the nonlinear dynamic behavior of a nonlocal functionally graded Euler-Bernoulli beam resting on a fractional visco-Pasternak foundation and subjected to harmonic loads. The proposed model captures both, nonlocal parameter considering the elastic stress gradient field and a material length scale parameter considering the strain gradient stress field. Additionally, the von Karman strain-displacement relation is used to describe the nonlinear geometrical beam behavior. The power-law model is utilized to represent the material variations across the thickness direction of the functionally graded beam. The following steps are conducted in this research study. At first, the governing equation of motion is derived using Hamilton's principle and then reduced to the nonlinear fractional-order differential equation through the single-mode Galerkin approximation. The methodology to determine steady-state amplitude-frequency responses via incremental harmonic balance method and continuation technique is presented. The obtained periodic solutions are verified against the perturbation multiple scales method for the weakly nonlinear case and numerical integration Newmark method in the case of strong nonlinearity. It has been shown that the application of the incremental harmonic balance method in the analysis of nonlocal strain gradient theory-based structures can lead to more reliable studies for strongly nonlinear systems. In the parametric study, it is shown that, on the one hand, parameters of the visco-Pasternak foundation and power-law index remarkable affect the amplitudes responses. On the contrary, the nonlocal and the length-scale parameters are having a small influence on the amplitude-frequency response. Finally, the effects of the fractional derivative order on the system's damping are displayed at time response diagrams and subsequently discussed.This is the peer reviewed version of the article: Nešić, N.; Cajić, M.; Karličić, D.; Obradović, A.; Simonović, J. Nonlinear Vibration of a Nonlocal Functionally Graded Beam on Fractional Visco-Pasternak Foundation. Nonlinear Dynamics 2022, 107 (3), 2003–2026. [https://doi.org/10.1007/s11071-021-07081-z

Antena solution for future communication devices in mm-wave range

Different type of printed antennas for millimeter ranges like: high gain (narrow beam) with linear and circular polarization, sector antennas with azimuth angle of 600, 900 and 1800, omnidirectional antennas are proposed. All type suitable for integration with active microwave and millimeter wave like amplifiers, down and up convectors. Also, proposed sector and omnidirectional antennas are practically applicable for lower microwave range of 5 GHz that is included in new generation of communication systems for 60 GHz range

AN INVESTIGATION OF SIDE LOBE SUPPRESSION IN INTEGRATED PRINTED ANTENNA STRUCTURES WITH 3D REFLECTORS

The paper discusses the problem of side lobe suppression in the radiation pattern of printed antenna arrays with different 3D reflector surfaces. The antenna array of eight symmetrical pentagonal dipoles with corner reflectors of various angles is examined. All investigated antenna arrays are fed by the same feeding network of impedance transformers enabling necessary amplitude distribution. Considering the different reflector surfaces, the influence of parasitic radiation from feeding network on side lobe suppression is studied to prevent the reception of unwanted noise and to increase a gai