The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
A radiation field of a radially oriented dipole located on a sphere was studied using an electric Green's function for the space outside of an impedance sphere. The directivity of the spherical antenna in wave zone was determined depending upon variations of the sphere diffraction radius and reactive impedance magnitudes.
Our previous work in studying the prospect of detecting termites using millimeter waves and in observing thermal and behavioral effects upon termites caused by irradiation by millimeter waves has caused us to investigate the study of acupuncture needle-like guiding structures which can concentrate and efficiently deliver millimeter wave energy into various dielectrics such as biological tissue or...
This paper presents a method of enhancing the aperture size and the effective number of elements of a millimeter wave radar array to make it competitive and complementary as an imaging system for collision avoidance and imaging in adverse environments. We increase aperture size by using a Vernier geometry, with a MIMO overlay to provide adaptive beamforming and multi-target tracking. We reduce the...
With a purpose of microwave equipment frequency range enlargement, and in order to improve quality factor of frequency-selective devices, thin dielectric resonators (DR) are investigated. The principles of microwave filters and phase shifters designs, based on thin dielectric resonators, are presented. Some new constructions of such devices are elaborated. Results of theoretical and experimental studies...
This paper presents the human EM exposure simulation study considering the presence of a hand, holding the handset. The inhomogeneous child model was used to simulate thermal response of head tissues exposed to RF energy at 900 MHz, 1900 MHz and 3700 MHz frequencies. The goal of proposed research is to study how the head and hand (fingers) positions (being in a near field of phone's antenna) can influence...
The paper describes an exploratory model (prototype) of the hardware-software unit for adaptive digital time processing of signals embedded in masking clutters. The prototype is built using the digital-signal-processor-based adaptive lattice filter. Results of pre-testing are given.
The fundamental characteristics of tunable microstrip disk patch antenna with operated shorting-vias were studied. Theoretical simulations and experiments showed the significant advantages of such antenna. This antenna provides a good matching in relatively wide band and it allows choosing the type of pattern characteristic.
The paper shows the results of simulation and analysis of the ATI SAR signatures of the stationary and moving targets for linear and non-linear airborne tracks. Estimated azimuthal displacement of the moving target is found for some simulated and experimental RAW data. It is proposed to use a backprojection algorithm with the estimated squint angle as the digital filter for the filtering of a stationary...
This paper is devoted to experimental study of the influence of surface defects such as localized defects specific for polycrystalline materials, subjected to ion sputtering, on optical ellipsometry data. The study was performed using ferrite substrates with ferrite parallelepipeds of different size located in the center of the sample. A quasioptical multiangle terahertz ellipsometer that operates...
We propose to use composite permanent magnet and iron insert focusing system for modern compact submm-waveband vacuum electron devices of the clinotron type that has the potential of improving by at least a quarter on the mass of the current in-house design while preserving the required values of guide magnetic field, simplifying the system assembly, and reducing the overall system dimensions.
Evaluation of opportunities to reduce radar visibility of objects which surface is formed by combination of flat conductive plates by applying a cover, which electromagnetic wave absorbing effect by its pass is determined by previously selected edge surface weighting grid function. Resulted backward scatter diagram of rectangular plates without cover, with even coverage and homogeneous coating of...
The review of magnetodynamic resonances in ferrite resonators and their mm-wave band applications was given. Ferrite resonator eigenexcitations classification has been presented. The analytical theory for modes resonant frequencies calculations is stated and a number of prototype electronically tunable mm-wave devices, utilizing the “above” and “below FMR” magnetodynamic resonances, including isolator,...
Diffraction by two semi-infinite gratings placed in the same plane is considered. The method of singular integral equations is used. The current on the strips is represented as the current on the semi-infinite periodic gratings and correction current. The convergence of the method is discussed and far-field patterns are represented.
We receive the first order analytical expression for the scalar potential transversal distribution of finite width uniform density axisymmetric relativistic charged-particle beam propagating in the unbounded in the longitudinal direction coaxial drift tube in the strong guide magnetic field, which exhibits nonlinear dependence on the beam injection current. Ranges of the injection current values that...
The work is devoted to the development of new radiophysical methods for diagnostics of the lower ionosphere by analyzing pulse signals of natural origin in the ELF — VLF frequency range propagating in the Earth — ionosphere waveguide — tweek-atmospherics (tweeks). The effective height of the first waveguide mode has been shown to be usually higher than the effective height of the second waveguide...
The 3D vector problem of diffraction of the field of the system of synphasely excited crossed half-wave wire dipoles of similar geometrical sizes, but with different surface impedances, and located parallel to the perfectly conducting rectangular screen, has been solved. On the base of the uniform geometric diffraction theory method with using the asymptotical expression for a current of an impedance...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.