Multifilar Helix Research Articles

Lightlike shell solitons of extremal space-time film

New exact solution class of Born—Infeld type nonlinear scalar field model is obtained. The variational principle of this model has a specific form which is characteristic for extremal four-dimensional hypersurface or hyper-film in five-dimensional space-time. Obtained solutions are singular solitons propagating with speed of light and having energy, momentum, and angular momentum which can be calculated for explicit conditions. Such solitons will be called the lightlike ones. The soliton singularity has a form of moving two-dimensional surface or shell. The lightlike soliton can have a set of tubelike singular shells with the appropriate cavities. A twisted lightlike soliton is considered. It is notable that its energy is proportional to its angular momentum in high-frequency approximation. A case with one tubelike cavity is considered. In this case the soliton shell is diffeomorphic to a cylindrical surface with threads by multifilar helix. The shell transverse size of the appropriate finite energy soliton can be converging to zero at infinity. The ideal gas of such lightlike solitons with minimal twist parameter is considered in a finite volume. Explicit conditions provide that the angular momentum of each soliton in the volume equals Planck constant. The equilibrium energy spectral density for the solitons is obtained. It has the form of Planck distribution in some approximation. A beam of the twisted lightlike solitons is considered. The representation of arbitrary polarization for the beam with the twisted lightlike solitons is discussed. It is shown that the effect of mechanical angular momentum transfer to absorbent by the circularly polarized beam can be provided. This effect is well known for photon beam. Thus the soliton solution which have determinate likeness with photon is obtained in particular.

A multifilar helical antenna on a sphere and the limits of broadbandness

An antenna in form of a dense multifilar helix of thin metal ribbons on a spherical surface with lower order transverse-electric and transverse-magnetic modes is considered. Averaged boundary conditions taking into account the capacitances between the edges of ribbons are formulated. Formulas for calculating the angle of inclination of ribbons and the required inter-edge capacitance from a given resonance frequency and approximate ellipticity coefficient are obtained. The inclination of the axes of the polarization ellipse and an improved ellipticity coefficient are determined. The fractional bandwidth of the antenna is expressed via the improved limits of the fractional bandwidth of linearly polarized antennas. The limits of the fractional bandwidth of circularly polarized antennas are found. It is established that the maximum fractional bandwidth is reached if the ellipticity coefficient is slightly different from unity.

Fabrication of multilayer dielectrically loaded antennas using aqueous electrophorectic deposition of polyether ether ketone

The paper presents proof of concept of a viable multilayer technology to enhance the performance of multifilar helix, receive-only satellite antennas. Approximately, 30-μm layers of polyether ether ketone (PEEK) were deposited onto the Cu filars of a single layer dielectrically loaded multifilar helix antenna using aqueous electrophoretic deposition (EPD). The PEEK coating was densified at ~400–420 °C in flowing N2 to prevent oxidation of the Cu filars. A second Cu metallisation was deposited onto the surface of the PEEK and the resulting antenna characterised. The multilayer antenna revealed a dual band response with peak radiation efficiencies >25 % and ~50 % increase in bandwidth. Multilayered surface architectures fabricated from PEEK using EPD, therefore, show great potential for the development of a broad range of high-performance multiband dielectrically loaded antennas whose peak frequencies may, in principle, be tuned by modifying the thickness of the PEEK layer.

Gas-puff liner implosion in the configuration with helical current return rods

Results of experiments with double-shell gas-puff liners carried out on a high-current MIG generator (2 MA, 80 ns) are presented. To stabilize the process of liner implosion and increase the efficiency of energy transfer from the generator to the liner plasma, a current return in the form of a multifilar helix was used. The effect of the configuration of the current return on the parameters of the generated pulses of argon and neon K-shell radiation (with photon energies of 3–5 and 0.9–1.5 keV, respectively) and the neutron yield from a deuterium liner were studied.

Analysis of the radiation from a class of finite-length structures using the Wiener-Hopf formulation: application to a multi-filar helix

An approximate procedure is proposed, to characterize the radiation from a class of open finite-length Wiener-Hopf (WH) structures, that is useful when a complete account of the direct feed radiation and of the open end effects is required, but the corresponding (exact) modified WH equation does not allow a closed-form evaluation. This procedure considers the finite-length problem as an appropriate superposition of two related semi-infinite WH problems, each one leading to an exact solution. It takes into consideration the discrete modes and the continuous spectrum waves launched at the feed end, and also at the structure open-end. The usefulness of this procedure is tested in the case of a finite-length multi-filar helix, fed by the open-end of a circular waveguide of the same diameter. Theoretical radiation patterns show a satisfactory agreement with experimental results.

Radiation from a sheath helix excited by a circular waveguide: a Wiener-Hopf analysis

The excitation of a semi-infinite sheath helix by the TE11 mode of a circular metallic waveguide with the same diameter is studied using the Wiener-Hopf technique. Expressions are presented for the TE11 reflection coefficient at the waveguide end and for the relative power in the sheath helix discrete modes. Numerical results corresponding to the current density at the sheath helix surface and to the far-field radiation patterns are presented. These are compared to previous results obtained from the modal analysis of an infinite sheath helix that is excited by a current sheet. Experimental patterns corresponding to a finite length multifilar helix show a satisfactory agreement with the theoretical patterns when the scanning mode is dominant.

Propagation of Waves in Helical Wave Guides

The field configuration near the conductors of a helical wave guide is obtained from the solution of the spatial-wave equation for a developed helix. This solution is first obtained for the case of tape conductors and then adapted to elliptical (including circular) conductors by conformal transformation. By comparing this solution with that of a developed-sheath helix, the impedance, attenuation, and other parameters of a wire helix are deduced approximately. These are expressed as the product of the corresponding sheath-helix parameter times a proper correction factor depending on frequency, conductor size, and shape. The analysis is extended to the multifilar helix. The results of this analysis provide a means of calculating the attenuation of wire helices and of choosing optimum wire configurations in the design of helical wave guides.