Array Of Dipole Elements Research Articles

Using a Tunable Transmit-Array Antenna to Improve the Propagation Environment

This letter proposes a method that uses a tunable transmit-array antenna to improve the multiple-input–multiple-output (MIMO) channel capacity in environments that suffer from the keyhole effect. A tunable transmit array of dipole elements is placed at the aperture between two rooms to increase the channel capacity. Varactor diodes are used as load impedances and attached to all dipole elements of the transmit array. This configuration makes the transmit array tunable. The channel capacity can be maximized by individually controlling all elements in the transmit array. The effectiveness of the transmit array in enhancing the channel capacity is confirmed by measurements. The results show that the channel capacity can be improved, and this well supports the effectiveness of the proposed method.

Analysis and development of a signal injection technique using transmission lines embedded at phased array aperture

In a performance monitoring/fault isolation and correction (PM/FIC) system of a phased array antenna, a built-in transmission line embedded in the array aperture is used for signal injection to check the signal flow. The authors present an analysis of electromagnetic coupling between a twin-lead transmission line and a dipole element. An analysis of the coupling between a transmission line and a linear array of dipole elements over a ground plane has also been developed. The calculated data compared with the measured data favorably. A development of microstrip-line signal injectors embedded in an aperture of a 2D array of monopole excited parallel-plate waveguides has also been made. Measurements of the feed and aperture distributions have been made and the measured distributions follow the designed feed distribution closely. >

A quasi-periodic design procedure for a traveling-wave array of dipoles

A simple iterative design procedure is given for a traveling-wave array of dipole elements fed in a shunt configuration by a meandering transmission line. The design procedure is based on a quasi-periodic analysis of the loaded line, which assumes a Bloch wave propagation on the structure. A design procedure is formulated for the cases of constant attenuation and tapered attenuation on the line. A ten-element array of vertical monopoles fed by a meandering stripline is used to illustrate the design technique. Results show that the design procedure based on power into the dipoles gives good agreement with one based on actual dipole currents if a certain assumption is used. It is important, however, to account for mutual coupling in the design procedure in order to obtain accurate patterns, especially for low sidelobe designs. >

Analysis of an infinite phased array of dipole elements with RAM coating on ground plane and covered with layered radome

An analysis of an infinite array of dipole elements over a radar absorbing material (RAM) coated ground plane and covered with a radome is presented. The radiation impedance of the dipole element is obtained when the array is in transmitting mode, and a scattering analysis is carried out when the array is excited by an incoming plane wave and the dipole elements are terminated in loads. The electric field Green's function in terms of Floquet mode expansion due to a periodic delta -function horizontal dipole source is derived to satisfy the layered boundary conditions. The method of moments is used to solve the current distribution on the dipole. Numerical calculation of the radiation impedance of a dipole array covered with a radome has been verified with results from waveguide simulator measurements. Numerical examples are given to show the effect of the RAM coated ground plane on the radiation impedance and the scattering characteristics. >

Submillimetre scattering antennae

The properties of parasitically coupled standing-wave antennae on thin dielectric substrates have been studied from their scattering characteristics at 891 GHz (337 mu m). Measurements of total and back-scattering cross-sections on arrays of dipole antennae are described. Arrays of dipole elements, in which each element is terminated by a length of short-circuited coplanar transmission line, are also investigated. The electrical properties of the coplanar transmission lines are found and the ability of standing-wave antennae to couple energy to them efficiently at this high frequency is verified.

Resonance phenomena on Yagi arrays

The Yagi antenna has been studied experimentally and theoretically and a class of resonance phenomena has been found to occur in a narrow frequency range immediately below the director array cutoff frequency. This resonant behaviour is characterized in the swept-frequency far-field graphs by a very narrowband reduction in gain and in the input impedance by very rapid fluctuations with frequency. The dispersion characteristics of arrays of dipole elements are used to suggest a design procedure which prevents the occurrence of such resonances.