Effect of helix turn angle on the performance of a half wavelength quadrifilar antenna

The impedance and radiation pattern parameters of a lambda/2 quadrifilar helix antenna (QHA) with turn angles in the range 0 degrees to 235 degrees are analyzed. It is shown that by selecting the helix turn angle to satisfy the minimum bandwidth and beamwidth requirements, an improved electrical performance and a reduction in the physical size of the antenna is obtained. This is demonstrated by comparing the performance of a conventional half turn QHA with structures having a smaller pitch length. The computed results are validated by experimental data at L-band.

Correction of dielectric losses in practical leaky-wave antenna designs

In this paper, the leaky-mode theory is applied to take into account for the dielectric losses in millimetre waveband inhomogeneous leaky-wave antennas. A practical dielectric-filled cosine-tapered periodic leaky-wave antenna working in the 45GHz band is studied, showing how the desired sidelobes level and directivity are spoilt due to the effect of the losses. An iterative procedure is used to correct the negative effects of the losses in the radiation patterns of the leaky-wave structure. It is also shown the practical limits of the proposed correction approach. The leaky-mode theory is applied for the first time to compensate the losses in a practical leaky-wave antenna in hybrid waveguide printed circuit technology. This leaky-mode theory is validated with full-wave three-dimensional finite element method simulations of the designed antenna.

Conference Reflections. Some Practice and Practical Implications of Banning the Physical Punishment of Children through Legislation.

This brief paper represents the reflections of a participant at the recent conference ‘The Physical Punishment of Children’ organised jointly by Child Care in Practice and The Office of Law Reform. The participant’s reflections are related to his roles both as a Family Therapist and as a Guardian Ad Litem. The writer largely accepts the academic and moral arguments in respect of making the physical punishment of children a legal offence, so eloquently put by the main speakers. He wishes, however, to draw out some of the practical and practice implications which need to be considered alongside the implementation of such legislative change.