Loss Characteristics of TeraHertz Surface Waves on Laser Micromachined Textured Metals

For the application of geometrically-induced THz surface wave technology for communication and sensing, a critical analysis of the propagation characteristics (i.e. dispersion and attenuation) for different textured surfaces should be studied and benchmarked. For the broadband characterisation of archetypal textured surfaces (e.g. corrugated plane, two-dimensional array of blind holes and bed of nails) supporting THz transverse magnetic (i.e., p-polarized) surface waves, we employ time-domain spectroscopy and edge-diffraction coupling methods. Measurements of laser micromachined prototypes demonstrate strong frequency-dependent dispersion and the large impact that surface roughness of the order of few μm has on the path loss, increasing it by a factor ranging from 1.6 to 4.3 compared to smooth textured surfaces. Together with numerical modelling, we disentangle all loss mechanisms (namely, ohmic, scattering, propagation divergence and phase mismatch) and highlight the challenge of loss estimation due to surface roughness in highly confined THz surface waves

Weber and church governance: religious practice and economic activity

The debate about the relationship between religion and economic activity in the wake of Weber has been cast largely in terms of belief and values. This article suggests an alternative focus on practice. It argues that taken for granted practices of church governance formed to-hand resources for the organization of economic activity. The argument is developed through an examination of the historical development of church governance practices in the Presbyterian Church of Scotland, with particular emphasis on the way in which theological belief gave rise to practices of accountability and record keeping. In turn such practices contributed to a ‘culture of organization’ which had implications for economic activity. A focus on governance practices can help to illuminate enduring patterns of difference in the organization of economic activity

High efficiency excitation of dielectric rods using a magnetic ring current

We describe a theoretical analysis of the excitation of the fundamental surface wave mode on an infinite dielectric rod by a magnetic ring current that is interior to the rod. Earlier work has provided results for an external ring source. Results obtained by us show that for an interior source excitation efficiencies close to 100% are possible for high permittivity dielectrics and launching efficiencies greater than 90% can be achieved over bandwidths greater than 20%. This is a higher efficiency than is possible with an exterior source. Simulation results verifying the theoretical analysis are presented for the practical case of a coaxial waveguide exciting the dielectric rod.4 page(s

A Focal-plane array of dielectric rod antennas for THz imaging

We investigate the radiation performance of dielectric rod antennas in a focal plane array. Mutual coupling between the rods is analysed as a function of spacing for E- and H-plane coupling. We show that the coupling is significant in densely packed arrays for rods with spacings less than 0.5λ especially for rods coupling in the E-plane.3 page(s

Antennas for future very-high throughput wireless LANs

We describe a possible very-high throughput system for future indoor wireless local area networks (WLAN) with data rates up to 40 Gbps. We show that to implement such networks, using components available in the foreseeable future, moderate gain multiple beam antennas will be required. Several antennas that can potentially meet the gain requirements and multiple beam functionality are proposed.4 page(s