No abstract

No abstract

Holograms-diffractive elements-are designed and fabricated for shaping millimetre-wave radio fields. Methods for the synthesis of hologram elements are discussed and several beam shapes are tested: plane waves, radio-wave vortices and Bessel beams. Here we present an overview of the methods applied and results obtained with quasi-optical hologram techniques using both amplitude and phase holograms.

A computer-generated binary amplitude hologram is used to transform an initial Gaussian electromagnetic field with spherical phase front at 310 GHz into a non-diffracting Bessel beam. The beam profile is measured with the help of a near field scanner. In contrast to the situation in the optical region, both amplitude and phase information is readily obtainable from the generated field.

This paper describes a prototype of a UHF RFID based log marking and tracking system developed for the challenging four-season outdoor conditions in Scandinavia. The RFID system comprises of novel pulping compatible EPC Class 1 Generation 2 transponders, and of robust readers with novel performance boosting features. A wedge-shaped transponder is inserted into the log end with a special tool so that it is protected and held firmly in place by wood during the transportation and processing of timber. A robust EPC-compliant RFID reader featuring an adaptive RF front end was developed for use in a harvesting machine. Readability tests at saw mills with test logs using specially adapted commercial UHF readers show nearly a 100 % readability for the transponders inside fresh moist logs.