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This contribution discusses the relationship between the number of degrees of freedom (DoF) and the maximum directivity for an arbitrary set of sources enclosed by a given spherical surface. In particular, it is shown that the number of DoF is equal to twice the maximum directivity. This provides a directivity limitation for arbitrarily sized antennas, thus, extending the validity of the known formulas...
This paper presents recent advances is a new waveguiding technology referred to as ridge gap waveguides. The main advantages of the ridge gap waveguides compared to hollow waveguides are that they are planar and much cheaper to manufacture, in particular at high frequencies such as for millimeter and submillimeter waves. In these waveguides there are no mechanical joints across which electric currents...
Multiport, decade bandwidth Eleven feed for prime focus reflector is ongoing development for VLBI 2010 applications. Current version of this feed uses four differential lines used to excite the log-periodic arrays above ground plane. These excitation lines packaged in small central region referred as centre puck shows radiation from lines above 10GHz causing distortion in feed pattern. This paper...
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