Browsing by Author "De Villiers D.I.L."
Now showing 1 - 7 of 7
Results Per Page
Sort Options
- ItemAnalytical evaluation of the efficiency improvement of shaped over classical offset dual-reflector antennas including sub-reflector diffraction(2011) De Villiers D.I.L.; Lehmensiek R.
- ItemDesign of a ten-way conical transmission line power Combiner(2007) De Villiers D.I.L.; Van Der Walt P.W.; Meyer P.Axially symmetric power combiners, such as radial line and conical line combiners, are very effective in combining the output signals from a large number of power amplifiers over a wide band with low losses. The main problem with radial lines is the behavior of the characteristic impedance against radial distance, which makes design of radial combiners difficult and normally optimization based. In this paper, a step-by-step design procedure is presented for the design of a conical line combiner. The design strategy relies on the transverse electromagnetic properties of the conical line to eliminate the need for complex full-wave optimization in the design process. Circuit models are instead employed and optimized to achieve a wide matched bandwidth. A ten-way proto-type was developed at X-band, which displayed more than an octave matched bandwidth with low insertion loss. © 2007 IEEE.
- ItemDesign of a wideband orthomode transducer(2009) De Villiers D.I.L.; Meyer P.; Palmer K.D.The design of an offset ridge quad-ridged waveguide (QRWG) orthomode transducer (OMT) is presented. By offsetting one of the ridges in the direction of propagation, a much wider single mode operating bandwidth can be achieved than that achievable in a traditional symmetric QRWG OMT's. This wide single mode operating bandwidth ensures that no higher order modes are excited at the feeds of the OMT, which in turn eliminates unwanted resonances often observed in traditional QRWG OMT's. The performance of the OMT is similar to that of traditional types, with reflections below -20 dB and cross coupling below -40 dB across most of the desired 1.7:1 bandwidth. © 2009 IEEE.
- ItemOffset dual-reflector antenna system efficiency predictions including subreflector diffraction(2011) De Villiers D.I.L.
- ItemSub-reflector extensions for reduced noise temperature in low-side sub-reflector offset Gregorian systems(2012) De Villiers D.I.L.; Lehmensiek R.This paper describes a simple and low cost method to improve the noise performance of low-noise offset Gregorian antenna systems using a low-side sub-reflector mount configuration. A low-side mount has some logistical and maintenance advantages over the high-side counterpart, since the feed can be accessed without the need for a crane. A simple extension to the bottom of the sub-reflector is proposed which is shown to improve the antenna noise performance over that of the standard high-side mount configuration. © 2012 IEEE.
- ItemWide flare angle axially corrugated conical horn design for a classical offset dual-reflector antenna(2012) Lehmensiek R.; De Villiers D.I.L.This paper outlines the design of a wide flare angle axially corrugated conical horn for a classical offset dual-reflector antenna system. The design minimizes the input reflection coefficient of the horn and maximizes the antenna efficiency of the antenna system by simultaneously limiting the sidelobe and cross-polarization levels to the system specifications. The effects of the number of corrugations in the horn and the number of parameters used in the optimization are also investigated. © 2012 IEEE.