The ideal ultra-wideband (UWB) antenna feed for lens and reflector systems radiates a uniform and customizable beamwidth vs. frequency. Here, a new antenna concept for radiating frequency-independent Gaussian beams with arbitrary bandwidths and beamwidths is reported. It is analytically shown how to resistively load a transmission line network to maintain a Gaussian amplitude taper across an antenna array aperture. In contrast to many other feed antennas, the radiation properties here can be tailored without time-consuming full wave optimizations. The radiated beamwidth, bandwidth, antenna size, radiation efficiency, and gain can all be quickly estimated using the derived closed-form expressions. An example, 16x16 Vivaldi element array is fed with a network of resistively loaded microstrip lines. The simulated array radiates a Gaussian beam with 10 dB full beamwidth of 35°±5° and directivity of 20 dB±1.5 dB over 6.5 GHz-19 GHz (3:1 bandwidth ratio). However, the radiation efficiency is inherently low due to the large loss associated with generating the Gaussian amplitude taper at all frequencies. The example array has a simulated radiation efficiency of 1% at the higher operating frequencies. The array was fabricated and measured. The measured beamwidths agree well with simulation to validate the reported theory. This architecture is a particularly attractive option for feed antennas that require customizable directivities, and can tolerate low radiation efficiencies such as test and measurement.
"Uniform Beamwidth UWB Feed Antenna Using Lossy Transmission Lines," Progress In Electromagnetics Research,
Vol. 165, 119-130, 2019. doi:10.2528/PIER19081202
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