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Designs of small, low-cost, ultra wideband (UWB) antennas have been widely reported in recent literature. However, a detailed performance analysis from impedance matching to pattern stability is rarely carried out. In this paper, two new low-cost, compact antennas, which operate in the upper half of the direct sequence spread spectrum UWB (DS-UWB ) band, are presented. These antennas are not only impedance matched, but also retain very good pattern stability over the operating band. The latter means that the UWB waveforms radiated in high-energy directions are similar (i.e., correlated). One L-slot antenna has a planar ground plane and the other modified L-slot antenna has a ground plane consisting of a planar section and two sidewalls. Measured radiation pattern at a selected in-band frequencies is presented to demonstrate the effect of ground plane modifications on radiation patterns. Wideband radiation characteristics and the pattern stability of these antennas are investigated with the help of pattern stability factor (PSF). This is done over principal planes as well as along selected range of directions (i.e., 10 dB energy beams), where significant proportion of energy is radiated.
Date of Publication: April 2008