The dual elliptically tapered antipodal slot antenna (DETASA) is a modified version of the antipodal Vivaldi antenna. The DETASA is formed by elliptical tapering of the inner and outer edges of the slotline conductors of the antipodal Vivaldi radiator. To enhance the performance of the DETASA, this paper presents a modified configuration by using curved conducting terminations at the end of the slotline conductors. The proposed DETASA has the advantages of extended lower operating frequency, flatter gain response, symmetrical radiation patterns, and improved impedance matching across the operating band over the conventional DETASA. As an example, a prototype covering the ultrawideband (UWB) frequency range (3.1--10.6 GHz) is designed and characterized in terms of impedance matching, gain, radiation pattern, transfer function, and group delay in the frequency domain, as well as impulse response and fidelity in the time domain. The prototype which is made on a 0.8128 mm Rogers RO4003 substrate with the dimensions of 80 ¿ 80 mm shows good impedance and radiation performance over 3--20 GHz: Return loss is less than --10 dB; gain variation is less than 4 dB (4--8 dBi); and symmetrical radiation patterns and constant group delay have also been achieved. In the time domain, the prototype features good impulse response and high fidelity (F is more than 0.9) as well. The simulated and measured results show that the proposed DETASA is capable of providing enhanced impedance and radiation performance suitable, in particular, for UWB applications.