Crossed exponentially tapered slot antenna
Image of the Crossed exponentially tapered slot antenna.

The crossed exponentially tapered slot antenna may find application in the FCC (and ETSI) defined ultra-wideband (UWB) radio band of 3.1 - 10.6 GHz. The antenna combines two crossed exponentially tapered slots with a star-shaped slot to produce a stable radiation pattern. Measured UWB figures of merit, like the fidelity factor and the pulse stretch ratio, indicate that the structure is able to serve as a Gaussian impulse shaping filter required for UWB radio. Essentially, the antennas used in UWB radio should only minimally distort the shape of the output pulse - both in the frequency, as well as the spatial domain. [Costa et al.]

The measured transfer function, indicating voltage at the receiving antenna vs. applied voltage at the transmitting antenna exhibits a relatively constant magnitude and almost linear phase. Furthermore, the measured group delay is also quite constant and close to zero.

The antenna achieves a good (S11 < -8 dB) match over a > 3.42:1 (110%) bandwidth for a 50 Ohm input impedance. This covers the official UWB frequency band of 3.1 - 10.6 GHz. The antenna radiates a bidirectional radiation pattern with the required polarisation purity, at an antenna efficiency of between 90 and 97%.

Typical total gain patterns at (a) fmin, (b) fcentre and (c) fmax
Reflection coefficient performance

Jorge R. Costa, Carla R. Medeiros and Carlos A. Fernandes, "Performance of a Crossed Exponentially Tapered Slot Antenna for UWB Systems," IEEE Transactions on Antennas and Propagation, vol. 57, no. 5, pp. 1345-1352, May 2009.