A New Loop Antenna for Directional UWB Links

Loop antennas of circumference greater than a wavelength are generally known to have a good directive radiation pattern. However, for use in UWB applications, the variation of the radiation pattern with frequency must also be taken into account. Besides a good wideband radiation pattern, the impedance bandwidth of the antenna is also very important. The quality of a transmitted and received UWB pulse from the antenna will be a combination of both these factors. In this paper, we first investigate the characteristics of loop antennas with respect to both these factors. Next, we propose a new loop antenna configuration to overcome the limitations of the standard loop antenna for UWB applications. The new antenna consists of two concentric half-loops directly coupled to each other. The proposed antenna is analyzed using the Method-of-Moments (MoM). The theoretical and measured results agree with each other closely and attest to the fact that the new antenna has a far superior impedance bandwidth when compared with conventional loop antennas. Further, it is shown that the new antenna has a good gain and a useful radiation pattern for directional wireless links. The advantages of the antenna are conclusively demonstrated by successfully deploying it in a very high speed (500 Mbps) point-to-point UWB link.