Radiation Characteristics of Loop Antennas Excited by Transients

Uninterrupted Wireless Data Transfer for Smart Grids in the Presence of High Power Transients

“…The radiation resistanceR rad has been obtained by averaging the frequency-dependent antenna impedance of the infinitely long antenna over the frequency components of the exciting pulse (up to the maximum significant frequency that is mainly determined by the rise time of the pulse). As a result, it has been illustrated in [21] that, if the two arms of a linear antenna have been bent to form a rectangular loop, the loop shows a radiation resistanceR rad of approximately 600 Ω as well. In [21], it has been also indicated that the electric field radiated from a rectangular antenna loop excited by a transient signal reaches its maximum in a direction normal to the loop.…”

“…As a result, it has been illustrated in [21] that, if the two arms of a linear antenna have been bent to form a rectangular loop, the loop shows a radiation resistanceR rad of approximately 600 Ω as well. In [21], it has been also indicated that the electric field radiated from a rectangular antenna loop excited by a transient signal reaches its maximum in a direction normal to the loop. Moreover, the shape of the radiated field resembles exactly the transient exciting current.…”

“…1 It has been shown in [21] and [22] that the shape of the radiated field of loop antennas when excited by a pulse depends on the matching condition between the source of the pulse and the radiation resistance of the antenna. The reason is that the pulse travels around the loop until it returns back to the feed point.…”

“…However, if there is no matching, the pulse will be reflected back at the feeding point after losing some of its energy to the source. The returned pulse will travel through the loop until it arrives to the feeding point again and so on [21], [22]. This implies that the shape of the radiated field when there is no matching is in the form of multiple replicas of the original pulse but with different delays and decreasing rise time.…”