Transmission and reception by ultra-wideband (UWB) antennas

Broadband antennas are very useful in many applications because they operate over a wide range of frequencies. The objective of this paper is to study the transient responses of various well-known antennas over broad frequency ranges. As such, the phase responses of these antennas as a function of frequency are of great interest. In the ensuing analysis, each antenna is excited by a monocycle pulse. Many antennas show resonant properties, and numerous reflections exist in the antennas' outputs. The first part of this paper deals with ways of converting various resonating antennas to traveling-wave antennas by using resistive loading. Appropriate loading increases the bandwidth of operation of the antennas. However, the drawback is the additional loss in the load applied to the antenna structure, leading to a loss of efficiency to around fifty percent. However, some of the antennas are inherently broadband, up to a 100:1 bandwidth. Hence, the transient responses of these antennas can be used to determine their suitability for wideband applications with a low cutoff frequency. The second part of the paper illustrates the radiation and reception properties of various conventional ultra-wideband (UWB) antennas in the time domain. An antenna's transient response can be used to determine the suitability of the antenna in wideband applications.