4Methodologies for Ultrawideband Distortionless Transmission/Reception of Power and Information

Summary

Broadband antennas are very useful in many applications as they operate over a wide range of frequencies. The objective of this chapter is to study the transient responses of various well‐known antennas over broad frequency ranges. It is illustrated that the well‐known frequency domain principles quite prevalent in many antenna text books are not applicable for time domain applications. Specifically, the impulse response of an antenna on transmit is the time derivative of the impulse response of the same antenna on receive and hence it is not possible to transmit and receive a broadband pulse without distortion using the same antenna. 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 at the antenna outputs. The first part of this chapter 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. But the drawback is the additional loss in the load applied to the antenna structure, leading to loss of efficiency to around fifty percent. However, some of the antennas are inherently broadband, up to a 100:1 bandwidth. Hence, they can be suitable in replacing multiband ...

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