The minimum phase property in frequency-independent antennas

The minimum phase property is desirable in broad-band antennas for pulse applications, because it determines whether it is feasible to perform broadband passive equalization of the antenna transfer function to obtain a narrow monopulse response in the time domain. It is well-known that certain classes of broadband antennas such as log-periodic antennas, spirals, and conical spirals are very difficult if not impossible to equalize for a monopulse response. In this paper we will show that this problem is inherent to such antennas, independent of the details of their structure, because it can be shown analytically that the transfer functions associated with them cannot be minimum phase.