Why antnenna UWB operates across the entire bandwith?

Some structures have physical shapes that allow them to operate over very wide bandwidths. Exponential slots and biconic antennas are examples. Others are a collection of narrow band antennas combined to provide wide coverage. A log-periodic dipole array is an example.

Vic Rumsey in the 60's started much work in this area by observing that antennas whose structures were defined by angles rather than lengths tended to be very broadband, think of spirals for example.

Kraus proposed a "volcano smoke" antenna for use as a broad band element.

Generally, "fat" antennas are broad band and "skinny antennas are frequency specific.

Is any design rule on the design of broadband antenna, a lot of new broadband monopole UWB design articles in IEEE paper, but all looks like black art, just try-and error? simulate it to see what happened? then pick the best result?

Are there any book has the basic rules collected?

thanks Azulykit!
I don't know cause to create across the entire bandwith. You can shown me th book mention it.

from Antenna Engineering Handbook 4th ed. (Volakis edition):

Chapter 16: Wideband Microstrip Antennas
Chapter 19: UWB Antennas
Chapter 24: Ultrawide Band Arrays
Chapter 37: Broadband Planar Antennas for High-speed Wireless
Chapter 52: Impedance Matching, Broadbanding and Baluns