In this paper, a novel synthesis method is presented to design of a class of multi-section ultra-wideband (UWB) Wilkinson power dividers (WPDs) with an arbitrary power ratio. The proposed UWB-WPD topology consists of N cascaded asymmetric coupled line sections (ACLSs) and N isolation resistors. Through even- and odd-mode analysis, the proposed synthesis method is demonstrated with a few unique novelties as summarized: (1) It is for the first time proved that the first kind Chebyshev equal-ripple performance can be exactly realized by the cascaded transmission-line transformer without Hansen's approximation; (2) It is also for the first time revealed that all the S-parameters (S11, S21, S31, S22, S33 and S32) of proposed WPD can achieve controllable in-band equal-ripple performance. To verify the effectiveness of proposed synthesis method, several design examples are presented and designed for demonstration of varied equal-ripple responses. Finally, two WPD circuits with N = 3 are fabricated, and the measured results well validate the predicted ones from proposed method.