Analysis of power null for broadband millimeter wave frequency multiplying applications

In this paper, we report on the formation mechanism and cancellation criterion of power null associated with a broadband W-band frequency tripler. In addition to the existed mechanism of harmonic cancellation, the mechanism of fundamental cancellation is studied by analyzing the phase behaviors of input and output embedding networks. It is proved that the fundamental cancellation has stronger effect on the flatness of output power than that of harmonics. Three phase regions of the embedding networks, that is, null free region, cancellation region and uncertain region, are defined to estimate the possibility of power null occurrence. A criterion related to the phase characteristics of the embedding networks is proposed to predict the phenomenon of power cancellation and the concomitant power null. As an application of the criterion, a prototype of W-band frequency tripler covering 75-110 GHz is designed and measured. Experimental results show that no power null appears over the 75-110 GHz frequency range.