Distributed parameter approach to pulse response analysis of n:1 balun transformers

Abstract

Balun transformers of an arbitrary turns ratio of n:1 were considered as two asymmetrically coupled transmission lines, whose four-port fundamental equations were introduced. Equivalent circuits of isolation-type and transmission-line-type balun transformers were derived for the calculation of pulse rise-time and flat-top responses. These transformers have two output ports, and the reason for this two-output-port voltage asymmetry was theoretically explicated by deriving the equivalent circuits. To improve the balance of the balun transformer outputs, compensation methods were presented. Pulse rise-time responses were evaluated for the parameters associated with the transformer parameters and terminations. Experimental balun transformers were constructed, the output voltage balance of which was much improved by the compensation method, and high-speed pulse rise-time responses were obtained. >