Although the transmission line transformer has been in existence for over five decades, it's only in the last few years where the importance of Guanella's designs have been recognized and where designs with rations other than n One technique for obtaining these new ratios incorporates windings greater than two in the bootstrap connection. Figure 6 shows a trifilar winding on a toroid that yields a natural impedance ration of 2.25:1 or a tapped ration very close to 2:1. Furthermore, by placing winding 5-6 between the other two windings, the effective characteristic impedance is lowered and the transformer works better in stepping down from 50 ohms. Figure 7 shows the tapped trifilar step-up design (like Figure 6) at three different impedance levels. note the With these very efficient and broadband ununs with rations very close to 1.5:1 and 2:1, it is now possible to put them in series with 1:1 and 4:1 baluns and achieve results which were not available before. A version of Guanella's For higher ratios, Guanella's approach can be used for 9:1 and 16:1 baluns (and ununs). Figure 8 shows the high frequency and low frequency models for his 9:1 transformer. His 16:1 transformer would obviously use four transmission lines. Ruthroff's "bootstrap" connection can also be used to obtain ununs with rations of 9:1 and 16:1. A 9:1 ration can be obtained simply by connecting, in Figure 6, the input to terminal 3 instead of terminal 5. By using a fourth winding above winding 5-6, a 16:1 ration is obtained. In fact, by using multiple inputs and outputs and various taps on the winding, broadband multimatch ununs now become available. Although the Guanella approach yields a much higher frequency capability, it is considerably more complex and not as versatile as Ruthroff's approach. |

353 West Grove Avenue, Orange, CA 92865, U.S.A.

**800-679-3184**

© 1996 - 2002

All Rights Reserved