An UWB Multi-frequency transformer

A novel multi-frequency transformer is developed based on dual frequency transformer reported recently. Different from dual frequency transformer, which has two steep poles, the return loss curve of the transformer developed in this paper has one steep pole with two gentle side poles. This transformer can achieve ultra-wideband because it makes use of big separation ratio between center frequencies as employed in dual frequency transformer. At the same time, the gentle side poles avoid sharp jump of peak values between two adjacent poles. The transmission line analysis shows that the three-pole transformer can achieve 120% bandwidth compared to 60% of dual frequency transformer