Effect of asymmetric coupled-line in ultra-wideband filter design

After authorized by FCC, ultra-wideband passband, whose frequency range is 3.1GHz-10.6GHz, has created a great interest in the whole world. UWB filter is an important part of UWB communication system. Coupled lines designing felicitously can insure better performance of the filter. Generally, traditional symmetric coupled-line is usually used in UWB filter design. In this paper, we propose a new kind of asymmetric coupled-line in stead of traditional symmetric coupled-line. Then, our work test different pairs of coupled-line, and the result show that the asymmetric coupled-line had a better performance than the traditional symmetric coupled-line without destroying the group delay.