An Elliptic-Function Bandpass Filter Employing Left-Handed Operations of an Inter-Digital Coupled Line

A new elliptic-function bandpass filter (BPF) is proposed, which utilizes an inter-digital coupled line (IDCPL) as a left-handed transmission line. The IDCPL is employed in order to realize a negative coupling between non-adjacent resonators in a wideband BPF. As the authors´ knowledge, the left-handed operations of the IDCPL has rarely utilized before, although the IDCPL itself has been widely used in many microwave circuits without being paid attention to the left-handed operations. Measured results of a 3-5GHz BPF for ultra wideband communication systems (UWB) are also presented in this paper.