Ultra wide band pass filters (UWBPF) based on complementary split rings resonators

In this work, a new strategy for the design of microstrip filters with ultra-wide bandwidths is proposed. This is based on the combination of square-shaped complementary split-ring resonators (CSRRs) etched in the ground plane and grounded stubs. Coupling between adjacent resonators is achieved by means of lambda/4 lines, acting as impedance inverters. To illustrate the potentiality of the approach, a prototype device with 90% fractional bandwidth has been designed for operation at C-band. The measured fractional bandwidth (87%), in-band losses (< 1.3 dB), and out-of-band rejection (> 30 dB), obtained on a device scaled down in frequency, point out the high performance achievable with this design methodology. Moreover, the first frequency parasitic (spurious) does not appear up to three times the central filter frequency. Due to the small dimensions, wide bandwidths, and compatibility with planar circuit technology, it is believed that the approach presented in this work can be of actual interest to the design of filters for ultra-wideband applications. (c) 2005 Wiley Periodicals, Inc.