Design of Compact and Miniaturized Band-pass Filters in Coplanar Waveguide (CPW) Technology

A new technique for designing compact, band-pass filters of arbitrary orders is presented in this paper. The proposed approach is based on the design and optimization of a second order band-pass filter, which acts as the unit cell of a higher order filter. This unit cell is composed of slow-wave transmission line resonators, separated from one another by an inductive impedance inverter network. For applications requiring a narrowband filter response, this unit cell is capacitively coupled to the outside world to increase the loaded quality factor of the resonators and achieve a narrower bandwidth. This mechanism provides a simple method of controlling the bandwidth and frequency response of the filter. Two different cascading topologies are used to achieve filters with either even (N = 2, 4, ...) or arbitrary orders (N=2, 3, 4, ...).