Compact Millimeter-wave filters using distributed capacitively loaded CPW resonators

In this paper, a method for reducing the size of coplanar-waveguide (CPW) resonators, used in the design of compact bandpass filters, is presented. This is accomplished by incorporating a distributed array of capacitive loads along a resonant CPW line. Design of a miniaturized bandpass filter using capacitively loaded CPW resonators, which are inductively coupled, is presented. Inductively coupled bandpass filters with the proposed capacitively loaded CPW line resonators are designed and a size reduction of 25%, compared with filters using a standard CPW line resonator, is demonstrated. It is shown that, through this size reduction, the insertion loss is minimally increased (<0.4 dB). A hybrid algorithm, combining the method of moments (MOM) and circuit simulation is used to facilitate design process. Few filters using this technique are designed, fabricated, and measured at W-band. An excellent agreement between the simulation and measurement responses of these filters is presented.