A novel concept for post-fabrication tuning of microwave filters

A novel method for global post-fabrication tuning of microwave filters is presented. The method is based on designing and adding a compensating passive circuit in parallel with the detuned filter. This concept, which is demonstrated by experimental results, has several advantages over traditional techniques for filter tuning that use screws. It can be employed to filter structures that are not easily amenable to the use of tuning screws such as planar filters. Another important advantage of the proposed concept is that it can be employed without knowing details of the filter configuration. The compensating circuit that is added in parallel to the detuned filter, does not affect the individual elements of the filter. The experimental results obtained demonstrate the validity of this concept.