Synthesis and diagnosis of RF filters in liquid crystalline polymer (LCP) substrate

Fault detection and diagnosis of RF circuits after fabrication is a time-consuming step in the manufacturing cycle. This paper presents the application of layout-level synthesis technique to the diagnosis of RF bandpass filters with embedded passives in LCP substrate. The proposed approach is based on a combination of segmented lumped circuit modeling, nonlinear mapping using polynomial functions and circuit level optimization. Bandpass filters for different electrical specifications were synthesized and fabricated. The results of synthesis are within 5% of EM measurement data. The fabricated designs require diagnosis of variations in performance metrics such as center frequency, bandwidth and transmission zeros that occurred due to process variations. Synthesis was applied to map the variations in electrical parameters to component geometries. The synthesized results predict the possible variations in physical parameters that have been confirmed with measurements of the fabricated devices.