Rapid modeling, characterization, optimization methodology and analysis for low cost RF filter design

The increasing popularity of the IEEE 802.11n wireless applications demand low cost and high quality RF applications in the 5 GHz spectrum region particularly for RF filters. Simulation performances and low cost implementations are given the spotlight in many RF filter designs proposed in the literatures but fail to address the importance of physical performances which are dependent on design, material of choice, design and fabrication methodologies and particularly, matching the physical RF feed. This paper presents the rapid modeling, characterization and optimization methodology to produce high performance RF filter design and showing the severe effect of imbalance feed structure when joining the filter feed with RF connectors. This paper also shows how two equal RF filters using parallel microstrip coupled line design with different feed structures connecting to RF connectors can have different performance. The filters are fabricated on Rogers R04350B substrate with dielectric 3.66 using computer numerical control (CNC) machine for rapid design characterization and optimization to achieve matching impedance at the joints and performance. High performance filter design with low insertion loss of 1 dB, return loss of 20 dB and wide operating bandwidth is achievable with the proposed methodology.