Parallel-coupled line filter design from an energetic coupling approach

In this study, the design of parallel-coupled line bandpass filters (BPFs) is investigated from an energetic coupling theory approach. The proposed filter design process allows the design of BPFs with improved characteristics. In particular, it is possible to implement filters with reduced occupation area, larger passband bandwidth and improved rejection performance. This is accomplished by controlling the coupling coefficient between resonators by means of the coupling section length. The suggested design technique is validated through the design, fabrication and measurement of several coupled line microstrip BPFs centred at 2.0 GHz.