Dual-band broadside-coupled based BPF with improved performance

This paper presents a unique structure of a dual-band microstrip bandpass filter (BPF) that works at 1.25 GHz, 1.9 GHz for global positioning systems (GPS) and TV broadcast auxiliary service applications, respectively. The proposed BPF provides compactness, small fractional bandwidth (FBW), small frequency separation, and low IL. The prospective filter is constructed employing broadside-coupling techniques to achieve low insertion loss (IL). The feeding structure is accomplished utilizing a 50 Omega co-planar waveguide (CPW) scheme due to its low loss characteristics. The small 3-dB FBW is accomplished by inserting four transmission zeros (TZs). The size of the overall structure, including I/O transmission lines, is 34.9 x 23.5 mm(2). The measured and simulated results fit well with each other and show an IL of 0.77 dB and 0.5 dB, and FBW of 7.6% and 8.4% at 1.25 GHz and 1.9 GHz, respectively.

Automated summary

The paper presents a unique dual-band microstrip bandpass filter structure for GPS and TV broadcast auxiliary service applications, achieving compactness, low insertion loss, and small frequency separation through broadside-coupling techniques and CPW design. The filter design includes insertion of transmission zeros to achieve small 3-dB fractional bandwidth and overall structure size of 34.9 x 23.5 mm(2). The measured and simulated results show good agreement with 0.77 dB and 0.5 dB insertion loss, and FBW of 7.6% and 8.4% at 1.25 GHz and 1.9 GHz.