Design and Optimization of Compact Microstrip Wideband Bandpass Filter Using Taguchi’s Method

This study presents a global optimization technique, Taguchi’s method, in conjunction with a full-wave electromagnetic simulator, to optimize a novel microstrip bandpass filter operating at 2.45 GHz to achieve wideband and high selectivity characteristics. The proposed wideband bandpass filter consists of multiple parallel edge-coupled lines, which offer inherent transmission zeros to improve the selectivity. The proposed bandpass filter is fabricated on a Rogers RO 4003C substrate with a compact size of
$0.25~\lambda \text{g}$
by
$0.28~\lambda \text{g}$
. Sufficient information, such as the filter design procedure and the optimization settings for Taguchi’s method, is described in this paper. After Taguchi’s optimization, the measured results of the proposed filter show superior outcomes. A 3 dB fractional wide bandwidth of 55.2%, a minimum insertion loss of 0.43 dB, and a return loss of more than 15 dB within the passband are achieved. Furthermore, high selectivity and steep skirt within the stopbands are also obtained. In addition, the simulated and measured scattering parameters agree well with each other, which demonstrate the validity of the proposed design.