Design and Optimization of Cost-Effective, Simple, and Miniature Tri-Band Bandpass Filter for GSM, WLL, and WIFI Applications

This article uses pair of meandered stub-loaded uniform impedance resonators (SL-UIRs) to develop a low-cost, compact, and simple microstrip tri-band bandpass filter (TBBPF). The proposed filter's center frequencies for the three pass bands are 1.64/3.04/4.9 GHz, making it suitable for GSM, WLL and Wi-Fi applications. For these three passbands, the fractional bandwidth (FBW) and minimum return loss are 14.7%, 11.6%, and 5.7% and 20.1 dB, 33.4 dB, and 31.89 dB respectively. Also, the interdigital coupling of used resonators facilitates the generation of five transmission zeros at frequencies of 1.27, 2.16, 3.55, 4.77 and 6.33 GHz, leading to high selectivity and excellent isolation.