Compact tri-band BPF based on embeded asymmetric T-shape stub-loaded resonators

In this article, a compact tri-band bandpass filter(BPF) is proposed by using T-shape asymmetrical stub-loaded resonators (ASLRs). The resonator, which consists of a main transmission line and T-shape-loaded stub is utilized to obtain two frequencies at 2.48 GHz and 4.48 GHz. Then, embedding into the sides of coupled-line a symmetrical to produce a passband at 3.58 GHz, so that a tri-band BPF is successfully designed. The fabricated tri-band BPF have compact sizes of 32 mm ×28 mm. In addition, good in-band return loss, and wide passband can be also observed. Good agreement is shown between the simulated and measured results.