Comments on “A Quasi Elliptic Function 1.75–2.25 GHz 3-Pole Bandpass Filter With Bandwidth Control”

In the above paper, a three-pole filter with tunable frequency and bandwidth is proposed based on a simple topology. The nonadjacent resonator coupling is introduced to generate a zero at the lower band for adjusting the bandwidth. Although the results are interesting, it appears that the design equations are mislabeled and the equivalent circuit model is inaccurate.