Compact dualband bandpass filter using triple-mode stub loaded resonator

A compact dual-band bandpass filter (BPF) with controllable bandwidths is designed using two stubs loaded on a half-wavelength resonator. The dual-band performance is realized using two similar resonator structures. The two resonators share a common circular via located at the midpoint of the resonators for smaller circuit size. The nearest unwanted spurious occurs outside the second passband. The filter is designed to have center frequencies at 2.4 GHz and 5.2 GHz. The measurement result shows that both passbands have 3dB bandwidths of 10.9% and 9.1% and insertion losses of 1.2dB and 1.6dB, respectively.