Dual-band Bandpass Filter Using Stubs to Controllable Passband

The dual band bandpass filter is presented with square ring-resonator structure. The stubs are inserted between the inside and outside ring-resonator for adjusting the second band. The first band is designed for supporting WLAN system at 2.45 GHz and the second band is covered within the radio altimeter system at 4.30 GHz. The measured results are agreed to the insertion losses are 2.01 dB, 2.18 dB and the return loss are 11.45 dB, 11.15 dB at the center frequency 2.45 GHz and 4.30 GHz, respectively.