Analysis and design of dual band-notched interdigital hairpin UWB bandpass filter

In this paper, a new dual band-notched UWB (Ultra Wideband) bandpass filter which is proposed to control harmonic components of 2.14 GHz is designed and tested. Interdigital hairpin structure is applied in the dual band-notched UWB bandpass filter design. By adding only one pair of folded fingers on both side extremities of single band notched UWB bandpass filter, the fabricated filter can suppress the second and third harmonics of fundamental frequency. The dual notched bands can be easily controlled by changing the parameters of each finger. Without changing the first notched frequency band, the second reject frequency band can be shifted by changing its corresponding parameter of finger independently. In this paper, one dual band-notched UWB bandpass filter are designed to control the second and third harmonics of 2.14 GHz. The measured result of the final fabricated circuit shows that insertion loss at 4.28 GHz and 6.42 GHz are 13.99 dB and 4.16 dB, respectively. Because of the folded finger structure, the filter is compact in size. The dimension of our proposed filter is 5.5 mm × 21.3 mm.