In this thesis, the wideband bandpass filters (BPFs) are studied with focus on the slotline structure. To this end, some existing slotline resonators filters are studied in chapter 2; a cross-shaped slotline resonator is analyzed in chapter 3; and two wideband BPF designs using this structure are introduced in chapter 4. Following this basic study in chapter 2, a simplified dual-band BPF with slotline is proposed, we can change the length of the slotline in order to achieve single and dual bandpass reconfigurable performance, and the transmission zeros near the passbands also can be adjusted by changing the lengths of slotline. Analysis of the cross-shaped slotlione resonator is given in the third chapter. Transmission zeros, poles, bandwidth and group delay are calculated, these results can help the people who is interested in the cross-shaped slotline resonator. Besides, a wideband BPF using cross-shaped slotline resonators is presented. It can achieve wideband response from 6.96 GHz to 12.48 GHz with three transmission poles at 7.78 GHz, 9.5 GHz, 11.84 GHz and two transmission zeros at 5.4 GHz, 13.86 GHz. The group delay is 0.62 ns and it has 10.9 dB matching in the passband and the passband insertion loss is around 1.35 dB. This filter achieve the purpose of relaxing from via implantation compared with terminated cross-shaped resonators (CSRs) with short circuit terminations. At last, a wideband BPF using cross-shaped slotline resonator with parallel slotline is proposed. It has a wider passband from 6.78 GHz to 12.91 GHz. And also it has two transmission zeros and three transmission poles