**5. Conclusions**

ε<sup>r</sup> = 3.5, loss tangent of 0.0018, and thickness of h = 0.8 mm. The layout of proposed UWB BPF with a notch band is depicted in **Figure 18**. As mentioned above, a dual-stub-loaded slot-line resonator is etched on the ground plane, and on the top layer, two folded microstrip feed lines and a microstrip triangular loop resonator are constructed. All the dimensions of the filter shown in **Figure 18** are *W*<sup>0</sup> = 1.8 mm, *L*<sup>1</sup> = 23.0 mm, *W*<sup>1</sup> = 2.0 mm, *L*<sup>2</sup> = 3.0 mm, *W*<sup>2</sup> = 0.3 mm, *L*<sup>3</sup> = 2.0 mm, *W*<sup>3</sup> = 0.8 mm, *L*<sup>4</sup> = 11.5 mm, *W*<sup>4</sup> = 0.6 mm, *L*<sup>5</sup> = 36 mm, *W*<sup>5</sup> = 0.3 mm,

Simulated and measured transmission and reflection coefficients of the constructed filter are plotted in **Figure 19**. Simulated results show that the 3-dB passband of the filter covers the ranges of 2.83–4.78 GHz and 6.29–10.33 GHz, respectively, while measured ones show that the 3-dB passband covers the ranges of 2.49–4.91 and 6.29–9.2 GHz. Measured minimum insertion losses of the first and second passband are 1.1 and 1.5 dB, respectively. Measured maximum return losses in the first and second passband are 13.2 and 13.5 dB, respectively. Simulated and measured maximum insertion loss in the notch band is 25 and 35 dB,

**Figure 18.** Schematic of the proposed band-notched UWB BPF with dual-mode triangular loop resonator-loaded dual-

**Figure 19.** Simulated and measured frequency responses of the designed band-notched UWB BPF.

and *S* = 0.6 mm.

56 UWB Technology and its Applications

stub slot-line MMR. (a) Top layer and (b) bottom layer.

Slot-line UWB BPFs and band-notched UWB filters are presented. UWB BPFs are implemented by using microstrip feed slot-line MMR. To acquire a notch band in the UWB passbands, microstrip resonators are loaded to the slot-line. Circuit model for microstrip resonatorloaded slot-line is given and analyzed. The design methodology has been finally verified by the measured results. Band-notched UBW BPFs are hot spots in a few years; there are some trends in this field, such as multiple notched band and tunable notched band.
