DESIGN OF A STOPBAND-IMPROVED UWB FILTER USING A PAIR OF SHUNT AND EMBEDDED OPEN STUBS

,passed from the Cgate to the bulk ground. In Figure 4, the measured MOS varactor flicker noise, where the dimensions of W L G B 1.6 0.4 8 64, has presented a different flicker noise level at 1.2 V as a result of the leakage current being one order of magnitude higher compared with other DC bias conditions. This can be explained by the fact that an increased modeling parameter for Igate results in an increased leakage current of NMOS varactor at 1.2 V. It was noticed that there was an increase in noise when the current was higher than 10 4 mA. This phenomenon did not occur when the leakage current is 10 5 and 10 6 mA at 1.2 and 0 V, respectively, Also, Igate changes the flicker noise level, as Igate rises above than 10 4 mA. Moreover, it was found that measured results for PMOS varactor are always lower than 10 5 mA between the 1.2 and 1.2 V, so would have no impact on the noise level variation. Although the measured noise of MOS varactor has a lower level than the one created by MOSFET, adding the fitting parameters to the simulator is an unavoidable trend as noise level rapidly increases with increased leakage current. 5. CONCLUSIONS In this study, we investigated the optimum 65 nm LP MOS varactors geometrical relation in terms of microwave characteristics and low frequency noise performances. The equivalent circuit model also achieves precisely extracting parasitic parameters and agrees with measured results. The Igate parameter of the MOS varactor model also can be validated as a relationship with flicker noise on MOS varactor. ACKNOWLEDGMENTS