Rf Analysis And Design Of Active Filters

Recently, dozens of wireless communication standards have been used for portable terminals, e.g. ISM bands, AMPS, GSM900/1800, DVBs, GPS, CDMA2000, WCDMA, TD-SCDMA, DECT, Bluetooth, IEEE 802.11a/b/g and WiMAX, and the standards use several frequency bands spreading in a quite crowding range such as several hundreds MHz to 6GHz with different channel widths. There are pressing needs for RF active filters with wide tuning range for use in multi-band and multi-mode wireless/mobile applications.Followings are the main contributions:First of all, A BiFET active bandpass filter with wide tuning range of 0.2GHz–3.2GHz is designed, the adjustable quality factor (Q) of 20–80 has been achieved using 0.35μm SiGe BiCMOS technology. Spurious-free-dynamic-range (SFDR) of 59 dB has been obtained at the center frequency of 2.45GHz with Q=30 for the Bluetooth application for instance. To the best knowledge of the authors, it is the first time to realize a BiFET RF active bandpass filter with Q-enhancement inductors, and this work has demonstrated the first wide tuning range active RF filter for GHz in silicon. The designed RF filter achieves the highest FOM according to the definition in [52] compared to the reported in the literature. With careful design, the proposed filter can be well-suited for multi-band and multi-mode wireless/mobile communication applications.Furthermore, this thesis addresses, for the first time, the completely stability analysis of RF active filters. The analysis approach is developed for arbitrary RF active filters. The proposed criteria can be conveniently applied to determine the stability issues of RF active filters using the S– parameters and signal flowing graphs. Three methods of stabilizing the potential unstable RF active filters are introduced. The first approach uses resistance to suppress the potential instability. Effects on noise figure (NF) has also been discussed. The second technology stabilizes the RF active filter by adding a capacitor in the input lead to prevent the oscillations. The final method employs inductance to stabilize the RF active filter. It demonstrates that the proposed stabilizing methods can improve the stability of RF active filters very well.In conclusion, future RF active filters with higher operation frequencies, higher quality factor (Q) and lower noise figure (NF) are expected to be even more challenging problems. Therefore investigations as presented in this paper will become essential during the analysis and design of such RF active filters.