An active triple band-notched filter with improved Q-factor for UWB system

In this paper, an active triple band-notched filter with improved quality factor (Q-factor) in 0.18-μm CMOS technology are presented. Due to the FCC´s stringent power-emission limitation at the transmitter, the received signal power in the UWB system is smaller than those in IEEE 802.11 a/b/g wireless local area network (WLAN), and the worldwide interoperability for microwave access (WiMAX). To avoid the interferences such as the WLAN and WiMAX signals in the UWB passband simultaneously, the proposed band-notched filter can be adopted to eliminate these interferences. Two techniques are introduced to enhance the ability of outband rejection. A cascode-grounded active inductor circuit topology is employed, which is composed of a feedback resistor to improve the quality factor (Q-factor) of the active band-notched filter. With an extra parallel capacitor, the rejection of notch band also is improved obviously. The measured 23/24/31 dB maximum rejections at 2.4/3.5/4.9 GHz while consuming a dc power of 13.5 mW at 1.8-V power supply.