Active bandpass filter using transformer feedback in 0.18-μm CMOS for 802.11a wireless LAN

An active bandpass filter topology with transformer- feedback g-enhancement technique in 0.18 mum CMOS technology is presented for IEEE 802.11a Wireless LAN applications. The novel transformer-feedback Q-enhancement technique utilizes the turns ratio of the primary coil and the secondary coil of the transformer for efficient loss compensation. The active bandpass filter is designed, simulated and laid out in a 0.18 mum CMOS process to illustrate the concept. The simulated results show that the center frequency of the active bandpass filter is 5.2 GHz and a bandwidth of 93 MHz. A 35-dB attenuation at 100 MHz away from the center frequency is achieved. The simulated input 1 dB compression point (P1dB) and noise figure are -6 dBm and 16.8 dB at center frequency, respectively. While showing a minimum gain of 1.5 dB of the entire passband, the active bandpass filter consumes 12.2 mA from a 1 V supply voltage.