An integrated 1.5 V 6 GHz Q-enhanced LC CMOS filter with automatic quality factor tuning using conductance reference

We report the design of an integrated 4/sup th/-order Q-enhanced LC bandpass filter with automatic Q tuning. The filter passband is centered at 6 GHz, and has a bandwidth of 100 MHz. The filter draws 15 mA from a 1.5 V supply, achieving a 1-dB compression point dynamic range of 43 dB, while the total output noise integrated over the passband is -70.5 dBm. The Q-tuning loop uses a resonator, which replicates those in the filter, as a voltage-controlled oscillator, and a conductance reference, rather than the conventional voltage reference, to achieve better controllability. The tuning system draws 14 mA from the power supply. The whole design occupies an area of 1.5/spl times/1.5 mm/sup 2/. The chip has been fabricated in the UMC, standard CMOS, 0.18 /spl mu/m process.