Active, self-adjusting L-S band MMIC filters

We describe the design and measured performance of active, tunable GaAs MMIC band-pass filters and matched closed-loop MMIC control circuits, both fabricated using a standard 1 /spl mu/m foundry process. Separate, 3-section filter circuits covered the 1.34-2.2 GHz and 1.84-2.7 GHz bands, with -3 dB bandwidths of 91/spl plusmn/7 MHz and 123/spl plusmn/12 MHz, respectively, and mean pass-band insertion losses of 0 dB at each tuning frequency. The control circuits generate filter tuning and Q-control bias voltages by tracking a sub-harmonic reference signal. This circuit automatically maintains the filter insertion loss to within /spl plusmn/0.5 dB over more than a 1.3:1 frequency-tuning range, and regulates the center-frequency and insertion loss to within better than /spl plusmn/1.2 MHz and /spl plusmn/0.3 dB over a temperature range of -50/spl deg/C to +75/spl deg/C.