RF CMOS active inductor band pass filter with post fabrication calibration

Abstract

This paper presents an active inductor bandpass filter (BPF) architecture with selectable 50Ω driving capability and post fabrication calibration for gain, center frequency, and quality factor. The design details, and performance assessment that facilitate selecting an offline calibration mode to measure and tune post fabrication BPF performance are discussed. A specific design example for a L1/L2 channel GPS receiver is included with a BPF that is required to pass the L2 signal centered at 1.227GHz with a gain of approximately16dB at the center frequency, have a 3dB bandwidth of 30MHz (Q=41) and rejection of the L1 signal at 1.575GHz by at least 60dB relative to the center frequency. A multistage active inductor BPF 90nm CMOS design is presented that meets these specifications with typical process parameters. It is demonstrated that the post fabrication design based on typical corner analysis can be re-tuned to the desired performance for process variations across the slow and fast corners using the offline measuring and tuning control inputs.