Synthesis of High-Order Continuously Tunable Low-Pass Active-R Filters

This work discusses the synthesis and design methodology of high-order and frequency-tunable low-pass active-R filter architectures for multi-standard wireless applications. Active-R filters use the inherent integrator-like behavior of amplifiers to realize their frequency response. The main advantages of this type of filter are high-frequency performance and a low integrated area. Active-R filters only need the Miller capacitor used in internally compensated amplifiers. In this work, amplifiers with configurable unity-gain frequencies enable the continuous tuning of active-R filters. Three different filter architectures realize a fifth-order Butterworth prototype tunable in the 1-50 MHz frequency range. These filters are designed, fabricated, and tested using the TSMC 0.18 mu m process. Each fifth-order filter consumes power in the range 7.45 mW to 9.38 mW from a 1.8 V supply and has an integrated area <= 0.33 mm(2). Compared with state-of-the-art active filters, the filters presented in this work have the largest tuning range without linearity degradation and the smallest area per tuning range ratio. Also, the measured filters show a competitive FoM 153.3 dB/J when operating at high frequencies.

Automated summary

This work discusses the synthesis and design methodology of high-order and frequency-tunable low-pass active-R filter architectures for multi-standard wireless applications. The filters presented in this work have the largest tuning range without linearity degradation and the smallest area per tuning range ratio, with competitive FoM when operating at high frequencies.