A 1-V +31 dBm IIP3, Reconfigurable, Continuously Tunable, Power-Adjustable Active-RC LPF

Abstract

This paper proposes a biquad design methodology and presents a baseband low-pass filter for wireless and wireline applications with reconfigurable frequency response (Chebyshev/Inverse Chebyshev), selectable order (1st/3rd/5th), continuously tunable cutoff frequency (1-20 MHz), and adjustable power consumption (3-7.5 mW). A discrete capacitor array coarsely tunes the low-pass filter, and a novel continuous impedance multiplier (CIM) then finely tunes the filter. Resistive/capacitive networks select between the Chebyshev and inverse Chebyshev approximation types. Also, a new stability metric for biquads, minimum acceptable phase margin (MAPM), is presented and discussed in the context of filter compensation and passband ripple considerations. Experimental results yield an IIP3 of 31.3 dBm, a THD of -40 dB at 447 mV_{pk, diff} input signal amplitude, and a DR of 71.4 dB. The filter's tunable range covers frequencies from 1 MHz to 20 MHz. In Inverse Chebyshev mode, the filter achieves a passband group delay variation less than plusmn2.5%. The design is fabricated in 0.13 mum CMOS, occupies 1.53 mm² , and operates from a 1-V supply.