A High SFDR Wide-Bandwidth Third-Order Low-Pass Elliptic Filter in 180 nm CMOS Technology

This article introduces a third-order low-pass elliptic filter implemented with a novel self-biased differential active inductor-based topology. The proposed third-order elliptic LPF is tunable over a center frequency of 0.5–1.5 GHz, which is achieved by varying <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\text {DD}}$</tex-math> </inline-formula> of the proposed active inductor, while the fine tuning (to achieve maximum passband to stopband attenuation for a center frequency) is attained by varying the cross-coupled feedback resistance <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{B}$</tex-math> </inline-formula>. The filter achieves passband-to-stopband attenuation of approximately −40 dB with a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> (quality factor) of 80 and a −3-dB bandwidth of 0.2 GHz and a total power consumption of 6.92 mW. The proposed filter occupies a minimum on-chip area of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.048~\text {mm}^{2}$</tex-math> </inline-formula> with spurious -free dynamic range (SFDR) of 80.133 dB and the best figure of merit (FOM) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.30\times 10^{-3}$</tex-math> </inline-formula> fJ when compared with other state-of-the-art implemented architectures.