A power/area-starved complementary-cross-coupled filter for integrated transmission line ΣΔ modulators

In this paper, an approach for decreasing the area and power consumption of an integrated transmission line sigma delta modulator (ITLSDM) is presented. The architecture is based on complementary-cross-coupled bandpass filter (C-BPF) with an auxiliary negative transconductance (ANG). A closed form formula is derived to specify the characteristics compared to a SDM based on NPN cross-coupled bandpass filters (N-BPFs). The matching requirements for the loop transmission lines are relaxed by using C-BPFs. The simulation results for a 4^th order BP-ITLSDM realized in a 0.25um BiCMOS technology show a reduction of 53% in the current consumption and 46% in the die area of a resonator compared to the N-BPF method. The improvement factor is more obvious for higher order BPSDMs.