A 250-GHz Wideband Direct-Conversion CMOS Receiver Adopting Baseband Equalized Low-Loss Resistive Passive Mixer

Abstract

This brief proposes a 250 GHz wideband mixer-first and direct-conversion RX adopting a baseband (BB) equalized single-balanced resistive mixer. The conventional resistive mixer suffers from the trade-off between gain and bandwidth, which hinders the wideband and low-loss mixer implementation. To address this challenge, the proposed RX employs the BB equalization technique that compensates for the narrowband response of the low-loss mixer by cascading it with the deliberately shaped response of the following BB amplifier, thereby achieving low-loss yet wideband characteristics of the overall receiver chain. Moreover, the conversion gain and the noise figure of the single-balanced mixer are further improved by adopting a lambda/4 open stub that suppresses the undesired LO leakage. Implemented in a 65 nm CMOS, the proposed RX achieves an effective 3-dB bandwidth of 26 GHz while dissipating a total dc power of 132 mW. Based on the calculated signal to noise-and-distortion ratio (SNDR), the proposed RX is expected to support a 16QAM demodulation with a data rate higher than 100 Gbps, in principle.