A high isolation 16–19 GHz down-conversion mixer in 0.18-μm SiGe Bi-CMOS

Abstract

This paper introduces a novel down-conversion mixer chip explicitly designed for low-orbit satellites operating in the K-band frequency range (16–19 GHz). The chip, fabricated using TSMC's 0.18-μm SiGe Bi-CMOS technology, offers a unique combination of MOS and HBT bipolar junction transistors (BJTs). The double-balanced mixer uses Marchand baluns on the RF and LO ports to convert single-ended signals to differential ones. Transformer coupling between the RF transconductance and LO switching stages ensures excellent isolation and linearity. The proposed series-parallel switching stage effectively increases the switching current at frequencies above 10 GHz and improves the conversion gain at low voltages. The measured results for the proposed mixer demonstrate a power conversion gain of 3.4–4.7 dB with a flat variation of ±0.7 dB and an input third-order intercept point (IIP3) ranging from −1.8 to 0 dBm. These results indicate the performance of the mixer in terms of power gain and linearity. The isolation of RF-to-LO, RF-to-IF, and LO-to-IF are 60, 62, and 30 dB at 19 GHz, respectively, which is crucial for preventing signal interference. The total DC power consumption for 1.1/1 V dual voltage with output buffer is 16.6 mW. The total chip size is 1.11 × 0.843 mm².