A Monolithic SiGe Heterojunction Bipolar Transistor Gilbert Upconverter with Inductor–Capacitor Current Mirror Load and Lumped-Element Rat-Race Balun

Abstract

A 5.2 GHz upconversion Gilbert mixer with single-ended intermediate frequency (IF), local oscillator (LO), and RF ports is demonstrated using 0.35 µm SiGe heterojunction bipolar transistor (HBT) technology. The upconverter has a single-ended IF port. In addition, a lumped-element rat-race hybrid is inserted in the LO input stage to maintain balanced LO signals. The physics of the lumped-element rat-race is discussed in this paper. A passive LC current mirror is used to convert the mixer's differential outputs into a single-ended output and double the output current. The design methodology of the LC current mirror and a new approach to improve the power gain with the output buffer are developed in this paper. The fully matched Gilbert upconverter has the conversion gain of -1 dB, OP1 dB of -10 dBm and OIP3 of 6 dBm when input IF=300 MHz, LO=4.9 GHz and output RF=5.2 GHz. The LO-IF isolation is -36 dB and the LO-RF isolation is -39 dB. The supply voltage is 3.3 V, the current consumption is 11.5 mA, and the die size is 0.98×0.83 mm2 with six integrated on-chip inductors.