A Darlington SiGe microwave monolithic integrated circuit

This paper presents a low noise Darlington SiGe microwave monolithic integrated circuit (MMIC). The circuit consisting of two SiGe hetero-junction bipolar transistors and four resistors is convenient to cascade without any other matching circuit. It is fabricated in a quasi-self-aligned process, with a nonselectively grown epitaxial SiGe base. The small resistor R4 is critical to smooth the gain band, lower the input and output voltage-static-wave ratio (VSWR) in a broad band, so it is made differently from the other three. The measurement results give the cutoff frequencies of SiGe HBTs 10.9 GHz and 9.2 GHz respectively. At 1 GHz, the noise figure of the circuit is 1.59 dB, the power gain is 16.1 dB, the input and output VSWR is 1.6 and 2.0.