A Tunable SiGe BiCMOS Quadrature LO Source with 31% Tuning Range for L, C and X-band Space-borne Remote Sensing

This paper presents a SiGe BiCMOS tunable quadrature (IQ) local oscillator (LO) source used in multichannel receiver (RX) front-ends for L, C and X-band space applications. The LO is based on a single X-band voltagecontrolled oscillator (VCO) and programmable frequency divider (FD) chain. The VCO implements a common-collector Colpitts topology with a transformer load and butter chain to isolate the VCO tank circuit from the FD. The FD comprises one divide-by2/3 and two divide-by-2 flip-flop based stages enabling division ratios up to 12 to support C and L-band. The circuit provides IQ differential signals in 1. 05-1.9GHz, 4.3-5.9 GHz and 8.6-11.8 GHz range derived from a single 10.2 GHz VCO with 31% tuning range and -99.7dBc/Hz worst case phase noise at lMHz offset from the carrier.