A 3.9-8.2-GHz Wideband Frequency Synthesizer With an Inductive Multiplexing Output Network for SATCOM Applications

Abstract

This brief presents a wideband frequency synthesizer with 3.9 to 8.2 GHz continuous frequency coverage for satellite communication applications. The core fractional-N phase locked loop utilizes four LC-VCOs achieving a 4.3 GHz tuning range with a 50-MHz reference frequency. The frequency mapping of the four VCOs, along with module-level parameter optimization, is performed to maintain a stable figure of merit and minimize loop jitter across the entire tuning range. A high-isolation low-loss inductive multiplexing output technique is proposed, which uses only one active buffer to drive both the internal loop and the external load, significantly reducing power consumption. Moreover, an on-chip active loop filter is implemented, reducing the capacitance area by 80% and enhancing chip integration. Fabricated in a 65-nm CMOS technology, the frequency synthesizer occupies a chip area of 2.28 mm2 while consumes power of 25–33.5 mW. The phase noise reaches –123.72 dBc/Hz and –116.31 dBc/Hz at 1-MHz offset under 3.9- and 8.2-GHz carriers, respectively. Measured reference and fractional spurs remain below –65 and –55 dBc.