Low-power quadrature VCO design for medical implant communication service

This paper presents two different implementations of a low-power quadrature frequency source generator for medical implant communication service (MICS) applications. The first circuit uses a current-reuse VCO running at double the target frequency followed by a divide-by-two frequency divider. The circuit dissipates only 230 μW and achieves low phase noise of -127 dBc/Hz@1MHz. The second one adopts a parallel-coupling scheme to combine two current-reuse VCOs (P-QVCO). The circuit exhibits a moderate power consumption of 960 μW and achieves very low phase noise of -138 dBc/Hz@1MHz.