The circuit analyses of four elemental building blocks for a quadrature signal generator are provided. From these block analyses, a set of equations forming a closed-loop relation in node voltages is obtained. This equation set represents a cross-coupled system that will oscillate in quadrature. By reconfiguring these building blocks, a novel integrated quadrature voltage-controlled oscillator (QVCO) utilizing two trifilar transformers can be constructed for the low-voltage / low-power operation. A 7-GHz QVCO based on this proposed configuration is successfully demonstrated in this paper. This oscillator core dissipates only 2.2 mW from a 1-V supply. The measured phase noise at 1-MHz and 10-MHz offset from the center frequency are around -111 dBc/Hz and -132 dBc/Hz, respectively, over the whole tuning range of 260 MHz.