This paper presents the design and implementation of a quadrature voltage-controlled ring oscillator with the improved figure of merit (FOM) using the four single-ended inverter topology. A new topology to prevent the latch-up in single ended ring oscillators is proposed. The design is implemented in 0.18 μm CMOS technology and the measurement results show a FOM of -163.8 dBc/Hz with the phase noise of -125.8 dBc/Hz at 4 MHz offset from the carrier frequency of 3.62 GHz. It exhibits a frequency tuning range from 1.23 GHz to 4.17 GHz with coarse and fine frequency sensitivity of 1.08 MHz/mV and 120 kHz/mV, respectively.