A very low phase-noise voltage-controlled-oscillator at X-band

An X-band VCO is designed by employing a compact tunable high-Q negative-resistance resonator. The implemented active resonator not only provides a high degree of frequency-selectivity, but also initiates and sustains the oscillations. The loaded-quality-factor of the resonator is 510. As a result, a simple and compact VCO has been designed by eliminating the need for the parallel feedback amplifier and external load coupling network. Therefore, size and DC power consumption are significantly reduced without degrading the phase-noise performance. The fabricated VCO operates at 8.2 GHz with 105 MHz tuning range. It shows a measured phase-noise of -149.5 dBc/Hz at 1 MHz frequency offset, and achieves a figure-of-merit (FOM) value of -211.7 dBc/Hz. To the best of author´s knowledge, the VCO presented in this paper achieves the lowest phase-noise and FOM compared to other planar oscillators reported to date.