Low phase noise VCO using broadside-coupled double spiral resonator

In this paper, a novel voltage-controlled oscillator (VCO) using the microstrip broadside-coupled double spiral resonators (BC-DSRs) is presented for reducing the phase noise. For the improvement of the phase noise, the spiral structure has been applied for the signal and ground plane at each in order to have the large coupling. Compared with the conventional VCO, the proposed VCO has the larger coupling coefficient constant, which makes a higher Q-factor, and has reduced the phase noise of the VCO. The proposed VCO with 1.8 V power supply has the phase noise of -121 ~ -117.16 dBc/Hz @ 100 kHz in the tuning range, 5.749 ~ 5.853 GHz and the figure-of-merit (FOM) of the proposed VCO is -198.45 ~ -194.77 dBc/Hz @ 100 kHz in the same tuning range, respectively.