A fully monolithic 5.8 GHz low phase noise coupled VCO network for phased-array systems

A fully monolithic coupled differential Voltage-Controlled-Oscillators (VCOs) network for phased-array applications is presented in this paper. The proposed integrated VCO array is implemented on a 0.25 µm BiCMOS SiGe process and is made of four LC-NMOS differential VCOs coupled through a resistive network. At 2.5 V power supply voltage and a power dissipation of 125 mW, the coupled VCO array features a measured best case phase noise of −106 dBc/Hz and −126.6 dBc/Hz at 100 kHz and 1 MHz frequency offset respectively from a 5.8 GHz carrier. Furthermore, thanks to the differential operation of the array, a continuously controlled phase shifting range from −46.6° to +49.2° and from −133.4° to +130.8° is obtained. This constant phase progression is established by detuning the end elements of the array by equal amounts but in opposite directions while maintaining a constant synchronization frequency. Hence, the proposed coupled VCO array is very attractive for use in phased-array applications.