МЕТОДИКА ПРОЕКТИРОВАНИЯ КМОП-ГЕНЕРАТОРОВ, УПРАВЛЯЕМЫХ НАПРЯЖЕНИЕМ, С ПЕРЕКРЕСТНЫМИ ОБРАТНЫМИ СВЯЗЯМИ И МАЛЫМ ЗНАЧЕНИЕМ УРОВНЯ ФАЗОВОГО ШУМА

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The CMOS LC cross-coupled voltage-controlled oscillators (VCO) design technique is presented. The technique is based on a set of steps to reduce phase noise during small-signal and nonlinear analysis. The technique consists of three interrelated stages and enables efficient optimization of the VCO's electrical circuit parameters to achieve low phase noise for a given output frequency range, control voltage range, and supply voltage. At the first stage, a preliminary calculation of the tank circuit is carried out. The basic approaches to reducing phase noise implemented at this stage consist of increasing the unloaded quality factor of the tank circuit, reducing the slope of the voltage-to-frequency tuning characteristic, and increasing the permissible RF power across the tank circuit. At the second stage, small-signal analysis is used to evaluate and ensure start-up oscillation conditions. At the third stage, a nonlinear analysis of the VCO is carried out in the frequency domain. The task of ensuring low phase noise, solved at this stage, comes down to finding the optimal parameters of the VCO's electrical circuit, which, on the one hand, ensure a sufficiently high RF power across the tank circuit and an acceptably low slope of the voltage-to-frequency tuning characteristic, and, on the other hand, ensure low values of the noise parameters of the MOSFETs. Using the proposed technique, a set of CMOS cross-coupled VCO's with operating frequencies of up to 3 GHz and a phase noise level of about -90 dBc/Hz at 100 kHz offset from the carrier frequency was developed.