Design Of Voltage-Controlled Oscillator With Wide Tuning Range, High Linearity And Low Phase Noise

Due to their easy integration, wide tuning range, high linearity and small area,etc, fully-integrated ring voltage-controlled oscillators(VCOs) have become an essential building block in many digital and communication systems. This paper mainly deals with VCO with wide tuning, high linearity range and low phase noise.After thorough analysis of the basic principles and main parameters of the VCOs, appropriate VCO's circuits structure is chosen according to their natures. Considering low cost, easy integration and other factors, ring voltage-controlled oscillators is designed by using standard CMOS process in this paper and that single-end and differential ring circuits style is studied respectively, the main achievements as follows:Firstly, to improve tuning range and linearity of the single-end VCO, a transmission-gate is introduced to the circuit. Simulation results with TSMC 0.25μm standard CMOS process by HSPICE shows that the three parameters mentioned above is: 288KHz~924MHz, 310KHz/mV, -85dBc/Hz (@600KHz in 800MHz carrier) and -104dBc/Hz(@6MHz in 800MHz carrier).Secondly, to extend the tuning range and improve the linearity of VCO, a linear controllable CMOS resistor is used as mirror tail current source of differential amplifiers, and the corresponding results are: 135MHz~4.21GHz, 1.77MHz/mV, -76dBc/Hz(@600KHz in 2GHz carrier) and -95dBc/Hz(@6MHz in 2GHz carrier). In this paper another approach to regulate the differential VCO's oscillation frequency is the dual-passage interpolation and simulation shows that the ratio of maximum to minimum frequency is 3:1.To get lower phase noise, the conventional differential amplifier is replaced by source capacitively coupled current amplifier(SC3A),which results in a better performance of -87dBc/Hz(@600KHz in 2GHz carrier) and -108dBc/Hz(@6MHz in 2GHz carrier).Finally, a solution to small oscillation swing of differential style VCO is developed in this paper, which makes it possible for VCO to output waveform swing larger than one volt in practical application.