The Design Of 0.2GHz-3.26GHz Interleaved Feedforward Voltage-controlled Oscillator Based On 0.18μm CMOS Technology

As a key component of Phase-locked loop, Clock and Data Recovery, VCO is widely used in many fields such as clock generator, Serdes for high speed serial communication .etc. In traditional CMOS technique, multi-gigahertz VCO applied LC tank structure which require more strict with manufacturing process, simultaneously, the die size of LC tank increases substantially. Thus, the cost of chip is raised dramtically.Therefore, it's very important to study the novel high frequency VCO in CMOS logic technology.In this paper, a high frequency, wide range and high linearity interleaved feedforward ring type VCO based on 0.18μm CMOS logic technology is proposed, the main contents as following:1. In this paper, it briefly introduces the basic principle and structure of ring type VCO, in addition, it also makes a research on its adjustable frequency range, working frequency, linearity and phase noise which combined with the mathematical model and the main performance parameters of the VCO.2. According to the performance requirements of VCO, an interleaved feedforward structure of ring type VCO is put forward, the structure can overcome such disadvantages as extensive area and accurate technique of high frequency VCO based on LC tank structure, which reduces chip size extensively, and cut down the cost effectively. What's more, it has such feature as a high working frequency, wide range and high linearity performance.3. It goes deep into the frequency characteristic of Interleaved Feedforward VCO. It penetrates into the problems, including the configurable features of the main loop and the fast loop, the impact of transmision gate on the oscillation frequency, as well as linearity and the initial voltage issues, through the VCO's frequency equation, for instance, those aspects are simulated and verified, and finally come up with the most suitable circuit structure and parameters.4. The layout of the proposed VCO has been done, and layout art for high performance analog circuit such as matching, guard ring has been applied. Consequently, the area is not only saved, the parasitic effect on the performance of VCO is but also reduced.5. The interleaved feedforward VCO has been implemented in 0.18μm CMOS logic technology. The post layout simulation results show that the center frequency of the VCO is 1.92GHz, the range of frequency is 200MHz～3.26GHz, the measured phase noise is -95.1dBc/Hz from a 3.125GHz frequency, the maximum power consumption is 8mW, which can meet the performance requirements of VCO design predefined.