The Design Of High-stability Fully-integrated 433MHz Oscillator

Oscillators are important part of many electronic systems, which are widely used in the microelectronics system circuit. LC oscillators are with large area which increase the cost of the chips, and are not easy to integrate. The output frequency of the ring oscillators varies significantly with process, power supply and temperature variations. So, to design a kind of CMOS oscillators which can realize fully integration on-chip and with a stable output has become a hot spot of research.The thesis’s main work is to design a fully-integrate oscillator based on ring oscillator with a closed-loop automatic frequency control module, and its frequency stability depends on the frequency-to-voltage converter module and the reference voltage. The thesis introduces the basic working principle and performance index of oscillators, and the overall architecture of the proposed fully-integrate oscillator are analyzed in detail. The thesis adopts a frequency-to-voltage converter with a high precision which improve the output frequency stability by adding a source follower between the charging capacitor and sampling switch and using a level shift circuit based on the negative feedback of op-amp. On the other hand, considering the influence of noise, it is necessary to reduce the sensitivity of the ring VCO, so the ring VCO in the thesis adopts a structure with switch capacitor array as its load. The proposed high-stability oscillator in the thesis reduces the use of capacitor, so it can be fully integrate in the piece.The thesis completes the design of the proposed circuit and its layout based on SMIC 0.18μm CMOS process, and the post-simulation is carried out. The results of the post-simulation shows when the power supply voltage range from 1.65V to 1.95V and the temperature changes from-20℃ to 100℃, the stability of output frequency can reach to less than 4MHz when the center frequency is 433MHz, and its phase noise is below-98dBc/Hz@1MHz, the current consumption is less than 1.6mA under 1.8V supply voltage, which meets the design requirements.