Design Of A Voltage-Controlled-Oscillator For PLL

With the development of modern communication technology, more and more requires in electronic equipment are brought to voltage controlled oscillator. In classic vco , it has high consume, poor frequency stability, narrow frequency range and it is hard to integrate. This article is concerning a monilithic integrated vco circuit which has high frequency stability and wide frequency range. It can be applied in lock loop circuit and meets needs of communication equipment. This oscillator is a constant-current relaxation oscillated component. The circuit is composed of four parts: band gap module, current source module, control-voltage-input module and current control oscillator module. A zero temperature coefficient voltage reference is achieved in band gap module. The current controlled oscillator is an improved structure based on emitter coupled relaxation voltage controlled oscillator. The circuit is symmetric configuration, and this helps to decrease noise effect. With particular emphasis on this two module optimized, the output frequency of oscillator is not depended on device parameter. This helps to minimize the effect of temperature drift in frequency. Independence output frequency make the vco steady. This design is based on 1.2um CMOS C12DDR process. By using the EDA tools Analog Artist of Cadence Design Systems Inc., the vco circuit was analyzed and simulated. The simulation results show that the vco described in the thesis can achieve the main required characteristics .