Design And Research Of CP And LPF For PLL

The invention and development of communication technology provide more convenience for life style. Since modern times, communication technology makes communication rapidly and simplicity. Microelectronics is the foundation of scientific and technological advancement, and microelectronics technology have made considerable progress. The technology of semi-conductor is constantly developing and progressing. Nowadays, it has entered a new period of nanometer and breakthrough constantly. Wireless transceiver's cell circuit can finish in a chip most by themselves. By using this technology, electronic devices shrank tremendously and the range of applications expend every day. The PLL-based is a key component in communication front end and it is widely used in many fields, such as Digital Video Broadcasting System. Due to Charge-Pump PLL (CPPLL) is powerful at obtaining frequency. Theoretic infinity frequency traction range and zero static state phase error. Therefore, CPPLL become the popular PLL structure of nowadays. Charge Pump and Low Pass Filter play the determinative role in the performance of CPPLL. These two parts have a large impact on phase noise, reference spur and lock time. The purpose of this paper is to design high performance CP and LPF for COPLL in Digital Video Broadcasting System, and the design requirement is low consumption and small space.This paper first gives an introduction to the system constitution and the basic work principle of CPPLL, and introduces the work principle of each module. The circuit structure, work principle and main effect of CP and LPF of CPPLL are anglicized. The performance parameter of CP and Low Pass Filter, which influent the whole performance of PLL, is described in detail.The chief function of CP is to transform the digital signal, which is outputted from PFD and LPF, into analog signal. After filtering by LPF, the signal can be used as the control signal of Voltage Controlled Oscillator. This paper first gives an introduction to the work principle of CP, and compares each kind of structure of CP. Moreover, the non-ideal of CP is computed and anglicized. Regulated-Cascode structure is used to restrain mismatching of the charge and discharge currents。The simulation of circuit of CP demonstrates that output voltage is steady and voltage jumping is eliminated. Moreover, charging current equals discharging current in everywhere. The advantage of this design is simple, speed and low power consumption, which can meet the need of Specific Integrated Circuits.Low Pass Filter depending largely on the performance of PLL, it's an important part of PLL. This paper gives an introduction to the basic work principle of Low Pass Filter and compares each kind of topology. The main function of LPF is to filter the noise of the circuit,optimize the bandwidth of the circuit and supply the steady control signal for Voltage Controlled Oscillator. By anglicizing and comparing the performance of one order Low Pass Filter, Passive proportional integral Low Pass Filter,Active proportional integral Low Pass Filter and second order passive proportional Low Passive Filter, second order passive proportional Low Passive Filter is selected. The simulation to this structure demonstrates that the main working parameters meet the need of design. This circuit structure can eliminate the noise of circuit and optimized the bandwidth. Moreover, this circuit can supply the steady control signal and meet requirement of low power consumption and small space.