| UWB has become the communications industry research priorities in recent years for its high transmission rate, low power consumption and low cost. It’s expected to be the next generation of short distance wireless transmission technology. And PLL plays an important role in the development of UWB technology to provide precision clock signal.The fully integrated continuous-time analog filter uses the OTA-C structure. Compared with other types of filter, OTA-C structure has the characteristics of high frequency, convenient adjustment and excellent electric control ability which has become an important research direction of filter.Using the characteristic that OTA’s transconductance can be adjusted by an external signal, this paper proposed a new type filter employed OTA-C structure and designed a new topology PLL whose loop bandwidth can be linearly regulated. The parameters of loop filter block in the new PLL can be linearly changed according to the different frequency of output signal which ensure the best phase noise. And compared with traditional structure filter, this design of OTA-C filter has better accuracy and smaller chip area. The PLL contains four different parts including voltage controlled oscillator(VCO), phase and frequency detector(PFD), the proposed OTA-C filter and divider. The OTA-C filter is composed of four transconductance operational amplifiers and transmits stable voltage to VCO by filtering out the high frequency signal from the output phase error of PFD. Then the PLL can obtain stable frequency of output signal through the loop negative feedback mechanism.The circuit and layout design of the proposed PLL was finished by using the standard CMOS 0.18μm process. From the results of simulation, we can get that the range of output signal frequency is 3GHz~3.6GHz, the bandwidth can vary from 100 KHz to 900 KHz,the chip area is 0.63mm*0.84 mm, power consumption is 10.2mW, the power of OTA-C filter is 260μW, and the core area is 70μm * 139μm. |
