Design And Research Of LC Voltage Controlled Oscillator And Its Prescaler

Due to its characteristics of low power consumption、low cost、distributed andself-organization，Wireless sensor network is widely used in many fields such as，smarthome，and it usually contains a large number of sensor nodes. These nodes are oftenpowered by batteries，so the design of system on chip must have lower cost and lowerpower consumption. With the micromation of wireless sensor network nodes，the chip willalso have higher integration.In recent years，along with the decrease of feature size，transistor density、device speedand signal processed capacity are gradually improved. While the rapid development ofwireless communication system，it will also contribute to research and develop low costand low power CMOS transceivers. In wireless communication，local oscillation is usuallyrequired to achieve frequency conversion and channel selection. As the core circuits oflocal oscillation，the power and the phase noise of voltage controlled oscillator andprescaler will directly affect the performance of the transceiver system!The purpose of this paper is to achieve the fully integrated LC voltage controlledoscillator and prescaler with low power and low phase noise based on CMOS process.They are used to IEEE802.15.4C standard applied780（China）/868（Europe）MHzwireless transceiver. The SOC is still in development stage at home for the band. As one ofthe core SOCs of wireless sensor network，it is of great significance to the research anddevelopment for the domestic Internet of things.780/868MHz voltage controlled oscillator and prescaler with low power consumptionand low phase noise are both implemented in this paper. Main Content and innovationinclude：1、The operation principles and structures of the negative resistance LC VCO areresearched，the structure and characteristics of passive components On-chip—integratedinductor and integrated variable varactor are focused on，then how to design a low KvcoVCO is discussed to improve its phase noise.2、The structure and operation principles of D flip-flops are researched in orthogonaldivide-by-2frequency divider，including design principles，finally the power consumptionof VCO is decreased by using the current reuse technique.3、the operation principles and design points of TSPC DFF is researched，finally thelow power consumption of4/5dual modulus prescaler is designed based on TSPC.4、Based on SMIC0.18μm1P6M CMOS process，the LC voltage controlled oscillatorand a4/5dual modulus prescaler are both implemented at a given1.80V DC supply voltage. The tests show：the tuning range780/868MHz LC VCO is from748to946MHz，the total power consumption is4.5mW. And the phase noise of the LC VCO are separatelyin the typical frequencys：fC1is849.73MHz，Pnoise is-99.02dBc/Hz@1MHz offset；fC2is784.03MHz，Pnoise is-104.32dBc/Hz@1MHz offset. The prescaler can achieve to dividewell the correct frequency in the PLL.