Research And Design Of Two-point Modulation Voltage Controlled Oscillation For AIS MOB

In recent years,the information technology has developed rapidly,with all kinds of new products applied to every aspect of the life-living.As one of the most fast-growing technology,Automatic Identification System?AIS?shows its typical strength in sea voyages and SAR.The AIS Man Overboard?AIS MOB?and Relaying-Floats,a new-type maritime emergency locator device,which widely used for searching and rescuing accident personnel at sea,have bringing the huge revolutionary to the industry.AIS MOB can send global positioning coordinates and UTC time information through the form of automatic broadcasting,so as to make the rescue force equipped with AIS receiving equipment receive timely,and improve the accuracy of search and rescue.AIS MOB uses PLL two-point modulation based GMSK modulation to spread the information.VCO gained the increasingly attention on its property as the key parts.The VCO of past devices are usually combined with separate components,the performance is poor and the process is complex.However,the development of CMOS IC provided the strong technical support on the revolution of integrated oscillator,following a vast market with simplified production process.In this paper,the AIS technology is introduced briefly,including the concept of AIS system and the principle of AIS MOB.The GMSK modulation method based on PLL two-point modulation implemented is analyzed in AIS MOB.On the basis of this,the technical parameters of the voltage controlled oscillation integrated circuit of PLL two-point modulation are determined in AIS MOB.Based on the detailed analysis of the principle of the oscillator and its two typical circuit structures,the design of the two-point modulation voltage controlled oscillation integrated circuit is accomplished by using the ring structure.The two-point modulation VCO is composed of four part delay unit.The difference delay unit uses the structure of the voltage control transistor and the cross-coupling transistor in parallel,and the access of two control voltage is realized through two sets of voltage control transistor.In addition,this paper analyzes and designs the band gap reference circuit,mirror current source circuit and other auxiliary circuits to improve the circuit performance.This paper uses the Empyrean integrated circuit design software Aether,based on standard of CSMC 0.35?m,a two-point modulation VCO simulation was completed.Simulation results shows,when the fine control pin V_ctrl input voltage is1V,the coarse control pin's voltage in the range of 0-3.3V,the frequency range of the output signal is 255MHZ-393MHZ,the center frequency is 324MHZ.When the coarse control pin is 2.2V,the fine control pin input voltage is 1V and 3V,corresponding to the output of 323.95 MHz and 324.05 MHz two fixed frequency.The effect of phase noise on the output signal is observed through the“eye diagram”.The results show that the output waveform of VCO has a good noise performance.Finally,this paper completes the layout design of the two-point modulation VCO,extracting parasitic parameters and doing post simulation test.This paper's two-point modulation VCO achieves the design goal.