The Design Of Adaptive Frequency Synthesizer For GNSS Navigation Receiver

As COMPASS navigation system is going to be more stable, multi-mode navigation system is the trend of the future navigation system. In order to meet the requirements of multi-band and multi-mode navigation, the local oscillator of multi-mode navigation receiver is designed in this paper to provide different local oscillator signals.At first, the general method of design the frequency synthesizer as local oscillator is analyzed, the PLL type frequency synthesizer is discussed. The PLL type frequency synthesizer always contain voltage controlled oscillator, frequency divider, phase frequency detector, charge pump, and loop filter. To meet the index of locked time, spectrum purity of frequency synthesizer, the method of fractional divider is used. In order to reduce the spur caused by fractional divider, the Sigma Delta modulator is employed. The theory and method of Sigma Delta modulator is investigated. Second, the MATLAB is used to model the frequency synthesizer with the transfer function and analyze the loop performance. Third, the VERILOG-A is used to model the blocks of frequency synthesizer on behavioral level, and the system parameter is translated into the circuit parameter. Finally, the circuit is designed with SMIC0.18um MIXED/RF process, and some self-adaptive method is proposed. The different blocks are laid out, and the post-simulation is carried out. The simulation results show that the reference frequency of the synthesizer is16.368MHz, the locked time is less than20us, the area of the layout is1071umX1176um。...