Research On Synchronization Algorithm Of BOC Modulated Signal And Its FPGA Implementation

Binary offset carrier modulation is a type of new modulation method whose main point is to pre-modulate non-modulated spread spectrum base-band signal with square wave to incur energy spectrum splitting so that the new signal's spectrum could be isolated from the original one.Due to its great potential in high-precision code tracking and multi-path interference elimination ability,BOC has been widely applied in military M code and Galileo satellite navigation system.Synchronization technology of BOC-modulated signal is deeply studied in the paper.And after a detailed introduction of BOC modulation principal,a viable signal generating method is presented and spectrum characteristic and self-correlation function characteristic of BOC modulation are analyzed. Considering features of BOC modulation code,SSB rapid acquisition method is adopted to de-spread the spread frequency code.And the scheme diagram is given according to which simulation experiment is conducted to verify the method's acquisition performance.Given the complexity of BOC-modulated signal tracking, a kind of unambiguous ASPECT algorithm is set forth to track BOC modulation code.And simulation work is done to observe the error characteristic of the ASPECT-based discriminator and the code-tracking precision.Costas loop is chosen to track the carrier phase.And math model of the loop is established to analyze its tracking performance.FPGA chip is taken as the hardware platform for BOC modulation signal synchronization algorithm and the signal processing module is composed of BOC modulated signal generator,code acquisition circuit,code tracking loop and carrier phase tracking circuit.Spectrum analyzer is applied to observe the output signal's spectrum with which the comparison of theory spectrum shows that the signal generator proposed in the paper is viable.On the basis of these,the synchronization process of the algorithm put forward in this paper is simulated and the results show that the acquisition-tracking circuit designed in the paper could realize signal synchronous processing and yield sound performance.