The Research On Digital Reception Based On DSSS In Intermediate-Frequency

The direction of SS technology will be high processing gain and high-speed data transport in wireless communication domain. Digital processing will play a good role in SS communication field.Firstly, this thesis introduces the characteristics of the SS communication system and the development related to SS technology at present in the world. It also introduces the outline of the thesis. The ways based on the PN sequence's self-correlation and co-correlation to synchronize are compared. Digital matched filter (DMF) is chose because it can greatly reduce the time of acquisition. The total system can be divided into two parts, i.e., transmitter and receiver unit. The transmitter unit mainly consisted of differential encoding, spread spectrum and BPSK modulation and so on.The receiver unit mainly consisted of the digital down converter, matched filter, integration and dump module, power detector, symbol tracking processor, differential demodulator and so on. After the character between the radio frequency (RF) sampling receiver and theintermediate frequency (IF) sampling receiver is compared, the later is selected.Then the scheme of digital recept in DSSS is proposed. The baseband design is based on modularization and different functional circuit is implemented in different module. The whole system is simulated in Simulink and the result is desirable.Finally, this thesis suggests that AD6620 can be applied for SS signal down-conversation and PN un-spreading. When processing the digitization and integration of circuit behind, the CPLD is used to realize the function of logic circuit.