A High-Speed Rf Analog Direct Sequence Spread Spectrum Method And Its Implementation

Multi-antenna receiver technology not only improves the channel capacity and spectral efficiency,but also brings challenges such as increased complexity and excessive power consumption.As the scale of multichannel communication system increases,miniaturization and low energy consumption demand become more and more important.Switching amplifier Analog direct sequence spread spectrum technology can realize highspeed spread spectrum in RF domain,combine multiple signals into one channel,and effectively reduce circuit area and power consumption by sharing RF,IF module and analog-to-digital converter(ADC),so it has attracted much attention.Based on the principle of direct sequence spread spectrum(DSSS),a S-band high-speed analog direct spread amplifier with switching amplifier as the main structure is studied and realized.By controlling the cutoff and saturation depth of the amplifier,the purpose of switching switch can be achieved quickly,so as to improve the spread rate.The high-speed analog spectrum expander can be further integrated.Thesis firstly introduces the background and significance of RF spread spectrum,analyzes the development status of analog spread spectrum and artificial transmission line,points out the advantages of switching amplifier analog spread spectrum mode compared with other spread spectrum mode in RF domain,and makes a preliminary selection for RF analog direct expansion device.Then,the principle of DSSS is studied,the hardware circuits of digital and analog spread spectrum are introduced,and the applicability of several spread spectrum implementation methods in multi-antenna receivers is analyzed.It is pointed out that the realization of the spread spectrum receiver which samples the RF signal directly is difficult,and the analog direct expansion method of switching amplifier is more realizable.Then,two analysis methods for artificial transmission lines are studied: infinite and finite period structures.The method of extracting equivalent media parameters is introduced.It is pointed out that the scattering parameter inversion algorithm is not suitable for extracting the characteristic impedance of artificial transmission lines whose electrical length is 180° due to the existence of thickness resonance.The equivalent lumped circuit method should be adopted.Then,thesis introduces the low noise amplifier(LNA)and the power divider which make up the circuit of switching amplifier analog spread spectrum,studies the gain and noise index of LNA,and introduces the design formula of Wilkinson power divider.Based on the research on the theory of switching amplifier analog spread spectrum,thesis designs the LNA and Wilkinson power divider based on Advanced Design system (ADS)according to the design index.The artificial transmission line is designed based on High Frequency Structure Simulator(HFSS).By tuning and optimizing the circuit parameters,the circuit performance is verified to meet the requirements.Finally,on the basis of simulation,the real object of switching amplifier analog spectrum expander is made,the test platform is built,and the circuit is adjusted and optimized.The final test results show that the combining gain is larger than 6d B,switching time of switching amplifier is 0.925 ns,switching phase difference is168°～ 174°,and a DSSS signal whose spread spectrum rate is 100 MBaud is generated.It meets the requirements of the design index,has a high switching speed.