Design Of Modem Based On Diversity Technology

With the development of science and technology,wireless technology is at a stage of rapid development,and has been widely used in various fields.In order to cope with the complex environment,various modulation and demodulation technologies emerge in endlessly.This article is mainly to design a modem based on diversity technology for scatter communication.As an important means of wireless transmission,scattered communication has been widely used in military defense science and technology in recent years due to its unique advantages.Scattering channel can be approximated to a Rayleigh fading channel,and its link loss is also a probability density function,which has randomness.Multipath fading and fast fading will all cause misjudgment of signals at the receiving end.Diversity technology is a commonly used technology in scattering communication,which can provide a certain anti-fading capability for the system,smooth the influence of fast fading on the system,and improve the performance of the system.Diversity technology uses the idea of decentralized transmission to "replicate" multiple copies of the same signal for retransmission,reducing the impact of fading on communications through the uncorrelated nature of the signal fading at the receiving end in frequency,time or space.In order to realize the normal application of diversity technology in communication,the first thing to be solved is the "division" and "set" of signals.Firstly,this paper introduces the basic classification of diversity technology and related diversity combining methods.Through theoretical analysis,the advantages and disadvantages of various diversity methods are elaborated in detail.Secondly,combined with the selected diversity method,design a suitable frame structure,and then design the modulator of this subject.Through the research and analysis of various algorithms in the modulator,the complete modulator design process is given Third,through the design of the modulator,a demodulator design scheme based on diversity combining is proposed,and the corresponding theoretical analysis,software simulation and FPGA algorithm design are performed for each module.Finally,the system is tested for the normalized signal-to-noise ratio through the baseband direct connection,and the performance analysis of the bit error performance in various rate modesThe results of the performance test show that:The diversity combining gain of the modem based on diversity technology designed in this paper accords with the design index,and the test result of normalized signal-to-noise ratio is basically consistent with the theoretical calculation result,which can meet the needs of system performance.