Modelling And Synthesis Of Test Signal For Spaceborne DBF Spread Spectrum Receiver

During the design and debugging states of a satellite-based DBF,it is necessary to simulate the practical input signal of a receiver in order to test its function and performance.And the match of the composite testing signal and the practical receiving signal is the key point to guarantee the accuracy and effectiveness.In reality,the input signal of a working receiver is transmitted from the ground and travels a long distance before its arrival.During the transmission,signal experiences a series of complex changes because of Doppler Effect,Near-far Effect,noise,ionospheric delay,tropospheric delay,etc.Apart from that,the DBF receiver adopts array antenna for signal receiving,therefore,the input signal for testing should be multichannel array signal.Based on the test of a satellite-based spread-spectrum DBF receiver,this paper studies how to model the testing signal for the receiver and to synthetizes the testing signal.And the major technique problems are listed as follows.(1)The mathematic model for testing signal.It means mathematically analyzing and modeling received signal when the receiver is working.It includes the structure analysis of transmitting signal,the mathematical analysis of the influence of transmission channel and the mathematical analysis and modeling for the final received signal.A good mathematic model is the precondition for accurate testing signal synthesis,thus,it is one of the major problems studied in this paper.(2)The design of synthesis method for testing signal.Based on the mathematic model,there are a few methods to synthe tize the testing signal.However,the accuracy,calculation complexity and cost vary among different methods.Therefore,it is another major problem to design sensible synthesis method for testing signal according to the characteristics of DBF receivers.(3)The design and realization of synthesis system for testing signal.Satellite-based receivers adopt array antenna to receive multiple uplink signals from a ground transmitter.Hence,it is more difficult to realize the synthesis of testing signal for DBF receiver than that for single transmitter and receiving antenna.However,realizing the synthesis of testing signal requires a synthesis system with sensible algorithm,which is also a major problem in this paper.To solve the above problems,this paper analyzes the influence of different factors during the signal transmission,establishes the mathematic model for conditions with different number of transmitters and different receiving antennas;designs a signal synthesis method based on pulse montage technique and direct digital synthesis technique.And the author also constructed the real physical system of signal synthesis.By using testing methods of DBF receivers,this paper proves the accuracy of the model for testing signal and the feasibility and effectiveness of the synthesis algorithm.