Reseach On Marching-on In-time Scheme And The Fast Algorithm Of Time Domain Integral Equation

Because of the vesatility of its hardware platform and flexibility of the software, SDR(Software Defined Radio) has obtained widespread concerns, and it has been and will continue to be widely used in milimatry and civilian applications.Owing to its technical matrurity and relativly simple form, the Wideband IF digital architecture is the mainly used structure in china to realize an SDR.In this structure, the perfprmance of the RF front end is crucial to the whole system, so it is very importante to research on its RF front end.This paper studied a superheterodyne receiver with two stages of mixers,which operating frequency coverage from 30 MHz to 1350 MHz,with 70 MHz IF output.The dissertation discussed the Variabling frequency channel,the frequency synthesizer and pre-selector in three chapters.Gain,Noise figure,linearity,and spurs level are the main concern in the design of the variabling frequency channel.The gain of each stage was carefully arranged to balance the demands of nosie figure and linearity,and the local oscillator frequencies also to be calculate to prevent low order mixer spur allocated in the output passband.The applied up conversion firstly and down covesion to enhance the mirror inhibition degree and make the frequency preselector can be designed easily.A single phase loked loop was applied to complish the first local osclliaor, which output range from 1930 MHz to 3250 MHz with 10 MHz steps.The second local osclliator employed PLL drived by a DDS(Direct Digital synthesizer) strategy to accomplish 1Hz resolution from 1825 MHz to 1835 MHz.And the frequency preselector was made up by seven filters and two frequency switchs.The last chapter shows the measurement results.The results decipt that all specification items were satisfied except the third order intercept and local oscillator spurs level, which beyond the specification slightly.