Design And Implementation Of UWB Signal Sampling System For Electronic Reconnaissance

Wireless receiver is the key unit of signal receiving in electronic reconnaissance,communication equipment,radar,telemetry and remote sensing system.The traditional wireless receiver uses mixer and local oscillator to convert the RF input signal to intermediate frequency,that is,superheterodyne structure.However,the circuit design of the structure is complex,and the requirements of local frequency source are high.There are still some problems such as picture frequency,combination frequency,intermediate frequency interference and so on.Another kind of system structure which uses high bandwidth analog-to-digital converter to realize RF direct sampling can solve the above problems,but it also puts forward strict requirements for the performance of analog-to-digital converter,especially the analog bandwidth index.Considering the problems above and the current level of analog-to-digital converter technology,this paper designs a new structure of wireless receiver,which uses wideband sample and hold circuit with analog-to-digital converter to realize RF direct sampling.The structure uses high bandwidth sample and hold circuit to realize the direct reception of RF signal,modulates the RF signal into the receiving bandwidth of analog-to-digital converter,reduces the requirement of high bandwidth of back-end analog-to-digital converter,and finally realizes the conversion of analog signal to digital signal.Starting from the development background of the wideband receiver,this paper studies the architecture type and working principle of the ultra wideband signal sampling system,develops the design of the ultra wideband signal sampling system,and finally completes the system test and verification.The system realizes the sampling bandwidth of 12 GHz,and the spurious free dynamic range(SFDR)is greater than 36 dB.This paper mainly conducts technical research from the following three aspects:1.Study the UWB sampling technology,use the wideband sample and hold circuit to complete the tracking and holding of the input signal,and keep the output signal value at the relatively constant sampling time,use the precise control timing to ensure that the analog-to-digital converter samples the signal value correctly.At the same time,the technology and architecture of the wideband sample and hold circuit are designed,and the input signal buffer circuit,sample and hold circuit core,output signal buffer circuit and sample clock buffer circuit are designed2.Study the design technology of RF signal transmission chain.When working in RF section,package,microstrip line,vias and connectors will bring parasitic effect and loss.Therefore,the whole link should be modeled and simulated during the design.According to the design requirements of RF circuit and simulation results,the PCB material selection,transmission line design and power supply integrity design should be completed to ensure the system's signal integrity.3.Study the design technology of single board integration and impedance matching of each module.In the design of specific circuit,when the various modules of the circuit are combined together,the layout and wiring shall be reasonably designed in strict accordance with the requirements of signal integrity,and the overall circuit modeling and simulation shall be carried out.Through simulation,the matching resistance between each module shall be accurately designed to ensure the normal function of the system.