Design And Implementation Of Signal Processing System For Millimeter Wave Field Strength Measurement

Maglev rail transportation is a new type of transportation.It has very low resistance and higher speed than traditional wheel-railway transportation for it is suspended on the track.At present,the maglev traffic test line of the Shanghai Maglev Transportation Engineering Technology Research Center at Shanghai Tongji University is currently the only high-speed maglev test line in China.Its vehicle-ground wireless communication system is based on 38 GHz millimeter waves.During "Thirteenth Five-Year Plan",the 600Km/h high-speed maglev transportation project will also use millimeter wave communication systems.Millimeter-wave communications also has some problems,such as small-scale fading,multipath propagation,large-scale fading,and path loss.These will affect the quality of communications.During the installation and maintenance of communication base stations designed in the laboratory,complex and expensive equipment such as spectrum analyzers are required to measure signal strength.In response to this situation,the system requires a portable field strength measurement system.The field strength measurement system measures the intermediate frequency of a wireless communication system.Because the communication system communicates through 38 GHz millimeter waves,it is necessary to receive signals through an antenna when measuring.The down-conversion system down-converts the millimeter wave to the intermediate frequency.Then,the signal processing system will first detect the intermediate frequency.The envelope detection circuit can accurately measure signals from DC to 6GHz.Second,the intermediate frequency signal can calculate the signal frequency through the FFT algorithm,which provides more reference indicators for system design..For the needs of field strength measurement of the millimeter wave communication system,this article designs a portable field strength measurement signal processing system.The main research contents are:1 Design and implement the detection circuit.In this thesis,use detector toenvelope detection.Use ADC chip to sample the DC signal from detector,sendthe field strength voltage to the upper computer through the ethernet module.2 Design and implement a signal processing hardware.Design a signalprocessingboard based on FPGA,and use FFT algorithm to calculate the field strength andfrequency of IF signal,and then sends the data to the host computer through the Ethernet module.The host computer program is designed to display the information sent by FPGA.