Development Of Field Intensity Test Front End For Millimeter Wave Wireless Communication System

With the progress of society and science,modern wireless communication system puts forward higher and higher requirements for communication capacity and anti-interference capability,whose working frequency developing towards millimeter wave band gradually.As the electromagnetic environment is becoming more and more complex,the monitoring of wireless environment has gone to be an increasing important research direction.In this paper,38 GHz millimeter is applied to the field intensity test for train-to-ground system.Based on the analysis of background and significance in combination with the research status at home and abroad,it introduces in detail the related theory of field intensity front end,including the main indicators,frequency synthesis technology,especially for the PLL theory,mixer theory,etc.Under the theory guidance,it determines the system scheme is determined,goes through analysis and simulation,accomplishes modular circuit design and structure design of cavity.In the end,it tests the modular circuit and the comprehensive system index,analysis the test result,then summarizes what needs to be improved and puts forward what to do next.The field intensity front end adopts double down conversion mode to ensure the stability and reliability of the system.It is divides into four parts: down conversion part,control part,IF part and DC regulated power supply part.The DC regulated power supply part provides needed driving voltage for the other three parts.The down conversion part mainly includes PLL and mixer design,the control part configures the registers of PLL to realize the design of local frequency source.Then the local oscillator signal is mixed with the two 38 GHz RF signals received by the antenna,to gain the IF signal with the center frequency of 2250 MHz and 2550 MHz separately,goes through the processing of IF part,the output gain can be adjusted.The conversion gain of the system is about 78 dB,the gain flatness is about 3dB,and the power consumption is less than 10 W.The cavity is designed with the upper and lower embedded structure,the assembly volume is 181 mm × 90 mm × 19 mm.