Design And Implementation Of Portable Digital Data Transmission Earth Equipment

In micro-satellite communication system,with the increase of satellite payload,the amount of data needed to be transmitted by satellite is increasing.The requirement of transmission rate and reliability of satellite-to-earth data transmission system is getting higher and higher.As the earth receiving device of satellite-to-earth data transmission system,the data transmission earth equipment undertakes a series of tasks such as receiving,demodulating,processing and forwarding of satellite data transmission signals,so it is an important part of satellite communication system.At the same time,the traditional earth equipment has many problems,such as large size,low integration,complex operation,not convenient to carry and so on.Therefore,with the development of microelectronics technology and the improvement of industrial manufacturing level,the miniaturization and integration of earth equipment and efficient data processing will become the hottest research topics in the satellite field.Aiming at the development demand of data transmission earth equipment at present,combined with the data transmission system of on-board transponder of project group,this paper will design and implement a portable data transmission earth equipment,which has small size,light weight,is flexible in use and convenient to carry.The device integrates RF receiver,digital baseband processing,data processing and other functions.It can realize downconversion of satellite RF signal,demodulation and decoding of digital baseband signal,data forwarding to PC,data processing and so on.The hardware module of the whole machine is mainly composed of two modules,the integrated module of RF and baseband and the STM32 communication module.Two modules are installed in the customized aluminum alloy shell with the size of 18cm×16cm×6cm.The integrated module of RF and baseband has integrated the superheterodyne RF receiver module and the digital baseband processing module.QPSK demodulation,symbol synchronization and RS decoding are implemented in the FPGA.And STM32 communication module realized UART,SPI and Ethernet communication interfaces based on real-time operating system ?C/OS-II.This module completes transmission communication of the equipment configuration instructions and digital data between earth equipment and PC terminal,and meets the real-time requirement of data transmission.After testing and analysis,the sensitivity of the RF receiver module of portable data transmission earth equipment is-100 dBm,the dynamic range is 60 dB.The data receiving code rate can be dynamically configured under the control of PC,which can be up to 1.5 Mbps.And the digital baseband processing can realize demodulation and decoding.The bit error rate is less than 1×10-6.Ethernet communication meets the real-time requirement of data transmission.The test results show that the device can better complete the earth receiving task of satellite-to-earth data transmission system,and has the characteristics of miniaturization and convenience.