Design And Implementation Of X-band High Speed Data Transmission Communicator

Microsatellites are with low cost and high functional density.They are flexible to use and easy for design.In recent years,microsatellites have been widely used in many fields such as aerospace,communication,remote sensing and microsystems.As the core component of microsatellite,spaceborne communicator is used for telemetry,telecommand,ranging,velocity measurement,and the data transmission between satellite and ground stations.The tasks on satellite largely hinge on the transmission rate of spaceborne communicator,with the increasing data transmitted by the satellite.Therefore,it is significant to design a high-speed and pint-sized spaceborne communicator with low low power consumption for microsatellites.In view of above application requirements,a spaceborne communicator,which works in X band and is integrated with Telemetry Telecommand&Control(TT&C)and high speed data transmission functions,is designed and implemented in this paper.The communicator consists of three modules:TT&C transceiver,data transmission unit(DTU)and digital processing module.The TT&C transceiver uses a heterodyne receiver with one-stage down-conversion and bandpass sub-sampling,and a two-stage up-conversion transmitter.To implement high-speed data trans-mission,the hardware link of DTU adopts the direct-modulation structure,where the modulation and up-conversion are both integrated on chip.For reliability,the LDPC(8160,7136)code,a channel coding method for high-speed digital communication,is studied and implemented ac-cording to the CCSDS standard.Furthermore,a closed-loop power control scheme based on digital attenuator and microstrip coupler is also proposed to keep the output power stable.The experiments show that,with the new power control scheme,the output power fluctuation of the data transmission link is less than 1dB when the temperature varies from-30? to +70?.The resulting product has an area of 180mmx 174mm.Its weight is about 259g and power consumption is less than 8.9W.For TT&C module,the receiver sensitivity is-112dBm,while the dynamic receiving range is more than 60dB and the transmitting power is 24dBm.The ranging and velocity measurement accuracy is less than 0.8m and 0.3cm/s,respectively.For DTU,the maximum transmission rate is 100Mbps and the EVM value of the modulated signal is less than 7.94%.Its magnitude error is less than 0.5dB and phase error is less than 3.29°.All the indicators are achieved.The experimental results show that the X-band communicator has both TT&C and high-speed data transmission capabilities,which meets the microsatellite engineering application requirements for miniaturization,low power consumption,high speed and integration.