Design And Implementation Of Micro Multi-Frequency Point Ka-Band TT&C Transponder

Micro-satellite have features of low cost and short development cycle and will become the new trend in satellite development.The rapid economic growth makes Micro-satellite have a multi-tasking and functional flexibility requirements.Multi-frequency configuration is the first choice to solve multi-task.The small satellites successfully launched in China mostly work in the S/X frequency band,which is not suitable for the deep space exploration,and it is very important to study TT &C transponder in the high frequency range under the limited frequency resources.The design scheme of the S-Ka topological type TT&C transponder is proposed based on the research for the design of the existing transponder.The reception and transmission links are designed and realized based on super heterodyne principle and multi-step frequency conversion method,respectively.The receiver is a two-stage down-conversion structure,and the transmitter is a three-stage up-conversion structure.First of all,the matching of selection parts and parameter after determining the link structure of Ka-band transponder are implemented in this dissertation.Meanwhile the link budget can be determined.In addition,the reception link achieves a dynamic range of 60 d Bm,and the output power in transmission link can be larger than 10 d Bm.The shortage of power is compensated by the software part.Second,the software depended on frequency can be adjustable through the method of remote control and program-controlled.During the process of configuration,while keeping the frequency of the baseband PLL unchanged,the configuration word of the front-end PLL is changed to achieve a 2GHz frequency band within the frequency range and the step is 1MHz.The frequency offset due to the frequency resolution of the PLL is compensated by software.Then,the transponder software is realized through the control of the closed-loop power.The output power does not fluctuate with the changes of ambient temperature.Finally,the baseband algorithm of the original X-band TT&C transponder is inherited and improved to realize carriertracking loop in the digital domain.And the configuration of multi-frequency software and closed-loop power control can also be achieve.Under the laboratory environment,the link hardware will be test.The results show that the design of the Ka-band transponder achieve the target needs.The received signals adjust with 1MHz step in the range of 29 GHz ~ 31 GHz,and the emission signals adjust with 1MHz step in the range of 19 GHz ~ 21 GHz.There is no interference between the emission and received signals.The sensitivity of receiver can reach-112 d Bm with the dynamic range of 60 d B.We choose three frequency point(19GHz,20 GHz,20.999GHz)to have a test,which show that the maximum spurious of the emission signals in the 100 MHz bandwidth can reach-50 d Bm and the phase noise is better than-85 d Bc@10k H.In addition,the output power maintained over 10 d Bm to satisfy the performance.The total power consumption of the TT&C transponder is less than 12 W.