Development Of Multi-Mode Telemetry Transmitter Based On Zero-IF

The wireless telemetry and remote-control system is an indispensable part of the aero spacecraft.The transmitter collects parameters,such as environmental parameters,electrical performance and power system on the aircraft,and sendes this information to the ground station for reception and analysis.The ground station effectively monitors the status of the aircraft.The quality of the transmitter in the telemetry system determines whether the signal can be accurately received by the ground station.The main function of the transmitter is to convert the collected bus data into high-frequency modulation signal suitable for wireless channel transmission.The super heterodyne system has a good performance and high stability as a system commonly used in telemetering remote control in China.But this structure has two kinds of defects.One problem is that the transmitter uses more analog separation components.It has a disadvantage of a complex structure and a large volume.Another problem is because of the use of multi-level inverts,a large number of high-performance filter are used,led to uncontrollable product cost.With the development of the semiconductor industry.Compared with the super heterodyne system,Zero-IF system relies on the advantages of no frequency planning,small size,and less spurious emission signals,So it is more suitable for today’s telemetry environment.The telemetry transmitter modulation methods mainly include three mainstream modulation systems:PCM/FM,SOQPSK,and ARTM-CPM.Among them,PCM/FM has developed for a long period of time,incorporated multiple symbol detection(MSD)and turbo product code(TPC)technologies.It makes the modulation more mature.SOQPSK has higher data transmission rate and lower frequency band occupancy compared to traditional FM system.This model effectively solves the problem of strained band resources caused by the increase in telemetry tasks.The ARTM-CPM system performs convolutional coding on the modulated data,this lead to a certain coding gain.By changing the parameters,different signal sets can be obtained and further improve the spectrum utilization.Each of the three modulation methods has its own characteristics and is suitable for different environments.This paper combines current development trends and utilizes the idea of software radio to develop a multimode telemetry transmitter,based on the Zero-IF system.The modulation methods include PCM/FM,SOQPSK,and ARTM-CPM.The developed transmitter uses a 28V power supply and the output signal power is higher than 4W.Experimental results show that the developed Zero-IF multimode telemetry transmitter has the characteristics of small size,complete functions and strong stability.After engineering verification,it can be widely used in today and future’s aerospace telemetry systems.