Research On The Future Advanced Modulation Digital Telemetry Transmitter Technology

The telemetry system is an important support system for the operation and testing of missiles and launch vehicles.It can monitor the dynamic system,electrical performance and environmental parameters of the spacecraft in real time.It plays a key role in the performance test and fault analysis of the spacecraft,to provide a strong guarantee for our military and national defense construction.As the core part of space telemetry system,telemetry transmitter’s main task is to modulate the encrypted,encoded data stream to the RF carrier,and output an RF modulation signal with certain power and bandwidth.Then the ground station can receive,demodulation and analysis.PCM/FM modulation system is one of the mainstream ways in the field of aerospace telemetry.The system improves the demodulation bit error performance of the ground station receiver by combining with MSD and TPC technology.However,with the development of new models such as heavy-duty launch vehicles in our country,the amount of aerial telemetry data has increased dramatically.Limited by its spectrum performance,PCM/FM system has been unable to meet the bandwidth requirements of the future high code rate telemetry system.In this paper,an S-band advanced modulation system digital telemetry transmitter of spacecraft telemetry is developed.The modulation method adopts SOQPSK-TG and ARTM CPM.The transmitter’s modulation mode,information transmission code rate,transmission frequency and other parameters can be flexibly configured by the PC set up software.It also has real-time storage function,to meet the current and future space telemetry system application requirements.The transmitter is based on software radio,taking the functional modular design.It mainly includes four parts:baseband signal processing module,radio frequency upconversion module,power amplifier module and power conversion module.The baseband signal processing module uses the digital circuit to realize the modulator output 70MHz intermediate frequency modulation signal,using the FPGA as the hardware processing platform.RF upconversion module uses two up-conversion circuit,which can effectively filter out clutter and limit the signal bandwidth.The power amplifier module ensures that the transmit power is not less than 7W.Through the surge suppression circuit and EMI filter circuit,power conversion module provides the operating voltage that the transmitter required.The experimental result shows that the main performance of the signal of the future advanced modulation digital telemetry transmitter developed in this project is better than the traditional PCM/FM system telemetry transmitter.It’s spectrum is narrow;the side lobe is low;the envelope is constant;the band utilization is high.It can be widely used in the future high code rate space telemetry system.