Design Of High Frequency Digital Modem Based On American Military Standard Appendix C MIL-STD-188-110C Code

With the rapid development of modern Internet technology,people's demand is higher and higher for the velocity information,therefore the research on high speed data transmission becomes more and more important.High speed digital modulation and demodulation has very important significance for high-definition images,radar,and other information.According to American military standard MIL-STD-188-110C Appendix C for the design of high performance HF modem.Implementation of a baseband coding,interleaving,scrambling to send data,modulation and other information processing,receiving data demodulation,descrambling,deinterleaving data processing.The design model of software simulation of the whole system,algorithm,implementation of high quality information transmission.Short wave communication has a long history of development in the last century 50's development to the heyday of the 80's when the U.S.military as an important means of war communications.Short wave communication equipment usually have compact and lightweight appearance,can quickly transfer and networking,communication distance far and power is very low,so it has important position in military communication.For a long time is one of various countries military communication research and development direction.Shortwave Modem is using a variety of techniques will convert digital signals for transmission over HF channel analog signal equipment,is a key component in HF data communication,but also in the field of military to ensure the main equipment of remote communication and its application scope is extremely broad,in great number.Traditional modem transmission rate is slow,anti interference is not strong,in the rapid development of digital information technology today,has been unable to meet the needs of modern digital communications.Leading technology of the short wave communications technology with the United States and other countries also have a big gap,the equipped with modems,widespread transmission rate is not high,low reliability of the phenomenon and there are many different kinds of models,communication standard not unified,difficult to achieve cooperative communication.In view of these deficiencies,this paper presents a new type of modem design.Using the idea of software radio is a universal hardware platform is designed.The signal digital processing,reducing the loss of signal and interference;using high speed data converters and digital signal processor can achieve real-time processing of speech and image signals.On the basis of the MIL-STD-188-110C and STANAG5066 standards,the design of the interface and the software can make the modem has a higher transmission efficiency and compatibility.The main work and achievements of this paper include the following aspects:(1)a new type of modem scheme for software radio architecture is designed.For the improvement of military communication standard MIL-STD-188-110C to the modem interleaving and coding technology to increase data transmission rate provides effective means that NATO shortwave communication standard STANAG5066 can improve equipment compatibility.According to these standards,combined with the software radio technology,digital signal processing technology,the design of the system program,can complete the high-speed digital signal processing.(2)hardware circuit design.Digital signal processing is the core of digital modem,using high performance TMS320C6748 DSP implementation,responsible for data processing and algorithm.According to the needs of DDR2 design,flash,the power supply circuit,and the design of the serial port and network interface communication and control interface;as a bridge between the analog and digital signals,signal sampling conversion module uses a sigma delta ADC/DAC with high anti aliasing and resolution,greatly reducing the noise in the signal,and McBSP interface can complete data transmission with high speed DSP and ADC/DAC.(3)PCB design.The design of PCB often affects the performance of equipment and electromagnetic radiation.Because the modem is powerful,the hardware circuit uses the device more,and the high speed signal is complex,so the design of PCB from the device to the circuit design,layout and wiring all need to consider a lot of factors.This paper from the PCB stack layer and impedance of the design to ensure quality of signal transmission,and from the design of the power supply chip selection,noise processing strictly control the noise generation and transmission.The simulation results show that the design has good effect.(4)circuit debugging and testing.After debugging the hardware circuit,the PCB board on the electrical work,in the CCS platform for DSP,memory and interface test,the results show that all the normal work,verify the feasibility of the program.