Based The Secondary Modulation Of Ultrashort Wave Aviation Data Communication System Design And Realization Of Research

When transmitting the voice information in VHF/UHF aviation communication, the pure voice radio is not only in low efficiency by lack of the capability to transmit complicated information data, but also it makes errors easily. Therefore, the transition to data communication system while supporting the voice communication will be the keystone of VHF/UHF aviation communication to increase the G-A communication information capacity, expand the communication coverage, and improve the inter operation of communication. In technology development and project implementation, the way, which will gain better effects both in technology and practicality, to utilize voice radio to transmit tactics data and ATC data, expand the function of the original voice radio so as to enable it to be a voice /data two way radio, which works to both be aviation voice communication and to support data transmission.The article starts with the application analysis, which analyses the transmission model and channel characteristics of the aviation communication, introduces the factors that affect the communication distance and adjudicate criteria of communication quality. It takes the chance of the R&D of the VHF/UHF aviation communication data transmission radio to particularly analyze the key technology of amendment from conventional voice radio to data transmission one from the aspects of validity, reliability and real timely of aviation data communication. It describes the collectivity framework such as composition, signal flow and interface sequence of the data transmission radio and makes emphases on how to realize the MODEM module and transmission/receiving channel that adopts the remodulation mode. It gives a detailed introduction and analysis on the hardware platform, function allocation, signal process and software flow of MODEM. As well as, it presents the hardware improvements proposal, which fit the remodulation system, such as the receiver front end, AGC, medium- frequency filter, FM modulator and demodulator, broadband linear power amplifier, Tx/Rx RF switch, etc. It lays great stress on the advantage of bandwidth utilance by adopting FM-PSK mode, counts the two grades signals'quality of FM-PSK and calculates the RF signal level required by error bit rate. It analyses the capability of error correction coding/decoding, expatiates the system frame format design and carrier wave with symbol synchronization design, describes the improvement points of receiving and transmitting channels and gives the detailed circuit design of these.In the research of this task, abundant technology analysis, theoretical demonstrations, experimentation simulation, experiment validation and comparative tests are used to test the specification as transmission power, Tx/Rx switch time, fluctuate in pass band, transmission and receiving delay, voice sensibility, data transmission sensibility and residual error rate. In end, it presents the test result and test conclusion that in the lab test and practical outfield test-fly, the preferable data transmission sensibility and communication distance are possessed, and the package lost rate is satisfied when the signal quality is good, which the communication distance and quality required by engineering application are completely met.