Research On Modulation And Demodulation Technology Of ACARS System In VHF Digital Link

VHF Air-ground Digital Link which was commonly implemented with ACARS (Aircraft Communication Addressing and Reporting System) has become a mature and practical Technology.In order to research Air-ground Digital Link deeply, achieve an efficient and low-cost real-time aircraft performance monitoring, this thesis designed a sample modem device of the VHF Air-ground Digital Link, which is based on deep research on Air-ground Digital Link.As a portable ACARS testing station, the PATS system can make advantage of different monitoring software to implement Data communication between ground station and airborne devices, which enhance its flexibility and practical value.Based on the analysis of the ACARS system, this thesis discussed ways to design and implement a MODEM device with DS5000-32-16 as the microprocessor in detail, using Protel 99SE to design the circuit schematics and PCB, designed and developed the MODEM hardware system, and finally implemented the algorithms of Minimum Shift Keying and the A/D conversion in a software approach. The hardware system was separated as microprocessor, isolation circuit, amplifier, A / D converter, D / A converter, serial data communication circuit, the radio state controlling circuit, and other auxiliary circuits.This thesis solved the problem of modulation and demodulation algorithm with the transmission speed under the 1200bit/s and 2400bit/s.we also simulated the modulation algorithm of MSK signal with MATLAB and analyzed the circuit with Multisim10, a circuit simulation software. All efforts above laid a solid foundation of the design of system software in later period. The analysis,simulation and test of the sample device showed that the hardware had achieved expected aim and suitable for modulation and demodulation of similar signal transmission in other fields.