Design And Implement Of All Digital MSK Modulator And Demodulator

MSK is an excellent digital modulation scheme which has continuous phase, constant2envelope and narrow-band, and can be widely used in a variety of communication systems. In the MSK modulation technology, broadband high-speed rate of MSK modulation technique is relatively mature, and large-scale application can be found in the short-wave frequency band. But the narrow-band low-rate of MSK modulation technique is not perfect, the hardware implementation is not resolved because of so many difficulties, therefore, this research mainly focuses on low-rate narrowband MSK modulation and demodulation in the paper.Firstly, the principle of MSK modulation and demodulation is studied, and a variety of modulation methods are simulated. According to simulation results, the frequency of direct synthesis method is determined to achieve the modulation. Secondly, several demodulation algorithms are studied. Considering the performance of demodulation and implement of hardware, we simulate and compare several demodulation algorithms. Lastly, the effect of carrier synchronization, bit synchronization, frame synchronization on the performance of the modulation is studied. Carrier synchronization, bit synchronization and frame synchronization algorithm are studied under the condition of the demodulation algorithm, and an improved algorithm is given based on the existing carrier synchronization algorithm. In the modem hardware design, DSP and FPGA using a combination of all-digital approach to data collection, computing, synthetic all digitally. Digital platform also makes the modem has a strong flexibility and scalability.In addition, some auxiliary measuring equipments are also made after completion of hardware. The performance of the whole system is tested and the test datum are analyzed and compared by the equipments.