Design and Realization of a Full Digitalization GMSK Modem on FPGA

Abstract

To implement GMSK modem with the characteristics of good spectrum, low complexity and fast acquisition, a full digitizationGMSKmodem scheme was proposed. Based on LUT method, the generation of GMSK signals has better spectrum characteristicand easy to realize. In receive terminal, a non-coherent digitized GMSKreceiver with fast signal detection and symbol timing acquisitionalgorithm was presented. Double sliding windows was used to conquer the influence of communication channel gain on the detection algorithm and realized within 6 symbols with accuracy. Additionally, in order to reduce the complexity of the receiver, the received signals are demodulated sample by sample in advance and then decided with the estimated symbol timing. The symbol timing acquisition algorithm proposed is realized based on a preamble sequence rapidly within only 8 symbols. Simulation results and integrated FPGA realizationprove its feasibility and superiority.