Generating and Demodulating

Open Access

Abstract

The views expressed in this report are those of the author and do not reflect the official policy or position of the Department of Defense or the United States Government. ; This paper discusses a technique for modulating and demodulating M-ary FSK using an FFT based modem typical of Coded Orthogonal Frequency Division Modulation (COFDM) systems. COFDM is one of the more promising spectrally efficient, high data rate modulation techniques for line-of-sight communications between mobile platforms. This paper will show that legacy FSK radios like the AN/MRC-142 (binary FSKmodulation at 144, 288, 576 kbps) used by the U.S. Marine Corps could be easily implemented in a COFDM modem orginally designed for higher data rates and better spectral efficiency than the legacy radio. In addition, the performance of such an implementation is analyzed in detail and shown to result in negligible performance degradation (0.05 dB or less). Digital processing speed requirements are analyzed and shown to be similar to digital implementation of conventional FSK receivers. MATLAB code is included that simulates the modem. ; This report was sponsored by NCCOSC RDTE Division. ; Approved for public release; distribution is unlimited.