The proliferation of computers in today's society has increased the demand for transmission of data over wireless links. Binary data, composed of sharp "one to zero" and "zero to one" transitions, results in a spectrum rich in harmonic content that is not well suited to RF transmission. Hence, the field of digital modulation has been flourishing. Recent standards such as Cellular Digital Packet Data (CDPD) and Mobitex*specify Gaussian filtered Minimum Shift Keying (GMSK) for their modulation method.
GMSK is a simple yet effective approach to digital modulation for wireless data transmission. To provide a good understanding of GMSK, we will review the basics of MSK and GMSK, as well as how GMSK is implemented in CDPD and Mobitex systems.
GMSK modems reduce system complexity, and in turn lower system cost. There are, however, some important implementation details to be considered. This paper will cover some of these details, focusing on interfacing a single chip baseband modem to the IF/RF section of a "typical" FM radio topology.
