A Class of MSK Baseband Pulse Formats with Sharp Spectral Roll-Off

Minimum frequency-shift-keying (MSK) is a very attractive modulation technique because of its spectral properties and the constant envelope property of the signal, but out-of-band energy spillover must sometimes be minimized to control co-channel interference. This problem has recently received attention in published articles and, since the pulse shape is the main parameter, many different MSK pulse formats have been described. In this note, a general shaping function, which allows various asymptotic spectral fall-off characteristics, is presented; then DSFSK (Double Sine Frequency Shift Keying) is derived from it, and its spectrum is computed, analyzed and compared with Rabzel's results.