Pulse design and efficient generation circuits for linear TDMA modulation

Abstract

In time-division multiple access (TDMA) radio systems, the on/off power transitions at burst boundaries must be carefully controlled to minimize spectral spreading while also minimizing transition times. Several methods of performing power transitions are examined. The first method uses a continuous modulator which is windowed with a raised cosine. The second method uses the addition of individual signaling pulses as a part of the modulator circuit. This method causes no excess spectral spreading from the on/off power transitions. A third method uses asymmetric pulse shapes during the transition times to minimize the transition times, while causing no excess spectral spreading. The design of these pulses and circuits to generate them are discussed. Since the circuit is completely digital with low complexity, it is suitable for VLSI implementation.<>