PHASE MAPPING FOR QPSK/QBL-MSK WAVEFORM

摘要

A method is described of pulse shaping a modulated sequence spread signal having serially formatted in-phase (I) and quadrature (Q) waveforms, each waveform includes a predetermined number of chips per symbol. The method includes (a) examining adjacent chips of the I and Q waveforms at a symbol boundary; (b) determining that one of the I or Q waveforms, at the symbol boundary, includes two adjacent first and second chips separated by a single chip period, where the first chip belongs to a previous symbol and the second chip belongs to a present symbol; (c) determining whether the first and second chips are of the same value; (d) if step (c) determines that the chips are of the same value, then extending a peak value between the first and second chips, and zeroing the other waveform of the I or Q waveform during the extended duration of the peak value; and (e) if step (c) determines that the chips are of opposite values, then zeroing one of the first chip or second chip, and inserting a chip into the other waveform of the I or Q waveform during the duration of the zeroed one pulse. Step (e) includes inserting the chip into the other waveform, wherein the inserted chip has a value that is the same as an immediately previous chip value; and extending a peak value between the immediately previous chip and the inserted chip to provide a flat-top there-between.