Patent ID: 7515645

Claim:
Method for dividing a bit rate of QPSK signals into at least two channels having band width limited filters in a modulator and a demodulator, by means of splitting a bit stream of the QPSK signals into two bit streams, comprising the following characteristics: Transmitting the two bit streams by means of at least two filter branches (P 1 P 1 *; P 2 P 2 *), into at least one purely real spectrum (P 1 ) and at least one purely imaginary spectrum (P 2 ), by means of filters (P 1 * and P 2 *) that form pulse former pairs, whereby the divided bit stream is transmitted at half the bit rate f 9 and, for an expansion to multi-carrier systems, an alternating real and imaginary spectra are implemented by a low-pass filter (P 1 ) and subsequent modulation with equidistant cosine and sine carriers, and remaining side band (RSB) filtering takes place, in which the purely imaginary spectrum (P 2 is determined from the difference of a low-pass having a band width f g and of the low-pass P 1 having the band width f g /2, whereby zero places of the pulse responses in the two filter branches (P 1 xP 1 * and P 2 xP 2 *) lie at a multiple of 1/f g , and the transmitted bit rate lies at f g , in each instance, and the spectra are band-limited; Modulating the divided QPSK signals with the sine carrier or the cosine carrier, in each instance; Transmitting the signal obtained in this manner to a receiver with the demodulator, and demodulation of the signal; Dividing the received signal by means of at least two filter branches with a purely real transmission function (P 1 *) and a purely imaginary transmission function (P 2 *) by means of at least two filter branches having filters (P 1 * and P 2 *) that form pulse former pairs, into at least two purely real spectra (P 1 xP 1 * and P 2 xP 2 *), whereby the divided signal is transmitted at half the bit rate f g ; Demodulating the signals having a higher frequency by means of RSB filtering and evaluation as a basic band signal; wherein the at least one purely real spectrum (P 1 ) has an upper flank and the at least one purely imaginary spectrum (P 2 ) has an upper flank and a lower flank; and wherein roots of the Nyquist flanks lie symmetrical to a frequency ω g /2 for the upper flank of P 1 and the lower flank of P 2, and lie at ω g for the upper flank of P 2 .