hrvatski

Digitalni off-set QPSK modulator

A construction of a digital off-set QPSK modulator is described and an analysis using Walsh functions is carried out. It is shown that an off-set signal could be represented by eight characteristic patterns of carrier signal for the case when an information bit of the odd parallel data stream Ln [Theta1-(k+2)] is not changed during the change of two information bits of the even parallel data stream Lp[Theta1-(k+1)], and vice versa. Off-set QPSK signal is obtained in a diode-resistor network by PSK modulation of rectangular carriers and addition of the two so obtained odd and even channels. Output signal of the digital off-set QPSK modulator is a three-level staircase approximation of the analog off-set QPSK signal, which can be obtained by pass-band filtering with the central filter frequency at 1/T. The off-set QPSK modulator is implemented using a digital IC technique

Digitalan; off-set QPSK; modulator

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