| 摘要 |
With the invention, the bandwidth requirement of k<2>-quadrature amplitude-modulation (QAM) systems (k = number of amplitude stages, k<2> = number of signal states) is intended to be reduced. A transmitting-end digital transverse filter structure with a low-pass character is used for this purpose, in which the binary input signal undergoes a binary k-stage coding prior to the conventional QAM coding. From statistically evenly distributed binary signals, the digital transverse filter structure generates k-stage signals with only single-stage transitions between consecutive symbols. It thus causes the relevant signal components to shift towards lower frequencies. At the receiving end, the k-stage coding is reversed in each case by means of k-1 threshold value discriminators, digital differentiators and flip-flops. In the case where k = 3, i.e. in a 9-QAM, no flip-flops are required in the decoder (Fig.1). <IMAGE>
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