A method is described for modifying classical N-dimensional trellis codes to provide baseband codes that combine a spectral null at DC with significant coding gain. The information rate of the classical code is decreased by one bit, and this extra redundancy is used to keep the running digital sum bounded. Equivalently, if the rate is held constant, then twice as many signal points are needed, causing a power penalty of 6/N dB. Baseband trellis codes are presented for several information rates together with complete spectral plots and performance comparisons. A method of constructing baseband codes with multiple spectral nulls is also described.
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机译：描述了一种用于修改经典的N维网格码以提供将DC处的频谱零点与有效编码增益相结合的基带码的方法。经典代码的信息速率降低了一位，并且这种额外的冗余用于使运行中的数字和保持有界。同样，如果速率保持恒定，则需要两倍的信号点，从而导致6 / N dB的功率损失。给出了几种信息速率的基带网格码，以及完整的频谱图和性能比较。还描述了一种构造具有多个频谱零点的基带代码的方法。
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