AbshacLThis paper describes a general method for calculating the power spectra of zero substitition coded signals and applies this method to calculate the B32S signal spectrum of the DS-3. Many digital radio systems transmit a signal which consists of DS-3 level baseband signals. Therefore, knowledge of the B3ZS spectral characteristics is important in DS-3 level interfeknce and systems studies.The method used for calculating spectral densities of substitution coded signals is based on signal-flow graph analysis. While signal-flow graph identities and Mason's gai. formula have been used in the past in the calculation of some substitution coded spectra, they become unduly cumbersome when applied towards ,ynplex spectra such as that of the B3ZS signal. In place of the graph identities and gain formula, two matrix techniques a& introduced that can be used in general to simplify spectral calculations for substitution coded signals.The methodology used in analyzing these communication signals can also be applied to other related fields such as coding of signals for magnetic recordings.
Memory‐based digital filtering is considered in the context of high‐speed (greater than 15 Mbaud) radio systems, where it finds application as an accurate and rapid approach to synthesizing band‐limited data signals for transmission over Nyquist channels. Following brief comments regarding the basic circuit architecture, feasibility models for 16‐and 64‐QAM 90‐Mb/s operation are experimentally evaluated. Performance is found to be consistent with digital radio objectives and superior to sophisticated analog designs.
Fractionally spaced equalizers have attained popularity because of their notable advantages, chiefly an ability to form an optimal linear receiver and provide performance quite insensitive to receiver timing phase. This work describes a time-domain Nyquist-rate algorithm that broadens the utility of fractional equalizers by permitting least-mean-square or true zero-forcing adaptation, more rapid convergence relative to synchronous coefficient updating, user specification of the end-to-end Nyquist channel, and elimination of the coefficient drift phenomenon. The investigation includes an analytical description of the algorithm, a functional circuit architecture, and reference to a computer simulation illustrating stable equalizer operation in the presence of dispersion on a digital subscriber loop.
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