Showing papers on "Anti-aliasing published in 1975"

Picture processing and digital filtering

Abstract: Two-Dimensional transforms.- Two-dimensional nonrecursive filters.- Two-dimensional recursive filtering.- Image enhancement and restoration.- Noise considerations in digital image processing hardware.- Recent advances in picture processing and digital filtering.

Digital speech communication system for minimizing quantizing noise

Abstract: A digital speech communication arrangement includes apparatus for partitioning a speech signal into a plurality of nonuniformly related, preassigned intelligibility contributing subbands, and quantized with an accuracy (bit allocation) based upon perceptual criteria. As a result, the quality of the coded signal is improved over that obtained from a single full-band coding of the total spectrum. "Integer-band" sampling may be employed to alias the signal in an advantageous way before coding. Each subband portion is digitally encoded after sampling at a rate related to the bandwidth of the subband. The digital codes of the subband are combined and applied to a common communication channel. A replica of each subband is formed by separating the digital codes, producing a sampled form of each digital coded signal and selecting the subband of the speech signal from said sampled form. The subbands are combined to reconstruct the speech signal. Other features include: aliasing for efficient frequency transposition.

Signal aliasing in system identification

Abstract: Signal aliasing in the digital identification of continuous systems is considered. Parametric identification methods are seen to be free of aliasing errors, provided that the poles of the continuous system are known to lie in specific s-plane regions. In the case of non-parametric identification, frequency response estimates based upon digital techniques are shown to be seriously distorted by signal aliasing. In particular, aliasing errors are shown to be phase sensitive and can therefore be controlled by suitable equalization of the relative phase of observed input-output signals.