Fundamental Studies on Delay Time and Time-Axis Transformation in Continuously Variable Delay Devices

Masayuki TANIMOTO  Takahiko MORI  Mataji KOMAI  

IEICE TRANSACTIONS (1976-1990)   Vol.E62   No.11   pp.754-761
Publication Date: 1979/11/25
Online ISSN: 
Print ISSN: 0000-0000
Type of Manuscript: PAPER
Category: Transmission Systems

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The transient characteristics of the delay time of a signal are analyzed in detail in the time-varying cases of the continuously variable delay devices, whose delay time can be varied by a control signal. A supposed delay time which corresponds directly to the instantaneous control signal is defined as an instantaneous delay time (t) to make clear the essential function of the variable delay devices. In such devices, first (t) is converted into the actual delay time τ(t) and then the amplitude and frequency of the input signal (only the frequency in case of CCDs) are modulated by a modulating signal, -. Although the /τ conversion is essentially nonlinear, τ(t) is basically a lowpass-filtered version of (t) and hence τ(t) is nearly equal to (t) only if (t) is a slowly varying function of time. 1 generally holds and any τ(t) satisfying this constraint can be realized in the variable delay devices. Such time-variation of the delay time causes the time-axis transformation (time-axis compression and expansion), which is one of the very useful applications in the signal processing. It is shown that any time-axis transformation and its inverse transformation can be performed in principle by the variable delay devices. Finally, fundamental experiments on the time-axis transformation and its inverse transformation are carried out by using CCDs as the variable delay devices and the major theoretical results are varified experimentally.