delay line

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delay line

[di′lā ‚līn]
A transmission line (as dissipationless as possible), or an electric network approximation of it, which, if terminated in its characteristic impedance, will reproduce at its output a waveform applied to its input terminals with little distortion, but at a time delayed by an amount dependent upon the electrical length of the line. Also known as artificial delay line.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Delay Line


a device used to delay signals by some predetermined time. The delay time τ is determined by the path length of an electromagnetic or acoustic wave within the delay line divided by the propagation velocity of the wave (however, this rule does not apply to artificial delay lines with lumped parameters).

Delay lines are used in color television equipment, in oscillograph equipment with a driven sweep, in radar stations with moving target selection, in devices providing optimum filtering of complicated radar signals, in coding, decoding, and selector devices, in memories, and in control devices of electronic computers. Delay lines are manufactured with values of τ ranging from fractions of a microsecond μsec) to tens of thousands of microseconds. They may have one or more outputs with different τ (multioutput delay lines); and τ may be constant or may depend on the frequency of the signal (dispersion delay lines). Delay lines have also been developed with adjustable τ (variable delay lines), with trimming of τ (magnetoelastic delay lines), with a low temperature coefficient of τ (thermally stable delay lines), and with internal signal amplification (active delay lines with phonon-photon or phonon-magnon interaction).

To produce small τ, electric lines with distributed parameters are used, such as conductive lines, strip lines, coaxial cables (particularly with an external helical conductor), and radio wave guides. In very long delay lines (several dozen meters), attenuation and wave dispersion (associated with electrical losses) distort the shape of the transmitted signal. The pass band of such delay lines does not exceed 10 megahertz (MHz). A greater τ (of the order of 01.-20.0 μsec) can be obtained in an electric artificial line with lumped parameters. The circuit of such a line is a series of networks, each of which consists of induction coils and capacitors. In such a line the value of τ depends on the number of networks, on the connection scheme of induction coils and capacitors in each network, and on the values of inductance and capacitance.

To produce τ of the order of 10 μsec to 10 msec, ultrasonic delay lines are used. In such lines electric input signals are first converted into ultrasonic signals by means of piezoelectric or magnetostrictive conversion, after which they pass through special matching layers (indium, epoxy resins, or glues) into an acoustic line. Acoustic lines may be of the cavity type (in the shape of a polyhedron), of the wave guide type (made of a ribbon or wire, usually wound as a helix), or of the multioutput type (bars made of piezoelectric materials with electrodes deposited on the bar). The signals propagate in the acoustic line with a velocity lower than the propagation velocity of electric signals by a factor of 105; they are converted back into electric signals by an output converter, which is analogous to the input converter. Materials used for acoustic lines include special steels; magnesium-aluminum alloys; single crystals of sodium chloride, potassium chloride, and potassium bromide; and fused quartz. To produce large τ in a small volume, an acoustic line is frequently shaped as a polyhedron (cavity acoustic line). In such a polyhedron the path length of ultrasonic waves is increased significantly because of multiple internal reflections of waves from the walls of the cavity.

The most commonly used delay lines are various kinds of electric delay lines with lumped parameters and some individual types of wave guide ultrasonic delay lines and ultrasonic delay lines with cavity acoustic lines, especially those with τ = 64 μsec, which are used for color television receivers.

The best parameters are exhibited by ultrasonic delay lines with cavity acoustic lines made of single crystals or fused quartz (τ ~ 1–5 msec; operating frequency, 20–60 MHz; pass band, 5–15 MHz; signal attenuation, of the order of 40–70 decibels [dB]; spurious signal level, 35–40 dB).


Eveleth, J. “Obzor ul’trazvukovykh linii zaderzhki, rabotaiushchikh na chastotakh nizhe 100 Mgts.” Trudy Instituta inzhenerov po elek-trotekhnike i radioelektronike, 1965, vol. 53, no. 10.
Mason, W. “Ul’trazvukovye linii zaderzhki s mnogokratnymi otra-zheniiami.” In Fizicheskaia akustika, vol. 1, part A. Moscow, 1966.
May, J. “Volnovodnye ul’trazvukovye linii zaderzhki.” Fizicheskaia akustika, vol. 1, part A. Moscow, 1966.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

delay line

A communications or electronic circuit that has a built-in delay. See delay line memory.
Copyright © 1981-2019 by The Computer Language Company Inc. All Rights reserved. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher.
References in periodicals archive ?
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Besides the delay lines, variations of the proposed topology can be used in other slow transition circuits.
In Section 2, the six-port-based delay line discriminator architecture is described.
Zomp, "Prototype binary fiber optic delay line," Optical Engineering, Vol.
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Martinelli, "A reconfigurable architecture for continuously variable optical slow-wave delay lines," Opt.
One work-around for this trigger delay is to add a delay line to the data path.
However, the current "delay line" devices for doing this are too large to use on a microchip.
Rather than attempting to measure the transit time directly at a resolution of a few picoseconds, the cavity serves as a delay line in the feedback loop of an operational amplifier.
To achieve phase alignment, each channel of the receiver array is applied to a tap of a delay line. Echoes from various locations within the body are detected by the probe and phase aligned corresponding to the tap delays.
Our in-line monitoring system consists of: 1) a homemade ultrasound probe, assembled by a homemade delay line, an adaptor, and a standard ultrasound transducer with a center frequency of 5 MHz; 2) an ultrasound pulser/receiver; and 3) a data acquisition system on a computer.