Mechanical Delay Line Research Articles

High-resolution THz spectrometer with kHz scan rates

We demonstrate a rapid scanning high-resolution THz spectrometer capable of acquiring THz field transients with 1 ns duration without mechanical delay line. The THz spectrometer is based on two 1-GHz Ti:sapphire femtosecond lasers which are linked with a fixed repetition rate difference in order to perform high-speed asynchronous optical sampling. One laser drives a high-efficiency large-area GaAs based THz emitter, the other laser is used for electro-optic detection of the emitted THz-field. At a scan rate of 9 kHz a time resolution of 230 fs is accomplished. High-resolution spectra from 50 GHz up to 3 THz are obtained and water absorption lines with a width of 11 GHz are observed. The use of femtosecond lasers with 1 GHz repetition rate is essential to obtain rapid scanning and high time-resolution at the same time.

Certain theorems on exact non-uniform transmission lines†

This correspondence establishes two now theorems and their converses on non-uniform transmission lines. On the basis of these theorems, new patterns of non–uniformity for a separate class of solvable transmission lines, termed ‘exact non-uniform lines’, may be obtained in terms of known solvable non-uniformities of any of the general classes of transmission lines. They may find applications in integrated circuitry and acoustics ; for example, in the design of horns, mechanical delay lines, etc.

Low Frequency Mechanical Delay Lines

Low Frequency Mechanical Delay Lines

Equivalent Distributed ParameterZ-Y-G∞Networks

The principle of electrical equivalence for distributed parameter (d.p.) networks is generalized and proved using the concept of ‘matrix parameter functions (m.p.f.)’ in terms of which all the voltage-current matrix parameters of any two-port three-terminal d.p. network may suitably be expressed. Exact mathematical expression for the equivalent length corresponding to each of the three different patterns of variation of per unit length (p.u.l.) parameters associated with any class of d.p. networks is presented. All specific member of d.p. networks, obtainable from the three patterns of variation of the p.u.l. parameters of a class of d.p. structures, may be shown to be electrically equivalent to one another, if their physical lengths are so chosen as to conform to the conditions of electrical equivalence. The equivalence principle may find applications in many other fields, such as acoustics, microwaves, design of mechanical delay lines and filters, etc., in which various devices are adequately represente...

Mechanical Audiofrequency Delay Line

The mechanical audiofrequency delay line reported at the sixtieth meeting of the Acoustical Society has been developed into a practical delay line. A time delay of 15 msec is obtained with a 0.4-mil-diam platinum-alloy wire with transverse wave velocity of 90 m/sec. Any number of magnets up to about 100 can be placed along the active length of the wire and adjusted to generate any signal within the limits of the time bandwidth of the delay line. Transverse waves propagating up the wire are detected by a displacement pickup located at the top, which consists of a lamp casting the shadow of the wire on the edge of a silicon solar cell. The transverse waves propagating down the wire, both from the originating magnet and the reflection off of the upper end, are absorbed by viscous damping in a liquid termination consisting of a 0.5-m height of liquid propane. The reflections from the termination are about 22 db down at 300 cps and much less at higher frequencies. The group delay at 15-msec delay corresponds to phase errors of less than 6° in the frequency range from 300 to 3000 cps.

Loudspeaker Accessory for the Production of Reverberant Sound

Organ music produced in small rooms having little natural reverberation can be enhanced by the addition of artificial reverberation. A direct method of adding the aftersound at the electroacoustic transducer itself is described. This is in contrast to the more conventional reverberation systems employing driving transducers, time-delay means, pickup transducers, and mixing and amplifying circuits. Multiply resonant helical mechanical delay lines store the energy and radiate it at a later time. In one model the coupling to the transducer is mechanical, and in the other model acoustical coupling provides a number of practical and acoustical advantages.